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GABA B receptors (GBRs) are G protein-coupled receptors for GABA, the main inhibitory neurotransmitter in the brain. GBRs regulate fast synaptic transmission by gating Ca 2+ and K + channels via the Gβγ subunits of the activated G protein. It has been demonstrated that auxiliary GBR subunits, the KCTD proteins, shorten onset and rise time and increase desensitization of receptor-induced K + currents. KCTD proteins increase desensitization of K + currents by scavenging Gβγ from the channel, yet the mechanism responsible for the rapid activation of K + currents has remained elusive. In this study, we demonstrate that KCTD proteins preassemble Gβγ at GBRs. The preassembly obviates the need for diffusion-limited G protein recruitment to the receptor, thereby accelerating G protein activation and, as a result, K + channel activation. Preassembly of Gβγ at the receptor relies on the interaction of KCTD proteins with a loop protruding from the seven-bladed propeller of Gβ subunits. The binding site is shared between Gβ1 and Gβ2, limiting the interaction of KCTD proteins to these particular Gβ isoforms. Substituting residues in the KCTD binding site of Gβ1 with those from Gβ3 hinders the preassembly of Gβγ with GBRs, delays onset and prolongs rise time of receptor-activated K + currents. The KCTD-Gβ interface, therefore, represents a target for pharmacological modulation of channel gating by GBRs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Promoting the establishment of collateral circulation is essential for chronic lower extremity ischemia. However, no effective therapeutic drugs have yet been developed. Recent studies discovered that in the peripheral arteries, there are γ-aminobutyric acid B1 (GABAB1) receptors expressed in endothelial cells and smooth muscle cells, these receptors may have some effects in regulating vascular functions, but the precise mechanism is not yet clear. This study explores the effect of GABAB1 receptor inhibition on angiogenesis and its regulatory mechanism. The expression of GABAB1 in human umbilical vein endothelial cells (HUVECs) was knocked down using shRNA transfection, and effects on HUVECs' proliferation, migration, and tube formation ability were detected. Western blot and RT-PCR were used to verify the signal pathway. The murine hind limb ischemia model was used to verify the effect of CGP35348, an antagonist of GABAB1R, on the recovery of blood flow perfusion and angiogenesis in ischemic tissues. Cell proliferation, migration, and tube formation ability were improved after GABAB1 receptor knockdown in HUVECs. The phosphorylation of the HIPPO/Yes-associated protein (YAP) pathway decreased, while the effect of promoting angiogenesis increased. After treating the ischemic hindlimbs of mice with GABAB1 receptor antagonists, the blood flow perfusion recovered and the angiogenesis increased. These findings demonstrate the effect of GABAB1 receptor inhibition on the HIPPO/YAP pathway in regulating angiogenesis, suggesting that inhibiting GABAB1 receptor levels might be a novel approach for chronic lower extremity ischemia diseases., (Copyright © 2024. Published by Elsevier Inc.)

Hippocamposeptal (HS) neurons send GABAergic projections from the hippocampus to the medial septum/diagonal band of Broca (MS/DBB) as part of a reciprocal loop that is critical for memory. HS neurons are proposed to be particularly sensitive to the deleterious effects of pathological exposure to amyloid-β (Aβ), as would occur during Alzheimer's disease (AD). However, it is not known how HS GABA release in the MS/DBB is altered during the progression of AD. To target HS neurons in a mouse model of AD, we crossed SST-Cre mice to 5XFAD mice and performed stereotaxic injections of Cre-dependent AAV containing mCherry/channelrhodopsin-2 (ChR2) into the hippocampus of offspring at 4, 6, 9, and 12 months. We used optogenetics to selectively stimulate HS terminals while performing whole-cell patch-clamp recordings from MS/DBB neurons in slices. There was a transient reduction in HS-inhibitory postsynaptic current (IPSC) amplitude in female 5XFAD mice at 6 months, but no difference in males at any age, and no difference in paired-pulse ratio in either sex at any age. When bath applying the GABA B R agonist, baclofen, we found a larger decrease in HS-IPSC amplitude in 5XFAD females at 9 months and 5XFAD males at 12 months. In 12-month-old 5XFAD females, response to baclofen was significantly reduced. These data suggest that there is a transient increase in responsiveness to GABA B R activation in 5XFAD mice that occurs earlier in females than in males. These sex-specific changes to HS function are likely to impact the relay of information between the hippocampus and MS/DBB., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Neurons coordinate inter-tissue protein homeostasis to systemically manage cytotoxic stress. In response to neuronal mitochondrial stress, specific neuronal signals coordinate the systemic mitochondrial unfolded protein response (UPR mt ) to promote organismal survival. Yet, whether chemical neurotransmitters are sufficient to control the UPR mt in physiological conditions is not well understood. Here, we show that gamma-aminobutyric acid (GABA) inhibits, and acetylcholine (ACh) promotes the UPR mt in the Caenorhabditis elegans intestine. GABA controls the UPR mt by regulating extra-synaptic ACh release through metabotropic GABA B receptors GBB-1/2. We find that elevated ACh levels in animals that are GABA-deficient or lack ACh-degradative enzymes induce the UPR mt through ACR-11, an intestinal nicotinic α7 receptor. This neuro-intestinal circuit is critical for non-autonomously regulating organismal survival of oxidative stress. These findings establish chemical neurotransmission as a crucial regulatory layer for nervous system control of systemic protein homeostasis and stress responses., (© 2024. The Author(s).)

Background: Drug addiction is a social and medical problem that must be urgently addressed. The nucleus accumbens (NAc) is closely related to addiction-related learning memory, and γ-aminobutyric acid type B receptor (GABA B R) is a potential target for the treatment of drug addiction. However, the role of GABA B R activity levels in the NAc in cocaine addiction is unclear., Methods: In this study, we established an animal model of cocaine dependence, modulated the level of GABA B R activity, applied a conditioned place preference assay (CPP) to assess the role of the NAc in reconsolidation of addiction memory, evaluated learning and memory functions by behavioral experiments, examined the expression of GB1, GB2, cyclic adenosine monophosphate response element binding protein (CREB), p-CREB, protein kinase A (PKA), protein kinase (ERK), and Brain-derived neurotrophic factor (BDNF) in the NAc by molecular biology experiments, and screened differentially significantly expressed genes by transcriptome sequencing., Results: Our study showed that the GABA B receptor agonist baclofen (BLF) had a significant effect on locomotor distance in rats, promoted an increase in GABA levels and significantly inhibited the PKA and ERK1/2/CREB/BDNF signaling pathways. Moreover, transcriptome sequencing showed that GABA B R antagonist intervention identified a total of 21 upregulated mRNAs and 21 downregulated mRNAs. The differentially expressed (DE) mRNA genes were mainly enriched in tyrosine metabolism; however, further study is needed., Conclusion: GABA B R activity in the NAc is involved in the regulation of cocaine addiction and may play an important role through key mRNA pathways., Competing Interests: Conflicts of interest: The authors declare that they have no conflicts of interest related to the subject matter or materials discussed in this article., (Copyright © 2024, the Chinese Medical Association.)

Even a transient period of hearing loss during the developmental critical period can induce long-lasting deficits in temporal and spectral perception. These perceptual deficits correlate with speech perception in humans. In gerbils, these hearing loss-induced perceptual deficits are correlated with a reduction of both ionotropic GABA A and metabotropic GABA B receptor-mediated synaptic inhibition in auditory cortex, but most research on critical period plasticity has focused on GABA A receptors. Therefore, we developed viral vectors to express proteins that would upregulate gerbil postsynaptic inhibitory receptor subunits (GABA A , Gabra1 ; GABA B , Gabbr1b ) in pyramidal neurons, and an enzyme that mediates GABA synthesis ( GAD65 ) presynaptically in parvalbumin-expressing interneurons. A transient period of developmental hearing loss during the auditory critical period significantly impaired perceptual performance on two auditory tasks: amplitude modulation depth detection and spectral modulation depth detection. We then tested the capacity of each vector to restore perceptual performance on these auditory tasks. While both GABA receptor vectors increased the amplitude of cortical inhibitory postsynaptic potentials, only viral expression of postsynaptic GABA B receptors improved perceptual thresholds to control levels. Similarly, presynaptic GAD65 expression improved perceptual performance on spectral modulation detection. These findings suggest that recovering performance on auditory perceptual tasks depends on GABA B receptor-dependent transmission at the auditory cortex parvalbumin to pyramidal synapse and point to potential therapeutic targets for developmental sensory disorders., Competing Interests: Competing interests statement:S.M. and D.H.S. submitted a patent application for the viruses used to express Gabra1 and Gabbr1b (U.S. Patent Application No. 63/359,724), and a provisional patent application for the virus to express GAD65 (U.S. Patent Provisional Application No. 63/507,894). R.F. and T.M.M. declare no competing financial interests.

