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Kang H, Lee CJ. Transmembrane proteins with unknown function (TMEMs) as ion channels: electrophysiological properties, structure, and pathophysiological roles. Exp Mol Med 2024; 56:850-860. [PMID: 38556553 PMCID: PMC11059273 DOI: 10.1038/s12276-024-01206-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 12/27/2023] [Accepted: 01/19/2024] [Indexed: 04/02/2024] Open
Abstract
A transmembrane (TMEM) protein with an unknown function is a type of membrane-spanning protein expressed in the plasma membrane or the membranes of intracellular organelles. Recently, several TMEM proteins have been identified as functional ion channels. The structures and functions of these proteins have been extensively studied over the last two decades, starting with TMEM16A (ANO1). In this review, we provide a summary of the electrophysiological properties of known TMEM proteins that function as ion channels, such as TMEM175 (KEL), TMEM206 (PAC), TMEM38 (TRIC), TMEM87A (GolpHCat), TMEM120A (TACAN), TMEM63 (OSCA), TMEM150C (Tentonin3), and TMEM43 (Gapjinc). Additionally, we examine the unique structural features of these channels compared to those of other well-known ion channels. Furthermore, we discuss the diverse physiological roles of these proteins in lysosomal/endosomal/Golgi pH regulation, intracellular Ca2+ regulation, spatial memory, cell migration, adipocyte differentiation, and mechanical pain, as well as their pathophysiological roles in Parkinson's disease, cancer, osteogenesis imperfecta, infantile hypomyelination, cardiomyopathy, and auditory neuropathy spectrum disorder. This review highlights the potential for the discovery of novel ion channels within the TMEM protein family and the development of new therapeutic targets for related channelopathies.
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Affiliation(s)
- Hyunji Kang
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Life Science Cluster, Institute for Basic Science (IBS), 55 Expo-ro, Yuseong-gu, Daejeon, 34126, Republic of Korea.
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2
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Ichimura A, Miyazaki Y, Nagatomo H, Kawabe T, Nakajima N, Kim GE, Tomizawa M, Okamoto N, Komazaki S, Kakizawa S, Nishi M, Takeshima H. Atypical cell death and insufficient matrix organization in long-bone growth plates from Tric-b-knockout mice. Cell Death Dis 2023; 14:848. [PMID: 38123563 PMCID: PMC10733378 DOI: 10.1038/s41419-023-06285-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 10/27/2023] [Accepted: 11/07/2023] [Indexed: 12/23/2023]
Abstract
TRIC-A and TRIC-B proteins form homotrimeric cation-permeable channels in the endoplasmic reticulum (ER) and nuclear membranes and are thought to contribute to counterionic flux coupled with store Ca2+ release in various cell types. Serious mutations in the TRIC-B (also referred to as TMEM38B) locus cause autosomal recessive osteogenesis imperfecta (OI), which is characterized by insufficient bone mineralization. We have reported that Tric-b-knockout mice can be used as an OI model; Tric-b deficiency deranges ER Ca2+ handling and thus reduces extracellular matrix (ECM) synthesis in osteoblasts, leading to poor mineralization. Here we report irregular cell death and insufficient ECM in long-bone growth plates from Tric-b-knockout embryos. In the knockout growth plate chondrocytes, excess pro-collagen fibers were occasionally accumulated in severely dilated ER elements. Of the major ER stress pathways, activated PERK/eIF2α (PKR-like ER kinase/ eukaryotic initiation factor 2α) signaling seemed to inordinately alter gene expression to induce apoptosis-related proteins including CHOP (CCAAT/enhancer binding protein homologous protein) and caspase 12 in the knockout chondrocytes. Ca2+ imaging detected aberrant Ca2+ handling in the knockout chondrocytes; ER Ca2+ release was impaired, while cytoplasmic Ca2+ level was elevated. Our observations suggest that Tric-b deficiency directs growth plate chondrocytes to pro-apoptotic states by compromising cellular Ca2+-handling and exacerbating ER stress response, leading to impaired ECM synthesis and accidental cell death.
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Affiliation(s)
- Atsuhiko Ichimura
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Yuu Miyazaki
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Hiroki Nagatomo
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Takaaki Kawabe
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Nobuhisa Nakajima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Ga Eun Kim
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Masato Tomizawa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Naoki Okamoto
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | | | - Sho Kakizawa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Miyuki Nishi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan
| | - Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan.
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3
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Tonelli F, Leoni L, Daponte V, Gioia R, Cotti S, Fiedler IAK, Larianova D, Willaert A, Coucke PJ, Villani S, Busse B, Besio R, Rossi A, Witten PE, Forlino A. Zebrafish Tric-b is required for skeletal development and bone cells differentiation. Front Endocrinol (Lausanne) 2023; 14:1002914. [PMID: 36755921 PMCID: PMC9899828 DOI: 10.3389/fendo.2023.1002914] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 01/03/2023] [Indexed: 01/24/2023] Open
Abstract
INTRODUCTION Trimeric intracellular potassium channels TRIC-A and -B are endoplasmic reticulum (ER) integral membrane proteins, involved in the regulation of calcium release mediated by ryanodine (RyRs) and inositol 1,4,5-trisphosphate (IP3Rs) receptors, respectively. While TRIC-A is mainly expressed in excitable cells, TRIC-B is ubiquitously distributed at moderate level. TRIC-B deficiency causes a dysregulation of calcium flux from the ER, which impacts on multiple collagen specific chaperones and modifying enzymatic activity, leading to a rare form of osteogenesis imperfecta (OI Type XIV). The relevance of TRIC-B on cell homeostasis and the molecular mechanism behind the disease are still unknown. RESULTS In this study, we exploited zebrafish to elucidate the role of TRIC-B in skeletal tissue. We demonstrated, for the first time, that tmem38a and tmem38b genes encoding Tric-a and -b, respectively are expressed at early developmental stages in zebrafish, but only the latter has a maternal expression. Two zebrafish mutants for tmem38b were generated by CRISPR/Cas9, one carrying an out of frame mutation introducing a premature stop codon (tmem38b-/- ) and one with an in frame deletion that removes the highly conserved KEV domain (tmem38bΔ120-7/Δ120-7 ). In both models collagen type I is under-modified and partially intracellularly retained in the endoplasmic reticulum, as described in individuals affected by OI type XIV. Tmem38b-/- showed a mild skeletal phenotype at the late larval and juvenile stages of development whereas tmem38bΔ120-7/Δ120-7 bone outcome was limited to a reduced vertebral length at 21 dpf. A caudal fin regeneration study pointed towards impaired activity of osteoblasts and osteoclasts associated with mineralization impairment. DISCUSSION Our data support the requirement of Tric-b during early development and for bone cell differentiation.
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Affiliation(s)
- Francesca Tonelli
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Laura Leoni
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Valentina Daponte
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Roberta Gioia
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Silvia Cotti
- Department of Biology, Ghent University, Ghent, Belgium
| | - Imke A. K. Fiedler
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Andy Willaert
- Department of Biomolecular Medicine, Center of Medical Genetics, Ghent University-University Hospital, Ghent, Belgium
| | - Paul J. Coucke
- Department of Biomolecular Medicine, Center of Medical Genetics, Ghent University-University Hospital, Ghent, Belgium
| | - Simona Villani
- Department of Public Health and Experimental and Forensic Medicine, Unit of Biostatistics and Clinical Epidemiology, University of Pavia, Pavia, Italy
| | - Björn Busse
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Roberta Besio
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Antonio Rossi
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
| | | | - Antonella Forlino
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
- *Correspondence: Antonella Forlino,
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4
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Zhou X, Li A, Lin PH, Zhou J, Ma J. TRIC-A regulates intracellular Ca 2+ homeostasis in cardiomyocytes. Pflugers Arch 2021; 473:547-556. [PMID: 33474637 PMCID: PMC7940156 DOI: 10.1007/s00424-021-02513-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/14/2020] [Accepted: 01/04/2021] [Indexed: 01/26/2023]
Abstract
Trimeric intracellular cation (TRIC) channels have been identified as monovalent cation channels that are located in the ER/SR membrane. Two isoforms discovered in mammals are TRIC-A (TMEM38a) and TRIC-B (TMEM38b). TRIC-B ubiquitously expresses in all tissues, and TRIC-B-/- mice is lethal at the neonatal stage. TRIC-A mainly expresses in excitable cells. TRIC-A-/- mice survive normally but show abnormal SR Ca2+ handling in both skeletal and cardiac muscle cells. Importantly, TRIC-A mutations have been identified in human patients with stress-induced arrhythmia. In the past decade, important discoveries have been made to understand the structure and function of TRIC channels, especially its role in regulating intracellular Ca2+ homeostasis. In this review article, we focus on the potential roles of TRIC-A in regulating cardiac function, particularly its effects on intracellular Ca2+ signaling of cardiomyocytes and discuss the current knowledge gaps.
