Journal of General Physiology最新文献_第4页

Epilepsy-associated Kv1.1 channel subunits regulate intrinsic cardiac pacemaking in mice. 癫痫相关 Kv1.1 通道亚基调节小鼠固有的心脏起搏。

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2024-09-02 Epub Date: 2024-07-22 DOI: 10.1085/jgp.202413578

Man Si, Ahmad Darvish, Kelsey Paulhus, Praveen Kumar, Kathryn A Hamilton, Edward Glasscock

{"title":"Epilepsy-associated Kv1.1 channel subunits regulate intrinsic cardiac pacemaking in mice.","authors":"Man Si, Ahmad Darvish, Kelsey Paulhus, Praveen Kumar, Kathryn A Hamilton, Edward Glasscock","doi":"10.1085/jgp.202413578","DOIUrl":"10.1085/jgp.202413578","url":null,"abstract":"The heartbeat originates from spontaneous action potentials in specialized pacemaker cells within the sinoatrial node (SAN) of the right atrium. Voltage-gated potassium channels in SAN myocytes mediate outward K+ currents that regulate cardiac pacemaking by controlling action potential repolarization, influencing the time between heartbeats. Gene expression studies have identified transcripts for many types of voltage-gated potassium channels in the SAN, but most remain of unknown functional significance. One such gene is Kcna1, which encodes epilepsy-associated voltage-gated Kv1.1 K+ channel α-subunits that are important for regulating action potential firing in neurons and cardiomyocytes. Here, we investigated the functional contribution of Kv1.1 to cardiac pacemaking at the whole heart, SAN, and SAN myocyte levels by performing Langendorff-perfused isolated heart preparations, multielectrode array recordings, patch clamp electrophysiology, and immunocytochemistry using Kcna1 knockout (KO) and wild-type (WT) mice. Our results showed that either genetic or pharmacological ablation of Kv1.1 significantly decreased the SAN firing rate, primarily by impairing SAN myocyte action potential repolarization. Voltage-clamp electrophysiology and immunocytochemistry revealed that Kv1.1 exerts its effects despite contributing only a small outward K+ current component, which we term IKv1.1, and despite apparently being present in low abundance at the protein level in SAN myocytes. These findings establish Kv1.1 as the first identified member of the Kv1 channel family to play a role in sinoatrial function, thereby rendering it a potential candidate and therapeutic targeting of sinus node dysfunction. Furthermore, our results demonstrate that small currents generated via low-abundance channels can still have significant impacts on cardiac pacemaking.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"156 9","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11261506/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141735693","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

Kv1.1 channels help set the pace. Kv1.1 通道有助于确定节奏。

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2024-09-02 Epub Date: 2024-08-07 DOI: 10.1085/jgp.202413649

Ben Short

引用次数: 0

ON and OFF starburst amacrine cells are controlled by distinct cholinergic pathways. 星爆肾上腺素细胞的 ON 和 OFF 受控于不同的胆碱能通路。

IF 3.8 2区医学

Journal of General Physiology Pub Date : 2024-08-05 Epub Date: 2024-06-05 DOI: 10.1085/jgp.202413550

Mie Gangi, Takuma Maruyama, Toshiyuki Ishii, Makoto Kaneda

{"title":"ON and OFF starburst amacrine cells are controlled by distinct cholinergic pathways.","authors":"Mie Gangi, Takuma Maruyama, Toshiyuki Ishii, Makoto Kaneda","doi":"10.1085/jgp.202413550","DOIUrl":"10.1085/jgp.202413550","url":null,"abstract":"Cholinergic signaling in the retina is mediated by acetylcholine (ACh) released from starburst amacrine cells (SACs), which are key neurons for motion detection. SACs comprise ON and OFF subtypes, which morphologically show mirror symmetry to each other. Although many physiological studies on SACs have targeted ON cells only, the synaptic computation of ON and OFF SACs is assumed to be similar. Recent studies demonstrated that gene expression patterns and receptor types differed between ON and OFF SACs, suggesting differences in their functions. Here, we compared cholinergic signaling pathways between ON and OFF SACs in the mouse retina using the patch clamp technique. The application of ACh increased GABAergic feedback, observed as postsynaptic currents to SACs, in both ON and OFF SACs; however, the mode of GABAergic feedback differed. Nicotinic receptors mediated GABAergic feedback in both ON and OFF SACs, while muscarinic receptors mediated GABAergic feedback in ON SACs only in adults. Neither tetrodotoxin, which blocked action potentials, nor LY354740, which blocked neurotransmitter release from SACs, eliminated ACh-induced GABAergic feedback in SACs. These results suggest that ACh-induced GABAergic feedback in ON and OFF SACs is regulated by different feedback mechanisms in adults and mediated by non-spiking amacrine cells other than SACs.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"156 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11153316/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141249087","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