GABBR1 receptors have been implicated in the progression of rheumatoid arthritis (RA), and p38 MAP kinase (MAPK) was shown to be downregulated by GABA and result in unchecked production of pro-inflammatory cytokine. GABBR1 is a member of GABA receptors, and it is known to be upregulated and plays a vital role in RA. Glucocorticoids are efficient therapeutics in rheumatoid arthritis (RA) and are known to regulate GABA actions; therefore, we intended to investigate the potential of glucocorticoids in RA concerning the potential pathway GABBR1/MAPK. Joint specimens were obtained from collagen-induced arthritis mouse model. A double-blind semi-quantitative analysis of vascularity, cell infiltration, as well as lining thickness by help of a 4-point scale setting was used to assess joint inflammation. Expression of GABBR1 and p38 was evaluated immunohistochemically. In vitro peripheral blood (PB), synovial fluid (SF), and mononuclear cells (MCs) were acquired from RA mice. Western blotting was used for detecting expression of GABBR1 and p38 proteins. The presence of high levels of GABBR1 and p38 was prevalent in RA joints relative to healthy joints and related to the inflammation level. Glucocorticoid treatment alters GABBR1 along with p38 protein expression in joints while reducing joint inflammation. Ex vivo and in vitro assays revealed glucocorticoids have a direct impact on p38, such as the decreased GABBR1 expression level after dexamethasone incubation with SFMC. GABBR1 together with p38 expression in RA joints depends on local inflammation and can be targeted by glucocorticoids.

GABA B receptors (GBRs), the G protein-coupled receptors for GABA, regulate synaptic transmission throughout the brain. A main synaptic function of GBRs is the gating of Cav2.2-type Ca 2+ channels. However, the cellular compartment where stable GBR/Cav2.2 signaling complexes form remains unknown. In this study, we demonstrate that the vesicular protein synaptotagmin-11 (Syt11) binds to both the auxiliary GBR subunit KCTD16 and Cav2.2 channels. Through these dual interactions, Syt11 recruits GBRs and Cav2.2 channels to post-Golgi vesicles, thus facilitating assembly of GBR/Cav2.2 signaling complexes. In addition, Syt11 stabilizes GBRs and Cav2.2 channels at the neuronal plasma membrane by inhibiting constitutive internalization. Neurons of Syt11 knockout mice exhibit deficits in presynaptic GBRs and Cav2.2 channels, reduced neurotransmitter release, and decreased GBR-mediated presynaptic inhibition, highlighting the critical role of Syt11 in the assembly and stable expression of GBR/Cav2.2 complexes. These findings support that Syt11 acts as a vesicular scaffold protein, aiding in the assembly of signaling complexes from low-abundance components within transport vesicles. This mechanism enables insertion of pre-assembled functional signaling units into the synaptic membrane., (© 2024. The Author(s).)

GABA B receptor (GBR) activation inhibits neurotransmitter release in axon terminals in the brain, except in medial habenula (MHb) terminals, which show robust potentiation. However, mechanisms underlying this enigmatic potentiation remain elusive. Here, we report that GBR activation on MHb terminals induces an activity-dependent transition from a facilitating, tonic to a depressing, phasic neurotransmitter release mode. This transition is accompanied by a 4.1-fold increase in readily releasable vesicle pool (RRP) size and a 3.5-fold increase of docked synaptic vesicles (SVs) at the presynaptic active zone (AZ). Strikingly, the depressing phasic release exhibits looser coupling distance than the tonic release. Furthermore, the tonic and phasic release are selectively affected by deletion of synaptoporin (SPO) and Ca 2+ -dependent activator protein for secretion 2 (CAPS2), respectively. SPO modulates augmentation, the short-term plasticity associated with tonic release, and CAPS2 retains the increased RRP for initial responses in phasic response trains. The cytosolic protein CAPS2 showed a SV-associated distribution similar to the vesicular transmembrane protein SPO, and they were colocalized in the same terminals. We developed the "Flash and Freeze-fracture" method, and revealed the release of SPO-associated vesicles in both tonic and phasic modes and activity-dependent recruitment of CAPS2 to the AZ during phasic release, which lasted several minutes. Overall, these results indicate that GBR activation translocates CAPS2 to the AZ along with the fusion of CAPS2-associated SVs, contributing to persistency of the RRP increase. Thus, we identified structural and molecular mechanisms underlying tonic and phasic neurotransmitter release and their transition by GBR activation in MHb terminals., Competing Interests: Competing interests statement:The authors declare no competing interest.

GABA B receptor-mediated inhibition is indispensable for maintaining a healthy neuronal excitation/inhibition balance. Many neurological diseases are associated with a disturbed excitation/inhibition balance and downregulation of GABA B receptors due to enhanced sorting of the receptors to lysosomal degradation. A key event triggering the downregulation of the receptors is the phosphorylation of S867 in the GABA B1 subunit mediated by CaMKIIβ. Interestingly, close to S867 in GABA B1 exists another phosphorylation site, T872. Therefore, the question arose as to whether phosphorylation of T872 is involved in downregulating the receptors and whether phosphorylation of this site is also mediated by CaMKIIβ or by another protein kinase. Here, we show that mutational inactivation of T872 in GABA B1 prevented the degradation of the receptors in cultured neurons. We found that, in addition to CaMKIIβ, also ERK1/2 is involved in the degradation pathway of GABA B receptors under physiological and ischemic conditions. In contrast to our previous view, CaMKIIβ does not appear to directly phosphorylate S867. Instead, the data support a mechanism in which CaMKIIβ activates ERK1/2, which then phosphorylates S867 and T872 in GABA B1 . Blocking ERK activity after subjecting neurons to ischemic stress completely restored downregulated GABA B receptor expression to normal levels. Thus, preventing ERK1/2-mediated phosphorylation of S867/T872 in GABA B1 is an opportunity to inhibit the pathological downregulation of the receptors after ischemic stress and is expected to restore a healthy neuronal excitation/inhibition balance.

Mechanical, thermal, and chemical pain sensation is conveyed by primary nociceptors, a subset of sensory afferent neurons. The intracellular regulation of the primary nociceptive signal is an area of active study. We report here the discovery of a Gβ5-dependent regulatory pathway within mechanical nociceptors that restrains antinociceptive input from metabotropic GABA-B receptors. In mice with conditional knockout (cKO) of the gene that encodes Gβ5 (Gnb5) targeted to peripheral sensory neurons, we demonstrate the impairment of mechanical, thermal, and chemical nociception. We further report the specific loss of mechanical nociception in Rgs7-Cre+/- Gnb5fl/fl mice but not in Rgs9-Cre+/- Gnb5fl/fl mice, suggesting that Gβ5 might specifically regulate mechanical pain in regulator of G protein signaling 7-positive (Rgs7+) cells. Additionally, Gβ5-dependent and Rgs7-associated mechanical nociception is dependent upon GABA-B receptor signaling since both were abolished by treatment with a GABA-B receptor antagonist and since cKO of Gβ5 from sensory cells or from Rgs7+ cells potentiated the analgesic effects of GABA-B agonists. Following activation by the G protein-coupled receptor Mrgprd agonist β-alanine, enhanced sensitivity to inhibition by baclofen was observed in primary cultures of Rgs7+ sensory neurons harvested from Rgs7-Cre+/- Gnb5fl/fl mice. Taken together, these results suggest that the targeted inhibition of Gβ5 function in Rgs7+ sensory neurons might provide specific relief for mechanical allodynia, including that contributing to chronic neuropathic pain, without reliance on exogenous opioids.

G protein-coupled receptors (GPCRs) represent the largest family of membrane proteins and are important drug targets. GPCRs are allosteric machines that transduce an extracellular signal to the cell by activating heterotrimeric G proteins. Herein, we summarize the recent advancements in the molecular activation mechanism of the γ-aminobutyric acid type B (GABA B ) and metabotropic glutamate (mGlu) receptors, the most important class C GPCRs that modulate synaptic transmission in the brain. Both are mandatory dimers, this quaternary structure being needed for their function The structures of these receptors in different conformations and in complexes with G proteins have revealed their asymmetric activation. This asymmetry is further highlighted by the recent discovery of mGlu heterodimers, where the eight mGlu subunits can form specific and functional heterodimers. Finally, the development of allosteric modulators has revealed new possibilities for regulating the function of these receptors by targeting the transmembrane dimer interface. This family of receptors never ceases to astonish and serve as models to better understand the diversity and asymmetric functioning of GPCRs. NEW & NOTEWORTHY γ-aminobutyric acid type B (GABA B ) and metabotropic glutamate (mGlu) receptors form constitutive dimers, which are required for their function. They serve as models to better understand the diversity and activation of G protein-coupled receptors (GPCRs). The structures of these receptors in different conformations and in complexes with G proteins have revealed their asymmetric activation. This asymmetry is further highlighted by the recent discovery of specific and functional mGlu heterodimers. Allosteric modulators can be developed to target the transmembrane interface and modulate the asymmetry.