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Affiliation(s)
- Xinyu Zhou
- Department of Surgery, The Ohio State University Columbus, Columbus, OH, 43210, USA
| | - Ang Li
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, 76019, USA
| | - Pei-Hui Lin
- Department of Surgery, The Ohio State University Columbus, Columbus, OH, 43210, USA
| | - Jingsong Zhou
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, 76019, USA
| | - Jianjie Ma
- Department of Surgery, The Ohio State University Columbus, Columbus, OH, 43210, USA.
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5
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Njegic A, Wilson C, Cartwright EJ. Targeting Ca 2 + Handling Proteins for the Treatment of Heart Failure and Arrhythmias. Front Physiol 2020; 11:1068. [PMID: 33013458 PMCID: PMC7498719 DOI: 10.3389/fphys.2020.01068] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 08/04/2020] [Indexed: 12/18/2022] Open
Abstract
Diseases of the heart, such as heart failure and cardiac arrhythmias, are a growing socio-economic burden. Calcium (Ca2+) dysregulation is key hallmark of the failing myocardium and has long been touted as a potential therapeutic target in the treatment of a variety of cardiovascular diseases (CVD). In the heart, Ca2+ is essential for maintaining normal cardiac function through the generation of the cardiac action potential and its involvement in excitation contraction coupling. As such, the proteins which regulate Ca2+ cycling and signaling play a vital role in maintaining Ca2+ homeostasis. Changes to the expression levels and function of Ca2+-channels, pumps and associated intracellular handling proteins contribute to altered Ca2+ homeostasis in CVD. The remodeling of Ca2+-handling proteins therefore results in impaired Ca2+ cycling, Ca2+ leak from the sarcoplasmic reticulum and reduced Ca2+ clearance, all of which contributes to increased intracellular Ca2+. Currently, approved treatments for targeting Ca2+ handling dysfunction in CVD are focused on Ca2+ channel blockers. However, whilst Ca2+ channel blockers have been successful in the treatment of some arrhythmic disorders, they are not universally prescribed to heart failure patients owing to their ability to depress cardiac function. Despite the progress in CVD treatments, there remains a clear need for novel therapeutic approaches which are able to reverse pathophysiology associated with heart failure and arrhythmias. Given that heart failure and cardiac arrhythmias are closely associated with altered Ca2+ homeostasis, this review will address the molecular changes to proteins associated with both Ca2+-handling and -signaling; their potential as novel therapeutic targets will be discussed in the context of pre-clinical and, where available, clinical data.
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Affiliation(s)
- Alexandra Njegic
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom.,Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Claire Wilson
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom.,Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Elizabeth J Cartwright
- Division of Cardiovascular Sciences, The University of Manchester, Manchester, United Kingdom
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6
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Shrestha N, Bacsa B, Ong HL, Scheruebel S, Bischof H, Malli R, Ambudkar IS, Groschner K. TRIC-A shapes oscillatory Ca2+ signals by interaction with STIM1/Orai1 complexes. PLoS Biol 2020; 18:e3000700. [PMID: 32330125 PMCID: PMC7202670 DOI: 10.1371/journal.pbio.3000700] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 05/06/2020] [Accepted: 04/09/2020] [Indexed: 01/08/2023] Open
Abstract
Trimeric intracellular cation (TRIC) channels have been proposed to modulate Ca2+ release from the endoplasmic reticulum (ER) and determine oscillatory Ca2+ signals. Here, we report that TRIC-A-mediated amplitude and frequency modulation of ryanodine receptor 2 (RyR2)-mediated Ca2+ oscillations and inositol 1,4,5-triphosphate receptor (IP3R)-induced cytosolic signals is based on attenuating store-operated Ca2+ entry (SOCE). Further, TRIC-A-dependent delay in ER Ca2+ store refilling contributes to shaping the pattern of Ca2+ oscillations. Upon ER Ca2+ depletion, TRIC-A clusters with stromal interaction molecule 1 (STIM1) and Ca2+-release-activated Ca2+ channel 1 (Orai1) within ER-plasma membrane (PM) junctions and impairs assembly of the STIM1/Orai1 complex, causing a decrease in Orai1-mediated Ca2+ current and SOCE. Together, our findings demonstrate that TRIC-A is a negative regulator of STIM1/Orai1 function. Thus, aberrant SOCE could contribute to muscle disorders associated with loss of TRIC-A.
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Affiliation(s)
- Niroj Shrestha
- Gottfried Schatz Research Center-Biophysics, Medical University of Graz, Graz, Austria
| | - Bernadett Bacsa
- Gottfried Schatz Research Center-Biophysics, Medical University of Graz, Graz, Austria
| | - Hwei Ling Ong
- Secretory Physiology Section, NIDCR, NIH, Bethesda, Maryland, United States of America
| | - Susanne Scheruebel
- Gottfried Schatz Research Center-Biophysics, Medical University of Graz, Graz, Austria
| | - Helmut Bischof
- Gottfried Schatz Research Center-Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Roland Malli
- Gottfried Schatz Research Center-Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Indu Suresh Ambudkar
- Secretory Physiology Section, NIDCR, NIH, Bethesda, Maryland, United States of America
| | - Klaus Groschner
- Gottfried Schatz Research Center-Biophysics, Medical University of Graz, Graz, Austria
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7
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Ehrlich KC, Lacey M, Ehrlich M. Epigenetics of Skeletal Muscle-Associated Genes in the ASB, LRRC, TMEM, and OSBPL Gene Families. EPIGENOMES 2020; 4:1. [PMID: 34968235 PMCID: PMC8594701 DOI: 10.3390/epigenomes4010001] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 01/21/2020] [Accepted: 01/28/2020] [Indexed: 02/07/2023] Open
Abstract
Much remains to be discovered about the intersection of tissue-specific transcription control and the epigenetics of skeletal muscle (SkM), a very complex and dynamic organ. From four gene families, Leucine-Rich Repeat Containing (LRRC), Oxysterol Binding Protein Like (OSBPL), Ankyrin Repeat and Socs Box (ASB), and Transmembrane Protein (TMEM), we chose 21 genes that are preferentially expressed in human SkM relative to 52 other tissue types and analyzed relationships between their tissue-specific epigenetics and expression. We also compared their genetics, proteomics, and descriptions in the literature. For this study, we identified genes with little or no previous descriptions of SkM functionality (ASB4, ASB8, ASB10, ASB12, ASB16, LRRC14B, LRRC20, LRRC30, TMEM52, TMEM233, OSBPL6/ORP6, and OSBPL11/ORP11) and included genes whose SkM functions had been previously addressed (ASB2, ASB5, ASB11, ASB15, LRRC2, LRRC38, LRRC39, TMEM38A/TRIC-A, and TMEM38B/TRIC-B). Some of these genes have associations with SkM or heart disease, cancer, bone disease, or other diseases. Among the transcription-related SkM epigenetic features that we identified were: super-enhancers, promoter DNA hypomethylation, lengthening of constitutive low-methylated promoter regions, and SkM-related enhancers for one gene embedded in a neighboring gene (e.g., ASB8-PFKM, LRRC39-DBT, and LRRC14B-PLEKHG4B gene-pairs). In addition, highly or lowly co-expressed long non-coding RNA (lncRNA) genes probably regulate several of these genes. Our findings give insights into tissue-specific epigenetic patterns and functionality of related genes in a gene family and can elucidate normal and disease-related regulation of gene expression in SkM.
