The Journal of General Physiology最新文献

{"title":"Tracking the sarcoplasmic reticulum membrane voltage in muscle with a FRET biosensor.","authors":"Colline Sanchez,&nbsp;Christine Berthier,&nbsp;Bruno Allard,&nbsp;Jimmy Perrot,&nbsp;Clément Bouvard,&nbsp;Hidekazu Tsutsui,&nbsp;Yasushi Okamura,&nbsp;Vincent Jacquemond","doi":"10.1085/jgp.201812035","DOIUrl":"https://doi.org/10.1085/jgp.201812035","url":null,"abstract":"<p><p>Ion channel activity in the plasma membrane of living cells generates voltage changes that are critical for numerous biological functions. The membrane of the endoplasmic/sarcoplasmic reticulum (ER/SR) is also endowed with ion channels, but whether changes in its voltage occur during cellular activity has remained ambiguous. This issue is critical for cell functions that depend on a Ca²⁺ flux across the reticulum membrane. This is the case for contraction of striated muscle, which is triggered by opening of ryanodine receptor Ca²⁺ release channels in the SR membrane in response to depolarization of the transverse invaginations of the plasma membrane (the t-tubules). Here, we use targeted expression of voltage-sensitive fluorescence resonance energy transfer (FRET) probes of the Mermaid family in differentiated muscle fibers to determine whether changes in SR membrane voltage occur during depolarization-contraction coupling. In the absence of an SR targeting sequence, FRET signals from probes present in the t-tubule membrane allow calibration of the voltage sensitivity and amplitude of the response to voltage-clamp pulses. Successful SR targeting of the probes was achieved using an N-terminal domain of triadin, which completely eliminates voltage-clamp-activated FRET signals from the t-tubule membrane of transfected fibers. In fibers expressing SR-targeted Mermaid probes, activation of SR Ca²⁺ release in the presence of intracellular ethyleneglycol-bis(β-amino-ethyl ether)-<i>N</i>,<i>N</i>,<i>N</i>',<i>N</i>'-tetra acetic acid (EGTA) results in an accompanying FRET signal. We find that this signal results from pH sensitivity of the probe, which detects cytosolic acidification because of the release of protons upon Ca²⁺ binding to EGTA. When EGTA is substituted with either 1,2-bis(<i>o</i>-aminophenoxy)ethane-<i>N</i>,<i>N</i>,<i>N</i>',<i>N</i>'-tetraacetic acid or the contraction blocker <i>N</i>-benzyl-<i>p</i>-toluene sulfonamide, we find no indication of a substantial change in the FRET response caused by a voltage change. These results suggest that the ryanodine receptor-mediated SR Ca²⁺ efflux is well balanced by concomitant counterion currents across the SR membrane.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"1163-1177"},"PeriodicalIF":3.8,"publicationDate":"2018-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201812035","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"36220267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family.","authors":"Claudia P Alvarez-Baron,&nbsp;Vadim A Klenchin,&nbsp;Baron Chanda","doi":"10.1085/jgp.201812031","DOIUrl":"https://doi.org/10.1085/jgp.201812031","url":null,"abstract":"<p><p>Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels generate rhythmic activity in the heart and brain. Isoform-specific functional differences reflect the specializations required for the various roles that they play. Despite a high sequence and structural similarity, HCN isoforms differ greatly in their response to cyclic nucleotides. Cyclic AMP (cAMP) enhances the activity of HCN2 and HCN4 isoforms by shifting the voltage dependence of activation to more depolarized potentials, whereas HCN1 and HCN3 isoforms are practically insensitive to this ligand. Here, to determine the molecular basis for increased cAMP efficacy in HCN2 channels, we progressively mutate residues in the C-linker and cyclic nucleotide-binding domain (CNBD) of the mouse HCN2 to their equivalents in HCN1. We identify two clusters of mutations that determine the differences in voltage-dependent activation between these two isoforms. One maps to the C-linker region, whereas the other is in proximity to the cAMP-binding site in the CNBD. A mutant channel containing just five mutations (M485I, G497D, S514T, V562A, and S563G) switches cAMP sensitivity of full-length HCN2 to that of HCN1 channels. These findings, combined with a detailed analysis of various allosteric models for voltage- and ligand-dependent gating, indicate that these residues alter the ability of the C-linker to transduce signals from the CNBD to the pore gates of the HCN channel.