The amino acid transmitter γ-aminobutyric acid (GABA) is suspected to play an important role in regulating the activity of the gonadotropin-releasing hormone (GnRH) neurons controlling fertility. Rodent GnRH neurons have a novel dendritic compartment termed the "distal dendron" through which action potentials pass to the axon terminals and where inputs from the kisspeptin pulse generator drive pulsatile GnRH secretion. Combining Gnrh1-Cre mice with the Cre-dependent calcium sensor GCaMP6 and confocal imaging of acute brain slices, we examined whether GABA regulated intracellular calcium concentrations ([Ca2+]) in the GnRH neuron distal dendron. Short puffs of GABA on the dendron evoked either a monophasic sustained suppression of [Ca2+] or a biphasic acute elevation in [Ca2+] followed by the sustained suppression. Application of muscimol to the dendron replicated the acute elevation in [Ca2+] while baclofen generated the sustained suppression. Robust GABAB receptor-mediated inhibition was observed in 80% to 100% of dendrons recorded from females across the estrous cycle and from approximately 70% of dendrons in males. In contrast, the GABAA receptor-mediated excitation was rare in males and varied across the estrous cycle, being most prominent at proestrus. The activation of GABAB receptors potently suppressed the stimulatory effect of kisspeptin on the dendron. These observations demonstrate that the great majority of GnRH neuron distal dendrons are regulated by GABAergic inputs in a sex- and estrous cycle-dependent manner, with robust GABAB receptor-mediated inhibition being the primary mode of signaling. This provides a new, kisspeptin-independent, pathway for the regulation of pulsatile and surge modes of GnRH secretion in the rodent., (© The Author(s) 2022.Published by Oxford University Press on behalf of the Endocrine Society.)

GABA B receptors are obligatory heterodimers responsible for prolonged neuronal inhibition in the central nervous system. The two receptor subunits are encoded by GABBR1 and GABBR2. Variants in GABBR2 have been associated with a Rett-like phenotype (MIM: 617903), epileptic encephalopathy (MIM: 617904), and milder forms of developmental delay with absence epilepsy. To date, however, no phenotypes associated with pathogenic variants of GABBR1 have been established. Through GeneMatcher, we have ascertained four individuals who each have a monoallelic GABBR1 de novo non-synonymous variant; these individuals exhibit motor and/or language delay, ranging from mild to severe, and in one case, epilepsy. Further phenotypic features include varying degrees of intellectual disability, learning difficulties, autism, ADHD, ODD, sleep disorders, and muscular hypotonia. We functionally characterized the four de novo GABBR1 variants, p.Glu368Asp, p.Ala397Val, p.Ala535Thr, and p.Gly673Asp, in transfected HEK293 cells. GABA fails to efficiently activate the variant receptors, most likely leading to an increase in the excitation/inhibition balance in the central nervous system. Variant p.Gly673Asp in transmembrane domain 3 (TMD3) renders the receptor completely inactive, consistent with failure of the receptor to reach the cell surface. p.Glu368Asp is located near the orthosteric binding site and reduces GABA potency and efficacy at the receptor. GABA exhibits normal potency but decreased efficacy at the p.Ala397Val and p.Ala535Thr variants. Functional characterization of GABBR1-related variants provides a rationale for understanding the severity of disease phenotypes and points to possible therapeutic strategies., Competing Interests: Declaration of interests S.E.A. is a cofounder and CEO of Medigenome, Swiss Institute of Genomic Medicine; he is also a member of the Scientific Advisory Board of the “Imagine Institute”, Paris. E.R. is also a cofounder and medical director of Medigenome, Swiss Institute of Genomic Medicine. M.L.C. is an intern in the federally recognized clinical training program for Genetic Medicine of Medigenome. L.N. was supported by the grant NV19-07-00136 from the Ministry of Health of the Czech Republi, and The National Center for Medical Genomics (LM2018132) for support with the WES analyses., (Copyright © 2022 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Methamphetamine (METH), a widely abused stimulant drug, induces psychosis in approximately half of abusers; this effect is becoming a major concern for society. Although the Notch1 signalling pathway has been shown to play a part in the pathogenesis of some psychiatric disorders, its role in METH-induced psychosis (MIP) is still unknown. Here, the METH-induced locomotor sensitization model in rodents is considered to represent the underlying neurochemical changes driving psychoses. We found that the Notch1 signalling was downregulated in the medial prefrontal cortex (mPFC) in sensitized mice. Direct genetic and pharmacological manipulations of Notch1 signalling bidirectionally altered METH-induced locomotor sensitization and other MIP-related behaviours through governing neuronal activity in the mPFC. Moreover, Notch1 signalling negatively regulated GABA B1 receptor expression in the mPFC of METH-sensitized mice through Hes1, a transcriptional repressor in Notch1 signalling. Further, we show that Hes1 can directly bind to the GABA B1 receptor promoter. Notably, pharmacological regulation of the GABA B receptor in the mPFC reversed the changes in METH-induced locomotor sensitization caused by the dysfunction of Notch1 signalling. Together, our findings uncover a previously unrecognised Notch1-Hes1-GABA B1 receptor-dependent mechanism involved in regulating mPFC neuronal activity and behavioural phenotypes in MIP. Our work provides mechanistic insight into the aetiology and pathophysiology of MIP., (© 2022. The Author(s).)

Metabotropic γ-aminobutyric acid receptor (GABA B R), a class C G protein-coupled receptor (GPCR) heterodimer, plays a crucial role in the central nervous system. Cryo-electron microscopy studies revealed a drastic conformational change upon activation and a unique G protein (GP) binding mode. However, little is known about the mechanism for GP coupling and activation for class C GPCRs. Here, we use molecular metadynamics computations to predict the mechanism by which the inactive GP induces conformational changes in the GABA B R transmembrane domain (TMD) to form an intermediate pre-activated state. We find that the inactive GP first interacts with TM3, which further leads to the TMD rearrangement and deeper insertion of the α5 helix that causes the Gα subunit to open, releasing GDP, and forming the experimentally observed activated structure. This mechanism provides fresh insights into the mechanistic details of class C GPCRs activation expected to be useful for designing selective agonists and antagonists., (© 2022. The Author(s).)

GABA B receptors in habenula cholinergic neurons mediate strong presynaptic excitation and control aversive memory expression. K + channel tetramerization domain (KCTD) proteins are key interacting partners of GABA B receptors; it remains unclear whether and how KCTDs contribute to GABA B excitatory signaling. Here, we show that KCTD8 and KCTD12 in these neurons facilitate the GABA B receptors expression in axonal terminals and contribute to presynaptic excitation by GABA B receptors. Genetically knocking out KCTD8/12/16 or KCTD8/12 , but not other combinations of the three KCTD isoforms, substantially reduced GABA B receptors-mediated potentiation of glutamate release and presynaptic Ca 2+ entry in response to axonal stimulation, whereas they had no effect on GABA B -mediated inhibition in the somata of cholinergic neurons within the habenulo-interpeduncular pathway in mice of either sex. The physiological phenotypes were associated with a significant decrease in the GABA B expression within the axonal terminals but not the somata. Overexpressing either KCTD8 or KCTD12 in the KCTD8/12/16 triple knock-out mice reversed the changes in axonal GABA B expression and presynaptic excitation. In mice lacking the KCTDs, aversion-predicting cues produced stronger neuronal activation in the interpeduncular nucleus, and the infusion of GABA B agonist in this nucleus produced a weaker effect on fear extinction. Collectively, our results reveal isoform-specific roles of KCTD proteins in enriching the axonal expression of GABA B receptors, facilitating their presynaptic signaling, and modulating aversion-related memory processes. SIGNIFICANCE STATEMENT GABA B receptors represent the principal inhibitory neurotransmitter receptor, but they mediate strong presynaptic excitation in the habenulo-interpeduncular pathway and modulate aversion memory expression. KCTD proteins are integral constituents of GABA B receptors. By analyzing the physiological, neuroanatomical, and behavioral phenotypes of multiple KCTD knock-out mouse lines, we show that KCTD8 and KCTD12 facilitate the axonal expression and hence presynaptic excitation of GABA B receptors in habenula cholinergic neurons and control cued-aversion memory formation and expression in the habenulo-interpeduncular pathway. These results expand the physiological and behavioral functions of KCTDs in modulating the brain neural circuits., (Copyright © 2022 the authors.)

Background: GABAergic system dysfunction has been implicated in the etiology of schizophrenia and of cognitive impairments in particular. Patients with treatment-resistant schizophrenia (TRS) generally suffer from profound cognitive impairments in addition to severe positive symptoms, suggesting that GABA system dysfunction could be involved more closely in patients with TRS., Methods and Results: In the present study, exome sequencing was conducted on fourteen TRS patients, whereby four SNPs were identified on GAD1, GABBR1 and GABBR2 genes. An association study for five SNPs including these 4 SNPs and rs3749034 on GAD1 as then performed among 357 patients with TRS, 682 non-TRS patients and 508 healthy controls (HC). The results revealed no significant differences in allelic and/or genetic distributions for any of the five SNPs. However, several subanalyses in comparisons between schizophrenia and HC groups, as well as between the three groups, showed nominal-level significance for rs3749034 on GAD1 and rs10985765/rs3750344 on GABBR2. In particular, in comparisons of female subjects, rigorous analysis for rs3749034 showed a statistical difference between the schizophrenia and HC groups and between the TRS and HC groups., Conclusions: Several positive results in subanalyses suggested that genetic vulnerability in the GABA system to schizophrenia or TRS could be affected by sex or sampling area, and overall, that rs3749034 on GAD1 and rs10985765 on GABBR2 could be related to TRS. In the present study, only a few SNPs were examined; it is possible that other important genetic variants in other regions of GABA-related genes were not captured in this preliminary study., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Neuroblastoma (NB) is a huge threat to children's health. Adipose-derived stem cells-derived extracellular vesicles (ADSC-Evs) can regulate tumor progression. This study aimed to identify the role of ADSC-Evs in NB. Following ADSC-Ev isolation and identification, PKH26-labeled ADSC-Evs were cocultured with NB cells to observe the internalization of ADSC-Evs. ADSC-Ev effects on NB cell proliferation, invasion, and migration were assessed. The regulatory molecules related to NB development were predicted. The expressions of and relations among LINC00622, transcriptional factor androgen receptor (AR), and gamma-aminobutyric acid B-type receptor 1 (GABRR1) were detected and verified. LINC00622 was inhibited in ADSCs to evaluate ADSC-Ev effects on NB cells. Xenograft tumor experiment in nude mice was further performed to evaluate the effects of ADSC-Evs-carried LINC00622 on NB in vivo. ADSC-Evs inhibited NB cell proliferation, invasion, and migration. ADSC-Evs increased GABBR1 expression in NB cells. ADSC-Evs-carried LINC00622 mediated AR to promote GABBR1 expression. Silencing LINC00622 in ADSCs weakened the inhibition of ADSC-Evs on NB cell malignant behaviors. ADSC-Evs reduced tumor growth in nude mice, which was restored after inhibiting LINC00622 expression in ADSCs. We highlighted that ADSC-Evs carried LINC00622 into NB cells to inhibit transcription factor AR and promote GABBR1 expression, thus inhibiting NB cell growth., (©2021 Society for Leukocyte Biology.)

