Journal of General Physiology最新文献

{"title":"Model of ocular surface ion and water transport predicts efficacy of dry eye therapeutics.","authors":"Varun Verma, Ethan S Lindgren, Marc H Levin, Onur Cil, Lukmanee Tradtrantip, Rongshan Yan, Neel D Pasricha, Alan S Verkman","doi":"10.1085/jgp.202513958","DOIUrl":"10.1085/jgp.202513958","url":null,"abstract":"<p><p>The composition and volume of tear fluid lining the ocular surface are governed by the rates of lacrimal gland secretion, tear film evaporation, nasolacrimal drainage, and epithelial ion and water transport. Tear fluid hyperosmolality and reduced volume are key drivers of dry eye disease (DED) pathogenesis. We constructed a mathematical model to compute the composition and volume of tear fluid and epithelial cell compartments, with transport parameters specified for the mouse eye based on published data and in vivo measurements of ocular surface potential differences. The model accounted for transcellular and paracellular transport across the epithelia under open-circuit conditions utilizing flux equations for individual transport mechanisms, with mass balance constraints on solute and water content in cytoplasm and tear fluid. Model computations revealed a rough orthogonality between the determinants of tear fluid volume and osmolality in which lacrimal secretion and nasolacrimal drainage primarily regulate tear fluid volume, whereas evaporation and transepithelial osmosis primarily regulate tear fluid osmolality. Under DED conditions established by reduced lacrimal secretion and increased evaporation, the model predicted the efficacy of currently available DED therapies, including punctal plugs, humidification goggles, lacrimal gland stimulation, and artificial tear eye drops. The model also predicted the limited efficacy of anti-absorptive and pro-secretory drugs targeting epithelial ion transporters and the high efficacy of targeting epithelial water permeability or paracellular ion permeability. The modeling herein provided quantitative predictions to prioritize drug targets for DED to drive the development of novel therapies.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13335528/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147989588","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":"Evolution of our understanding of the sodium channel fast inactivation: From Hodgkin and Huxley to the structural era.","authors":"Yichen Liu, Cesar A Amaya-Rodriguez, Victoria Collio, Gabriel Ibañez, Ramón Latorre, Francisco Bezanilla","doi":"10.1085/jgp.202613980","DOIUrl":"10.1085/jgp.202613980","url":null,"abstract":"<p><p>Voltage-gated sodium (Nav) channels enable the rapid influx of sodium ions that are essential to generating the rising phase of the action potential. As originally described by Hodgkin and Huxley, once the Nav channel is activated, it switches to an inactivated state within milliseconds, a process they called inactivation. Internal perfusion of the giant axon of the squid with proteolytic enzymes eliminated inactivation, implying that the inactivation gate is an internal protein structure of the Nav channel. This result, together with the charge immobilization of the gating currents, led to the ball and chain model of inactivation. Deletion of the linker between domains III and IV of the four homologous domains of the Nav channel was found to remove fast inactivation. These observations evolved the ball and chain model to the hinged-lid model of fast inactivation, which dominated the field for nearly 30 years. Surprisingly, the structures of the Nav channel, determined by cryo-EM, showed that the IFM was not at the site predicted by the hinged-lid model. Upending the Na channel field, biophysical and mutagenesis studies revealed that the binding of the IFM motif allosterically closes an inactivation gate at the internal entrance of the Nav conduction system. In this Review, we compile the historical and structural evolution of the fast inactivation process, from the first functional descriptions to current models based on structural data.