Journal of General Physiology最新文献

{"title":"An epilepsy-associated KV3.1 potassium channel variant acts via dominant-positive effect.","authors":"Jerome Clatot, Hubert Monnerie, Axel Panzer, Konrad Platzer, Ethan M Goldberg","doi":"10.1085/jgp.202513962","DOIUrl":"10.1085/jgp.202513962","url":null,"abstract":"<p><p>Variants in KCNC1 encoding the voltage-gated potassium (K+) channel subunit KV3.1 are an emerging cause of a spectrum of neurological disease including developmental delay/intellectual disability, ataxia, myoclonus, and epilepsy, including progressive myoclonus epilepsy and developmental and epileptic encephalopathy. Here, we report novel biophysical properties of a recurrent de novo missense variant in KCNC1 c.1196C>T (p.Thr399Met) associated with epilepsy, mild developmental delay, and nonprogressive ataxia. The variant is localized to the highly conserved pore region of the channel, and voltage-clamp electrophysiological recording demonstrated a complete loss of function, as seen in more severe forms of KCNC1-related disorders. When expressed with wild-type (WT) to mimic the heterozygous state of the variant as would occur in a disease context, current density was not markedly reduced; however, resulting currents displayed a ∼20 mV hyperpolarizing shift of the voltage dependence of activation along with slowed deactivation kinetics, consistent with gain of function. In order to better understand this \"dominant-positive effect\" exerted on the WT channel, we co-expressed the KV3.1 p.Thr399Met variant with the recurrent p.Ala421Val variant known to act via loss of function with near-complete absence of current and associated with severe KCNC1-related disease. Co-expression of the two nonfunctioning variants led to a mild rescue of K+ current compared with the KCNC1-p.Ala421Val variant alone, further supporting a dominant-positive effect. Both KCNC1-p.Thr399Met and p.Ala421Val displayed trafficking deficiency. These results suggest that inclusion of the p.Thr399Met variant in heterotetrameric KV3 channels alters the gating kinetics of WT channel subunits, and highlight the unique features of this variant. The apparent complete loss of function of the p.Thr399Met variant when expressed alone is inconsistent with the relatively mild clinical presentation of the patient, subsequently explained via the \"dominant-positive\" action when combined with WT subunits.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 5","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13296753/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148320449","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":"Equivalent gain-of-function variants in KCNK3 and KCNK9 and their contribution to distinct TASK K2P channelopathies.","authors":"Kate M Crowther, Thibault R H Jouen-Tachoire, Peter Proks, Peter Rory Hall, Emma L Veale, Janina Sörmann, Karin E J Rödström, Thomas Müller, Saskia B Wortmann, Nina Barisic, Natalie Hauser, Vincenzo Salpietro, RaeLynn Forsyth, Linford Williams, Nora Derrabi, Carlos A Bacino, Jill A Rosenfeld, Henry Houlden, Simon Newstead, Caroline F Wright, James Fasham, Alistair A Mathie, Reza Maroofian, Stephen J Tucker","doi":"10.1085/jgp.202613989","DOIUrl":"10.1085/jgp.202613989","url":null,"abstract":"<p><p>Gain-of-function (GoF) missense variants in the two-pore domain (K2P) K+ channel TASK-1 (KCNK3) result in developmental delay with sleep apnea (DDSA), a neurodevelopmental channelopathy, while loss-of-function (LoF) variants cause pulmonary arterial hypertension. However, for the related TASK-3 channel (KCNK9), both LoF and GoF variants underlie a distinct neurodevelopmental disorder, KCNK9 imprinting syndrome (KIS). The relationship between genotype and phenotype in these disorders is further complicated because TASK-1 and TASK-3 can co-assemble into heteromeric channels with distinct functional properties. Here, we report additional patients with missense variants in KCNK3 and KCNK9 and investigate the effect of four novel genetic variants on the functional properties of homomeric and heteromeric TASK channels. Interestingly, two of these new pathogenic GoF variants (R131H and L122V) are found in both TASK-1 and TASK-3 and have equivalent functional effects on heteromeric TASK-1/TASK-3 channel activity, yet result in different clinical phenotypes. We have also determined a cryo-EM structure for the pathogenic L122V mutant TASK-3 channel, which suggests that subtle changes in gating and permeation within the inner cavity are responsible for its activatory effect. Overall, these results highlight the dominant role that homomeric TASK channels likely play in defining their associated channelopathies as well as the complexity of interpreting K+ channel dysfunction in pathophysiology.