Different fluorescent labels report distinct components of spHCN channel voltage sensor movement. 不同的荧光标签报告了 spHCN 通道电压传感器运动的不同组成部分。

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2024-08-05 Epub Date: 2024-07-05 DOI: 10.1085/jgp.202413559

Magdalena N Wojciechowski, Chaseley E McKenzie, Andrew Hung, Alibek Kuanyshbek, Ming S Soh, Christopher A Reid, Ian C Forster

{"title":"Different fluorescent labels report distinct components of spHCN channel voltage sensor movement.","authors":"Magdalena N Wojciechowski, Chaseley E McKenzie, Andrew Hung, Alibek Kuanyshbek, Ming S Soh, Christopher A Reid, Ian C Forster","doi":"10.1085/jgp.202413559","DOIUrl":"10.1085/jgp.202413559","url":null,"abstract":"We used voltage clamp fluorometry to probe the movement of the S4 helix in the voltage-sensing domain of the sea urchin HCN channel (spHCN) expressed in Xenopus oocytes. We obtained markedly different fluorescence responses with either ALEXA-488 or MTS-TAMRA covalently linked to N-terminal Cys332 of the S4 helix. With hyperpolarizing steps, ALEXA-488 fluorescence increased rapidly, consistent with it reporting the initial inward movement of S4, as previously described. In contrast, MTS-TAMRA fluorescence increased more slowly and its early phase correlated with that of channel opening. Additionally, a slow fluorescence component that tracked the development of the mode shift, or channel hysteresis, could be resolved with both labels. We quantitated this component as an increased deactivation tail current delay with concomitantly longer activation periods and found it to depend strongly on the presence of K+ ions in the pore. Using collisional quenching experiments and structural predictions, we established that ALEXA-488 was more exposed to solvent than MTS-TAMRA. We propose that components of S4 movement during channel activation can be kinetically resolved using different fluorescent probes to reveal distinct biophysical properties. Our findings underscore the need to apply caution when interpreting voltage clamp fluorometry data and demonstrate the potential utility of different labels to interrogate distinct biophysical properties of voltage-gated membrane proteins.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"156 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11223168/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141538955","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

Fusion pore flux controls the rise-times of quantal synaptic responses. 融合孔通量控制着量子突触反应的上升时间。

IF 3.8 2区医学

Journal of General Physiology Pub Date : 2024-08-05 Epub Date: 2024-06-11 DOI: 10.1085/jgp.202313484