G protein-coupled receptors (GPCRs) are among the most promising drug targets. They often form homo- and heterodimers with allosteric cross-talk between receptor entities, which contributes to fine-tuning of transmembrane signaling. Specifically controlling the activity of GPCR dimers with ligands is a good approach to clarify their physiological roles and validate them as drug targets. Here, we examined the mode of action of positive allosteric modulators (PAMs) that bind at the interface of the transmembrane domains of the heterodimeric GABA B receptor. Our site-directed mutagenesis results show that mutations of this interface impact the function of the three PAMs tested. The data support the inference that they act at the active interface between both transmembrane domains, the binding site involving residues of the TM6s of the GABA B1 and the GABA B2 subunit. Importantly, the agonist activity of these PAMs involves a key region in the central core of the GABA B2 transmembrane domain, which also controls the constitutive activity of the GABA B receptor. This region corresponds to the sodium ion binding site in class A GPCRs that controls the basal state of the receptors. Overall, these data reveal the possibility of developing allosteric compounds able to specifically modulate the activity of GPCR homo- and heterodimers by acting at their transmembrane interface., Competing Interests: LL, ZF, XR, LX, SR, IB, MX, JP, PR, JL No competing interests declared, (© 2021, Liu et al.)

Two distinct types of neuronal activity result in long-term depression (LTD) of electrical synapses, with overlapping biochemical intracellular signaling pathways that link activity to synaptic strength, in electrically coupled neurons of the thalamic reticular nucleus (TRN). Because components of both signaling pathways can also be modulated by GABA B receptor activity, here we examined the impact of GABA B receptor activation on the two established inductors of LTD in electrical synapses. Recording from patched pairs of coupled rat neurons in vitro, we show that GABA B receptor inactivation itself induces a modest depression of electrical synapses and occludes LTD induction by either paired bursting or metabotropic glutamate receptor (mGluR) activation. GABA B activation also occludes LTD from either paired bursting or mGluR activation. Together, these results indicate that afferent sources of GABA, such as those from the forebrain or substantia nigra to the reticular nucleus, gate the induction of LTD from either neuronal activity or afferent glutamatergic receptor activation. These results add to a growing body of evidence that the regulation of thalamocortical transmission and sensory attention by TRN is modulated and controlled by other brain regions. Significance: We show that electrical synapse plasticity is gated by GABA B receptors in the thalamic reticular nucleus. This effect is a novel way for afferent GABAergic input from the basal ganglia to modulate thalamocortical relay and is a possible mediator of intra-TRN inhibitory effects.

The identity of the mechanism that controls aggressive behavior in rodents is unclear. Serotonin (5-HT) and GABA are associated with aggressive behavior in rodents. However, the regulatory relationship between these chemicals in the different brain regions of rats has not been fully defined. This study aimed to clarify the role of GABABR1 in DRN-mediated GABA to regulate 5-HT expression in multiple brain regions in male rats with high and low aggressive behavior. Rat models of highly and less aggressive behavior were established through social isolation plus resident intruder. On this basis, GABA content in the DRN and 5-HT contents in the PFC, hypothalamus, hippocampus and DRN were detected using ELISA. Co-expression of 5-HT and GB1 in the DRN was detected by immunofluorescence and immunoelectron microscopy at the tissue and subcellular levels, respectively. GB1-specific agonist baclofen and GB1-specific inhibitor CGP35348 were injected into the DRN by stereotaxic injection. Changes in 5-HT levels in the PFC, hypothalamus and hippocampus were detected afterward. After modeling, rats with highly aggressive behavior exhibited higher aggressive behavior scores, shorter latencies of aggression, and higher total distances in the open field test than rats with less aggressive behavior. The contents of 5-HT in the PFC, hypothalamus and hippocampus of rats with high and low aggressive behavior (no difference between the two groups) were significantly decreased, but the change in GABA content in the DRN was the opposite. GB1 granules could be found on synaptic membranes containing 5-HT granules, which indicated that 5-HT neurons in the DRN co-expressed with GB1, which also occurred in double immunofluorescence results. At the same time, we found that the expression of GB1 in the DRN of rats with high and low aggressive behavior was significantly increased, and the expression of GB1 in the DRN of rats with low aggressive behavior was significantly higher than that in rats with high aggressive behavior. Nevertheless, the expression of 5-HT in DRN was opposite in these two groups. After microinjection of baclofen into the DRN, the 5-HT contents in the PFC, hypothalamus and hippocampus of rats in each group decreased significantly. In contrast, the 5-HT contents in the PFC, hypothalamus and hippocampus of rats in each group increased significantly after injection with CGP35348. The significant increase in GABA in the DRN combined with the significant increase in GB1 in the DRN further mediated the synaptic inhibition effect, which reduced the 5-HT level of 5-HT neurons in the DRN, resulting in a significant decrease in 5-HT levels in the PFC, hypothalamus and hippocampus. Therefore, GB1-mediated GABA regulation of 5-HT levels in the PFC, hypothalamus and hippocampus is one of the mechanisms of highly and less aggressive behavior originating in the DRN. The increased GB1 level in the DRN of LA-behavior rats exhibited a greater degree of change than in the HA-group rats, which indicated that differently decreased 5-HT levels in the DRN may be the internal mechanisms of high and low aggression behaviors., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Reduction in glutamate release is a key mechanism for neuroprotection and we investigated the effect of isoliquiritigenin (ISL), an active ingredient of Glycyrrhiza with neuroprotective activities, on glutamate release in rat cerebrocortical nerve terminals (synaptosomes). ISL produced a concentration-dependent inhibition of glutamate release and reduced the intraterminal [Ca 2+ ] increase. The inhibition of glutamate release by ISL was prevented after removing extracellular Ca 2+ or blocking P/Q-type Ca 2+ channels. This inhibition was mediated through the γ-aminobutyric acid type B (GABA B ) receptors because ISL was unable to inhibit glutamate release in the presence of baclofen (an GABA B agonist) or CGP3548 (an GABA B antagonist) and docking data revealed that ISL interacted with GABA B receptors. Furthermore, the ISL inhibition of glutamate release was abolished through the inhibition of G i/o -mediated responses or G βγ subunits, but not by 8-bromoadenosine 3',5'-cyclic monophosphate or adenylate cyclase inhibition. The ISL inhibition of glutamate release was also abolished through the inhibition of protein kinase C (PKC), and ISL decreased the phosphorylation of PKC. Thus, we inferred that ISL, through GABA B receptor activation and G βγ -coupled inhibition of P/Q-type Ca 2+ channels, suppressed the PKC phosphorylation to cause a decrease in evoked glutamate release at rat cerebrocortical nerve terminals.

Previous studies suggest that signaling by the gamma-aminobutyric acid (GABA) type B receptor (GABA B R) is involved in the regulation of binge eating, a disorder which might contribute to the development of obesity. Here, we show that intermittent access to a high fat diet (HFD) induced binge-like eating behavior with activation of dopamine receptor d1 (drd1)-expressing neurons in the caudate putamen (CPu) and nucleus accumbens (NAc) in wild-type (WT) mice. The activation of drd1-expressing neurons during binge-like eating was substantially increased in the CPu, but not in the NAc, in corticostriatal neuron-specific GABA B R-deficient knockout (KO) mice compared to WT mice. Treatment with the GABA B R agonist, baclofen, suppressed binge-like eating behavior in WT mice, but not in KO mice, as reported previously. Baclofen also suppressed the activation of drd1-expressing neurons in the CPu, but not in the NAc, during binge-like eating in WT mice. Thus, our data suggest that GABA B R signaling in CPu neurons expressing drd1 suppresses binge-like consumption during a HFD in mice., (© 2021. The Author(s).)