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 5","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13446175/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148681121","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, hibernation, and inactivation of voltage-gated Na channels.","authors":"John S Willis","doi":"10.1085/jgp.202513923","DOIUrl":"10.1085/jgp.202513923","url":null,"abstract":"<p><p>At 6°C, when atria of most mammals cannot be activated, isolated atria of 13-lined ground squirrels, a model hibernator, have intracellular action potentials (AP) that are enlarged in duration and overshoot. Avoidance or delay of inactivation was postulated as playing a role in the retention and enhancement of the AP. In a published genomic study, the TTX-sensitive voltage-gated Na channel Nav1.2 was identified as being \"more rapidly evolving.\" In published sequences of this channel in five species of hibernators, a methionine replaces leucine in the sequence, NQATL, of transmembrane segment six of domain one (DIS6), but not in any of the 10 species of nonhibernating placental mammals. Among other TTX-sensitive channels, Nav1.1 possesses the same mutation in 8 of 9 hibernators as does Nav1.4 in bats and Nav1.3 in groundhogs, but those isoforms do not possess the mutation in any nonhibernator. All four channels occur in the heart muscle. While far less abundant than Nav1.5, they may supplement it during physiological stress. In a model of Nav1.4A, methionine replacing leucine in NEATL (homolog of NQATL) was found to form two hydrogen bonds with the asparagine of NEATL. Leucine formed none. That asparagine is highly conserved in all members of the Nav1 family and mpdulates both fast and slow inactivation. Hypothesis: At temperatures approaching 0°C, greater stickiness of methionine enhances the nearby arginine's modulation of fast and slow inactivation, thus helping to sustain excitability in hearts of hibernators that possess the M-for-L mutation.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 5","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13340909/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148406900","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":"Label-free real-time imaging of mitochondrial matrix volume changes and permeability transition in living cells.","authors":"Yaw Akosah, Ioannis Azoidis, Dane D Jensen, Paolo Bernardi, Evgeny V Pavlov","doi":"10.1085/jgp.202613979","DOIUrl":"10.1085/jgp.202613979","url":null,"abstract":"<p><p>Along with the membrane potential and respiration, mitochondrial matrix volume is a critical parameter that determines mitochondrial function. Mitochondria undergo constant changes in matrix volume and crista dynamics, and in processes that are critical for normal metabolic rates and pathophysiological responses. Changes in matrix volume cannot be easily measured by conventional fluorescence imaging techniques due to the size of the suborganellar structures, which are below resolution. This challenge was successfully resolved in studies of isolated mitochondria with the use of scattered light. Here, we use dark-field imaging, which relies on scattered light contrast, to measure matrix volume dynamics in living cells. We demonstrate that mitochondrial volume changes can be easily detected as changes in intensity of the scattered light following matrix volume modulation with K+ ionophores or by onset of the permeability transition. Specifically, we found that stimulation of K+ influx leads to an increase in mitochondrial matrix volume, while stimulation of K+ efflux leads to matrix shrinkage, and that activation of the permeability transition leads to high-amplitude mitochondrial swelling in wild-type but not in cells lacking subunit c of ATP synthase. These results directly demonstrate the dynamic nature of mitochondrial matrix volume and its link to physiological and pathological ion transport.