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Several studies have demonstrated the therapeutic potential of applying microtubule- (MT-) stabilizing agents (MSAs) that cross the blood-brain barrier to promote axon regeneration and prevent axonal dystrophy in rodent models of spinal cord injury and neurodegenerative diseases. Paradoxically, administration of MSAs, which have been widely prescribed to treat malignancies, is well known to cause debilitating peripheral neuropathy and axon degeneration. Despite the growing interest of applying MSAs to treat the injured or degenerating central nervous system (CNS), consequences of MSA exposure to neurons in the central and peripheral nervous system (PNS) have not been thoroughly investigated. Here, we have examined and compared the effects of a brain-penetrant MSA, epothilone B, on cortical and sensory neurons in culture and show that epothilone B exhibits both beneficial and detrimental effects, depending on not only the concentration of drug but also the type and age of a neuron, as seen in clinical settings. Therefore, to exploit MSAs to their full benefit and minimize unwanted side effects, it is important to understand the properties of neuronal MTs and strategies should be devised to deliver minimal effective concentration directly to the site where needed. [ABSTRACT FROM AUTHOR]

Fear conditioning has been used to study pathogenic mechanisms underlying anxiety disorders. Several studies have shown that humans with anxiety disorders exhibit strong fear responses during the acquisition of conditioned fear. However, there have been no studies investigating whether basal anxiety within the normal range is related to conditioned fear in rodents. We hypothesized that individual differences in conditioned fear are correlated to the basal anxiety level of each individual. To test this hypothesis, we measured the basal anxiety of mice by using the elevated-plus maze (EPM) and open field test (OFT) and correlated these data with contextual freezing during contextual fear conditioning (CFC). Strong correlation was found between the basal anxiety level measured in the OFT and contextual freezing in the CFC. Baseline freezing was also strongly correlated with the contextual freezing level during the retrieval phase of CFC. However, the basal anxiety level measured in the EPM was correlated neither with conditioned fear nor with baseline freezing in the CFC. These results suggest that both basal anxiety in the OFT and baseline freezing are related to contextually conditioned fear. [ABSTRACT FROM AUTHOR]

The evolutionary trajectory of glioblastoma (GBM) is a multifaceted biological process that extends beyond genetic alterations alone. Here, we perform an integrative proteogenomic analysis of 123 longitudinal glioblastoma pairs and identify a highly proliferative cellular state at diagnosis and replacement by activation of neuronal transition and synaptogenic pathways in recurrent tumors. Proteomic and phosphoproteomic analyses reveal that the molecular transition to neuronal state at recurrence is marked by post-translational activation of the wingless-related integration site (WNT)/ planar cell polarity (PCP) signaling pathway and BRAF protein kinase. Consistently, multi-omic analysis of patient-derived xenograft (PDX) models mirror similar patterns of evolutionary trajectory. Inhibition of B-raf proto-oncogene (BRAF) kinase impairs both neuronal transition and migration capability of recurrent tumor cells, phenotypic hallmarks of post-therapy progression. Combinatorial treatment of temozolomide (TMZ) with BRAF inhibitor, vemurafenib, significantly extends the survival of PDX models. This study provides comprehensive insights into the biological mechanisms of glioblastoma evolution and treatment resistance, highlighting promising therapeutic strategies for clinical intervention. [Display omitted] • Longitudinal proteogenomic analysis reveals increased neuronal state at recurrence • Neuronal transition associates with activation of WNT/PCP pathway and BRAF kinase • Resistance to therapy via neuronal transition is recapitulated in GBM PDX models • BRAF kinase inhibition impairs the neuronal transition of GBM at recurrence Kim et al. reveal that glioblastoma develops therapeutic resistance through a neuronal transition caused by changes in the WNT/PCP pathway and BRAF kinase, as shown by extensive proteogenomic analysis. Notably, inhibiting BRAF kinase disrupts this lethal transformation, offering potential therapeutic avenues. [ABSTRACT FROM AUTHOR]

Neur1 and Neur2, mouse homologs of the Drosophila neur gene, consist of two neuralized homology repeat domains and a RING domain. Both Neur1 and Neur2 are expressed in the whole adult brain and encode E3 ubiquitin ligases, which play a crucial role in the Notch signaling pathways. A previous study reported that overexpression of Neur1 enhances hippocampus‐dependent memory, whereas the role of Neur2 remains largely unknown. Here, we aimed to elucidate the respective roles of Neur1 and Neur2 in hippocampus‐dependent memory using three lines of genetically modified mice: Neur1 knock‐out, Neur2 knock‐out, and Neur1 and Neur2 double knock‐out (D‐KO). Our results showed that spatial memory was impaired when both Neur1 and Neur2 were deleted, but not in the individual knock‐out of either Neur1 or Neur2. In addition, basal synaptic properties estimated by input–output relationships and paired‐pulse facilitation did not change, but a form of long‐term potentiation that requires protein synthesis was specifically impaired in the D‐KO mice. These results collectively suggest that Neur1 and Neur2 are crucially involved in hippocampus‐dependent spatial memory and synaptic plasticity. [ABSTRACT FROM AUTHOR]