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"1203-1213"},"PeriodicalIF":3.8,"publicationDate":"2018-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201812031","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"36290256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Na,K-ATPase α2 activity in mammalian skeletal muscle T-tubules is acutely stimulated by extracellular K+.","authors":"Marino DiFranco,&nbsp;Hesamedin Hakimjavadi,&nbsp;Jerry B Lingrel,&nbsp;Judith A Heiny","doi":"10.1085/jgp.201511407","DOIUrl":"https://doi.org/10.1085/jgp.201511407","url":null,"abstract":"The K+ affinity of the Na,K-ATPase α2 isoform matches its activity to the range of extracellular K+ concentrations in the T-tubules at rest and during contraction, maintaining the excitability of active muscle.","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"281-94"},"PeriodicalIF":3.8,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201511407","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34174764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel Ca2+-feedback mechanism extends the operating range of mammalian rods to brighter light.","authors":"Frans Vinberg,&nbsp;Teemu T Turunen,&nbsp;Hanna Heikkinen,&nbsp;Marja Pitkänen,&nbsp;Ari Koskelainen","doi":"10.1085/jgp.201511412","DOIUrl":"https://doi.org/10.1085/jgp.201511412","url":null,"abstract":"<p><p>Sensory cells adjust their sensitivity to incoming signals, such as odor or light, in response to changes in background stimulation, thereby extending the range over which they operate. For instance, rod photoreceptors are extremely sensitive in darkness, so that they are able to detect individual photons, but remain responsive to visual stimuli under conditions of bright ambient light, which would be expected to saturate their response given the high gain of the rod transduction cascade in darkness. These photoreceptors regulate their sensitivity to light rapidly and reversibly in response to changes in ambient illumination, thereby avoiding saturation. Calcium ions (Ca2+) play a major role in mediating the rapid, subsecond adaptation to light, and the Ca2+-binding proteins GCAP1 and GCAP2 (or guanylyl cyclase-activating proteins [GCAPs]) have been identified as important mediators of the photoreceptor response to changes in intracellular Ca2+. However, mouse rods lacking both GCAP1 and GCAP2 (GCAP-/-) still show substantial light adaptation. Here, we determined the Ca2+ dependency of this residual light adaptation and, by combining pharmacological, genetic, and electrophysiological tools, showed that an unknown Ca2+-dependent mechanism contributes to light adaptation in GCAP-/- mouse rods. We found that mimicking the light-induced decrease in intracellular [Ca2+] accelerated recovery of the response to visual stimuli and caused a fourfold decrease of sensitivity in GCAP-/- rods. About half of this Ca2+-dependent regulation of sensitivity could be attributed to the recoverin-mediated pathway, whereas half of it was caused by the unknown mechanism. Furthermore, our data demonstrate that the feedback mechanisms regulating the sensitivity of mammalian rods on the second and subsecond time scales are all Ca2+ dependent and that, unlike salamander rods, Ca2+-independent background-induced acceleration of flash response kinetics is rather weak in mouse rods.