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Affiliation(s)
- Kenneth C. Ehrlich
- Center for Bioinformatics and Genomics, Tulane University Health Sciences Center, New Orleans, LA 70112, USA;
| | - Michelle Lacey
- Department of Mathematics, Tulane University, New Orleans, LA 70118, USA;
- Tulane Cancer Center, Tulane University Health Sciences Center, New Orleans, LA 70112, USA
| | - Melanie Ehrlich
- Center for Bioinformatics and Genomics, Tulane University Health Sciences Center, New Orleans, LA 70112, USA;
- Tulane Cancer Center, Tulane University Health Sciences Center, New Orleans, LA 70112, USA
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8
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Zhou X, Park KH, Yamazaki D, Lin PH, Nishi M, Ma Z, Qiu L, Murayama T, Zou X, Takeshima H, Zhou J, Ma J. TRIC-A Channel Maintains Store Calcium Handling by Interacting With Type 2 Ryanodine Receptor in Cardiac Muscle. Circ Res 2019; 126:417-435. [PMID: 31805819 DOI: 10.1161/circresaha.119.316241] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
RATIONALE Trimeric intracellular cation (TRIC)-A and B are distributed to endoplasmic reticulum/sarcoplasmic reticulum intracellular Ca2+ stores. The crystal structure of TRIC has been determined, confirming the homotrimeric structure of a potassium channel. While the pore architectures of TRIC-A and TRIC-B are conserved, the carboxyl-terminal tail (CTT) domains of TRIC-A and TRIC-B are different from each other. Aside from its recognized role as a counterion channel that participates in excitation-contraction coupling of striated muscles, the physiological function of TRIC-A in heart physiology and disease has remained largely unexplored. OBJECTIVE In cardiomyocytes, spontaneous Ca2+ waves, triggered by store overload-induced Ca2+ release mediated by the RyR2 (type 2 ryanodine receptor), develop extrasystolic contractions often associated with arrhythmic events. Here, we test the hypothesis that TRIC-A is a physiological component of RyR2-mediated Ca2+ release machinery that directly modulates store overload-induced Ca2+ release activity via CTT. METHODS AND RESULTS We show that cardiomyocytes derived from the TRIC-A-/- (TRIC-A knockout) mice display dysregulated Ca2+ movement across sarcoplasmic reticulum. Biochemical studies demonstrate a direct interaction between CTT-A and RyR2. Modeling and docking studies reveal potential sites on RyR2 that show differential interactions with CTT-A and CTT-B. In HEK293 (human embryonic kidney) cells with stable expression of RyR2, transient expression of TRIC-A, but not TRIC-B, leads to apparent suppression of spontaneous Ca2+ oscillations. Ca2+ measurements using the cytosolic indicator Fura-2 and the endoplasmic reticulum luminal store indicator D1ER suggest that TRIC-A enhances Ca2+ leak across the endoplasmic reticulum by directly targeting RyR2 to modulate store overload-induced Ca2+ release. Moreover, synthetic CTT-A peptide facilitates RyR2 activity in lipid bilayer reconstitution system, enhances Ca2+ sparks in permeabilized TRIC-A-/- cardiomyocytes, and induces intracellular Ca2+ release after microinjection into isolated cardiomyocytes, whereas such effects were not observed with the CTT-B peptide. In response to isoproterenol stimulation, the TRIC-A-/- mice display irregular ECG and develop more fibrosis than the WT (wild type) littermates. CONCLUSIONS In addition to the ion-conducting function, TRIC-A functions as an accessory protein of RyR2 to modulate sarcoplasmic reticulum Ca2+ handling in cardiac muscle.
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Affiliation(s)
- Xinyu Zhou
- From the Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University, Columbus (X. Zhou, K.H.P., P.-h.L., J.M.)
| | - Ki Ho Park
- From the Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University, Columbus (X. Zhou, K.H.P., P.-h.L., J.M.)
| | - Daiju Yamazaki
- Department of Biological Chemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Japan (D.Y., M.N., H.T.)
| | - Pei-Hui Lin
- From the Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University, Columbus (X. Zhou, K.H.P., P.-h.L., J.M.)
| | - Miyuki Nishi
- Department of Biological Chemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Japan (D.Y., M.N., H.T.)
| | - Zhiwei Ma
- Department of Physics and Astronomy, Dalton Cardiovascular Research Center (Z.M., L.Q., X. Zou), University of Missouri, Columbia.,Department of Biochemistry (Z.M., L.Q., X. Zou), University of Missouri, Columbia
| | - Liming Qiu
- Department of Physics and Astronomy, Dalton Cardiovascular Research Center (Z.M., L.Q., X. Zou), University of Missouri, Columbia.,Department of Biochemistry (Z.M., L.Q., X. Zou), University of Missouri, Columbia
| | - Takashi Murayama
- Department of Pharmacology, Juntendo University School of Medicine, Tokyo, Japan (T.M.)
| | - Xiaoqin Zou
- Department of Physics and Astronomy, Dalton Cardiovascular Research Center (Z.M., L.Q., X. Zou), University of Missouri, Columbia.,Department of Biochemistry (Z.M., L.Q., X. Zou), University of Missouri, Columbia
| | - Hiroshi Takeshima
- Department of Biological Chemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Japan (D.Y., M.N., H.T.)
| | - Jingsong Zhou
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington (J.Z.)
| | - Jianjie Ma
- From the Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University, Columbus (X. Zhou, K.H.P., P.-h.L., J.M.)
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9
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O'Brien F, Eberhardt D, Witschas K, El‐Ajouz S, Iida T, Nishi M, Takeshima H, Sitsapesan R, Venturi E. Enhanced activity of multiple TRIC-B channels: an endoplasmic reticulum/sarcoplasmic reticulum mechanism to boost counterion currents. J Physiol 2019; 597:2691-2705. [PMID: 30907436 PMCID: PMC6567852 DOI: 10.1113/jp277241] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 03/20/2019] [Indexed: 01/27/2023] Open
Abstract
KEY POINTS There are two subtypes of trimeric intracellular cation (TRIC) channels but their distinct single-channel properties and physiological regulation have not been characterized. We examined the differences in function between native skeletal muscle sarcoplasmic reticulum (SR) K+ -channels from wild-type (WT) mice (where TRIC-A is the principal subtype) and from Tric-a knockout (KO) mice that only express TRIC-B. We find that lone SR K+ -channels from Tric-a KO mice have a lower open probability and gate more frequently in subconducting states than channels from WT mice but, unlike channels from WT mice, multiple channels gate with high open probability with a more than six-fold increase in activity when four channels are present in the bilayer. No evidence was found for a direct gating interaction between ryanodine receptor and SR K+ -channels in Tric-a KO SR, suggesting that TRIC-B-TRIC-B interactions are highly specific and may be important for meeting counterion requirements during excitation-contraction coupling in tissues where TRIC-A is sparse or absent. ABSTRACT The trimeric intracellular cation channels, TRIC-A and TRIC-B, represent two subtypes of sarcoplasmic reticulum (SR) K+ -channel but their individual functional roles are unknown. We therefore compared the biophysical properties of SR K+ -channels derived from the skeletal muscle of wild-type (WT) or Tric-a knockout (KO) mice. Because TRIC-A is the major TRIC-subtype in skeletal muscle, WT SR will predominantly contain TRIC-A channels, whereas Tric-a KO SR will only contain TRIC-B channels. When lone SR K+ -channels were incorporated into bilayers, the open probability (Po) of channels from Tric-a KO mice was markedly lower than that of channels from WT mice; gating was characterized by shorter opening bursts and more frequent brief subconductance openings. However, unlike channels from WT mice, the Po of SR K+ -channels from Tric-a KO mice increased as increasing channel numbers were present in the bilayer, driving the channels into long sojourns in the fully open state. When co-incorporated into bilayers, ryanodine receptor channels did not directly affect the gating of SR K+ -channels, nor did the presence or absence of SR K+ -channels influence ryanodine receptor activity. We suggest that because of high expression levels in striated muscle, TRIC-A produces most of the counterion flux required during excitation-contraction coupling. TRIC-B, in contrast, is sparsely expressed in most cells and, although lone TRIC-B channels exhibit low Po, the high Po levels reached by multiple TRIC-B channels may provide a compensatory mechanism to rapidly restore K+ gradients and charge differences across the SR of tissues containing few TRIC-A channels.
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Affiliation(s)
- Fiona O'Brien
- Department of PharmacologyUniversity of OxfordOxfordUK
| | | | | | - Sam El‐Ajouz
- Department of PharmacologyUniversity of OxfordOxfordUK
| | - Tsunaki Iida
- Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | - Miyuki Nishi
- Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | - Hiroshi Takeshima
- Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | | | - Elisa Venturi
- Department of PharmacologyUniversity of OxfordOxfordUK
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10
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Zsolnay V, Fill M, Gillespie D. Sarcoplasmic Reticulum Ca 2+ Release Uses a Cascading Network of Intra-SR and Channel Countercurrents. Biophys J 2019; 114:462-473. [PMID: 29401443 DOI: 10.1016/j.bpj.2017.11.3775] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 11/14/2017] [Accepted: 11/27/2017] [Indexed: 11/17/2022] Open
Abstract
In muscle, Ca2+ release from the sarcoplasmic reticulum (SR) into the cytosol is mediated through the ryanodine receptors (RyRs) and sustained by countercurrents that keep the SR membrane potential near 0 mV. Likewise, Ca2+ reuptake by the sarco/endoplasmic reticulum Ca2+ ATPase pump requires countercurrent. Although evidence has suggested that TRIC K+ channels and/or RyR K+ influx provide these countercurrents, the exact sources have not yet been determined. We used an equivalent circuit compartment model of a cardiac SR, the surrounding cytosol, and the dyadic cleft to probe the sources of countercurrent during a complete cardiac cycle. By removing and relocating TRIC K+ channels, as well as limiting when they are active, we explored the various possible sources of SR countercurrent under many conditions. Our simulations indicate that no single channel type is essential for countercurrent. Rather, a cascading network of countercurrents is present with anion fluxes within the SR redistributing charges throughout the full SR volume. This allows ion channels in the entire SR membrane, far from the Ca2+ fluxes through the RyRs in the junctional SR and sarco/endoplasmic reticulum Ca2+ ATPase pump in the nonjunctional SR, to mediate countercurrents that support Ca2+ release and reuptake. This multifactorial network of countercurrents allows Ca2+ release to be remarkably robust.
