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PKD1 regulates a number of cellular processes through the formation of complexes with the PKD2 ion channel or transient receptor potential classical (TRPC) 4 in the endothelial cells. Although Ca 2+ modulation by polycystins has been reported between PKD1 and TRPC4 channel or TRPC1 and PKD2, the function with TRPC subfamily regulated by PKD2 has remained elusive. We confirmed TRPC4 or TRPC5 channel activation via PKD1 by modulating G-protein signaling without change in TRPC4/C5 translocation. The activation of TRPC4/C5 channels by intracellular 0.2 mM GTPγS was not significantly different regardless of the presence or absence of PKD1. Furthermore, the C-terminal fragment (CTF) of PKD1 did not affect TRPC4/C5 activity, likely due to the loss of the N-terminus that contains the G-protein coupled receptor proteolytic site (GPS). We also investigated whether TRPC1/C4/C5 can form a heterodimeric channel with PKD2, despite PKD2 being primarily retained in the endoplasmic reticulum (ER). Our findings show that PKD2 is targeted to the plasma membrane, particularly by TRPC5, but not by TRPC1. However, PKD2 did not coimmunoprecipitate with TRPC5 as well as with TRPC1. PKD2 decreased both basal and La 3+ -induced TRPC5 currents but increased M 3 R-mediated TRPC5 currents. Interestingly, PKD2 increased STAT3 phosphorylation with TRPC5 and decreased STAT1 phosphorylation with TRPC1. To be specific, PKD2 and TRPC1 compete to bind with TRPC5 to modulate intracellular Ca 2+ signaling and reach the plasma membrane. This interaction suggests a new therapeutic target in TRPC5 channels for improving vascular endothelial function in polycystic kidney disease.

With the increasing volume of synthetic fiber waste, interest in plastic reuse technologies has grown. To address this issue, physical and chemical recycling techniques for polyamide, a major component of textile waste, have been developed. This study investigates the remelting and reforming properties of four types of pristine and recycled polyamide 6, focusing on how the microstructural arrangement of recycled polyamides affects polymer fiber formation. DSC and FT-IR were used to determine the thermal properties and chemical composition of the reformed thin films. Differences in the elongation behavior of molten fibers during the spinning process were also observed, and the morphology of the resulting fibers was examined via SEM. Birefringence analysis revealed that the uniformity of the molecular structure greatly influenced differences in the re-fiberization process, suggesting that chemically recycled polyamide is the most suitable material for re-fiberization with its high structural similarity to pristine polyamide.

Transient receptor potential canonical 3 (TRPC3) is a calcium-permeable, non-selective cation channel known to be regulated by components of the phospholipase C (PLC)-mediated signaling pathway, such as Ca 2+ , diacylglycerol (DAG) and phosphatidylinositol 4,5-biphosphate (PI(4,5)P 2 ). However, the molecular gating mechanism by these regulators is not yet fully understood, especially its regulation by PI(4,5)P 2 , despite the importance of this channel in cardiovascular pathophysiology. Recently, Clarke et al. (2024) have reported that PI(4,5)P 2 is a positive modulator for TRPC3 using molecular dynamics simulations and patch-clamp techniques. They have demonstrated a multistep gating mechanism of TRPC3 with the binding of PI(4,5)P 2 to the lipid binding site located at the pre-S1/S1 nexus, and the propagation of PI(4,5)P 2 sensing to the pore domain via a salt bridge between the TRP helix and the S4-S5 linker., Competing Interests: Declaration of competing interest Authors have no competing financial interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Transient receptor potential (TRP) ion channels have a crucial role as cellular sensors, mediating diverse physical and chemical stimuli. The formation of heteromeric structures expands the functionality of TRP channels; however, their molecular architecture remains largely unknown. Here we present the cryo-electron microscopy structures of the human TRPC1/TRPC4 heteromer in the apo and antagonist-bound states, both consisting of one TRPC1 subunit and three TRPC4 subunits. The heteromer structure reveals a distinct ion-conduction pathway, including an asymmetrically constricted selectivity filter and an asymmetric lower gate, primarily attributed to the incorporation of TRPC1. Through a structure-guided electrophysiological assay, we show that both the selectivity filter and the lower part of the S6 helix participate in deciding overall preference for permeating monovalent cations. Moreover, we reveal that the introduction of one lysine residue of TRPC1 into the tetrameric central cavity is enough to render one of the most important functional consequences of TRPC heteromerization: reduced calcium permeability. Our results establish a framework for addressing the structure-function relationship of the heteromeric TRP channels., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)