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147846260","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":"Vesicular monoamine transporters (VMATs): From discovery to therapeutic targets.","authors":"Shimon Schuldiner","doi":"10.1085/jgp.202614012","DOIUrl":"10.1085/jgp.202614012","url":null,"abstract":"<p><p>Vesicular monoamine transporters (VMAT) are proteins essential for life. They play central roles in neurotransmission and hormone storage and are targets of neuroactive drugs. This retrospective chronicles the decades-long journey of studying VMAT, from early biochemical explorations to the recent surge of structural information. We delve into the serendipitous discoveries, methodological innovations, and collaborations that enhanced our understanding of monoamine storage and synaptic transmission. Importantly, this narrative highlights that a degree of initial \"optimistic ignorance\"-a failure to fully appreciate the system's complexity-can, paradoxically, be a driving force in scientific exploration. Our early, naïve assumption about VMAT's abundance, while ultimately an oversimplification, was instrumental in launching the project to identify, purify, and characterize the protein. An unprecedented flood of cryo-EM structures now provides invaluable molecular insights into the molecule's intricate workings, synergistically complementing functional studies and offering the crucial framework needed to mechanistically link structure to its function.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148201227","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":"Stressed lysosome: A theoretical model of lysosomal pH regulation applied to stress conditions.","authors":"Sofia F Nazarova, Vadim A Alekhin, Vladislav V Pavlov, Yury S Semenov, Siarhei M Bukhalovich, Fedor M Tsybrov, Andrey O Bogorodskiy, Diana F Bagaeva, Olga V Moiseeva, Anastasiia D Vlasova, Anatolii E Mikhailov, Yayu Wang, Andrey V Rogachev, Semen V Nesterov, Valentin I Borshchevskiy, Chunlei Cang, Piotr D Bregestovski, Valentin I Gordeliy, Nikolay S Ilyinsky","doi":"10.1085/jgp.202413745","DOIUrl":"https://doi.org/10.1085/jgp.202413745","url":null,"abstract":"<p><p>Lysosomes are essential organelles in eukaryotic cells, required for autophagy, endocytosis, pathogen defense, cell signaling, and metabolic homeostasis. A model of lysosomal ion and water fluxes that captures the synchronized, interdependent operation of ion transporters and diffusion enables prediction of organellar responses to external perturbations and supports the design and interpretation of experiments. Particularly with the advent of organelle-targeted rhodopsin-based optogenetics, there is a pressing need to predict cellular outcomes following light-driven, specific ion transport in lysosomes and other organelles. Currently, no models of lysosomal ion balance fully align with existing experimental data or enable simulation of the organelle's response to stress. Here, we present an updated interactive model that recapitulates appropriate stress responses. We incorporated the functional activities of TPC1 and TMEM165, in addition to the previously included vATPase, ClC-7, TRPML1, and passive ion and water fluxes. The model remains robust during lysosomal maturation, membrane permeabilization, swelling, deacidification induced by vATPase inhibition or additional optogenetics-like proton efflux, and accumulation of weakly basic cationic amphiphilic drugs. Our simulations indicate that lysosomal Ca2+ depletion couples with organellar deacidification triggered by either increased proton leakage or vATPase inhibition, with potential involvement of TMEM165 weakening. Beyond predicting stress-response dynamics, the model enables investigation of highly selective perturbations that can be experimentally induced using optogenetics. Elucidating the mechanisms underlying stable, stress-resilient lysosomal function offers insights for developing anti-disease and antiaging interventions. Further model refinement critically depends on experimental characterization of the lysosomal NHE-like protein mediating sodium influx.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148273886","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":"Brain voltage-gated Ca2+ channels and calmodulin: Teaming up in calmodulinopathies?","authors":"Jörg Striessnig","doi":"10.1085/jgp.202613981","DOIUrl":"10.1085/jgp.202613981","url":null,"abstract":"<p><p>Calmodulin (CaM) serves as one of the key cellular Ca2+ sensors with >300 targets and a highly conserved structure since its appearance in early eukaryogenesis. Three distinct CaM genes (CALM1, CALM2, and CALM3) encode one identical CaM protein in mammals. This low tolerance for structural changes highlights that CaM mutations are likely not well tolerated and therefore cause disease in humans. The first calmodulinopathies reported were catecholaminergic polymorphic ventricular tachycardia (CPVT) and a severe, early-onset cardiac arrhythmia syndrome with long-QT syndrome (LQTS). This led to recognition that CaM-modulated cardiac Cav1.2 L-type Ca2+ channels and RYR2 ryanodine receptors are key targets mediating the severe cardiac phenotype of CaM mutants . In this issue of the JGP, Hussey et al. (https://doi.org/10.1085/jgp.202413734) addressed the important question of whether dysregulation of voltage-gated Ca2+ channels in the brain could contribute to neurological/neurodevelopmental symptoms that are also associated with calmodulinopathies.