Meyer B Jackson, Chung-Wei Chiang, Jinbo Cheng

{"title":"Fusion pore flux controls the rise-times of quantal synaptic responses.","authors":"Meyer B Jackson, Chung-Wei Chiang, Jinbo Cheng","doi":"10.1085/jgp.202313484","DOIUrl":"10.1085/jgp.202313484","url":null,"abstract":"The release of neurotransmitter from a single synaptic vesicle generates a quantal response, which at excitatory synapses in voltage-clamped neurons is referred to as a miniature excitatory postsynaptic current (mEPSC). We analyzed mEPSCs in cultured mouse hippocampal neurons and in HEK cells expressing postsynaptic proteins enabling them to receive synaptic inputs from cocultured neurons. mEPSC amplitudes and rise-times varied widely within and between cells. In neurons, mEPSCs with larger amplitudes had longer rise-times, and this correlation was stronger in neurons with longer mean rise-times. In HEK cells, this correlation was weak and unclear. Standard mechanisms thought to govern mEPSCs cannot account for these results. We therefore developed models to simulate mEPSCs and assess their dependence on different factors. Modeling indicated that longer diffusion times for transmitters released by larger vesicles to reach more distal receptors cannot account for the correlation between rise-time and amplitude. By contrast, incorporating the vesicle size dependence of fusion pore expulsion time recapitulated experimental results well. Larger vesicles produce mEPSCs with larger amplitudes and also take more time to lose their content. Thus, fusion pore flux directly contributes to mEPSC rise-time. Variations in fusion pores account for differences among neurons, between neurons and HEK cells, and the correlation between rise-time and the slope of rise-time versus amplitude plots. Plots of mEPSC amplitude versus rise-time are sensitive to otherwise inaccessible properties of a synapse and offer investigators a means of assessing the role of fusion pores in synaptic release.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"156 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11167452/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141302127","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

Mathematical modeling of intracellular osmolarity and cell volume stabilization: The Donnan effect and ion transport. 细胞内渗透压和细胞体积稳定的数学建模：唐南效应和离子传输

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2024-08-05 Epub Date: 2024-07-12 DOI: 10.1085/jgp.202413554

Zahra Aminzare, Alan R Kay

{"title":"Mathematical modeling of intracellular osmolarity and cell volume stabilization: The Donnan effect and ion transport.","authors":"Zahra Aminzare, Alan R Kay","doi":"10.1085/jgp.202413554","DOIUrl":"10.1085/jgp.202413554","url":null,"abstract":"The presence of impermeant molecules within a cell can lead to an increase in cell volume through the influx of water driven by osmosis. This phenomenon is known as the Donnan (or Gibbs-Donnan) effect. Animal cells actively transport ions to counteract the Donnan effect and regulate their volume, actively pumping Na+ out and K+ into their cytosol using the Na+/K+ ATPase (NKA) pump. The pump-leak equations (PLEs) are a system of algebraic-differential equations to model the membrane potential, ion (Na+, K+, and Cl-), and water flux across the cell membrane, which provide insight into how the combination of passive ions fluxes and active transport contribute to stabilizing cell volume. Our broad objective is to provide analytical insight into the PLEs through three lines of investigation: (1) we show that the provision of impermeant extracellular molecules can stabilize the volume of a passive cell; (2) we demonstrate that the mathematical form of the NKA pump is not as important as the stoichiometry for cell stabilization; and (3) we investigate the interaction between the NKA pump and cation-chloride co-transporters (CCCs) on cell stabilization, showing that NCC can destabilize a cell while NKCC and KCC can stabilize it. We incorporate extracellular impermeant molecules, NKA pump, and CCCs into the PLEs and derive the exact formula for the steady states in terms of all the parameters. This analytical expression enables us to easily explore the effect of each of the system parameters on the existence and stability of the steady states.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"156 8","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11247275/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141592119","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

Correction: A dual-clock-driven model of lymphatic muscle cell pacemaking to emulate knock-out of Ano1 or IP3R. 更正：双时钟驱动的淋巴肌细胞起搏模型，以模拟敲除 Ano1 或 IP3R。

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2024-08-05 Epub Date: 2024-07-01 DOI: 10.1085/jgp.20231335506112024c

Edward J Hancock, Scott D Zawieja, Charlie Macaskill, Michael J Davis, Christopher D Bertram

引用次数: 0

Hydrophobic residues in S1 modulate enzymatic function and voltage sensing in voltage-sensing phosphatase. S1 中的疏水残基调节电压感应磷酸酶的酶功能和电压感应。

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2024-07-01 Epub Date: 2024-05-21 DOI: 10.1085/jgp.202313467

Vamseedhar Rayaprolu, Heini M Miettinen, William D Baker, Victoria C Young, Matthew Fisher, Gwendolyn Mueller, William O Rankin, John T Kelley, William J Ratzan, Lee Min Leong, Joshua A Davisson, Bradley J Baker, Susy C Kohout