This study assessed the relationship between daily life changes and mental health in Korean adolescents during the COVID-19 pandemic. Data from middle and high school students who responded to the relevant survey items the 2021 Korea Youth Risk Behavior Survey were analyzed (n = 53,868). The survey assessed changes in economic status, physical activity, skipping breakfast, drinking, smoking, and mental health, including stress, depression, generalized anxiety disorder, and suicidal ideation, due to the COVID-19 pandemic. The overall prevalence of perceived stress, depression, generalized anxiety disorder, and suicidal ideation was 38.6%, 26.4%, 12.2%, and 12.4%. Adolescents whose economic status worsened due to COVID-19 had a higher risk of perceived stress, depression, generalized anxiety disorder, and suicidal ideation. Changes in physical activity and breakfast consumption due to the COVID-19 pandemic were significantly associated with increases in perceived stress, depression, generalized anxiety disorder, and suicidal ideation. Adolescents who increased their alcohol consumption had the highest risk of perceived stress, depression, generalized anxiety disorder, and suicidal ideation. Changes in economic status and health behaviors caused by the COVID-19 pandemic had a negative effect on the mental health of Korean adolescents. These results can be used to identify adolescents at high risk of developing mental health problems., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

GPCR-G i protein pathways are involved in the regulation of vagus muscarinic pathway under physiological conditions and are closely associated with the regulation of internal visceral organs. The muscarinic receptor-operated cationic channel is important in GPCR-G i protein signal transduction as it decreases heart rate and increases GI rhythm frequency. In the SA node of the heart, acetylcholine binds to the M2 receptor and the released Gβγ activates GIRK (I(K,ACh)) channel, inducing a negative chronotropic action. In gastric smooth muscle, there are two muscarinic acetylcholine receptor (mAChR) subtypes, M2 and M3. M2 receptor activates the muscarinic receptor-operated nonselective cationic current (mIcat, NSCC(ACh)) and induces positive chronotropic effect. Meanwhile, M3 receptor induces hydrolysis of PIP 2 and releases DAG and IP 3 . This IP 3 increases intracellular Ca 2+ and then leads to contraction of GI smooth muscles. The activation of mIcat is inhibited by anti-G i/o protein antibodies in GI smooth muscle, indicating the involvement of Gα i/o protein in the activation of mIcat. TRPC4 channel is a molecular candidate for mIcat and can be directly activated by constitutively active Gα i QL proteins. TRPC4 and TRPC5 belong to the same subfamily and both are activated by G i/o proteins. Initial studies suggested that the binding sites for G protein exist at the rib helix or the CIRB domain of TRPC4/5 channels. However, recent cryo-EM structure showed that IYY 58-60 amino acids at ARD of TRPC5 binds with G i3 protein. Considering the expression of TRPC4/5 in the brain, the direct G protein activation on TRPC4/5 is important in terms of neurophysiology. TRPC4/5 channels are also suggested as a coincidence detector for G i and G q pathway as G q pathway increases intracellular Ca 2+ and the increased Ca 2+ facilitates the activation of TRPC4/5 channels. More complicated situation would occur when GIRK, KCNQ2/3 (I M ) and TRPC4/5 channels are co-activated by stimulation of muscarinic receptors at the acetylcholine-releasing nerve terminals. This review highlights the effects of GPCR-G i protein pathway, including dopamine, μ-opioid, serotonin, glutamate, GABA, on various oragns, and it emphasizes the importance of considering TRPC4/5 channels as crucial players in the field of neuroscience., 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 © 2024 Kang, Kim, Park, Jeong and So.)

Traditionally prescribed for mood disorders, tricyclic antidepressants (TCAs) have shown promising therapeutic effects on chronic neuralgia and irritable bowel syndrome. However, the mechanism by which these atypical effects manifest is unclear. Among the proposed mechanisms is the well-known pain-related inhibitory G-protein coupled receptor, namely the opioid receptor (OR). Here, we confirmed that TCA indeed stimulates OR and regulates the gating of TRPC4, a downstream signaling of the G i -pathway. In an ELISA to quantify the amount of intracellular cAMP, a downstream product of OR/G i -pathway, treatment with amitriptyline (AMI) showed a decrease in [cAMP] i similar to that of the μOR agonist. Next, we explored the binding site of TCA by modeling the previously revealed ligand-bound structure of μOR. A conserved aspartate residue of ORs was predicted to participate in salt bridge interaction with the amine group of TCAs, and in aspartate-to-arginine mutation, AMI did not decrease the FRET-based binding efficiency between the ORs and Gα i2 . As an alternative way to monitor the downstream signaling of G i -pathway, we evaluated the functional activity of TRPC4 channel, as it is well known to be activated by Gα i . TCAs increased the TRPC4 current through ORs, and TCA-evoked TRPC4 activation was abolished by an inhibitor of Gα i2 or its dominant-negative mutant. As expected, TCA-evoked activation of TRPC4 was not observed in the aspartate mutants of OR. Taken together, OR could be proclaimed as a promising target among numerous binding partners of TCA, and TCA-evoked TRPC4 activation may help to explain the nonopioid analgesic effect of TCA. NEW & NOTEWORTHY Endogenous opioid systems modulate pain perception, but concerns about opioid-related substance misuse limit their use. This study has raised TRPC4 channel as a candidate target for alternative analgesics, tricyclic antidepressants (TCAs). TCAs have been shown to bind to and activate opioid receptors (ORs), leading to downstream signaling pathways involving TRPC4. The functional selectivity and biased agonism of TCA towards TRPC4 in dependence on OR may provide a better understanding of its efficacy or side effects.

