Journal of General Physiology最新文献

{"title":"PIP2-driven cytoplasmic domain motions are coupled to Kir2 channel gating.","authors":"Eva-Maria Zangerl-Plessl, Anna Stary-Weinzinger, Colin G Nichols, Sun-Joo Lee","doi":"10.1085/jgp.202513864","DOIUrl":"10.1085/jgp.202513864","url":null,"abstract":"<p><p>Inwardly rectifying potassium (Kir) channel activity is important in the control of membrane potentials in both excitable and non-excitable cells and is regulated through various ligands, including specific membrane lipids. Phosphatidyl-4,5-bisphosphate (PIP2) is required for activity of all Kir channels, binding to the cytoplasmic domain in a compact conformation tightly tethered to the transmembrane domain. Most Kir2 channel structures determined in complex with PIP2 molecules are nevertheless in a closed state, requiring additional conformational changes for channel opening. We have carried out full atomistic MD simulations, which indicate PIP2-dependent conformational changes that are coupled to opening and closing of the channel. In the presence of bound PIP2, the cytoplasmic domain performs clockwise twisting motions, with a pivot residing near the C-linker in each subunit. These motions are reduced when PIP2 is removed, leading to narrowing of the critical gate at the M2 helix bundle crossing (HBC), but expansion at the region G-loop, as well as reduced overall fourfold symmetry, in turn coupled to cessation of ion permeation.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12493300/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145214542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Altered NaV1.9 channel activity in two Tyr66Ser variant carriers with small fiber dysfunction.","authors":"Noortje W M van den Braak, Samuel Kuehs, Greta Z Peschke, Barbara Namer, Annette Lischka, Katja Eggermann, Christina Dumke, Vishal Sudha Bhagavath Eswaran, Stefan Nikolin, Joachim Weis, Jörg B Schulz, Angelika Lampert, Ingo Kurth, Roman Rolke, Enrico Leipold, Maike F Dohrn","doi":"10.1085/jgp.202413691","DOIUrl":"10.1085/jgp.202413691","url":null,"abstract":"<p><p>Pain perception is a complex experience, the initiation of which is mediated, among others, by voltage-gated sodium channels. Pathogenic variants in the sodium channel gene SCN11A encoding for NaV1.9 have been associated with various pain loss and neuropathic pain conditions. We herein describe the novel heterozygous SCN11A variant c.197A>C; p.(Tyr66Ser) that is absent in controls and cosegregates with small fiber neuropathy in a mother-and-son duo. To a variable degree, but progressively over time, both patients developed positive and negative sensory symptoms and milder autonomic signs. Upon quantitative sensory testing, we found significant thermal hypoesthesia and pinprick hyperalgesia in both individuals. Rectangle, half-sine-, and sine-wave stimulation applied to hands and feet in both individuals revealed signs of axonal on/off-like hyperexcitability, possibly due to continuous activation of CMi-fibers that are insensitive to mechanical stimulation (also known as sleeping nociceptors). Nerve conduction studies were unremarkable, whereas pain-related evoked potentials showed pathological responses in both individuals. The intraepidermal nerve fiber density was reduced at the index patient's distal leg. Patch-clamp analyses revealed that p.(Tyr66Ser) shifted both the voltage dependence of activation and steady-state inactivation of NaV1.9 to more depolarized potentials, accompanied by accelerated deactivation and a slowdown of the channel's inactivation kinetics. In addition, overexpression of the variant in mouse sensory neurons shortened the duration of individual action potentials and enhanced action potentials after hyperpolarization. In this translational n-of-two study, we present longitudinal data on disease progression and provide functional evidence that the SCN11A variant p.(Tyr66Ser) is a strong candidate to contribute to the patients' phenotype.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145356755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The origins of oscillations.","authors":"Ben Short","doi":"10.1085/jgp.202513904","DOIUrl":"10.1085/jgp.202513904","url":null,"abstract":"<p><p>JGP study (Horie et al. https://doi.org/10.1085/jgp.202413749) explains why mice lacking TRPM1 exhibit oscillatory firing of their retinal ganglion cells, and suggests that the same mechanism causes similar oscillations in other outer retinal diseases.