Introduction: Although there has been increasing recognition of the occurrence of non-epileptic involuntary movements in developmental and epileptic encephalopathies (DEEs), the spectrum of dystonic presentations associated with these conditions remains poorly described. We sought to expand the catalogue of dystonia-predominant phenotypes in monogenic DEEs, building on the recently introduced concept of an epilepsy-movement disorder spectrum., Methods: Cases were identified from a whole-exome-sequenced cohort of 45 pediatric index patients with complex dystonia (67% sequenced as parent-child trios). Review of molecular findings in DEE-associated genes was performed. For five individuals with identified DEE-causing variants, detailed information about presenting phenotypic features and the natural history of disease was obtained., Results: De-novo pathogenic and likely pathogenic missense variants in GABRA1, GABBR2, GNAO1, and FOXG1 gave rise to infantile-onset persistent and paroxysmal dystonic manifestations, beginning in the limb or truncal musculature and progressing gradually to a generalized state. Coexisting, less prominent movement-disorder symptoms were observed and included myoclonic, ballistic, and stereotypic abnormal movements as well as choreoathetosis. Dystonia dominated over epileptic neurodevelopmental comorbidities in all four subjects and represented the primary indication for molecular genetic analysis. We also report the unusual case of an adult female patient with dystonia, tremor, and mild learning disability who was found to harbor a pathogenic frameshift variant in MECP2., Conclusions: Dystonia can be a leading clinical manifestation in different DEEs. A monogenic basis of disease should be considered on the association of dystonia and developmental delay-epilepsy presentations, justifying a molecular screening for variants in DEE-associated genes., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Regulation of reward signaling in the brain is critical for appropriate judgement of the environment and self. In Drosophila , the protocerebral anterior medial (PAM) cluster dopamine neurons mediate reward signals. Here, we show that localized inhibitory input to the presynaptic terminals of the PAM neurons titrates olfactory reward memory and controls memory specificity. The inhibitory regulation was mediated by metabotropic gamma-aminobutyric acid (GABA) receptors clustered in presynaptic microdomain of the PAM boutons. Cell type-specific silencing the GABA receptors enhanced memory by augmenting internal reward signals. Strikingly, the disruption of GABA signaling reduced memory specificity to the rewarded odor by changing local odor representations in the presynaptic terminals of the PAM neurons. The inhibitory microcircuit of the dopamine neurons is thus crucial for both reward values and memory specificity. Maladaptive presynaptic regulation causes optimistic cognitive bias., Competing Interests: NY, TE, TT, HW, HT No competing interests declared, (© 2021, Yamagata et al.)

Gamma-Aminobutyric Acid Type B Receptor (GABABR) plays essential roles in tumor progression. However, the function of GABABR in colorectal cancer (CRC) needs further clarification. As the main part of GABABR, GABABR1 expression was identified significantly lower in tumor tissues than those in non-tumor normal tissues and that CRC patients with high GABABR1 expression lived longer. Further studies indicated that knockdown of GABABR1 elevated CRC cell proliferation, migration, and invasion. Furthermore, knockdown of GABABR1 activated the expression of the epithelial-mesenchymal transition (EMT)-related proteins N-cadherin and Vimentin, whereas decrease the protein level of E-cadherin. In addition, activation of Hippo/YAP1 signaling contributes to the GABABR1 down-regulation promoted proliferation, migration, invasion and EMT in CRC cells. At last, we verified the contribution of Hippo/YAP1 signaling in the GABABR1 down-regulation impaired biological phenotype of colon cancer cells in vivo . In summary, these data indicate that GABABR1 impairs the migration and invasion of CRC cells by inhibiting EMT and the Hippo/YAP1 pathway, suggesting that GABABR1 could be a potential therapeutic target for CRC., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

The synaptic connection from medial habenula (MHb) to interpeduncular nucleus (IPN) is critical for emotion-related behaviors and uniquely expresses R-type Ca 2+ channels (Cav2.3) and auxiliary GABA B receptor (GBR) subunits, the K + -channel tetramerization domain-containing proteins (KCTDs). Activation of GBRs facilitates or inhibits transmitter release from MHb terminals depending on the IPN subnucleus, but the role of KCTDs is unknown. We therefore examined the localization and function of Cav2.3, GBRs, and KCTDs in this pathway in mice. We show in heterologous cells that KCTD8 and KCTD12b directly bind to Cav2.3 and that KCTD8 potentiates Cav2.3 currents in the absence of GBRs. In the rostral IPN, KCTD8, KCTD12b, and Cav2.3 co-localize at the presynaptic active zone. Genetic deletion indicated a bidirectional modulation of Cav2.3-mediated release by these KCTDs with a compensatory increase of KCTD8 in the active zone in KCTD12b-deficient mice. The interaction of Cav2.3 with KCTDs therefore scales synaptic strength independent of GBR activation., Competing Interests: PB, DV, DF, TF, DK, CÖ, JM, MG, PJ, AK, BB, RS, PK No competing interests declared, (© 2021, Bhandari et al.)

Although clinical efficacy of waggle needling has been confirmed, therapeutic mechanisms still remain poorly understood. Reduction of GABA was involved in the etiology of spasticity. Recently, accumulated evidences suggest that the inhibitory effect of GABA is determined by low intracellular chloride concentration, which is predominantly mediated by KCC2. This study was designed to investigate whether KCC2-GABA A pathway was involved in the mechanism underlying acupuncture intervention in rats with middle cerebral artery occlusion (MCAO). Three days after modeling, the rats received waggle needling, routine needling and placebo needling for 7 consecutive days. After treatment, the muscle spasticity, motor function and infarct volumes were tested. KCC2 and GABA A γ2 levels were detected via western blotting, RT-PCR and immunofluorescence. KCC2 antagonist and agonist were administered after the last intervention. We found that acupuncture, particularly waggle needling, could remarkably alleviate muscle spasticity, reverse motor deficits and reduce cerebral infraction in MCAO rats, possibly due to its effects on up-regulating expressions of KCC2 and GABA A γ2 in the cortical infarct regions. However, the effects were blocked by KCC2 antagonist. In summary, this study suggests that improvements in muscle spasticity and motor function induced by waggle needling correlates with the activation of KCC2-GABA A pathway., (Copyright © 2021. Published by Elsevier B.V.)

There is a growing body of evidence demonstrating the significant involvement of the sigma-1 chaperone protein in the modulation of seizures. Several sigma-1 receptor (Sig1R) ligands have been demonstrated to regulate the seizure threshold in acute and chronic seizure models. However, the mechanism by which Sig1R modulates the excitatory and inhibitory pathways in the brain has not been elucidated. The aim of this study was to compare the susceptibility to seizures of wild type (WT) and Sig1R knockout (Sig1R-/-) mice in intravenous pentylenetetrazol (PTZ) and (+)-bicuculline (BIC) infusion-induced acute seizure and Sig1R antagonist NE-100-induced seizure models. To determine possible molecular mechanisms, we used quantitative PCR, Western blotting and immunohistochemistry to assess the possible involvement of several seizure-related genes and proteins. Peripheral tissue contractile response of WT and Sig1R-/- mice was studied in an isolated vasa deferentia model. The most important finding was the significantly decreased expression of the R2 subunit of the GABA-B receptor in the hippocampus and habenula of Sig1R-/- mice. Our results demonstrated that Sig1R-/- mice have decreased thresholds for PTZ- and BIC-induced tonic seizures. In the NE-100-induced seizure model, Sig1R-/- animals demonstrated lower seizure scores, shorter durations and increased latency times of seizures compared to WT mice. Sig1R-independent activities of NE-100 included downregulation of the gene expression of iNOS and GABA-A γ2 and inhibition of KCl-induced depolarization in both WT and Sig1R-/- animals. In conclusion, the results of this study indicate that the lack of Sig1R resulted in decreased expression of the R2 subunit of the GABA-B receptor and increased susceptibility to seizures. Our results confirm that Sig1R is a significant molecular target for seizure modulation and warrants further investigation for the development of novel anti-seizure drugs., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objective: The epidemiological characteristics of patients with antibody-medicated autoimmune encephalitis in China remain unclear, and a large-scale epidemiological survey is necessary. Methods: A multiple-center retrospective study was performed. We collected 1,047 patients with suspected autoimmune encephalitis and ultimately enrolled 778 defined patients across centers in China. All patients were positive for serum [or cerebrospinal fluid (CSF)] antibodies. Demographic information and clinical data from January 2014 to January 2019 from 22 centers in China were reviewed. Results: A total of 778 patients with autoimmune encephalitis were enrolled in the study. In general, the ratio of males to females was ~1.2:1. The main subtypes of autoimmune encephalitis were NMDAR-AE (61.35%), LGI-1-AE (20.61%), and GABAbR-AE (12.40%). According to the characteristics of age of onset, the incidence of autoimmune encephalitis showed a "double peak" distribution entailing a 20-year-old age group and a 60-year-old age group. We next analyzed the proportion of patients with tumors in this cohort. More specifically, there were 34 patients with tumors and 85 with tumor marker positivity. Relapse occurred in 81 patients within at least 1 year's follow up study: 52 with NMDAR-AE (18.2%); 19 with LGI-1-AE (16.8%); 5 with GABAbR-AE (9%); and 3 with CASPR2-AE. Interpretation: Due to the vast differences in demographic features, the incidence of cancer and the genetic characteristics between the populations in China and Western countries, the demographics, sex distribution, concomitant tumor rate, clinical features, and relapse characteristics associated with autoimmune encephalitis in China shows a similar profile with Western countries with some minor differences., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Shan, Yang, Wang and on behalf of China Autoimmune Encephalitis Group.)