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Affiliation(s)
- Vilmos Zsolnay
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, Illinois; The Graduate Program in Biophysical Sciences, University of Chicago, Chicago, Illinois
| | - Michael Fill
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, Illinois
| | - Dirk Gillespie
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, Illinois.
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11
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Structural basis for activity of TRIC counter-ion channels in calcium release. Proc Natl Acad Sci U S A 2019; 116:4238-4243. [PMID: 30770441 DOI: 10.1073/pnas.1817271116] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Trimeric intracellular cation (TRIC) channels are thought to provide counter-ion currents that facilitate the active release of Ca2+ from intracellular stores. TRIC activity is controlled by voltage and Ca2+ modulation, but underlying mechanisms have remained unknown. Here we describe high-resolution crystal structures of vertebrate TRIC-A and TRIC-B channels, both in Ca2+-bound and Ca2+-free states, and we analyze conductance properties in structure-inspired mutagenesis experiments. The TRIC channels are symmetric trimers, wherein we find a pore in each protomer that is gated by a highly conserved lysine residue. In the resting state, Ca2+ binding at the luminal surface of TRIC-A, on its threefold axis, stabilizes lysine blockage of the pores. During active Ca2+ release, luminal Ca2+ depletion removes inhibition to permit the lysine-bearing and voltage-sensing helix to move in response to consequent membrane hyperpolarization. Diacylglycerol is found at interprotomer interfaces, suggesting a role in metabolic control.
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12
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曾 林, 刘 静. [Mitochondrial calcium overload in the masseter muscle of rats with occlusal interference: ionic changes and regulation by calmodulin kinase II]. NAN FANG YI KE DA XUE XUE BAO = JOURNAL OF SOUTHERN MEDICAL UNIVERSITY 2018; 38:755-760. [PMID: 29997101 PMCID: PMC6765715 DOI: 10.3969/j.issn.1673-4254.2018.06.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Indexed: 06/08/2023]
Abstract
OBJECTIVE To investigate the changes in mitochondrial calcium and extracellular sodium concentrations in the masseter muscle of rats with occlusal interference and the regulatory mechanism of mitochondrial Ca2+ overload by calmodulin kinase II (CaMK II). METHODS SD rat models of occlusal interference were established by placing a stainless steel segments (0.8 mm in diameter) to raise the occlusal surface of the upper right first molar. At 3, 7, 14, and 21 days after occlusal interference and at 3 days after removal of occlusal interference, HE staining was used to observe the histomorphological changes of the masseter muscle. Mitochondrial calcium concentration in the masseter muscle was detected using fluorescence spectrophotometry, and direct turbidimetry with potassium pyroantimonate was used to detect the extracellular sodium concentration; the expression levels of masseter muscle p-CaMK II (Thr287) and CaMK II were detected using Western blotting. RESULTS Compared with those in the corresponding control groups, mitochondrial Ca2+ concentration in the masseter muscle on occlusal interference side increased significantly at 3, 7, 14 and 21 days after occlusal interference (P<0.05), but was significantly lowered at 3 days after removal of the interference (P<0.05). The concentration of extracellular Na+ increased progressively with time at 3, 7, 14 and 21 days after occlusal interference (P<0.05), and was significantly decreased at 3 days after interference removal (P<0.05). Occlusal interference for 3, 7 and 14 days resulted in significantly increased expressions of p-CaMK II (Thr287) and CaMK II (P<0.05), which was significantly decreased at 21 days compared with those in the control groups (P<0.05) and further decreased after removal of occlusal interference (P<0.05). Similar changes were also observed on the side without interference, but the changes on the interference side were more obvious (P<0.05). CONCLUSION Occlusal interference causes elevated mitochondrial Ca2+ and extracellular Na+ concentrations in the masseter muscle of rats to lead to calcium overload; the increase in mitochondrial Ca2+ concentration is correlated with the phosphorylation level of CaMK II signaling pathway, suggesting a negative feedback regulation mechanism by the CaMK II signal pathway.
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Affiliation(s)
- 林 曾
- 暨南大学 口腔医学院,广东 广州 510632College of Stomatology, Jinan University, Guangzhou 510632, China
- 华侨医院口腔科,广东 广州 510630Department of Stomatology, First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - 静 刘
- 暨南大学 口腔医学院修复学教研室,广东 广州 510632Department of Prosthodontics, College of Stomatology, Jinan University, Guangzhou 510632, China
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13
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曾 林, 刘 静. [Mitochondrial calcium overload in the masseter muscle of rats with occlusal interference: ionic changes and regulation by calmodulin kinase II]. NAN FANG YI KE DA XUE XUE BAO = JOURNAL OF SOUTHERN MEDICAL UNIVERSITY 2018; 38:755-760. [PMID: 29997101 PMCID: PMC6765715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Indexed: 07/30/2024]
Abstract
OBJECTIVE To investigate the changes in mitochondrial calcium and extracellular sodium concentrations in the masseter muscle of rats with occlusal interference and the regulatory mechanism of mitochondrial Ca2+ overload by calmodulin kinase II (CaMK II). METHODS SD rat models of occlusal interference were established by placing a stainless steel segments (0.8 mm in diameter) to raise the occlusal surface of the upper right first molar. At 3, 7, 14, and 21 days after occlusal interference and at 3 days after removal of occlusal interference, HE staining was used to observe the histomorphological changes of the masseter muscle. Mitochondrial calcium concentration in the masseter muscle was detected using fluorescence spectrophotometry, and direct turbidimetry with potassium pyroantimonate was used to detect the extracellular sodium concentration; the expression levels of masseter muscle p-CaMK II (Thr287) and CaMK II were detected using Western blotting. RESULTS Compared with those in the corresponding control groups, mitochondrial Ca2+ concentration in the masseter muscle on occlusal interference side increased significantly at 3, 7, 14 and 21 days after occlusal interference (P<0.05), but was significantly lowered at 3 days after removal of the interference (P<0.05). The concentration of extracellular Na+ increased progressively with time at 3, 7, 14 and 21 days after occlusal interference (P<0.05), and was significantly decreased at 3 days after interference removal (P<0.05). Occlusal interference for 3, 7 and 14 days resulted in significantly increased expressions of p-CaMK II (Thr287) and CaMK II (P<0.05), which was significantly decreased at 21 days compared with those in the control groups (P<0.05) and further decreased after removal of occlusal interference (P<0.05). Similar changes were also observed on the side without interference, but the changes on the interference side were more obvious (P<0.05). CONCLUSION Occlusal interference causes elevated mitochondrial Ca2+ and extracellular Na+ concentrations in the masseter muscle of rats to lead to calcium overload; the increase in mitochondrial Ca2+ concentration is correlated with the phosphorylation level of CaMK II signaling pathway, suggesting a negative feedback regulation mechanism by the CaMK II signal pathway.