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145350070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigating the role of the I-II linker in Nav1.5 channel function.","authors":"Emily Wagner, Martina Marras, Shashi Kumar, Jacob Kelley, Kiersten Ruff, Jonathan Silva","doi":"10.1085/jgp.202413692","DOIUrl":"10.1085/jgp.202413692","url":null,"abstract":"<p><p>The cardiac voltage-gated sodium channel, Nav1.5, initiates the cardiac action potential. Its dysfunction can lead to dangerous arrhythmias, sudden cardiac arrest, and death. The functional Nav1.5 core consists of four homologous repeats (I, II, III, and IV), each formed from a voltage sensing and a pore domain. The channel also contains three cytoplasmic linkers (I-II, II-III, and III-IV). While Nav1.5 structures have been published, the I-II and II-III linkers have remained absent, are predicted to be disordered, and their functional role is not well understood. We divided the I-II linker into eight regions ranging in size from 32 to 52 residues, chosen based on their distinct properties. Since these regions had unique sequence properties, we hypothesized that they may have distinct effects on channel function. We tested this hypothesis with experiments with individual Nav1.5 constructs with each region deleted. These deletions had small effects on channel gating, though two (430-457del and 556-607del) reduced peak current. Phylogenetic analysis of the I-II linker revealed five prolines (P627, P628, P637, P640, and P648) that were conserved in mammals but absent from the Xenopus sequence. We created mutant channels, where these were replaced with their Xenopus counterparts. The only mutation that had a significant effect on channel gating was P627S, which depolarized channel activation (10.13 ± 2.28 mV). Neither a phosphosilent (P627A) nor a phosphomimetic (P627E) mutation had a significant effect, suggesting that either phosphorylation or another specific serine property is required. Since deletion of large regions had little effect on channel gating while a point mutation had a conspicuous impact, the I-II linker role may be to facilitate interactions with other proteins. Variants may have a larger impact if they create or disrupt these interactions, which may be key in evaluating the pathogenicity of variants.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13398361/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144994424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SUMOylation and an ATS1 variant converge to disrupt PIP2-dependent gating of Kir2.1.","authors":"Aishwarya Chandrashekar, Yu Xu, Xinyi Ma, Anne K Yauch, Elizabeth Scholl, Yuchen Yang, Kirin D Gada, Takeharu Kawano, Meng Cui, Leigh D Plant","doi":"10.1085/jgp.202513837","DOIUrl":"10.1085/jgp.202513837","url":null,"abstract":"<p><p>Precise control of Kir2.1 channel gating is essential for maintaining membrane potential and enabling repolarization in excitable cells. Disruption of Kir2.1 function can cause Andersen-Tawil syndrome type 1 (ATS1), a multisystem channelopathy that predisposes patients to ventricular dysrhythmias and increases the risk of sudden cardiac death. Kir2.1 activity depends on interactions with the membrane phospholipid PIP2, and these interactions can be weakened by genetic mutations or posttranslational modifications. Here, we identify a shared mechanism by which hypoxia-induced SUMOylation and a heterozygous ATS1-linked variant, R67Q, independently and cooperatively suppress Kir2.1 function. We found that SUMOylation reduces Kir2.1 current in a stoichiometric manner, with up to two SUMO proteins per channel tetramer diminishing current by ∼24% each. Channels containing heterozygous R67Q subunits are disproportionately sensitive to hypoxic suppression. Inhibiting the SUMO pathway with TAK-981 prevents this suppression and enhances current in both WT and R67Q-containing channels. Further analysis revealed that both SUMOylation and the R67Q mutation reduce the stability of Kir2.1-PIP2 interactions, indicating a convergent gating defect. These findings support a two-hit model of channel dysfunction, in which a genetic variant and an environmental stressor act through a common structural mechanism to impair Kir2.1 gating. By identifying PIP2 destabilization as the point of convergence, this work provides new insight into how stress-sensitive channelopathies arise and suggests that SUMO pathway inhibition may offer a strategy to restore function under adverse physiological conditions.