Hematopoietic and nervous systems are linked via innervation of bone marrow (BM) niche cells. Hematopoietic stem/progenitor cells (HSPCs) express neurotransmitter receptors, such as the γ-aminobutyric acid (GABA) type B receptor subunit 1 (GABBR1), suggesting that HSPCs could be directly regulated by neurotransmitters like GABA that directly bind to GABBR1. We performed imaging mass spectrometry and found that the endogenous GABA molecule is regionally localized and concentrated near the endosteum of the BM niche. To better understand the role of GABBR1 in regulating HSPCs, we generated a constitutive Gabbr1-knockout mouse model. Analysis revealed that HSPC numbers were significantly reduced in the BM compared with wild-type littermates. Moreover, Gabbr1-null hematopoietic stem cells had diminished capacity to reconstitute irradiated recipients in a competitive transplantation model. Gabbr1-null HSPCs were less proliferative under steady-state conditions and upon stress. Colony-forming unit assays demonstrated that almost all Gabbr1-null HSPCs were in a slow or noncycling state. In vitro differentiation of Gabbr1-null HSPCs in cocultures produced fewer overall cell numbers with significant defects in differentiation and expansion of the B-cell lineage. To determine whether a GABBR1 agonist could stimulate human umbilical cord blood (UCB) HSPCs, we performed brief ex vivo treatment prior to transplant into immunodeficient mice, with significant increases in long-term engraftment of HSPCs compared with GABBR1 antagonist or vehicle treatments. Our results indicate a direct role for GABBR1 in HSPC proliferation, and identify a potential target to improve HSPC engraftment in clinical transplantation., (© 2021 by The American Society of Hematology.)

Background and Objectives: IgA nephropathy is the most common form of primary GN worldwide. The evidence of geographic and ethnic differences, as well as familial aggregation of the disease, supports a strong genetic contribution to IgA nephropathy. Evidence for genetic factors in IgA nephropathy comes also from genome-wide association patient-control studies. However, few studies have systematically evaluated the contribution of coding variation in IgA nephropathy., Design, Setting, Participants, & Measurements: We performed a two-stage exome chip-based association study in 13,242 samples, including 3363 patients with IgA nephropathy and 9879 healthy controls of Han Chinese ancestry. Common variant functional annotation, gene-based low-frequency variants analysis, differential mRNA expression, and gene network integration were also explored., Results: We identified three non-HLA gene regions ( FBXL21 , CCR6 , and STAT3 ) and one HLA gene region ( GABBR1 ) with suggestive significance ( P meta <5×10 -5 ) in single-variant associations. These novel non-HLA variants were annotated as expression-associated single-nucleotide polymorphisms and were located in enhancer regions enriched in histone marks H3K4me1 in primary B cells. Gene-based low-frequency variants analysis suggests CFB as another potential susceptibility gene. Further combined expression and network integration suggested that the five novel susceptibility genes, TGFBI , CCR6 , STAT3 , GABBR1 , and CFB , were involved in IgA nephropathy., Conclusions: Five novel gene regions with suggestive significance for IgA nephropathy were identified and shed new light for further mechanism investigation., (Copyright © 2021 by the American Society of Nephrology.)

GABA interneurons play a critical role in higher brain functions. Astrocytic glial cells interact with synapses throughout the whole brain and are recognized as regulatory elements of excitatory synaptic transmission. However, it is largely unknown how GABAergic interneurons and astrocytes interact and contribute to stable performance of complex behaviors. Here, we found that genetic ablation of GABA B receptors in medial prefrontal cortex astrocytes altered low-gamma oscillations and firing properties of cortical neurons, which affected goal-directed behaviors. Remarkably, working memory deficits were restored by optogenetic stimulation of astrocytes with melanopsin. Furthermore, melanopsin-activated astrocytes in wild-type mice enhanced the firing rate of cortical neurons and gamma oscillations, as well as improved cognition. Therefore, our work identifies astrocytes as a hub for controlling inhibition in cortical circuits, providing a novel pathway for the behaviorally relevant midrange time-scale regulation of cortical information processing and consistent goal-directed behaviors.

The metabotropic gamma-aminobutyric acid B receptor (GABA B R) is a G protein-coupled receptor that mediates neuronal inhibition by the neurotransmitter GABA. While GABA B R-mediated signalling has been suggested to play central roles in neuronal differentiation and proliferation across evolution, it has mostly been studied in the mammalian brain. Here, we demonstrate that ectopic activation of GABA B R signalling affects neurogenic functions in the sea anemone Nematostella vectensis. We identified four putative Nematostella GABA B R homologues presenting conserved three-dimensional extracellular domains and residues needed for binding GABA and the GABA B R agonist baclofen. Moreover, sustained activation of GABA B R signalling reversibly arrests the critical metamorphosis transition from planktonic larva to sessile polyp life stage. To understand the processes that underlie the developmental arrest, we combined transcriptomic and spatial analyses of control and baclofen-treated larvae. Our findings reveal that the cnidarian neurogenic programme is arrested following the addition of baclofen to developing larvae. Specifically, neuron development and neurite extension were inhibited, resulting in an underdeveloped and less organized nervous system and downregulation of proneural factors including NvSoxB(2), NvNeuroD1 and NvElav1. Our results thus point to an evolutionarily conserved function of GABA B R in neurogenesis regulation and shed light on early cnidarian development.

Adrenocortical carcinoma (ACC) is a rare but deadly cancer for which few treatments exist. Here, we have undertaken a targeted bioinformatics study of The Cancer Genome Atlas (TCGA) ACC dataset focusing on the 30 genes encoding the γ-aminobutyric acid (GABA) system-an under-studied, evolutionarily-conserved system that is an emerging potential player in cancer progression. Our analysis identified a subset of ACC patients whose tumors expressed a distinct GABA system transcriptome. Transcript levels of ABAT (encoding a key GABA shunt enzyme), were upregulated in over 40% of tumors, and this correlated with several favorable clinical outcomes including patient survival; while enrichment and ontology analysis implicated two cancer-related biological pathways involved in metastasis and immune response. The phenotype associated with ABAT upregulation revealed a potential metabolic heterogeneity among ACC tumors associated with enhanced mitochondrial metabolism. Furthermore, many GABA A receptor subunit-encoding transcripts were expressed, including two ( GABRB2 and GABRD) prognostic for patient survival. Transcripts encoding GABA B receptor subunits and GABA transporters were also ubiquitously expressed. The GABA system transcriptome of ACC tumors is largely mirrored in the ACC NCI-H295R cell line, suggesting that this cell line may be appropriate for future functional studies investigating the role of the GABA system in ACC cell growth phenotypes and metabolism.

The neurotransmitter γ-aminobutyric acid (GABA) activates the metabotropic GABA B receptor to generate slow, prolonged inhibitory signals that regulate the neural circuitry. The GABA B receptor is an obligate heterodimeric G protein-coupled receptor (GPCR) comprised of GBR1 and GBR2 subunits, each with extracellular, seven-helix transmembrane (7TM), and coiled-coil domains. To understand how GABA-driven conformational changes in the extracellular domain are transmitted to the 7TM domain during signal transduction, we determined cryo-electron microscopy (EM) structures of GABA B in two different states: an antagonist-bound inactive state, and an active state in which both the GABA agonist and a positive allosteric modulator (PAM) are bound. In the inactive state, the TM3 and TM5 helices in the two 7TM domains engage in cholesterol-mediated as well as direct interactions, resulting in an open conformation. GABA binding forces the extracellular domains of GBR1 and GBR2 into a compact form, relocating the linkers that connect the extracellular and 7TM domains closer to each other. The movement of the linker along with the associated extracellular loop 2 of the 7TM domain reorients the two 7TM domains and creates a new interface with the TM5, TM6 and TM7 helices in a closed conformation. PAM binding to the interface between the TM6 and TM6 helices stabilizes the active 7TM domain conformation. The relayed structural rearrangement results in significant conformational changes in the TM helices, as well as intracellular loop 3 in GBR2, which may promote the binding and activation of the Gi/o proteins., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Objective: This study aimed to explore the effects of activating GABAB1 receptor by baclofen on proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) of ovarian cancer cells., Results: One hundred μmol/L, 200 μmol/L and 300 μmol/L were selected as low, medium and high baclofen concentrations respectively. Cells were divided into four groups: Control, 100 μmol/L, 200 μmol/L and 300 μmol/L. Compared with the control group, the viability, colony formation, migration and invasion of SKOV3 cells were inhibited, and the apoptosis of SKOV3 cells were enhanced significantly at 200 μmol/L and 300 μmol/L baclofen. Moreover, they changed significantly with the increase of baclofen concentration. Compared with the control group, the expression of E-cadherin and GABAB1 increased and the N-cadherin expression decreased significantly in 200 μmol/L and 300 μmol/L groups. Higher concentration of baclofen induced higher expression of E-cadherin and lower expression of N-cadherin., Conclusion: Baclofen inhibited the proliferation, cloning, migration, invasion and EMT of ovarian cancer cells by activating GABAB1 receptor. These results might contribute a lot to clarify the role and possible mechanism of GABAB1 receptor in ovarian cancer.