G-protein coupled receptors (GPCRs) and ion channels serve as key molecular switches through which extracellular stimuli are transformed into intracellular effects, and it has long been postulated that ion channels are direct effector molecules of the alpha subunit of G-proteins (Gα). However, no complete structural evidence supporting the direct interaction between Gα and ion channels is available. Here, we present the cryo-electron microscopy structures of the human transient receptor potential canonical 5 (TRPC5)-Gα i3 complexes with a 4:4 stoichiometry in lipid nanodiscs. Remarkably, Gα i3 binds to the ankyrin repeat edge of TRPC5 ~ 50 Å away from the cell membrane. Electrophysiological analysis shows that Gα i3 increases the sensitivity of TRPC5 to phosphatidylinositol 4,5-bisphosphate (PIP 2 ), thereby rendering TRPC5 more easily opened in the cell membrane, where the concentration of PIP 2 is physiologically regulated. Our results demonstrate that ion channels are one of the direct effector molecules of Gα proteins triggered by GPCR activation-providing a structural framework for unraveling the crosstalk between two major classes of transmembrane proteins: GPCRs and ion channels., (© 2023. The Author(s).)

Transient receptor potential canonical (TRPC) channels are non-selective calcium-permeable cation channels. It is suggested that TRPC4β is regulated by phospholipase C (PLC) signaling and is especially maintained by phosphatidylinositol 4,5-bisphosphate (PIP 2 ). In this study, we present the regulation mechanism of the TRPC4 channel with PIP 2 hydrolysis which is mediated by a channel-bound PLCδ1 but not by the G q PCR signaling pathway. Our electrophysiological recordings demonstrate that the Ca 2+ via an open TRPC4 channel activates PLCδ1 in the physiological range, and it causes the decrease of current amplitude. The existence of PLCδ1 accelerated PIP 2 depletion when the channel was activated by an agonist. Interestingly, PLCδ1 mutants which have lost the ability to regulate PIP 2 level failed to reduce the TRPC4 current amplitude. Our results demonstrate that TRPC4 self-regulates its activity by allowing Ca 2+ ions into the cell and promoting the PIP 2 hydrolyzing activity of PLCδ1.

The objective of this study was to investigate on the effect of mixing intensity (G) and mixing duration (t(d)) on struvite precipitation in the chemical mechanical polishing (CMP) wastewater generated from the semiconductor manufacturing process. Batch-scale experiments revealed that struvite crystallization was affected by both G and t(d). The mixing effect was to enhance the mass transfer of solute to the crystals in the process, resulting in the improvement of struvite crystallization and growth. By forming struvite, removal efficiencies of N and P increased logarithmic with the multiple values of G and t(d), i.e., Gt(d). Insufficient mixing energy with the Gt(d) value less than 10(5) caused an increase in the formation potential of unexpected precipitate unlike to pure struvite, causing a decrease in removal efficiencies of N and P in the process. At the Gt(d) value over 10(6), struvite precipitation was not restricted by fluoride, of which high level inherently contained in the CMP wastewater. The study results can be taken into consideration in the design and operation of the struvite precipitation process for both nutrient (N and P) removal and recovery.

Many proteins involved in DNA replication and repair undergo post-translational modifications such as phosphorylation and ubiquitylation. Proliferating cell nuclear antigen (PCNA; a homotrimeric protein that encircles double-stranded DNA to function as a sliding clamp for DNA polymerases) is monoubiquitylated by the RAD6-RAD18 complex and further polyubiquitylated by the RAD5-MMS2-UBC13 complex in response to various DNA-damaging agents. PCNA mono- and polyubiquitylation activate an error-prone translesion synthesis pathway and an error-free pathway of damage avoidance, respectively. Here we show that replication factor C (RFC; a heteropentameric protein complex that loads PCNA onto DNA) was also ubiquitylated in a RAD18-dependent manner in cells treated with alkylating agents or H(2)O(2). A mutant form of RFC2 with a D228A substitution (corresponding to a yeast Rfc4 mutation that reduces an interaction with replication protein A (RPA), a single-stranded DNA-binding protein) was heavily ubiquitylated in cells even in the absence of DNA damage. Furthermore RFC2 was ubiquitylated by the RAD6-RAD18 complex in vitro, and its modification was inhibited in the presence of RPA. The inhibitory effect of RPA on RFC2 ubiquitylation was relatively specific because RAD6-RAD18-mediated ubiquitylation of PCNA was RPA-insensitive. Our findings suggest that RPA plays a regulatory role in DNA damage responses via repression of RFC2 ubiquitylation in human cells.

This study was conducted to improve struvite precipitation for NH4-N removal purpose in landfill leachate. For this purpose, we evaluated the effect of the feeding sequence of precipitating reagents (magnesium, orthophosphate, and buffering reagent) on NH4-N removal by forming struvite deposits. Struvite precipitation effectively proceeded by an addition of excess magnesium and phosphate sources followed by an addition of the buffering reagent, in which condition the local formation of inappropriate deposits or the contamination of the desired struvite was minimized. We also tested the effect of struvite addition as the seeding materials on NH4-N removal. Seed addition would increase the potential for the struvite crystal growth, which enhanced NH4-N removal performance in landfill leachate treatment.