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145287718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A mechanism for pathological oscillations in mouse retinal ganglion cells in a model of night blindness.","authors":"Sho Horie, Konan Sakuta, Keigo Tada, Haruki Tokumoto, Taketo Nishimoto, Katsunori Kitano, Masao Tachibana, Chieko Koike","doi":"10.1085/jgp.202413749","DOIUrl":"10.1085/jgp.202413749","url":null,"abstract":"<p><p>TRPM1 channels, regulated by mGluR6 at the dendrites of retinal ON bipolar cells (BCs), play a crucial role in visual signal transduction. Both Trpm1 knockout (KO) and mGluR6 KO mice are models of congenital stationary night blindness with grossly normal morphology. However, robust pathological spontaneous oscillations in retinal ganglion cells (RGCs) have been observed in Trpm1 KO retinas but not in mGluR6 KO retinas. We investigated the mechanism underlying these oscillations in the Trpm1 KO retina using whole-cell clamp techniques. We found that inhibitory and excitatory synaptic inputs produced anti-phase oscillations in OFF and ON RGCs, respectively, and that oscillations could be suppressed by blockers targeting the AII amacrine cell (AC) pathway. The rd1 retina, a model for retinitis pigmentosa with severe photoreceptor degeneration, displays similar oscillations to the Trpm1 KO retina. Morphological and immunohistochemical analyses revealed similar alterations in the Trpm1 KO and rd1 retinas when compared to the mGluR6 KO and wild-type retinas: namely, rod BCs (RBCs) in both Trpm1 KO and rd1 retinas showed reduced dendritic TRPM1 labeling and smaller axon terminals. Furthermore, RBCs in the Trpm1 KO retina were significantly hyperpolarized. In silico simulation of the BC-AII AC-RGC network suggests that the reduction of RBC and ON cone BC outputs to AII ACs contributes to RGC oscillations. Our findings suggest that TRPM1 deficiency in ON BCs produces RGC oscillations in association with RBC axon remodeling and reduced ON BC outputs, and may represent a shared circuit mechanism underlying pathological oscillations across different causes of outer retinal diseases.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12530179/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145304458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Voltage-gated sodium channels: Mechanisms, disease, and a growing research community.","authors":"Hugues Abriel, Angelika Lampert","doi":"10.1085/jgp.202513878","DOIUrl":"10.1085/jgp.202513878","url":null,"abstract":"<p><p>In this special issue of the Journal of General Physiology (JGP), we bring together a collection of studies that exemplify the multidimensional progress in physiology, pharmacology, and structure-function analysis of voltage-gated sodium (NaV) channels. From computational studies and single-residue mutagenesis to insights into drug interactions and electrophysiological variability, the assembled papers illustrate the richness and continuing momentum of this field.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145276696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Muscle fatigue arising intrinsically from SUR2- but not Kir6.1-dependent gain-of-function in Cantu syndrome mice.","authors":"Rosa Scala, Maya Mukadam, Yuezhou Chen, Courtney Frazier, Nathaniel W York, Robert C Tryon, Gretchen A Meyer, Colin G Nichols","doi":"10.1085/jgp.202513781","DOIUrl":"10.1085/jgp.202513781","url":null,"abstract":"<p><p>Cantu syndrome (CS) is a rare disease caused by gain-of-function (GOF) mutations of Kir6.1 or SUR2 subunits of ATP-sensitive potassium (KATP) channels. CS patients with SUR2 and Kir6.1 variants display a similar constellation of symptoms, including muscle weakness and fatigue. The effects of CS mutations on skeletal muscle KATP channels, and any consequent direct effects on contractility, are currently unclear. Here, we used two knock-in mouse models of CS, respectively, carrying GOF mutations Kir6.1[V65M] or SUR2[A478V], to assess KATP channel properties and contractility in isolated fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles. Electrophysiological recordings in isolated myofibers showed normal resting potentials, and excised patch-clamp recordings showed normal KATP channel density in both genotypes, but enhanced Mg-nucleotide activation only in SUR2[A478V] fibers, consistent with muscle KATP channels being formed predominantly as complexes of SUR2A and Kir6.2 subunits. Ex vivo testing of isolated SUR2[A478V], but not Kir6.1[V65M], muscles showed an earlier onset of fatigue and a marked intra-tetanic decline of force compared with littermate controls. Importantly, normal contractile behavior was restored ex vivo and in vivo in SUR2[A478V] muscles in the presence of the FDA-approved KATP channel inhibitor glibenclamide, indicating that the increased fatigue of isolated muscles is a direct consequence of overactive sarcolemmal KATP channels. These results shed light on the pathophysiologic relevance of SUR2-dependent KATP channel subunits in skeletal muscle and highlight their role in fatiguing conditions, as well as identifying potential therapeutic benefit of skeletal muscle KATP inhibition in CS.