Pancreatic cancer is one of the most aggressive and deadly malignancies with a very poor prognosis. Pancreatic cancer-induced visceral pain is very common and is generally presented among the initial symptoms in patients; such pain is strongly associated with poor quality of life, impaired functional activity, and decreased survival. However, the principal neurobiological mechanisms of pain caused by pancreatic cancer have not been fully elucidated. Accumulating studies have shown that miRNAs play a major role in chronic pain by suppressing key molecules involved in nociception. In the present study, we report that microRNA (miR)-330 is highly expressed in the spinal dorsal horn (SDH) of nude mice with pancreatic cancer pain. Mimicking pancreatic carcinoma-induced SDH miR-330 upregulation by microinjection of miR-330 mimic into the SDH significantly induced abdominal mechanical allodynia in normal nude mice. Additionally, we found that the expression of GABA B R2 was significantly decreased in the SDH of nude mice with pancreatic cancer pain and was regulated directly by miR-330 both in vitro and in vivo. Furthermore, inhibition of miR-330 rescued the expression of GABA B R2 and alleviated pancreatic carcinoma-induced abdominal pain hypersensitivity in nude mice with pancreatic carcinoma. These results show that miR-330 participates in the genesis of pancreatic carcinoma-induced pain hypersensitivity by inhibiting GABA B R2 expression in the SDH and might be a potential therapeutic target for pancreatic cancer pain.

Down syndrome is a complex genetic disorder caused by the presence of three copies of the chromosome 21 in humans. The most common models, carrying extra-copies of overlapping fragments of mouse chromosome 16 that is syntenic to human chromosome 21, are Ts2Cje, Ts1Cje and Ts1Rhr mice. In electrophysiological analyses using hippocampal slices, we found that the later phase of the depolarization during tetanic stimulation, which was regulated by GABA B receptors, was significantly smaller in Ts1Cje and Ts2Cje mice than that in WT controls but not in Ts1Rhr mice. Furthermore, isolated GABA B receptor-mediated inhibitory synaptic responses were larger in Ts1Cje mice. To our knowledge, this is the first report that directly shows the enhancement of GABA B receptor-mediated synaptic currents in Ts1Cje mice. These results suggest that GABA B receptor-mediated synaptic inhibition was enhanced in Ts1Cje and Ts2Cje mice but not in Ts1Rhr mice. The Cbr1 gene, which is present in three copies in Ts1Cje and Ts2Cje but not in Ts1Rhr, encodes carbonyl reductase that may facilitate GABA B -receptor activity through a reduction of prostaglandin E2 (PGE2). Interestingly, we found that a reduction of PGE2 and an memory impairment in Ts1Cje mice were alleviated when only Cbr1 was set back to two copies (Ts1Cje;Cbr1 +/+/- ). However, the GABA B receptor-dependent enhancement of synaptic inhibition in Ts1Cje was unaltered in Ts1Cje;Cbr1 +/+/- mice. These results indicate that Cbr1 is one of the genes responsible for DS cognitive impairments and the gene(s) other than Cbr1, which is included in Ts1Cje but not in Ts1Rhr, is responsible for the GABA B receptor-dependent over-inhibition.

G protein-coupled receptors are seven transmembrane signaling molecules that are involved in a wide variety of physiological processes. They constitute a large protein family of receptors with almost 300 members detected in human pancreatic islet preparations. However, the functional role of these receptors in pancreatic islets is unknown in most cases. We generated a new stable human beta cell line from neonatal pancreas. This cell line, named ECN90 expresses both subunits (GABBR1 and GABBR2) of the metabotropic GABA B receptor compared to human islet. In ECN90 cells, baclofen, a specific GABA B receptor agonist, inhibits cAMP signaling causing decreased expression of beta cell-specific genes such as MAFA and PCSK1, and reduced insulin secretion. We next demonstrated that in primary human islets, GABBR2 mRNA expression is strongly induced under cAMP signaling, while GABBR1 mRNA is constitutively expressed. We also found that induction and activation of the GABA B receptor in human islets modulates insulin secretion.

We present the first large-scale methylome-wide association studies (MWAS) for major depressive disorder (MDD) to identify sites of potential importance for MDD etiology. Using a sequencing-based approach that provides near-complete coverage of all 28 million common CpGs in the human genome, we assay methylation in MDD cases and controls from both blood (N = 1132) and postmortem brain tissues (N = 61 samples from Brodmann Area 10, BA10). The MWAS for blood identified several loci with P ranging from 1.91 × 10 -8  to 4.39 × 10 -8 and a resampling approach showed that the cumulative association was significant (P = 4.03 × 10 -10 ) with the signal coming from the top 25,000 MWAS markers. Furthermore, a permutation-based analysis showed significant overlap (P = 5.4 × 10 -3 ) between the MWAS findings in blood and brain (BA10). This overlap was significantly enriched for a number of features including being in eQTLs in blood and the frontal cortex, CpG islands and shores, and exons. The overlapping sites were also enriched for active chromatin states in brain including genic enhancers and active transcription start sites. Furthermore, three loci located in GABBR2, RUFY3, and in an intergenic region on chromosome 2 replicated with the same direction of effect in the second brain tissue (BA25, N = 60) from the same individuals and in two independent brain collections (BA10, N = 81 and 64). GABBR2 inhibits neuronal activity through G protein-coupled second-messenger systems and RUFY3 is implicated in the establishment of neuronal polarity and axon elongation. In conclusion, we identified and replicated methylated loci associated with MDD that are involved in biological functions of likely importance to MDD etiology.

Lack of GABA B receptors in GABA B1 knockout mice decreases neonatal ARC kisspeptin 1 ( Kiss1 ) expression in the arcuate nucleus of the hypothalamus (ARC) in females, which show impaired reproduction as adults. Our aim was to selectively impair GABA B signaling during a short postnatal period to evaluate its impact on the reproductive system. Neonatal male and female mice were injected with the GABA B antagonist CGP 55845 (CGP, 1 mg/kg body wt sc) or saline from postnatal day 2 ( PND2 ) to PND6 , three times per day (8 AM, 1 PM, and 6 PM). One group was killed on PND6 for collection of blood samples (hormones by radioimmunoassay), brains for gene expression in the anteroventral periventricular nucleus-periventricular nucleus continuum (AVPV/PeN), and ARC micropunches [quantitative PCR (qPCR)] and gonads for qPCR, hormone contents, and histology. A second group of mice was injected with CGP (1 mg/kg body wt sc) or saline from PND2 to PND6 , three times per day (8 AM, 1 PM, and 6 PM), and left to grow to adulthood. We measured body weight during development and parameters of sexual differentiation, puberty onset, and estrous cycles. Adult mice were killed, and trunk blood (hormones), brains for qPCR, and gonads for qPCR and hormone contents were obtained. Our most important findings on PND6 include the CGP-induced decrease in ARC Kiss1 and increase in neurokinin B ( Tac2 ) in both sexes; the decrease in AVPV/PeN tyrosine hydroxylase ( Th ) only in females; the increase in gonad estradiol content in both sexes; and the increase in primordial follicles and decrease in primary and secondary follicles. Neonatally CGP-treated adults showed decreased ARC Kiss1 and ARC gonadotropin-releasing hormone ( Gnrh1 ) and increased ARC glutamic acid decarboxylase 67 ( Gad1 ) only in males; increased ARC GABA B receptor subunit 1 ( Gabbr1 ) in both sexes; and decreased AVPV/PeN Th only in females. We demonstrate that ARC Kiss1 expression is chronically downregulated in males and that the normal sex difference in AVPV/PeN Th expression is abolished. In conclusion, neonatal GABAergic input through GABA B receptors shapes gene expression of factors critical to reproduction.

The aim of the study was to determine the expression profiles of GABA A , GABA B , and GAT1 using RT-PCR and the immunoreactivity of GAT1 via immunohistochemical and immunofluorescence assays in CDV-infected brain tissue of dogs. For this purpose, dogs with CDV and dogs without CDV were selected. The mRNA transcript levels of GABA A , GABA B , and GAT1 were significantly downregulated in brain tissue in the CDV-infected group as compared with that in non-CDV-infected brain tissue in the control group (p < 0.01, p < 0.001). In addition, the immunoreactivity of GAT1 in CDV-infected brain tissue was significantly lower than in the uninfected group (p < 0.05). We conclude that one of the main causes of myoclonus in CDV infections may be the blockage of postsynaptic inhibition in neurons or a lack of metabolism of GABA. In addition, a GABA neurotransmission imbalance could play a role in demyelination in CDV infections.