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Affiliation(s)
- 林 曾
- 暨南大学 口腔医学院,广东 广州 510632College of Stomatology, Jinan University, Guangzhou 510632, China
- 华侨医院口腔科,广东 广州 510630Department of Stomatology, First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - 静 刘
- 暨南大学 口腔医学院修复学教研室,广东 广州 510632Department of Prosthodontics, College of Stomatology, Jinan University, Guangzhou 510632, China
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14
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Vierra NC, Dickerson MT, Jordan KL, Dadi PK, Katdare KA, Altman MK, Milian SC, Jacobson DA. TALK-1 reduces delta-cell endoplasmic reticulum and cytoplasmic calcium levels limiting somatostatin secretion. Mol Metab 2018; 9:84-97. [PMID: 29402588 PMCID: PMC5870147 DOI: 10.1016/j.molmet.2018.01.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 01/19/2018] [Indexed: 01/17/2023] Open
Abstract
OBJECTIVE Single-cell RNA sequencing studies have revealed that the type-2 diabetes associated two-pore domain K+ (K2P) channel TALK-1 is abundantly expressed in somatostatin-secreting δ-cells. However, a physiological role for TALK-1 in δ-cells remains unknown. We previously determined that in β-cells, K+ flux through endoplasmic reticulum (ER)-localized TALK-1 channels enhances ER Ca2+ leak, modulating Ca2+ handling and insulin secretion. As glucose amplification of islet somatostatin release relies on Ca2+-induced Ca2+ release (CICR) from the δ-cell ER, we investigated whether TALK-1 modulates δ-cell Ca2+ handling and somatostatin secretion. METHODS To define the functions of islet δ-cell TALK-1 channels, we generated control and TALK-1 channel-deficient (TALK-1 KO) mice expressing fluorescent reporters specifically in δ- and α-cells to facilitate cell type identification. Using immunofluorescence, patch clamp electrophysiology, Ca2+ imaging, and hormone secretion assays, we assessed how TALK-1 channel activity impacts δ- and α-cell function. RESULTS TALK-1 channels are expressed in both mouse and human δ-cells, where they modulate glucose-stimulated changes in cytosolic Ca2+ and somatostatin secretion. Measurement of cytosolic Ca2+ levels in response to membrane potential depolarization revealed enhanced CICR in TALK-1 KO δ-cells that could be abolished by depleting ER Ca2+ with sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) inhibitors. Consistent with elevated somatostatin inhibitory tone, we observed significantly reduced glucagon secretion and α-cell Ca2+ oscillations in TALK-1 KO islets, and found that blockade of α-cell somatostatin signaling with a somatostatin receptor 2 (SSTR2) antagonist restored glucagon secretion in TALK-1 KO islets. CONCLUSIONS These data indicate that TALK-1 reduces δ-cell cytosolic Ca2+ elevations and somatostatin release by limiting δ-cell CICR, modulating the intraislet paracrine signaling mechanisms that control glucagon secretion.
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Affiliation(s)
- Nicholas C Vierra
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Matthew T Dickerson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Kelli L Jordan
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Ketaki A Katdare
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Molly K Altman
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Sarah C Milian
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
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15
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Crystal structures of the TRIC trimeric intracellular cation channel orthologues. Cell Res 2017; 26:1288-1301. [PMID: 27909292 PMCID: PMC5143425 DOI: 10.1038/cr.2016.140] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 10/23/2016] [Accepted: 10/27/2016] [Indexed: 12/30/2022] Open
Abstract
Ca2+ release from the sarcoplasmic reticulum (SR) and endoplasmic reticulum (ER) is crucial for muscle contraction, cell growth, apoptosis, learning and memory. The trimeric intracellular cation (TRIC) channels were recently identified as cation channels balancing the SR and ER membrane potentials, and are implicated in Ca2+ signaling and homeostasis. Here we present the crystal structures of prokaryotic TRIC channels in the closed state and structure-based functional analyses of prokaryotic and eukaryotic TRIC channels. Each trimer subunit consists of seven transmembrane (TM) helices with two inverted repeated regions. The electrophysiological, biochemical and biophysical analyses revealed that TRIC channels possess an ion-conducting pore within each subunit, and that the trimer formation contributes to the stability of the protein. The symmetrically related TM2 and TM5 helices are kinked at the conserved glycine clusters, and these kinks are important for the channel activity. Furthermore, the kinks of the TM2 and TM5 helices generate lateral fenestrations at each subunit interface. Unexpectedly, these lateral fenestrations are occupied with lipid molecules. This study provides the structural and functional framework for the molecular mechanism of this ion channel superfamily.
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16
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El-Ajouz S, Venturi E, Witschas K, Beech M, Wilson AD, Lindsay C, Eberhardt D, O'Brien F, Iida T, Nishi M, Takeshima H, Sitsapesan R. Dampened activity of ryanodine receptor channels in mutant skeletal muscle lacking TRIC-A. J Physiol 2017; 595:4769-4784. [PMID: 28387457 PMCID: PMC5509884 DOI: 10.1113/jp273550] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 03/29/2017] [Indexed: 01/02/2023] Open
Abstract
KEY POINTS The role of trimeric intracellular cation (TRIC) channels is not known, although evidence suggests they may regulate ryanodine receptors (RyR) via multiple mechanisms. We therefore investigated whether Tric-a gene knockout (KO) alters the single-channel function of skeletal RyR (RyR1). We find that RyR1 from Tric-a KO mice are more sensitive to inhibition by divalent cations, although they respond normally to cytosolic Ca2+ , ATP, caffeine and luminal Ca2+ . In the presence of Mg2+ , ATP cannot effectively activate RyR1 from Tric-a KO mice. Additionally, RyR1 from Tric-a KO mice are not activated by protein kinase A phosphorylation, demonstrating a defect in the ability of β-adrenergic stimulation to regulate sarcoplasmic reticulum (SR) Ca2+ -release. The defective RyR1 gating that we describe probably contributes significantly to the impaired SR Ca2+ -release observed in skeletal muscle from Tric-a KO mice, further highlighting the importance of TRIC-A for normal physiological regulation of SR Ca2+ -release in skeletal muscle. ABSTRACT The type A trimeric intracellular cation channel (TRIC-A) is a major component of the nuclear and sarcoplasmic reticulum (SR) membranes of cardiac and skeletal muscle, and is localized closely with ryanodine receptor (RyR) channels in the SR terminal cisternae. The skeletal muscle of Tric-a knockout (KO) mice is characterized by Ca2+ overloaded and swollen SR and by changes in the properties of SR Ca2+ release. We therefore investigated whether RyR1 gating behaviour is modified in the SR from Tric-a KO mice by incorporating native RyR1 into planar phospholipid bilayers under voltage-clamp conditions. We find that RyR1 channels from Tric-a KO mice respond normally to cytosolic Ca2+ , ATP, adenine, caffeine and to luminal Ca2+ . However, the channels are more sensitive to the inactivating effects of divalent cations, thus, in the presence of Mg2+ , ATP is inadequate as an activator. Additionally, channels are not characteristically activated by protein kinase A even though the phosphorylation levels of Ser2844 are similar to controls. The results of the present study suggest that TRIC-A functions as an excitatory modulator of RyR1 channels within the SR terminal cisternae. Importantly, this regulatory action of TRIC-A appears to be independent of (although additive to) any indirect consequences to RyR1 activity that arise as a result of K+ fluxes across the SR via TRIC-A.
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Affiliation(s)
- Sam El-Ajouz
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Elisa Venturi
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Katja Witschas
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Matthew Beech
- Department of Pharmacology, University of Oxford, Oxford, UK
| | | | - Chris Lindsay
- Department of Pharmacology, University of Oxford, Oxford, UK.,Department of Chemistry, University of Oxford, Oxford, UK
| | - David Eberhardt
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Fiona O'Brien
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Tsunaki Iida
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Miyuki Nishi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
| | - Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
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17
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Structural basis for conductance through TRIC cation channels. Nat Commun 2017; 8:15103. [PMID: 28524849 PMCID: PMC5477506 DOI: 10.1038/ncomms15103] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 02/28/2017] [Indexed: 01/08/2023] Open
Abstract
Mammalian TRICs function as K+-permeable cation channels that provide counter ions for Ca2+ handling in intracellular stores. Here we describe the structures of two prokaryotic homologues, archaeal SaTRIC and bacterial CpTRIC, showing that TRIC channels are symmetrical trimers with transmembrane pores through each protomer. Each pore holds a string of water molecules centred at kinked helices in two inverted-repeat triple-helix bundles (THBs). The pores are locked in a closed state by a hydrogen bond network at the C terminus of the THBs, which is lost when the pores assume an open conformation. The transition between the open and close states seems to be mediated by cation binding to conserved residues along the three-fold axis. Electrophysiology and mutagenesis studies show that prokaryotic TRICs have similar functional properties to those of mammalian TRICs and implicate the three-fold axis in the allosteric regulation of the channel. Trimeric intracellular cation channels (TRICs) elicit K+ currents to counteract luminal negative potential during Ca2+ release from intracellular stores. Here the authors present structures of prokaryotic TRICs in their open and closed states, obtaining molecular insight into TRICs' function.
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18
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Abstract
Trimeric intracellular cation (TRIC) channel subtypes, namely TRIC-A and TRIC-B, are expressed in the endoplasmic/sarcoplasmic reticulum and nuclear envelope, and likely function as monovalent cation channels in various cell types. Our studies using knockout mice so far suggest that TRIC subtypes support Ca2+ release from intracellular stores by mediating counter-cationic fluxes. Several genetic mutations within the TRIC-B locus were recently identified in autosomal recessive osteogenesis imperfecta (OI) patients. However, the molecular mechanism by which the mutations cause human disease is not fully addressed. We found that Tric-b-knockout mice exhibit poor bone ossification and thus serve as an OI-model animal. Studies on Tric-b-knockout bones and cultured cell lines derived from the patients currently reveal the main part of the pathophysiological mechanism involved in the TRIC-B-mutated OI form. This mini-review focuses on the essential role of TRIC-B channels in bone ossification.