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 5","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148354727","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":"Crying time: Modeling tear formation.","authors":"Alan M Weinstein","doi":"10.1085/jgp.202614026","DOIUrl":"https://doi.org/10.1085/jgp.202614026","url":null,"abstract":"<p><p>Verma et al. (https://doi.org/10.1085/jgp.202513958) provide a mathematical model of the ocular surface that can be used to guide assessment and selection of treatment options for dry eye disease, favoring volume-directed over cell-directed therapies.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 5","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148762225","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 mitochondrial swelling channel.","authors":"Elizabeth A Jonas, Eleanora Margulis, Ava Yu, Nelli Mnatsakanyan","doi":"10.1085/jgp.202614066","DOIUrl":"10.1085/jgp.202614066","url":null,"abstract":"<p><p>Early bioenergeticists who described the principles of chemiosmosis were aware that swelling of mitochondria was a likely and even frequent event, based on the large electrochemical gradient of K+ ions across the mitochondrial inner membrane. Swelling could be measured as a change in electron density by electron microscopy or by spectrophotometry in isolated mitochondria. The mitochondrial permeability transition (mPT) was originally described as an acute swelling change in mitochondria, later determined to be caused by the rapid opening of a pore (mPTP) defined biophysically and pharmacologically as a Ca2+- and voltage-dependent, cyclosporine A-sensitive large-conductance channel. The identity of the pore is controversial, but the ATP synthase c-subunit is a major candidate. In their breakthrough study (Akosah et al. https://doi.org/10.1085/jgp.202613979), they establish a novel dark-field imaging approach, allowing detection of mitochondrial swelling in living cells. Swollen mitochondria exhibit decreased light scattering and, therefore, microscopically \"disappear.\" The cell-based imaging technique enables dissection of two separate processes, mitochondrial swelling, and depolarization. The authors demonstrate that K+ influx causes swelling but not immediate mitochondrial depolarization in wild-type cells, whereas in ATP synthase c-subunit knockout cells, Ca2+-dependent mitochondrial depolarization occurs without swelling, suggesting a lack of K+ influx. The results suggest that the ATP synthase c-subunit channel is the key member of a channel complex constituting the \"swelling channel\" of the mPTP.</p>","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"158 5","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148714754","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":"Unfurling the role of dysferlin's C2A domain.","authors":"Ben Short","doi":"10.1085/jgp.202614054","DOIUrl":"10.1085/jgp.202614054","url":null,"abstract":"<p><p>JGP study (Lukyanenko et al. https://doi.org/10.1085/jgp.202513844) shows that, in the absence of full-length dysferlin, its C2A domain alone can support normal Ca2+ signaling and sarcolemma repair, suggesting that it could be used in gene replacement therapies.</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":"148229087","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":"Extrinsic inputs underscore heterogeneities of ELL pyramidal cell neural activity in awake, behaving weakly electric fish.","authors":"Amin Akhshi, Myriah Haggard, Mariana M Marquez, Saeed Farjami, Maurice J Chacron, Anmar Khadra","doi":"10.1085/jgp.202513841","DOIUrl":"10.1085/jgp.202513841","url":null,"abstract":"<p><p>Heterogeneity in spiking activity is ubiquitous among neurons even within a given cell type. To date, the relative contributions of extrinsic mechanisms (e.g., synaptic bombardment), intrinsic mechanisms (e.g., conductances), and cell morphology toward determining spiking activity remain poorly understood. Here, we addressed this important question using a combination of extracellular in vivo recordings of electrosensory pyramidal cells within weakly electric fish with computational modeling. Specifically, by varying parameters of a conductance-based computational model, we successfully reproduced the highly heterogeneous spiking activities seen experimentally. Model parameters that varied the most were then used to gauge the relative contributions of extrinsic vs. intrinsic mechanisms. Overall, extrinsic synaptic input was predicted to be the main factor accounting for spiking heterogeneity. We tested this prediction experimentally by performing two different manipulations: (1) pharmacologically