Ethanol consumption is correlated with different neurobiological and behavioral impairments. Acute and chronic exposure to this drug is associated with alterations in the regulation of the mesolimbic dopaminergic system as well as with transcriptional modulation of other receptors in the central nervous system and can unleash seeking behavior or behavioral adaptations and phenotypes such as loss of control, dependence and tolerance. In the present work, we characterized the chronological effects of acute and chronic intermittent exposure to ethanol (1% v/v) in an adult zebrafish population (Danio rerio). During sixteen days of ethanol exposure, we associated the neuromodulation of target genes (drd1, drd2, gabra2a, gabbr1a, gabbr1b) in the central nervous system with behavioral parameters, assessed by social preference, antipredatory capacity and anxiety-like analysis. Transcriptional and behavioral data were collected in days 0, 1, 4, 8, 12 and 16, after ethanol exposure. In days 1 and 4, ethanol exposure increased exploratory behavior regardless of the risk involved (less time spent close to conspecifics and lower avoidance reaction to predator). Along with the reduction of drd2, grin1a and gabra2a transcription seen in the same days, these results suggest an anxiolytic effect of acute ethanol exposure. Interestingly, in days 8, 12 and 16, an attenuation of the behavioral effects was observed. The social preference, antipredatory behavior, perception and exploration parameters were reconstituted. This behavioral re-establishment, accompanied by the increase in drd1, drd2 and gabbr1a transcription in the 8th day could be an indicative of an adaptation to chronic exposure to ethanol. The modulation of drd2 gene combined with the behavioral characterization observed in the study suggests this signalling pathway as a key participant in the phenotypic outcomes of a long-term chronic exposure to ethanol. Lastly, our results reaffirm the ethanol deleterious impacts in perception, ability to respond to adverse stimuli and in anxiety-like behavior., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Leptin is well acknowledged as an anorexigenic hormone that plays an important role in feeding control. Hypothalamic GABA system plays a significant role in leptin regulation on feeding and metabolism control. However, the pharmacological relationship of leptin and GABA receptor is still obscure. Therefore, we investigated the effect of leptin or combined with baclofen on the food intake in fasted mice. We detected the changes in hypothalamic c-Fos expression, hypothalamic TH, POMC and GAD67 expression, plasma insulin, POMC and GABA levels to demonstrate the mechanisms. We found that leptin inhibit fasting-induced increased food intake and activated hypothalamic neurons. The inhibitory effect on food intake induced by leptin in fasted mice can be reversed by pretreatment with baclofen. Baclofen reversed leptin's inhibition on c-Fos expression of PAMM in fasted mice. Therefore, these results indicate that leptin might inhibit fasting-triggered activation of PVN neurons via presynaptic GABA synaptic functions which might be partially blocked by pharmacological activating GABA-B. Our findings identify the role of leptin in the regulation of food intake., (© 2020 The Authors. Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

Shrm4 is a protein that is exclusively expressed in polarized tissues. The physiological function of Shrm4 in the brain was required to be elucidated. Thus, we aimed to explore how the Shrm4-mediated gamma-aminobutyric acid (GABA) pathway affected neural stem cells (NSCs). At first, the Nestin expression in cultured NSCs was identified. After determination of the interaction of Shrm4 and GABA B1 , a series of in vitro experiment were performed to detect cell proliferation, the ability of cell colony formation, degree that NSCs differentiated into neurons, the apoptosis rate, and cell cycle. The levels of Shrm4, GABA B1 , Bcl-2-associated protein x (Bax), B cell lymphoma 2 (Bcl-2), cleaved Caspase-3, microtubule-associated protein 2 (MAP-2) as well as suppressor of cytokine signaling 2 (SOCS2) were detected to further assess the role of Shrm4 and GABA pathway in NSCs. Initially, we found that Shrm4 could bind to GABA B1 , and overexpression of Shrm4 or activation of GABA B1 increased the number of positive cells, and promoted cell viability, colony formation rate and differentiation of NSCs. After overexpression of Shrm4 or activation of GABA B1 , cells in the G1 phase were decreased, while those in the S phase were increased with an inhibited cell apoptosis rate in the NSCs. Besides, the overexpression of Shrm4 or activation of GABA B1 upregulated the levels of Shrm4, GABA B1 , Bcl-2, MAP-2 and SOCS2, while downregulated Bax and cleaved Caspase-3 in NSCs. Overall, overexpression of Shrm4 activated GABA B1 to stimulate the proliferation and differentiation of NSCs. Thus, Shrm4 might be considered as a novel target for promoting the proliferation and differentiation of NSCs.

Objective: Next-generation sequencing (NGS) was performed to identify genes that were differentially expressed between normal thyroid tissue and papillary thyroid carcinoma (PTC)., Materials and Methods: Six candidate genes were selected and further confirmed with quantitative real-time polymerase chain reaction (qRT-PCR), and immunohistochemistry in samples from 24 fresh thyroid tumors and adjacent normal tissues. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis was used to investigate signal transduction pathways of the differentially expressed genes., Results: In total, 1690 genes were differentially expressed between samples from patients with PTC and the adjacent normal tissue. Among these, SFRP4, ZNF90, and DCN were the top three upregulated genes, whereas KIRREL3, TRIM36, and GABBR2 were downregulated with the smallest p values. Several pathways were associated with the differentially expressed genes and involved in cellular proliferation, cell migration, and endocrine system tumor progression, which may contribute to the pathogenesis of PTC. Upregulation of SFRP4, ZNF90, and DCN at the mRNA level was further validated with RT-PCR, and DCN expression was further confirmed with immunostaining of PTC samples., Conclusion: These results provide new insights into the molecular mechanisms of PTC. Identification of differentially expressed genes should not only improve the tumor signature for thyroid tumors as a diagnostic biomarker but also reveal potential targets for thyroid tumor treatment., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

There is no previous study on the effect of pinocembrin on ovarian cancer to the best of our knowledge. Moreover, the effects of pinocembrin on the expression of GABAB1 and GABAB2 genes are not studied before. Therefore, this study aimed to investigate effects of pinocembrin on the growth of ovarian cancer cells and the expression of cadherin and GABAB receptor to explore whether pinocembrin was helpful in the treatment of epithelial ovarian cancer. SKOV3 cells were divided into six groups: Control (blank control), DDP (cisplatin as positive control; cells were incubated with 15 μg/ml DDP), 25 μM (cells were incubated with 25 μM pinocembrin), 50 μM (cells were incubated with 50 μM pinocembrin), 100 μM (cells were incubated with 100 μM pinocembrin), and 200 μM (cells were incubated with 200 μM pinocembrin). CCK8 assay, cell scratch assay and Annexin V-FITC/PI staining found that when pinocembrin concentration reached 100 μM and the treatment time reached 48 h, pinocembrin could inhibit the cell proliferation and migration and promote the cell apoptosis, and this effect was enhanced with the increase of pinocembrin concentration. Western blotting found that the protein expression of E-cadherin, N-cadherin, GABAB1 and GABAB2 was not significantly affected by pinocembrin. RT-PCR found that pinocembrin also had no significant influence on the E-cadherin mRNA level, but it could reduce the mRNA levels of N-cadherin, GABAB1 and GABAB2. In conclusion, pinocembrin inhibited the proliferation and migration and promoted the apoptosis of ovarian cancer cells through down-regulating the mRNA levels of N-cadherin and GABAB receptor., (Copyright © 2019 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Complex circuit interactions within the nucleus accumbens (NAc) facilitate goal-directed behavior. Medium spiny neurons (MSNs) mediate NAc output by projecting to functionally divergent brain regions, a property conferred, in part, by the differential projection patterns of D1- and D2 dopamine receptor-expressing MSNs. Glutamatergic afferents to the NAc direct MSN output by recruiting feedforward inhibitory microcircuits comprised of parvalbumin (PV)-expressing interneurons (INs). Furthermore, the GABA B heteroreceptor (GABA B R), a G i/o -coupled G-protein-coupled receptor, is expressed at glutamatergic synapses throughout the mesolimbic network, yet its physiological context and synaptic mechanism within the NAc remains unknown. Here, we explored GABA B R function at glutamatergic synapses within PV-IN-embedded microcircuits in the NAc core of male mice. We found that GABA B R is expressed presynaptically and recruits a noncanonical signaling mechanism to reduce glutamatergic synaptic efficacy at D1(+) and D1(-) (putative D2) MSN subtypes. Furthermore, PV-INs, a robust source of neuronal GABA in the NAc, heterosynaptically target GABA B R to selectively modulate glutamatergic transmission onto D1(+) MSNs. These findings elucidate a new mechanism of feedforward inhibition and refine mechanisms by which GABA B heteroreceptors modulate mesolimbic circuit function. SIGNIFICANCE STATEMENT Glutamatergic transmission in the nucleus accumbens (NAc) critically contributes to goal-directed behaviors. However, intrinsic microcircuit mechanisms governing the integration of these synapses remain largely unknown. Here, we show that parvalbumin-expressing interneurons within feedforward microcircuits heterosynaptically target GABA B heteroreceptors (GABA B R) on glutamate terminals. Activation of presynaptically-expressed GABA B R decreases glutamatergic synaptic strength by engaging a non-canonical signaling pathway that interferes with vesicular exocytotic release machinery. These findings offer mechanistic insight into the role of GABA B heteroreceptors within reward circuitry, elucidate a novel arm to feedforward inhibitory networks, and inform the growing use of GABA B R-selective pharmacotherapy for various motivational disorders, including addiction, major depressive disorder, and autism (Cousins et al., 2002; Kahn et al., 2009; Jacobson et al., 2018; Stoppel et al., 2018; Pisansky et al., 2019)., (Copyright © 2019 the authors.)