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19
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Tan T, Ko YG, Ma J. Dual function of MG53 in membrane repair and insulin signaling. BMB Rep 2017; 49:414-23. [PMID: 27174502 PMCID: PMC5070728 DOI: 10.5483/bmbrep.2016.49.8.079] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Indexed: 12/20/2022] Open
Abstract
MG53 is a member of the TRIM-family protein that acts as a key component of the cell membrane repair machinery. MG53 is also an E3-ligase that ubiquinates insulin receptor substrate-1 and controls insulin signaling in skeletal muscle cells. Since its discovery in 2009, research efforts have been devoted to translate this basic discovery into clinical applications in human degenerative and metabolic diseases. This review article highlights the dual function of MG53 in cell membrane repair and insulin signaling, the mechanism that underlies the control of MG53 function, and the therapeutic value of targeting MG53 function in regenerative medicine. [BMB Reports 2016; 49(8): 414-423]
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Affiliation(s)
- Tao Tan
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Young-Gyu Ko
- Division of Life Sciences, Korea University, Seoul 02841, Korea
| | - Jianjie Ma
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
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20
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Frederick DW, Loro E, Liu L, Davila A, Chellappa K, Silverman IM, Quinn WJ, Gosai SJ, Tichy ED, Davis JG, Mourkioti F, Gregory BD, Dellinger RW, Redpath P, Migaud ME, Nakamaru-Ogiso E, Rabinowitz JD, Khurana TS, Baur JA. Loss of NAD Homeostasis Leads to Progressive and Reversible Degeneration of Skeletal Muscle. Cell Metab 2016; 24:269-82. [PMID: 27508874 PMCID: PMC4985182 DOI: 10.1016/j.cmet.2016.07.005] [Citation(s) in RCA: 249] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 05/06/2016] [Accepted: 07/14/2016] [Indexed: 11/19/2022]
Abstract
NAD is an obligate co-factor for the catabolism of metabolic fuels in all cell types. However, the availability of NAD in several tissues can become limited during genotoxic stress and the course of natural aging. The point at which NAD restriction imposes functional limitations on tissue physiology remains unknown. We examined this question in murine skeletal muscle by specifically depleting Nampt, an essential enzyme in the NAD salvage pathway. Knockout mice exhibited a dramatic 85% decline in intramuscular NAD content, accompanied by fiber degeneration and progressive loss of both muscle strength and treadmill endurance. Administration of the NAD precursor nicotinamide riboside rapidly ameliorated functional deficits and restored muscle mass despite having only a modest effect on the intramuscular NAD pool. Additionally, lifelong overexpression of Nampt preserved muscle NAD levels and exercise capacity in aged mice, supporting a critical role for tissue-autonomous NAD homeostasis in maintaining muscle mass and function.
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Affiliation(s)
- David W Frederick
- Department of Physiology and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Emanuele Loro
- Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ling Liu
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Antonio Davila
- Department of Physiology and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Karthikeyani Chellappa
- Department of Physiology and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ian M Silverman
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - William J Quinn
- Department of Physiology and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sager J Gosai
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Elisia D Tichy
- Department of Orthopaedic Surgery, Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - James G Davis
- Department of Physiology and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Foteini Mourkioti
- Department of Orthopaedic Surgery, Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Brian D Gregory
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Philip Redpath
- School of Pharmacy, Queen's University Belfast, Belfast, BT9 7BL Northern Ireland, UK
| | - Marie E Migaud
- School of Pharmacy, Queen's University Belfast, Belfast, BT9 7BL Northern Ireland, UK
| | - Eiko Nakamaru-Ogiso
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Joshua D Rabinowitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Tejvir S Khurana
- Department of Physiology and Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Joseph A Baur
- Department of Physiology and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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21
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Zhao C, Ichimura A, Qian N, Iida T, Yamazaki D, Noma N, Asagiri M, Yamamoto K, Komazaki S, Sato C, Aoyama F, Sawaguchi A, Kakizawa S, Nishi M, Takeshima H. Mice lacking the intracellular cation channel TRIC-B have compromised collagen production and impaired bone mineralization. Sci Signal 2016; 9:ra49. [PMID: 27188440 DOI: 10.1126/scisignal.aad9055] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The trimeric intracellular cation (TRIC) channels TRIC-A and TRIC-B localize predominantly to the endoplasmic reticulum (ER) and likely support Ca(2+) release from intracellular stores by mediating cationic flux to maintain electrical neutrality. Deletion and point mutations in TRIC-B occur in families with autosomal recessive osteogenesis imperfecta. Tric-b knockout mice develop neonatal respiratory failure and exhibit poor bone ossification. We investigated the cellular defect causing the bone phenotype. Bone histology indicated collagen matrix deposition was reduced in Tric-b knockout mice. Osteoblasts, the bone-depositing cells, from Tric-b knockout mice exhibited reduced Ca(2+) release from ER and increased ER Ca(2+) content, which was associated with ER swelling. These cells also had impaired collagen release without a decrease in collagen-encoding transcripts, consistent with a defect in trafficking of collagen through ER. In contrast, osteoclasts, the bone-degrading cells, from Tric-b knockout mice were similar to those from wild-type mice. Thus, TRIC-B function is essential to support the production and release of large amounts of collagen by osteoblasts, which is necessary for bone mineralization.
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Affiliation(s)
- Chengzhu Zhao
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Atsuhiko Ichimura
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan. Keihanshin Consortium for Fostering the Next Generation of Global Leaders in Research (K-CONNEX), Kyoto University, Kyoto 606-8501, Japan
| | - Nianchao Qian
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Tsunaki Iida
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Daiju Yamazaki
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Naruto Noma
- Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Masataka Asagiri
- Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | - Koji Yamamoto
- Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
| | | | - Chikara Sato
- National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8568, Japan
| | - Fumiyo Aoyama
- Faculty of Medicine, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Akira Sawaguchi
- Faculty of Medicine, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Sho Kakizawa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Miyuki Nishi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
| | - Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
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22
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Abstract
Sarcoplasmic reticulum (SR) K+ channels are voltage-regulated channels that are thought to be actively gating when the membrane potential across the SR is close to zero as is expected physiologically. A characteristic of SR K+ channels is that they gate to subconductance open states but the relevance of the subconductance events and their contribution to the overall current flowing through the channels at physiological membrane potentials is not known. We have investigated the relationship between subconductance and full conductance openings and developed kinetic models to describe the voltage sensitivity of channel gating. Because there may be two subtypes of SR K+ channels (TRIC-A and TRIC-B) present in most tissues, to conduct our study on a homogeneous population of SR K+ channels, we incorporated SR vesicles derived from Tric-a knockout mice into artificial membranes to examine the remaining SR K+ channel (TRIC-B) function. The channels displayed very low open probability (Po) at negative potentials (≤0 mV) and opened predominantly to subconductance open states. Positive holding potentials primarily increased the frequency of subconductance state openings and thereby increased the number of subsequent transitions into the full open state, although a slowing of transitions back to the sublevels was also important. We investigated whether the subconductance gating could arise as an artifact of incomplete resolution of rapid transitions between full open and closed states; however, we were not able to produce a model that could fit the data as well as one that included multiple distinct current amplitudes. Our results suggest that the apparent subconductance openings will provide most of the K+ flux when the SR membrane potential is close to zero. The relative contribution played by openings to the full open state would increase if negative charge developed within the SR thus increasing the capacity of the channel to compensate for ionic imbalances.
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23
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Worman HJ, Schirmer EC. Nuclear membrane diversity: underlying tissue-specific pathologies in disease? Curr Opin Cell Biol 2015; 34:101-12. [PMID: 26115475 PMCID: PMC4522394 DOI: 10.1016/j.ceb.2015.06.003] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 06/05/2015] [Accepted: 06/10/2015] [Indexed: 11/16/2022]
Abstract
Human 'laminopathy' diseases result from mutations in genes encoding nuclear lamins or nuclear envelope (NE) transmembrane proteins (NETs). These diseases present a seeming paradox: the mutated proteins are widely expressed yet pathology is limited to specific tissues. New findings suggest tissue-specific pathologies arise because these widely expressed proteins act in various complexes that include tissue-specific components. Diverse mechanisms to achieve NE tissue-specificity include tissue-specific regulation of the expression, mRNA splicing, signaling, NE-localization and interactions of potentially hundreds of tissue-specific NETs. New findings suggest these NETs underlie tissue-specific NE roles in cytoskeletal mechanics, cell-cycle regulation, signaling, gene expression and genome organization. This view of the NE as 'specialized' in each cell type is important to understand the tissue-specific pathology of NE-linked diseases.