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147935553","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":"Subunit composition of the KATP channels that modulate contractility of skeletal muscle during fatigue.","authors":"Rosa Scala, Yuezhou Chen, Berk Mizrak, Gretchen A Meyer, Colin G Nichols","doi":"10.1085/jgp.202613986","DOIUrl":"10.1085/jgp.202613986","url":null,"abstract":"<p><p>ATP-sensitive potassium (KATP) channels are among the most expressed ion channels in skeletal muscle sarcolemma. While all KATP subunits can be detected in skeletal muscles, transcripts are enriched for KCNJ11 and ABCC9, suggesting that noncanonical Kir6.2/SUR2A assembly may constitute the majority of sarcolemmal KATP channels, but there has been no systematic dissection of KATP makeup in skeletal muscles. Here, we used a unique collection of murine lines selectively lacking specific channel-forming subunits (knockout, KO), and combined a genetic and pharmacological approach to determine which subunits of KATP channels are functionally relevant for skeletal muscle contraction. Under fatiguing conditions, isometric tetanic contraction experiments on murine extensor digitorum longus (EDL) revealed delayed loss of stimulated forces, and significant development of unstimulated forces, in muscles lacking Kir6.2 or SUR2 subunits, whereas loss of the SUR1 subunit did not impact muscle functionality. While pharmacological inhibition of sarcolemmal channels with glibenclamide causes comparable development of unstimulated force in wild-type muscles, acute pharmacological modulators of sarcolemmal KATP channels in isolated Kir6.2 or SUR2 KO muscles resulted in no changes in contractility properties, further consistent with no additional sarcolemmal KATP channels including Kir6.1 or SUR1 subunits. Our data show that fast-twitch skeletal muscle EDL relies on functional noncanonical KATP channels only made by ABCC9 (SUR2) and KCNJ11 (Kir6.2) gene products for contraction and suggest that similar contractile deficits will be present in ABCC9-dependent intellectual disability myopathy syndrome and KCNJ11-dependent congenital hyperinsulinism.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147977278","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":"Will the real KATP please stand up? Kir6.2/SUR2A takes the stand in the tiring case of skeletal muscle fatigue.","authors":"Richard D Rainbow, Richard Barrett-Jolley","doi":"10.1085/jgp.202614036","DOIUrl":"https://doi.org/10.1085/jgp.202614036","url":null,"abstract":"<p><p>Scala et al. (https://doi.org/10.1085/jgp.202613986) use combined genetic and pharmacological approaches to demonstrate that Kir6.2/SUR2-containg KATP potassium ion channels are the functionally relevant isoform that modulate contractile behavior of fast-twitch muscle during fatigue.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148254408","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":"Regulation of olfactory chloride and cyclic nucleotide-gated channels by cholesterol.","authors":"Samsudeen Ponissery Saidu, Alexander Kross, Michele Dibattista, Katharina Gaus, Johannes Reisert","doi":"10.1085/jgp.202513963","DOIUrl":"10.1085/jgp.202513963","url":null,"abstract":"<p><p>Odorants in the inhaled air bind to odorant receptors embedded in cilia of olfactory receptor neurons, triggering the opening of the two ciliary olfactory transduction channels; first, a cationic heterotetrameric cAMP-gated channel, followed by an excitatory Ca2+-activated Cl- channel TMEM16B (also called anoctamin 2), which gives rise to a transduction current. While cholesterol is known to modulate ion channels, its effect on the olfactory channels, specifically TMEM16B, is unclear. We addressed how membrane cholesterol regulates these transduction channels. We heterologously expressed the main subunit of the olfactory cyclic nucleotide-gated (CNG) channel, CNGA2, and the Cl- channel TMEM16B and recorded their function in control, cholesterol-depleted, and cholesterol-enriched membranes. Maximal cAMP- or Ca2+-evoked currents were not altered by varying cholesterol levels. TMEM16B showed a progressive reduction in current upon repeated exposure to Ca2+ (\"rundown\"), which was accelerated in cholesterol-depleted membranes but decelerated in cholesterol-enriched