inactivating feedback from higher brain areas and (2) applying the neuromodulator serotonin. Our model showed that feedback inactivation should reduce spiking heterogeneity, whereas serotonin application should increase it, two predictions that were corroborated experimentally. Importantly, for serotonin application, increased heterogeneity occurred despite a strong reduction in intrinsic membrane conductance, further demonstrating that extrinsic synaptic input is the primary determinant of spiking heterogeneity in vivo. Taken together, our results demonstrate that devising a computational model to capture spiking heterogeneities in vivo and assessing which parameters are responsible can successfully determine the relative contributions of extrinsic inputs, intrinsic properties, and neural morphology.</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":"147789747","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":"Dysferlin's C2A domain supports normal Ca2+ signaling and membrane repair in dysferlin-null myofibers.","authors":"Valeriy Lukyanenko, Joaquin Muriel, Kassidy K Banford, Thomas A Kwiatkowski, Hannah R Bulgart, Noah Weisleder, Robert J Bloch","doi":"10.1085/jgp.202513844","DOIUrl":"10.1085/jgp.202513844","url":null,"abstract":"<p><p>Dysferlin is required for the health of skeletal muscle, where it mediates at least two seemingly distinct processes, repair of the sarcolemmal membrane and stabilization of Ca2+ release after injury. Dysferlin is a ∼230-kDa protein comprised of multiple C2 domains, Fer and Dysf domains, and a transmembrane domain that anchors it to the transverse tubule membrane at the triad junction (TJ). Here we show that replacing C2A with other C2 domains yields fusion proteins that are less active in supporting Ca2+ signaling than WT dysferlin. We also show that the most N-terminal of dysferlin's C2 domains, C2A (DysfC2A), is sufficient to support normal Ca2+ signaling and sarcolemmal repair in dysferlin-null muscle, though it accumulates at TJs inefficiently. The C2A domains of myoferlin and PKCα, though homologous, are less active. The C2 domain of PKCα (PKCαC2) targets the TJ more efficiently than DysfC2A, however. Fusion proteins containing one or two PKCαC2 domains accumulate at the TJ and are active in sarcolemmal membrane repair, but they do not support normal Ca2+ signaling unless linked to DysfC2A Control of Ca2+ signaling is fully restored when the PKCαC2 domain, alone or in pairs, is linked to DysfC2A. This suggests that the DysfC2A is sufficient to support two major functions of dysferlin in skeletal muscle, and that its effect on Ca2+ signaling is specific. We propose that the PKCαC2-PKCαC2-DysfC2A fusion protein is a promising candidate for future viral gene therapy treatment for dysferlinopathy.</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":"147943797","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":"Structural determinants at KCNE4 position 145 govern Kv1.3 channel function.","authors":"Magalí Colomer-Molera, Daniel Sastre, Antonio Felipe","doi":"10.1085/jgp.202513936","DOIUrl":"10.1085/jgp.202513936","url":null,"abstract":"<p><p>Kv1.3 channels participate in the activation and proliferation of leukocytes. The KCNE4 regulatory subunit associates with the channel and functions as a negative regulator. KCNE4, via its transmembrane and C-terminal domains, interacts with Kv1.3, impairing forward plasma membrane trafficking, decreasing macroscopic currents, and accelerating slow C-type inactivation of the channel. A negatively charged 145D/E polymorphic variant of KCNE4 has been associated with immune system disorders, such as allergic rhinitis and childhood acute lymphoblastic leukemia. In this work, we investigated the functional effects of these KCNE4 variants on Kv1.3 activity. Both variants similarly impaired forward trafficking of the channel. However, we observed a variant-dependent decrease in Kv1.3 currents with minor kinetic effects. In addition, we explored the effects of different residues at this position and analyzed the importance of the central amino acid of the polymorphism within the anionic (D-D/E-E) triplet. We suggest that the size and charge of the central position of the cluster are crucial for controlling Kv1.3 currents.</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/PMC13189056/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147977275","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}