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"307-21"},"PeriodicalIF":3.8,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201511412","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34111105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A chimeric prokaryotic pentameric ligand-gated channel reveals distinct pathways of activation.","authors":"Nicolaus Schmandt,&nbsp;Phanindra Velisetty,&nbsp;Sreevatsa V Chalamalasetti,&nbsp;Richard A Stein,&nbsp;Ross Bonner,&nbsp;Lauren Talley,&nbsp;Mark D Parker,&nbsp;Hassane S Mchaourab,&nbsp;Vivien C Yee,&nbsp;David T Lodowski,&nbsp;Sudha Chakrapani","doi":"10.1085/jgp.201511478","DOIUrl":"https://doi.org/10.1085/jgp.201511478","url":null,"abstract":"<p><p>Recent high resolution structures of several pentameric ligand-gated ion channels have provided unprecedented details of their molecular architecture. However, the conformational dynamics and structural rearrangements that underlie gating and allosteric modulation remain poorly understood. We used a combination of electrophysiology, double electron-electron resonance (DEER) spectroscopy, and x-ray crystallography to investigate activation mechanisms in a novel functional chimera with the extracellular domain (ECD) of amine-gated Erwinia chrysanthemi ligand-gated ion channel, which is activated by primary amines, and the transmembrane domain of Gloeobacter violaceus ligand-gated ion channel, which is activated by protons. We found that the chimera was independently gated by primary amines and by protons. The crystal structure of the chimera in its resting state, at pH 7.0 and in the absence of primary amines, revealed a closed-pore conformation and an ECD that is twisted with respect to the transmembrane region. Amine- and pH-induced conformational changes measured by DEER spectroscopy showed that the chimera exhibits a dual mode of gating that preserves the distinct conformational changes of the parent channels. Collectively, our findings shed light on both conserved and divergent features of gating mechanisms in this class of channels, and will facilitate the design of better allosteric modulators. </p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"323-40"},"PeriodicalIF":3.8,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201511478","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34111556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diffusion of myosin light chain kinase on actin: A mechanism to enhance myosin phosphorylation rates in smooth muscle.","authors":"Feng Hong,&nbsp;Richard K Brizendine,&nbsp;Michael S Carter,&nbsp;Diego B Alcala,&nbsp;Avery E Brown,&nbsp;Amy M Chattin,&nbsp;Brian D Haldeman,&nbsp;Michael P Walsh,&nbsp;Kevin C Facemyer,&nbsp;Josh E Baker,&nbsp;Christine R Cremo","doi":"10.1085/jgp.201511483","DOIUrl":"https://doi.org/10.1085/jgp.201511483","url":null,"abstract":"<p><p>Smooth muscle myosin (SMM) light chain kinase (MLCK) phosphorylates SMM, thereby activating the ATPase activity required for muscle contraction. The abundance of active MLCK, which is tightly associated with the contractile apparatus, is low relative to that of SMM. SMM phosphorylation is rapid despite the low ratio of MLCK to SMM, raising the question of how one MLCK rapidly phosphorylates many SMM molecules. We used total internal reflection fluorescence microscopy to monitor single molecules of streptavidin-coated quantum dot-labeled MLCK interacting with purified actin, actin bundles, and stress fibers of smooth muscle cells. Surprisingly, MLCK and the N-terminal 75 residues of MLCK (N75) moved on actin bundles and stress fibers of smooth muscle cell cytoskeletons by a random one-dimensional (1-D) diffusion mechanism. Although diffusion of proteins along microtubules and oligonucleotides has been observed previously, this is the first characterization to our knowledge of a protein diffusing in a sustained manner along actin. By measuring the frequency of motion, we found that MLCK motion is permitted only if acto-myosin and MLCK-myosin interactions are weak. From these data, diffusion coefficients, and other kinetic and geometric considerations relating to the contractile apparatus, we suggest that 1-D diffusion of MLCK along actin (a) ensures that diffusion is not rate limiting for phosphorylation, (b) allows MLCK to locate to areas in which myosin is not yet phosphorylated, and (c) allows MLCK to avoid getting \"stuck\" on myosins that have already been phosphorylated. Diffusion of MLCK along actin filaments may be an important mechanism for enhancing the rate of SMM phosphorylation in smooth muscle. </p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"267-80"},"PeriodicalIF":3.8,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201511483","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34111104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reconciling