patches when compared with control patches. Maximal cAMP-gated currents were stable over time, but their sensitivity was altered, with lower and higher cholesterol levels increasing and decreasing the channel's sensitivity, respectively. Cholesterol depletion of patches excised from mouse olfactory cilia containing native channels entirely abolished the TMEM16B current, while the maximal current of the native CNG channel remained unaltered. Reduced cholesterol did not change the sensitivity of the native CNG channel. Thus, while both olfactory transduction channels are sensitive to changes in membrane cholesterol in differing ways, the precise channel stoichiometry and the specific membrane environment also contribute to their function.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13321229/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148304069","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":"A kinetic trap mechanism underlies hHv1 inhibition by NZ-58.","authors":"Adam Feher, Geraldo Jorge Domingos, Martina Piga, Tihomir Tomašič, Nace Zidar, Zoltan Varga","doi":"10.1085/jgp.202513945","DOIUrl":"10.1085/jgp.202513945","url":null,"abstract":"<p><p>A recent publication by our research team has introduced a novel group of hHv1 inhibitors, the 5-phenyl-2-aminoimidazoles. To guide rational drug design of selective derivatives, our goal was to map the molecular mechanism of compound 13 (i.e., NZ-58), a potent member of the series. For this, we utilized site-directed mutagenesis and conventional patch-clamp technique. Applying NZ-58 at various membrane potentials, and using different pulse frequencies, we could unveil the binding mode, which showed closed-state inhibition and no use dependence. The changes in inhibition of mutated hHv1 constructs confirmed the binding pocket suggested by molecular docking comprising countercharges D112 and D185. Combining the results of ionic and gating current measurements revealed an interesting molecular mechanism that traps the S4 helix. Knowing the interacting partners of NZ-58, this mechanism aligned well with previously found functional models of hHv1. By integrating pharmacological and biophysical perspectives, this work lays the groundwork for future advancements in rational drug design.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148044870","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":"Long-term inactivation mediated by different FGF-A homologues on heterologously expressed NaV1.2 currents.","authors":"Yenisleidy Lorenzo-Ceballos, Pedro L Martinez-Espinosa, Xiao-Ming Xia, Christopher J Lingle","doi":"10.1085/jgp.202613985","DOIUrl":"10.1085/jgp.202613985","url":null,"abstract":"<p><p>A-isoforms of cytosolic growth factor homologous factors (FGF11-14) mediate long-term inactivation (LTI) of voltage-dependent sodium (NaV) channels. LTI is a rapid onset process that is competitive with the fast inactivation (IF) intrinsic to NaV channels, with little or no interconversion between inactivated states. Since recovery from LTI is orders of magnitude slower than recovery from IF, repetitive depolarizations lead to use-dependent accumulation of NaV channels in slow recovery states, thereby limiting NaV availability during trains of action potentials. Of the two or more N-terminal splice variants of the various FGF homologues, LTI specifically arises only from the A-isoform of each FGF subunit. Although there is substantial homology among the N termini of the four FGF-A paralogs, to what extent LTI generated by the different FGF-A homologues may differ has not been directly addressed. Here, using heterologous expression in HEK293T cells, we evaluate the kinetics of onset and recovery from LTI mediated by hFGF11-14A in association with WT hNaV1.2. We also use NaV channels with fast inactivation removed (IQM) to measure rates of LTI-mediated inactivation and recovery in the absence of intrinsic fast inactivation. Among the four FGF-A homologues, we identify two features that can differ. First, different FGF-A's differ in the rate of onset into LTI. Second, the rate of recovery from inactivation, whether measured with WT NaV1.2 or with NaV1.2_IQM, differs among FGF-A's. The functional differences among FGF-A homologues differentially sculpt the time course and extent of use-dependent accumulation of NaV1.2 channels into LTI. This, in turn, would differentially impact on NaV availability during repetitive firing.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13196787/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147989282","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}