Journal of General Physiology最新文献

Differential state-dependent Nav1.8 inhibition by suzetrigine, LTGO-33, and A-887826.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-07-07 Epub Date: 2025-03-26 DOI: 10.1085/jgp.202413719

Sooyeon Jo, Akie Fujita, Tomás Osorno, Robert G Stewart, Patric M Vaelli, Bruce P Bean

{"title":"Differential state-dependent Nav1.8 inhibition by suzetrigine, LTGO-33, and A-887826.","authors":"Sooyeon Jo, Akie Fujita, Tomás Osorno, Robert G Stewart, Patric M Vaelli, Bruce P Bean","doi":"10.1085/jgp.202413719","DOIUrl":"10.1085/jgp.202413719","url":null,"abstract":"Nav1.8 sodium channels are expressed in pain-sensing neurons, and some Nav1.8 inhibitors significantly reduce pain in clinical trials. Several Nav1.8 inhibitors have an unusual state dependence whereby inhibition is relieved by depolarization. We compared the state-dependent action of several Nav1.8 channel inhibitors to test whether inhibition is relieved during action potential (AP) firing under physiological conditions to produce \"reverse use dependence.\" A-887826 inhibition was substantially relieved by AP waveforms applied at 20 Hz at 37°C. In contrast, there was no relief during AP trains with suzetrigine (VX-548) or LTGO-33, even though inhibition could be effectively removed by long, strong depolarizations. These differences were explained by differences in the voltage dependence and kinetics with which the compounds dissociate from depolarized channels and rebind to resting state channels. Suzetrigine required the strongest depolarizations for relief (midpoint +33 mV) and relief was slow (tau >300 ms at +20 mV), so almost no relief occurred during an AP waveform. Relief from A-887826 required weaker depolarizations (midpoint +13 mV) and was much faster, so some relief occurred during each AP waveform and accumulated during 20-Hz trains. LTGO-33 required the weakest depolarizations for relief (midpoint -11 mV) and relief was even faster than for A-887826, but reinhibition between AP waveforms was far faster than for A-887826, so that relief did not accumulate during AP trains at 20 Hz. The results show that, unlike A-887826, there is no use-dependent relief of inhibition by suzetrigine or LTGO-33 with physiological voltage waveforms at physiological temperatures, but each for different reasons.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11938940/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143712189","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}

引用次数: 0

Mechanisms underlying the distinct K+ dependencies of periodic paralysis. 周期性麻痹的不同 K+ 依赖性的内在机制。

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-02-04 DOI: 10.1085/jgp.202413610

Brent D Foy, Chris Dupont, Phillip V Walker, Kirsten Denman, Kathrin L Engisch, Mark M Rich

{"title":"Mechanisms underlying the distinct K+ dependencies of periodic paralysis.","authors":"Brent D Foy, Chris Dupont, Phillip V Walker, Kirsten Denman, Kathrin L Engisch, Mark M Rich","doi":"10.1085/jgp.202413610","DOIUrl":"10.1085/jgp.202413610","url":null,"abstract":"Patients with periodic paralysis have attacks of weakness precipitated by depolarization of muscle. Each form of periodic paralysis is associated with unique changes in serum K+ during attacks of weakness. In hypokalemic periodic paralysis (hypoKPP), the mutation-induced gating pore current causes weakness associated with low serum K+. In hyperkalemic periodic paralysis (hyperKPP), mutations increase a non-inactivating Na+ current (Na persistent or NaP), which causes weakness associated with elevation of extracellular K+. In Andersen-Tawil syndrome, mutations causing loss of Kir channel function cause weakness associated with either low or high K+. We developed a computer model to address two questions: (1) What mechanisms are responsible for the distinct K+ dependencies of muscle depolarization-induced weakness in the three forms of periodic paralysis? (2) Why does extracellular K+ become elevated during attacks of weakness in hyperKPP, reduced in hypoKPP, and both elevated and reduced in Andersen-Tawil syndrome? We experimentally tested the model assumptions about resting potential in normal K+ solution in hyperKPP and hypoKPP. Recreating the distinct K+ dependence of all three forms of periodic paralysis required including the K+ and voltage dependence of current through Kir channels, the extracellular K+ and intracellular Na+ dependence of the Na/K ATPase activity, and the distinct voltage dependencies of the gating pore current and NaP. A key factor determining whether muscle would depolarize was the direction of small net K+ and net Na+ fluxes, which altered ion concentrations over hours. Our findings may aid in development of novel therapy for diseases with dysregulation of muscle excitability.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 3","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11792889/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143191162","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}