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12629551/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145240403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cortical spreading depression dynamics are altered by topical D2 receptor ligands.","authors":"Sonia Carolina Guerrero Prieto, Michael Cabrera Baez, Rubem Carlos Araújo Guedes","doi":"10.1085/jgp.202513843","DOIUrl":"10.1085/jgp.202513843","url":null,"abstract":"<p><p>Cortical spreading depression (CSD) is a transient wave of neuronal and glial depolarization that propagates slowly through the cerebral cortex and is implicated in neurological events such as migraine aura. While glutamate, GABA, and serotonin have established roles in CSD modulation, the contribution of dopaminergic signaling, particularly via D2 receptors (D2Rs), remains unclear. In this study, we examined whether topical cortical application of D2R-targeting agents alters CSD propagation and neuronal activation in vivo. Using a KCl-induced CSD model in anesthetized male Wistar rats, we applied metoclopramide (MCP), raclopride (RCP), and quinpirole (QNP) directly onto the cortex. MCP completely blocked CSD propagation at all time points. RCP and QNP produced opposing, time-dependent effects: RCP initially reduced CSD speed, followed by an increase after prolonged exposure, whereas QNP transiently accelerated propagation at 5 min but suppressed it with longer exposure. These changes were accompanied by alterations in waveform morphology, particularly in the secondary negative deflection. c-Fos immunoreactivity revealed reduced neuronal activation in MCP- and QNP-treated animals, mainly in superficial cortical layers, while RCP showed no significant effect. To support these findings, a reaction-diffusion computational model incorporating drug diffusion, receptor binding kinetics, and excitability parameters successfully reproduced the experimental CSD propagation profiles. Together, these results demonstrate that cortical D2R ligands modulate CSD dynamics and neuronal activation in a ligand-specific and time-dependent manner. This study provides mechanistic insight into how dopaminergic signaling influences cortical excitability and CSD propagation, advancing our understanding of dopamine's role in fundamental neurophysiological processes.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145240361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Resolving zone-specific regulation of cardiac myosin.","authors":"Shane R Nelson","doi":"10.1085/jgp.202513838","DOIUrl":"10.1085/jgp.202513838","url":null,"abstract":"<p><p>Cardiac contractility is driven by shortening of ∼2-μm-long, macromolecular assemblies known as sarcomeres. During contraction, the motor protein myosin binds to, and exerts force upon actin filaments, utilizing energy from the hydrolysis of ATP. When not actively contracting, myosin partition into two subpopulations, distinguished by their basal rates of ATP hydrolysis, known as the \"Disordered Relaxed\" (DRX) and \"Super Relaxed\" (SRX) states. Additionally, the slower hydrolyzing SRX state has been proposed as a sequestered or \"reserve pool\" of myosin that do not contribute to contraction but can be recruited for enhanced contractility in response to external stimuli. Thus, the fraction of myosin in the SRX state is thought to reflect the overall regulatory state of the myosin population. In this volume of the Journal of General Physiology, a study by Pilagov et al. explores how the SRX state is regulated by phosphorylation or haploinsufficiency of a key regulatory protein, Myosin Binding Protein-C (MyBP-C). Surprisingly, they found that perturbations of MyBP-C led to a negligible change in the overall abundance of SRX. Instead, they found a rearrangement of SRX myosin throughout the sarcomere - specifically a decrease in SRX in regions of the sarcomere that contain MyBP-C and a compensatory increase in SRX in regions lacking MyBP-C. Their findings suggest that the influence of MyBP-C extends beyond its immediate vicinity and can simultaneously exert both positive and negative effects in a location-specific manner.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 6","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12990060/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144979416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}