depressed Ca2+ sparks occurrence with enhanced RyR2 activity in failing mice cardiomyocytes.","authors":"Gema Ruiz-Hurtado,&nbsp;Linwei Li,&nbsp;María Fernández-Velasco,&nbsp;Angélica Rueda,&nbsp;Florence Lefebvre,&nbsp;Yueyi Wang,&nbsp;Philippe Mateo,&nbsp;Cécile Cassan,&nbsp;Barnabas Gellen,&nbsp;Jean Pierre Benitah,&nbsp;Ana María Gómez","doi":"10.1085/jgp.201511366","DOIUrl":"https://doi.org/10.1085/jgp.201511366","url":null,"abstract":"<p><p>Abnormalities in cardiomyocyte Ca2+ handling contribute to impaired contractile function in heart failure (HF). Experiments on single ryanodine receptors (RyRs) incorporated into lipid bilayers have indicated that RyRs from failing hearts are more active than those from healthy hearts. Here, we analyzed spontaneous Ca2+ sparks (brief, localized increased in [Ca2+]i) to evaluate RyR cluster activity in situ in a mouse post-myocardial infarction (PMI) model of HF. The cardiac ejection fraction of PMI mice was reduced to ∼30% of that of sham-operated (sham) mice, and their cardiomyocytes were hypertrophied. The [Ca2+]i transient amplitude and sarcoplasmic reticulum (SR) Ca2+ load were decreased in intact PMI cardiomyocytes compared with those from sham mice, and spontaneous Ca2+ sparks were less frequent, whereas the fractional release and the frequency of Ca2+ waves were both increased, suggesting higher RyR activity. In permeabilized cardiomyocytes, in which the internal solution can be controlled, Ca2+ sparks were more frequent in PMI cells (under conditions of similar SR Ca2+ load), confirming the enhanced RyR activity. However, in intact cells from PMI mice, the Ca2+ sparks frequency normalized by the SR Ca2+ load in that cell were reduced compared with those in sham mice, indicating that the cytosolic environment in intact cells contributes to the decrease in Ca2+ spark frequency. Indeed, using an internal \"failing solution\" with less ATP (as found in HF), we observed a dramatic decrease in Ca2+ spark frequency in permeabilized PMI and sham myocytes. In conclusion, our data show that, even if isolated RyR channels show more activity in HF, concomitant alterations in intracellular media composition and SR Ca2+ load may mask these effects at the Ca2+ spark level in intact cells. Nonetheless, in this scenario, the probability of arrhythmogenic Ca2+ waves is enhanced, and they play a potential role in the increase in arrhythmia events in HF patients.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"295-306"},"PeriodicalIF":3.8,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201511366","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34174762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Of bipolar cell synapses, light-activated K+ channels, and substrate binding to DAT.","authors":"Elizabeth M Adler","doi":"10.1085/jgp.201511449","DOIUrl":"https://doi.org/10.1085/jgp.201511449","url":null,"abstract":"This month’s installment of Generally Physiological considers a previously undescribed structure found in the synaptic terminals of retinal bipolar cells, a photoactivatable K+ channel, how the dopamine transporter distinguishes substrates from inhibitors, and recent JGP Video Summaries.\u0000\u0000![Figure","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"1-2"},"PeriodicalIF":3.8,"publicationDate":"2015-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201511449","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33428509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regulation of the transient receptor potential channel TRPM3 by phosphoinositides.","authors":"Balázs I Tóth,&nbsp;Maik Konrad,&nbsp;Debapriya Ghosh,&nbsp;Florian Mohr,&nbsp;Christian R Halaszovich,&nbsp;Michael G Leitner,&nbsp;Joris Vriens,&nbsp;Johannes Oberwinkler,&nbsp;Thomas Voets","doi":"10.1085/jgp.201411339","DOIUrl":"https://doi.org/10.1085/jgp.201411339","url":null,"abstract":"<p><p>The transient receptor potential (TRP) channel TRPM3 is a calcium-permeable cation channel activated by heat and by the neurosteroid pregnenolone sulfate (PregS). TRPM3 is highly expressed in sensory neurons, where it plays a key role in heat sensing and