引用次数: 0

Marfan syndrome cardiomyocytes show excess of titin isoform N2BA and extended sarcomeric M-band.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-03-10 DOI: 10.1085/jgp.202413690

Dalma Kellermayer, Cristina M Șulea, Hedvig Tordai, Kálmán Benke, Miklós Pólos, Bence Ágg, Roland Stengl, Máté Csonka, Tamás Radovits, Béla Merkely, Zoltán Szabolcs, Miklós Kellermayer, Balázs Kiss

{"title":"Marfan syndrome cardiomyocytes show excess of titin isoform N2BA and extended sarcomeric M-band.","authors":"Dalma Kellermayer, Cristina M Șulea, Hedvig Tordai, Kálmán Benke, Miklós Pólos, Bence Ágg, Roland Stengl, Máté Csonka, Tamás Radovits, Béla Merkely, Zoltán Szabolcs, Miklós Kellermayer, Balázs Kiss","doi":"10.1085/jgp.202413690","DOIUrl":"10.1085/jgp.202413690","url":null,"abstract":"Marfan syndrome (MFS) is an autosomal dominant disease caused by mutations in the gene (FBN1) of fibrillin-1, a major determinant of the extracellular matrix (ECM). Functional impairment in the cardiac left ventricle (LV) of these patients is usually a consequence of aortic valve disease. However, LV passive stiffness may also be affected by chronic changes in mechanical load and ECM dysfunction. Passive stiffness is determined by the giant sarcomeric protein titin that has two main cardiac splice isoforms: the shorter and stiffer N2B and the longer and more compliant N2BA. Their ratio is thought to reflect myocardial response to pathologies. Whether this ratio and titin's sarcomeric layout is altered in MFS is currently unknown. Here, we studied LV samples from MFS patients carrying FBN1 mutation, collected during aortic root replacement surgery. We found that the N2BA:N2B titin ratio was elevated, indicating a shift toward the more compliant isoform. However, there were no alterations in the total titin content compared with healthy humans based on literature data. Additionally, while the gross sarcomeric structure was unaltered, the M-band was more extended in the MFS sarcomere. We propose that the elevated N2BA:N2B titin ratio reflects a general adaptation mechanism to the increased volume overload resulting from the valvular disease and the direct ECM disturbances so as to reduce myocardial passive stiffness and maintain diastolic function in MFS.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 3","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11893164/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143588307","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}

引用次数: 0

Novel Ca2+ wave mechanisms in cardiac myocytes revealed by multiscale Ca2+ release model.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-03-06 DOI: 10.1085/jgp.202413543

Morris Vysma, James S Welsh, Derek R Laver

{"title":"Novel Ca2+ wave mechanisms in cardiac myocytes revealed by multiscale Ca2+ release model.","authors":"Morris Vysma, James S Welsh, Derek R Laver","doi":"10.1085/jgp.202413543","DOIUrl":"10.1085/jgp.202413543","url":null,"abstract":"Integrating cellular sarcoplasmic reticulum (SR) Ca2+ release with the known Ca2+ activation properties of RyR2s remains challenging. The sharp increase in SR Ca2+ permeability above a threshold SR luminal [Ca2+] is not reflected in RyR2 kinetics from single-channel studies. Additionally, the current paradigm that global Ca2+ release (Ca2+ waves) arises from interacting local events (Ca2+ sparks) faces a key issue that these events rarely activate neighboring sites. We present a multiscale model that reproduces Ca2+ sparks and waves in skinned ventricular myocytes using experimentally validated RyR2 kinetics. The model spans spatial domains from 10-8 to 10-4 m and timescales from 10-6 to 10 s. Ca2+ release sites are distributed in cubic voxels (0.25-µm sides) informed by super-resolution micrographs. We use parallel computing to calculate Ca2+ transport, diffusion, and buffering. Substantial increases in SR Ca2+ release occur, and Ca2+ waves initiate when Ca2+ sparks become prolonged above a threshold SR [Ca2+]. These prolonged events (Ca2+ embers) are much more likely than Ca2+ sparks to activate release from neighboring sites and accumulate increases in cytoplasmic [Ca2+] along with an associated fall in Ca2+ buffering power. This primes the cytoplasm for Ca2+-induced Ca2+ release (CICR) that produces Ca2+ waves. Thus, Ca2+ ember formation and CICR are both essential for initiation and propagation of Ca2+ waves. Cell architecture, along with the differential effects of RyR2 opening and closing rates, collectively determines the SR [Ca2+] threshold for Ca2+ embers, waves, and the phenomenon of store overload-induced Ca2+ release.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 3","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11893170/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143568862","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}