{"title":"Hydrophobic residues in S1 modulate enzymatic function and voltage sensing in voltage-sensing phosphatase.","authors":"Vamseedhar Rayaprolu, Heini M Miettinen, William D Baker, Victoria C Young, Matthew Fisher, Gwendolyn Mueller, William O Rankin, John T Kelley, William J Ratzan, Lee Min Leong, Joshua A Davisson, Bradley J Baker, Susy C Kohout","doi":"10.1085/jgp.202313467","DOIUrl":"10.1085/jgp.202313467","url":null,"abstract":"The voltage-sensing domain (VSD) is a four-helix modular protein domain that converts electrical signals into conformational changes, leading to open pores and active enzymes. In most voltage-sensing proteins, the VSDs do not interact with one another, and the S1-S3 helices are considered mainly scaffolding, except in the voltage-sensing phosphatase (VSP) and the proton channel (Hv). To investigate its contribution to VSP function, we mutated four hydrophobic amino acids in S1 to alanine (F127, I131, I134, and L137), individually or in combination. Most of these mutations shifted the voltage dependence of activity to higher voltages; however, not all substrate reactions were the same. The kinetics of enzymatic activity were also altered, with some mutations significantly slowing down dephosphorylation. The voltage dependence of VSD motions was consistently shifted to lower voltages and indicated a second voltage-dependent motion. Additionally, none of the mutations broke the VSP dimer, indicating that the S1 impact could stem from intra- and/or intersubunit interactions. Lastly, when the same mutations were introduced into a genetically encoded voltage indicator, they dramatically altered the optical readings, making some of the kinetics faster and shifting the voltage dependence. These results indicate that the S1 helix in VSP plays a critical role in tuning the enzyme's conformational response to membrane potential transients and influencing the function of the VSD.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"156 7","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11109755/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141071063","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

Carboxyl-group compounds activate voltage-gated potassium channels via a distinct mechanism. 羧基化合物通过一种独特的机制激活电压门控钾通道。

IF 3.8 2区医学

Journal of General Physiology Pub Date : 2024-07-01 Epub Date: 2024-06-04 DOI: 10.1085/jgp.202313516

Olle Rönnelid, Fredrik Elinder

{"title":"Carboxyl-group compounds activate voltage-gated potassium channels via a distinct mechanism.","authors":"Olle Rönnelid, Fredrik Elinder","doi":"10.1085/jgp.202313516","DOIUrl":"10.1085/jgp.202313516","url":null,"abstract":"Voltage-gated ion channels are responsible for the electrical excitability of neurons and cardiomyocytes. Thus, they are obvious targets for pharmaceuticals aimed to modulate excitability. Compounds activating voltage-gated potassium (KV) channels are expected to reduce excitability. To search for new KV-channel activators, we performed a high-throughput screen of 10,000 compounds on a specially designed Shaker KV channel. Here, we report on a large family of channel-activating compounds with a carboxyl (COOH) group as the common motif. The most potent COOH activators are lipophilic (4 < LogP <7) and are suggested to bind at the interface between the lipid bilayer and the channel's positively charged voltage sensor. The negatively charged form of the COOH-group compounds is suggested to open the channel by electrostatically pulling the voltage sensor to an activated state. Several of the COOH-group compounds also activate the therapeutically important KV7.2/7.3 channel and can thus potentially be developed into antiseizure drugs. The COOH-group compounds identified in this study are suggested to act via the same site and mechanism of action as previously studied COOH-group compounds, such as polyunsaturated fatty acids and resin acids, but distinct from sites for several other types of potassium channel-activating compounds.","PeriodicalId":54828,"journal":{"name":"Journal of General Physiology","volume":"156 7","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11148469/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141238841","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 S1 helix is a VIP in VSP. S1 螺旋线是 VSP 的 VIP。

IF 3.3 2区医学

Journal of General Physiology Pub Date : 2024-07-01 Epub Date: 2024-06-11 DOI: 10.1085/jgp.202413612

Ben Short

引用次数: 0