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Affiliation(s)
- Howard J Worman
- Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, USA; Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, USA
| | - Eric C Schirmer
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, UK.
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24
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Kuum M, Veksler V, Kaasik A. Potassium fluxes across the endoplasmic reticulum and their role in endoplasmic reticulum calcium homeostasis. Cell Calcium 2014; 58:79-85. [PMID: 25467968 DOI: 10.1016/j.ceca.2014.11.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 11/07/2014] [Accepted: 11/10/2014] [Indexed: 12/16/2022]
Abstract
There are a number of known and suspected channels and exchangers in the endoplasmic reticulum that may participate in potassium flux across its membrane. They include trimeric intracellular cation channels permeable for potassium, ATP-sensitive potassium channels, calcium-activated potassium channels and the potassium-hydrogen exchanger. Apart from trimeric intracellular cation channels, which are specific to the endoplasmic reticulum, other potassium channels are also expressed in the plasma membrane and/or mitochondria, and their specific role in the endoplasmic reticulum has not yet been fully established. In addition to these potassium-selective channels, the ryanodine receptor and, potentially, the inositol 1,4,5-trisphosphate receptor are permeable to potassium ions. Also, the role of potassium fluxes across the endoplasmic reticulum membrane has remained elusive. It has been proposed that their main role is to balance the charge movement that occurs during calcium release and uptake from or to the endoplasmic reticulum. This review aims to summarize current knowledge on endoplasmic reticulum potassium channels and fluxes and their potential role in endoplasmic reticulum calcium uptake and release.
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Affiliation(s)
- Malle Kuum
- Department of Pharmacology, Centre of Excellence for Translational Medicine, University of Tartu, Ravila 19, Tartu, Estonia
| | - Vladimir Veksler
- INSERM, U-769, Châtenay-Malabry F-92296, France; Univ Paris-Sud, Châtenay-Malabry F-92296, France
| | - Allen Kaasik
- Department of Pharmacology, Centre of Excellence for Translational Medicine, University of Tartu, Ravila 19, Tartu, Estonia.
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25
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Zang YL, Xia L. Cellular mechanism of cardiac alternans: an unresolved chicken or egg problem. J Zhejiang Univ Sci B 2014; 15:201-11. [PMID: 24599685 DOI: 10.1631/jzus.b1300177] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
T-wave alternans, a specific form of cardiac alternans, has been associated with the increased susceptibility to cardiac arrhythmias and sudden cardiac death (SCD). Plenty of evidence has related cardiac alternans at the tissue level to the instability of voltage kinetics or Ca(2+) handling dynamics at the cellular level. However, to date, none of the existing experiments could identify the exact cellular mechanism of cardiac alternans due to the bi-directional coupling between voltage kinetics and Ca(2+) handling dynamics. Either of these systems could be the origin of alternans and the other follows as a secondary change, therefore making the cellular mechanism of alternans a difficult chicken or egg problem. In this context, theoretical analysis combined with experimental techniques provides a possibility to explore this problem. In this review, we will summarize the experimental and theoretical advances in understanding the cellular mechanism of alternans. We focus on the roles of action potential duration (APD) restitution and Ca(2+) handling dynamics in the genesis of alternans and show how the theoretical analysis combined with experimental techniques has provided us a new insight into the cellular mechanism of alternans. We also discuss the possible reasons of increased propensity for alternans in heart failure (HF) and the new possible therapeutic targets. Finally, according to the level of electrophysiological recording techniques and theoretical strategies, we list some critical experimental or theoretical challenges which may help to determine the origin of alternans and to find more effective therapeutic targets in the future.
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Affiliation(s)
- Yun-Liang Zang
- Key Lab of Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China; Department of Pharmacology, University of California, Davis, CA 95616, USA
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26
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Zhou X, Lin P, Yamazaki D, Park KH, Komazaki S, Chen SRW, Takeshima H, Ma J. Trimeric intracellular cation channels and sarcoplasmic/endoplasmic reticulum calcium homeostasis. Circ Res 2014; 114:706-16. [PMID: 24526676 DOI: 10.1161/circresaha.114.301816] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Trimeric intracellular cation channels (TRIC) represents a novel class of trimeric intracellular cation channels. Two TRIC isoforms have been identified in both the human and the mouse genomes: TRIC-A, a subtype predominantly expressed in the sarcoplasmic reticulum (SR) of muscle cells, and TRIC-B, a ubiquitous subtype expressed in the endoplasmic reticulum (ER) of all tissues. Genetic ablation of either TRIC-A or TRIC-B leads to compromised K(+) permeation and Ca(2+) release across the SR/ER membrane, supporting the hypothesis that TRIC channels provide a counter balancing K(+) flux that reduces SR/ER membrane depolarization for maintenance of the electrochemical gradient that drives SR/ER Ca(2+) release. TRIC-A and TRIC-B seem to have differential functions in Ca(2+) signaling in excitable and nonexcitable cells. Tric-a(-/-) mice display defective Ca(2+) sparks and spontaneous transient outward currents in arterial smooth muscle and develop hypertension, in addition to skeletal muscle dysfunction. Knockout of TRIC-B results in abnormal IP3 receptor-mediated Ca(2+) release in airway epithelial cells, respiratory defects, and neonatal lethality. Double knockout mice lacking both TRIC-A and TRIC-B show embryonic lethality as a result of cardiac arrest. Such an aggravated lethality indicates that TRIC-A and TRIC-B share complementary physiological functions in Ca(2+) signaling in embryonic cardiomyocytes. Tric-a(-/-) and Tric-b(+/-) mice are viable and susceptible to stress-induced heart failure. Recent evidence suggests that TRIC-A directly modulates the function of the cardiac ryanodine receptor 2 Ca(2+) release channel, which in turn controls store-overload-induced Ca(2+) release from the SR. Thus, the TRIC channels, in addition to providing a countercurrent for SR/ER Ca(2+) release, may also function as accessory proteins that directly modulate the ryanodine receptor/IP3 receptor channel functions.
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Affiliation(s)
- Xinyu Zhou
- From the Department of Surgery, Davis Heart and Lung Research Institute, Wexner Medical Center, The Ohio State University, Columbus (X.Z., P.L., K.H.P., J.M.); Department of Biological Chemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Kyoto, Japan (D.Y., H.T.); Department of Anatomy, Saitama Medical University, Saitama, Japan (S.K.); and Departments of Physiology and Pharmacology, and Biochemistry and Molecular Biology, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada (W.C.)
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27
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Guo T, Nani A, Shonts S, Perryman M, Chen H, Shannon T, Gillespie D, Fill M. Sarcoplasmic reticulum K(+) (TRIC) channel does not carry essential countercurrent during Ca(2+) release. Biophys J 2014; 105:1151-60. [PMID: 24010658 DOI: 10.1016/j.bpj.2013.07.042] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 06/17/2013] [Accepted: 07/15/2013] [Indexed: 01/30/2023] Open
Abstract
The charge translocation associated with sarcoplasmic reticulum (SR) Ca(2+) efflux is compensated for by a simultaneous SR K(+) influx. This influx is essential because, with no countercurrent, the SR membrane potential (Vm) would quickly (<1 ms) reach the Ca(2+) equilibrium potential and SR Ca(2+) release would cease. The SR K(+) trimeric intracellular cation (TRIC) channel has been proposed to carry the essential countercurrent. However, the ryanodine receptor (RyR) itself also carries a substantial K(+) countercurrent during release. To better define the physiological role of the SR K(+) channel, we compared SR Ca(2+) transport in saponin-permeabilized cardiomyocytes before and after limiting SR K(+) channel function. Specifically, we reduced SR K(+) channel conduction 35 and 88% by replacing cytosolic K(+) for Na(+) or Cs(+) (respectively), changes that have little effect on RyR function. Calcium sparks, SR Ca(2+) reloading, and caffeine-evoked Ca(2+) release amplitude (and rate) were unaffected by these ionic changes. Our results show that countercurrent carried by SR K(+) (TRIC) channels is not required to support SR Ca(2+) release (or uptake). Because K(+) enters the SR through RyRs during release, the SR K(+) (TRIC) channel most likely is needed to restore trans-SR K(+) balance after RyRs close, assuring SR Vm stays near 0 mV.