Highlights • Retrieval of contextual fear memory increases the membrane excitability. • Propranolol or NMDAR and PKA inhibition diminishes membrane hyperexcitability. • β-adrenergic signaling is required for the destabilization of contextual fear memory. Abstract Memory reconsolidation is the process by which previously consolidated memories reenter a labile state through reactivation of the memory trace and are actively consolidated through de novo protein synthesis. Although extensive studies have shown that β-adrenergic signaling plays a critical role in the restabilization of reactivated memory, its role in the destabilization of long-term memory is not well-studied. In this study, we found that membrane excitability increased in hippocampal CA1 neurons immediately after the retrieval of contextual fear memory. Interestingly, this increase in membrane excitability diminished after treatment with propranolol (a β-adrenergic receptor antagonist), an NMDA receptor antagonist, and a PKA inhibitor. In addition, we found that administration of propranolol prior to, but not after, the retrieval of fear memory ameliorated the memory impairment caused by anisomycin, indicating that inhibition of β-adrenergic signaling blocks the destabilization of contextual fear memory. Taken together, these results indicate that β-adrenergic signaling via NMDA receptors and PKA signaling pathway induces a labile state of long-term memory through increased neuronal membrane excitability. [ABSTRACT FROM AUTHOR]

• Transient elevation of cAMP during systems consolidation leads to increased miniature excitatory synaptic currents in the ACC. • Transient elevation of cAMP in the ACC during systems consolidation induces remote memory enhancement. • During systems consolidation, the ACC plays a key role in the cAMP-dependent regulation of remote memory. Memory is stored in our brains over a temporally graded transition. With time, recently formed memories are transformed into remote memories for permanent storage; multiple brain regions, such as the hippocampus and neocortex, participate in this process. In this study, we aimed to understand the molecular mechanism of systems consolidation of memory and to investigate the brain regions that contribute to this regulation. We first carried out a contextual fear memory test using a transgenic mouse line, which expressed exogenously-derived Aplysia octopamine receptors in the forebrain region, such that, in response to octopamine treatment, cyclic adenosine monophosphate (cAMP) levels could be transiently elevated. From this experiment, we revealed that transient elevation of cAMP levels in the forebrain during systems consolidation led to an enhancement in remote fear memory and increased miniature excitatory synaptic currents in layer II/III of the anterior cingulate cortex (ACC). Furthermore, using an adeno-associated-virus-driven DREADD system, we investigated the specific regions in the forebrain that contribute to the regulation of memory transfer into long-term associations. Our results implied that transient elevation of cAMP levels was induced chemogenetically in the ACC, but not in the hippocampus, and showed a significant enhancement of remote memory. This finding suggests that neuronal activation during systems consolidation through the elevation of cAMP levels in the ACC contributes to remote memory enhancement. [ABSTRACT FROM AUTHOR]

Background: Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of familial and sporadic Parkinson’s disease (PD). Elevated kinase activity is associated with LRRK2 toxicity, but the substrates that mediate neurodegeneration remain poorly defined. Given the increasing evidence suggesting a role of LRRK2 in membrane and vesicle trafficking, here we systemically screened Rab GTPases, core regulators of vesicular dynamics, as potential substrates of LRRK2 and investigated the functional consequence of such phosphorylation in cells and in vivo. Methods: In vitro LRRK2 kinase assay with forty-five purified human Rab GTPases was performed to identify Rab family proteins as substrates of LRRK2. We identified the phosphorylation site by tandem mass-spectrometry and confirmed it by assessing phosphorylation in the in vitro LRRK2 kinase assay and in cells. Effects of Rab phosphorylation on neurodegeneration were examined in primary cultures and in vivo by intracranial injection of adeno-associated viral vectors (AAV) expressing wild-type or phosphomutants of Rab35. Results: Our screening revealed that LRRK2 phosphorylated several Rab GTPases at a conserved threonine residue in the switch II region, and by using the kinase-inactive LRRK2-D1994A and the pathogenic LRRK2-G2019S along with Rab proteins in which the LRRK2 site was mutated, we verified that a subset of Rab proteins, including Rab35, were authentic substrates of LRRK2 both in vitro and in cells. We also showed that phosphorylation of Rab regulated GDP/GTP-binding property in cells. Moreover, in primary cortical neurons, mutation of the LRRK2 site in several Rabs caused neurotoxicity, which was most severely induced by phosphomutants of Rab35. Furthermore, intracranial injection of the AAV-Rab35 -T72A or AAV-Rab35-T72D into the substantia nigra substantially induced degeneration of dopaminergic neurons in vivo. Conclusions: Here we show that a subset of Rab GTPases are authentic substrates of LRRK2 both in vitro and in cells. We also provide evidence that dysregulation of Rab phosphorylation in the LRRK2 site induces neurotoxicity in primary neurons and degeneration of dopaminergic neurons in vivo. Our study suggests that Rab GTPases might mediate LRRK2 toxicity in the progression of PD. [ABSTRACT FROM AUTHOR]