inflammatory hyperalgesia, and in pancreatic β cells, where its activation enhances glucose-induced insulin release. However, despite its functional importance, little is known about the cellular mechanisms that regulate TRPM3 activity. Here, we provide evidence for a dynamic regulation of TRPM3 by membrane phosphatidylinositol phosphates (PIPs). Phosphatidylinositol 4,5-bisphosphate (PI[4,5]P2) and ATP applied to the intracellular side of excised membrane patches promote recovery of TRPM3 from desensitization. The stimulatory effect of cytosolic ATP on TRPM3 reflects activation of phosphatidylinositol kinases (PI-Ks), leading to resynthesis of PIPs in the plasma membrane. Various PIPs directly enhance TRPM3 activity in cell-free inside-out patches, with a potency order PI(3,4,5)P3 > PI(3,5)P2 > PI(4,5)P2 ≈ PI(3,4)P2 >> PI(4)P. Conversely, TRPM3 activity is rapidly and reversibly inhibited by activation of phosphatases that remove the 5-phosphate from PIPs. Finally, we show that recombinant TRPM3, as well as the endogenous TRPM3 in insuloma cells, is rapidly and reversibly inhibited by activation of phospholipase C-coupled muscarinic acetylcholine receptors. Our results reveal basic cellular mechanisms whereby membrane receptors can regulate TRPM3 activity. </p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"51-63"},"PeriodicalIF":3.8,"publicationDate":"2015-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201411339","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33428510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rem uncouples excitation-contraction coupling in adult skeletal muscle fibers.","authors":"Donald Beqollari,&nbsp;Christin F Romberg,&nbsp;Dilyana Filipova,&nbsp;Ulises Meza,&nbsp;Symeon Papadopoulos,&nbsp;Roger A Bannister","doi":"10.1085/jgp.201411314","DOIUrl":"https://doi.org/10.1085/jgp.201411314","url":null,"abstract":"<p><p>In skeletal muscle, excitation-contraction (EC) coupling requires depolarization-induced conformational rearrangements in L-type Ca(2+) channel (Ca(V)1.1) to be communicated to the type 1 ryanodine-sensitive Ca(2+) release channel (RYR1) of the sarcoplasmic reticulum (SR) via transient protein-protein interactions. Although the molecular mechanism that underlies conformational coupling between Ca(V)1.1 and RYR1 has been investigated intensely for more than 25 years, the question of whether such signaling occurs via a direct interaction between the principal, voltage-sensing α(1S) subunit of Ca(V)1.1 and RYR1 or through an intermediary protein persists. A substantial body of evidence supports the idea that the auxiliary β(1a) subunit of Ca(V)1.1 is a conduit for this intermolecular communication. However, a direct role for β(1a) has been difficult to test because β(1a) serves two other functions that are prerequisite for conformational coupling between Ca(V)1.1 and RYR1. Specifically, β(1a) promotes efficient membrane expression of Ca(V)1.1 and facilitates the tetradic ultrastructural arrangement of Ca(V)1.1 channels within plasma membrane-SR junctions. In this paper, we demonstrate that overexpression of the RGK protein Rem, an established β subunit-interacting protein, in adult mouse flexor digitorum brevis fibers markedly reduces voltage-induced myoplasmic Ca(2+) transients without greatly affecting Ca(V)1.1 targeting, intramembrane gating charge movement, or releasable SR Ca(2+) store content. In contrast, a β(1a)-binding-deficient Rem triple mutant (R200A/L227A/H229A) has little effect on myoplasmic Ca(2+) release in response to membrane depolarization. Thus, Rem effectively uncouples the voltage sensors of Ca(V)1.1 from RYR1-mediated SR Ca(2+) release via its ability to interact with β(1a). Our findings reveal Rem-expressing adult muscle as an experimental system that may prove useful in the definition of the precise role of the β(1a) subunit in skeletal-type EC coupling.</p>","PeriodicalId":173753,"journal":{"name":"The Journal of General Physiology","volume":" ","pages":"97-108"},"PeriodicalIF":3.8,"publicationDate":"2015-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1085/jgp.201411314","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33389518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}