引用次数: 0

A complete set of rate constants for a transporter's catalytic cycle.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-02-21 DOI: 10.1085/jgp.202513766

Michael L Jennings

引用次数: 0

How the Blind Watchmaker messed around with potassium channels.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-03-19 DOI: 10.1085/jgp.202513783

Lawrence Salkoff

引用次数: 0

Ctenophores and parahoxozoans independently evolved functionally diverse voltage-gated K+ channels.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-03-18 DOI: 10.1085/jgp.202413740

Benjamin T Simonson, Zhaoyang Jiang, Joseph F Ryan, Timothy Jegla

{"title":"Ctenophores and parahoxozoans independently evolved functionally diverse voltage-gated K+ channels.","authors":"Benjamin T Simonson, Zhaoyang Jiang, Joseph F Ryan, Timothy Jegla","doi":"10.1085/jgp.202413740","DOIUrl":"10.1085/jgp.202413740","url":null,"abstract":"The ctenophore species Mnemiopsis leidyi is known to have a large set of voltage-gated K+ channels, but little is known about the functional diversity of these channels or their evolutionary history in other ctenophore species. Here, we searched the genomes of two additional ctenophore species, Beroe ovata and Hormiphora californensis, for voltage-gated K+ channels and functionally expressed a subset of M. leidyi channels. We found that the last common ancestor of these three disparate ctenophore lineages probably had at least 33 voltage-gated K+ channels. Two of these genes belong to the EAG family, and the remaining 31 belong to the Shaker family and form a single clade within the animal/choanoflagellate Shaker phylogeny. We additionally found evidence for 10 of these Shaker channels in a transcriptome of the early branching ctenophore lineage Euplokamis dunlapae, suggesting that the diversification of these channels was already underway early in ctenophore evolution. We functionally expressed 16 Mnemiopsis Shakers and found that they encode a diverse array of voltage-gated K+ conductances with functional orthologs for many classic Shaker family subtypes found in cnidarians and bilaterians. Analysis of Mnemiopsis transcriptome data show these 16 Shaker channels are expressed in a wide variety of cell types, including neurons, muscle, comb cells, and colloblasts. Ctenophores therefore appear to have independently evolved much of the voltage-gated K+ channel diversity that is shared between cnidarians and bilaterians.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 3","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11917167/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143658984","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}

引用次数: 0

Projections from ventral hippocampus to nucleus accumbens' cholinergic neurons are altered in depression.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-03-07 DOI: 10.1085/jgp.202413693

Lucian Medrihan, Margarete G Knudsen, Tatiana Ferraro, Pedro Del Cioppo Vasques, Yevgeniy Romin, Sho Fujisawa, Paul Greengard, Ana Milosevic

{"title":"Projections from ventral hippocampus to nucleus accumbens' cholinergic neurons are altered in depression.","authors":"Lucian Medrihan, Margarete G Knudsen, Tatiana Ferraro, Pedro Del Cioppo Vasques, Yevgeniy Romin, Sho Fujisawa, Paul Greengard, Ana Milosevic","doi":"10.1085/jgp.202413693","DOIUrl":"10.1085/jgp.202413693","url":null,"abstract":"The cholinergic interneurons (ChIs) of the nucleus accumbens (NAc) have a critical role in the activity of this region, specifically in the context of major depressive disorder. To understand the circuitry regulating this behavior, we sought to determine the areas that directly project to these interneurons by utilizing the monosynaptic cell-specific tracing technique. Mapping showed monosynaptic projections that are exclusive to NAc ChIs. To determine if some of these projections are altered in a depression mouse model, we used mice that do not express the calcium-binding protein p11 specifically in ChIs (ChAT-p11 cKO) and display a depressive-like phenotype. Our data demonstrated that while the overall projection areas remain similar between wild type and ChAT-p11 cKO mice, the number of projections from the ventral hippocampus (vHIP) is significantly reduced in the ChAT-p11 cKO mice. Furthermore, using optogenetics and electrophysiology we showed that glutamatergic projections from vHIP to NAc ChIs are severely altered in mutant mice. These results show that specific alterations in the circuitry of the accumbal ChIs could play an important role in the regulation of depressive-like behavior, reward-seeking behavior in addictions, or psychiatric symptoms in neurodegenerative diseases.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 3","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11893161/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143574619","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}

引用次数: 0

Examination of conformational dynamics of AdiC transporter with fluorescence-polarization microscopy.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-02-20 DOI: 10.1085/jgp.202413709

John H Lewis, Yufeng Zhou, Zhe Lu

{"title":"Examination of conformational dynamics of AdiC transporter with fluorescence-polarization microscopy.","authors":"John H Lewis, Yufeng Zhou, Zhe Lu","doi":"10.1085/jgp.202413709","DOIUrl":"10.1085/jgp.202413709","url":null,"abstract":"To understand the mechanism underlying the ability of individual AdiC molecules to transport arginine and agmatine, we used a recently developed high-resolution single-molecule fluorescence-polarization microscopy method to investigate conformation-specific changes in the emission polarization of a bifunctional fluorophore attached to an AdiC molecule. With this capability, we resolved AdiC's four conformations characterized by distinct spatial orientations in the absence or presence of the two substrates, and furthermore, each conformation's two energetic states, totaling 24 states. From the lifetimes of individual states and state-to-state transition probabilities, we determined 60 rate constants characterizing the transitions and 4 KD values characterizing the interactions of AdiC's two sides with arginine and agmatine, quantitatively defining a 24-state model. This model satisfactorily predicts the observed Michaelis-Menten behaviors of AdiC. With the acquired temporal information and existing structural information, we illustrated how to build an experiment-based integrative 4D model to capture and exhibit the complex spatiotemporal mechanisms underlying facilitated transport of substrates. However, inconsistent with what is expected from the prevailing hypothesis that AdiC is a 1:1 exchanger, all observed conformations transitioned among themselves with or without the presence of substrates. To corroborate this unexpected finding, we performed radioactive flux assays and found that the results are also incompatible with the hypothesis. As a technical advance, we showed that a monofunctional and the standard bifunctional fluorophore labels report comparable spatial orientation information defined in a local frame of reference. Here, the successful determination of the complex conformation-kinetic mechanism of AdiC demonstrates the unprecedented resolving power of the present microscopy method.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 3","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11841622/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143460854","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}

引用次数: 0

The architecture of invaginating rod synapses slows glutamate diffusion and shapes synaptic responses.

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2025-05-05 Epub Date: 2025-02-28 DOI: 10.1085/jgp.202413746

Wallace B Thoreson, Thomas M Bartol, Nicholas H Conoan, Jeffrey S Diamond

{"title":"The architecture of invaginating rod synapses slows glutamate diffusion and shapes synaptic responses.","authors":"Wallace B Thoreson, Thomas M Bartol, Nicholas H Conoan, Jeffrey S Diamond","doi":"10.1085/jgp.202413746","DOIUrl":"10.1085/jgp.202413746","url":null,"abstract":"Synapses of retinal rod photoreceptors involve deep invaginations occupied by second-order rod bipolar cell (RBP) and horizontal cell (HC) dendrites. Synaptic vesicles are released into this invagination at multiple sites beneath an elongated presynaptic ribbon. To study the impact of this architecture on glutamate diffusion and receptor activity, we reconstructed four rod terminals and their postsynaptic dendrites from serial electron micrographs of the mouse retina. We incorporated these structures into anatomically realistic Monte Carlo simulations of neurotransmitter diffusion and receptor activation. By comparing passive diffusion of glutamate in realistic structures with geometrically simplified models, we found that glutamate exits anatomically realistic synapses 10-fold more slowly than previously predicted. Constraining simulations with physiological data, we modeled activity of EAAT5 glutamate transporters in rods, AMPA receptors on HC dendrites, and metabotropic glutamate receptors (mGluR6) on RBP dendrites. Simulations suggested that ∼3,000 EAAT5 populate rod membranes. While uptake by surrounding glial Müller cells retrieves most glutamate released by rods, binding and uptake by EAAT5 influence RBP kinetics. Glutamate persistence allows mGluR6 on RBP dendrites to integrate the stream of vesicles released by rods in darkness. Glutamate's tortuous diffusional path confers quantal variability, as release from nearby ribbon sites exerts larger effects on RBP and HC receptors than release from more distant sites. Temporal integration supports slower sustained release rates, but additional quantal variability can impede postsynaptic detection of changes in release produced by rod light responses. These results show an example of the profound impact that synaptic architecture can have on postsynaptic responses.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"157 3","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11869902/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143525136","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}

引用次数: 0