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Affiliation(s)
- Tao Guo
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, USA
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28
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de Las Heras JI, Meinke P, Batrakou DG, Srsen V, Zuleger N, Kerr AR, Schirmer EC. Tissue specificity in the nuclear envelope supports its functional complexity. Nucleus 2013; 4:460-77. [PMID: 24213376 PMCID: PMC3925691 DOI: 10.4161/nucl.26872] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Nuclear envelope links to inherited disease gave the conundrum of how mutations in near-ubiquitous proteins can yield many distinct pathologies, each focused in different tissues. One conundrum-resolving hypothesis is that tissue-specific partner proteins mediate these pathologies. Such partner proteins may have now been identified with recent proteome studies determining nuclear envelope composition in different tissues. These studies revealed that the majority of the total nuclear envelope proteins are tissue restricted in their expression. Moreover, functions have been found for a number these tissue-restricted nuclear envelope proteins that fit with mechanisms proposed to explain how the nuclear envelope could mediate disease, including defects in mechanical stability, cell cycle regulation, signaling, genome organization, gene expression, nucleocytoplasmic transport, and differentiation. The wide range of functions to which these proteins contribute is consistent with not only their involvement in tissue-specific nuclear envelope disease pathologies, but also tissue evolution.
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Affiliation(s)
- Jose I de Las Heras
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology; University of Edinburgh; Edinburgh, UK
| | - Peter Meinke
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology; University of Edinburgh; Edinburgh, UK
| | - Dzmitry G Batrakou
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology; University of Edinburgh; Edinburgh, UK
| | - Vlastimil Srsen
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology; University of Edinburgh; Edinburgh, UK
| | - Nikolaj Zuleger
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology; University of Edinburgh; Edinburgh, UK
| | - Alastair Rw Kerr
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology; University of Edinburgh; Edinburgh, UK
| | - Eric C Schirmer
- Wellcome Trust Centre for Cell Biology and Institute of Cell Biology; University of Edinburgh; Edinburgh, UK
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29
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Tao S, Yamazaki D, Komazaki S, Zhao C, Iida T, Kakizawa S, Imaizumi Y, Takeshima H. Facilitated hyperpolarization signaling in vascular smooth muscle-overexpressing TRIC-A channels. J Biol Chem 2013; 288:15581-9. [PMID: 23592776 DOI: 10.1074/jbc.m112.435396] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The TRIC channel subtypes, namely TRIC-A and TRIC-B, are intracellular monovalent cation-specific channels and likely mediate counterion movements to support efficient Ca(2+) release from the sarco/endoplasmic reticulum. Vascular smooth muscle cells (VSMCs) contain both TRIC subtypes and two Ca(2+) release mechanisms; incidental opening of ryanodine receptors (RyRs) generates local Ca(2+) sparks to induce hyperpolarization and relaxation, whereas agonist-induced activation of inositol trisphosphate receptors produces global Ca(2+) transients causing contraction. Tric-a knock-out mice develop hypertension due to insufficient RyR-mediated Ca(2+) sparks in VSMCs. Here we describe transgenic mice overexpressing TRIC-A channels under the control of a smooth muscle cell-specific promoter. The transgenic mice developed congenital hypotension. In Tric-a-overexpressing VSMCs from the transgenic mice, the resting membrane potential decreased because RyR-mediated Ca(2+) sparks were facilitated and cell surface Ca(2+)-dependent K(+) channels were hyperactivated. Under such hyperpolarized conditions, L-type Ca(2+) channels were inactivated, and thus, the resting intracellular Ca(2+) levels were reduced in Tric-a-overexpressing VSMCs. Moreover, Tric-a overexpression impaired inositol trisphosphate-sensitive stores to diminish agonist-induced Ca(2+) signaling in VSMCs. These altered features likely reduced vascular tonus leading to the hypotensive phenotype. Our Tric-a-transgenic mice together with Tric-a knock-out mice indicate that TRIC-A channel density in VSMCs is responsible for controlling basal blood pressure at the whole-animal level.
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Affiliation(s)
- Shengchen Tao
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
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30
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Venturi E, Matyjaszkiewicz A, Pitt SJ, Tsaneva-Atanasova K, Nishi M, Yamazaki D, Takeshima H, Sitsapesan R. TRIC-B channels display labile gating: evidence from the TRIC-A knockout mouse model. Pflugers Arch 2013; 465:1135-48. [PMID: 23467973 PMCID: PMC3732801 DOI: 10.1007/s00424-013-1251-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 01/24/2013] [Accepted: 02/11/2013] [Indexed: 11/25/2022]
Abstract
Sarcoplasmic/endoplasmic reticulum (SR) and nuclear membranes contain two related cation channels named TRIC-A and TRIC-B. In many tissues, both subtypes are co-expressed, making it impossible to distinguish the distinct single-channel properties of each subtype. We therefore incorporated skeletal muscle SR vesicles derived from Tric-a-knockout mice into bilayers in order to characterise the biophysical properties of native TRIC-B without possible misclassification of the channels as TRIC-A, and without potential distortion of functional properties by detergent purification protocols. The native TRIC-B channels were ideally selective for cations. In symmetrical 210 mM K+, the maximum (full) open channel level (199 pS) was equivalent to that observed when wild-type SR vesicles were incorporated into bilayers. Analysis of TRIC-B gating revealed complex and variable behaviour. Four main sub-conductance levels were observed at approximately 80 % (161 pS), 60 % (123 pS), 46 % (93 pS), and 30 % (60 pS) of the full open state. Seventy-five percent of the channels were voltage sensitive with Po being markedly reduced at negative holding potentials. The frequent, rapid transitions between TRIC-B sub-conductance states prevented development of reliable gating models using conventional single-channel analysis. Instead, we used mean-variance plots to highlight key features of TRIC-B gating in a more accurate and visually useful manner. Our study provides the first biophysical characterisation of native TRIC-B channels and indicates that this channel would be suited to provide counter current in response to Ca2+ release from the SR. Further experiments are required to distinguish the distinct functional properties of TRIC-A and TRIC-B and understand their individual but complementary physiological roles.
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Affiliation(s)
- Elisa Venturi
- School of Physiology & Pharmacology, NSQI and Bristol Heart Institute, University of Bristol, Bristol, BS8 1TD UK
| | - Antoni Matyjaszkiewicz
- School of Physiology & Pharmacology, NSQI and Bristol Heart Institute, University of Bristol, Bristol, BS8 1TD UK
- Department of Engineering Mathematics, University of Bristol, Bristol, BS8 1TR UK
- Bristol Centre for Complexity Sciences, University of Bristol, Bristol, BS8 1TR UK
| | - Samantha J. Pitt
- School of Medicine, University of St Andrews, St Andrews, KY16 9TF UK
| | | | - Miyuki Nishi
- Graduate School of Pharmaceutical Sciences and Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, 606-8501 Japan
| | - Daiju Yamazaki
- Graduate School of Pharmaceutical Sciences and Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, 606-8501 Japan
| | - Hiroshi Takeshima
- Graduate School of Pharmaceutical Sciences and Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, 606-8501 Japan
| | - Rebecca Sitsapesan
- School of Physiology & Pharmacology, NSQI and Bristol Heart Institute, University of Bristol, Bristol, BS8 1TD UK
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31
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TRIC channels supporting efficient Ca2+ release from intracellular stores. Pflugers Arch 2012; 465:187-95. [DOI: 10.1007/s00424-012-1197-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 11/30/2012] [Accepted: 11/30/2012] [Indexed: 12/22/2022]
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32
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Effect of aging on calcium signaling in C57Bl6J mouse cerebral arteries. Pflugers Arch 2012; 465:829-38. [DOI: 10.1007/s00424-012-1195-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 11/28/2012] [Accepted: 11/29/2012] [Indexed: 01/08/2023]
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33
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Park KH, Brotto L, Lehoang O, Brotto M, Ma J, Zhao X. Ex vivo assessment of contractility, fatigability and alternans in isolated skeletal muscles. J Vis Exp 2012:e4198. [PMID: 23149471 PMCID: PMC3499085 DOI: 10.3791/4198] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Described here is a method to measure contractility of isolated skeletal muscles. Parameters such as muscle force, muscle power, contractile kinetics, fatigability, and recovery after fatigue can be obtained to assess specific aspects of the excitation-contraction coupling (ECC) process such as excitability, contractile machinery and Ca(2+) handling ability. This method removes the nerve and blood supply and focuses on the isolated skeletal muscle itself. We routinely use this method to identify genetic components that alter the contractile property of skeletal muscle though modulating Ca(2+) signaling pathways. Here, we describe a newly identified skeletal muscle phenotype, i.e., mechanic alternans, as an example of the various and rich information that can be obtained using the in vitro muscle contractility assay. Combination of this assay with single cell assays, genetic approaches and biochemistry assays can provide important insights into the mechanisms of ECC in skeletal muscle.
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Affiliation(s)
- Ki Ho Park
- Department of Physiology and Biophysics, UMDNJ-Robert Wood Johnson Medical School, USA
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34
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Yamazaki D. [TRIC(trimeric intracellular cation)-A channels contribute to blood pressure maintenance in vascular smooth muscle]. YAKUGAKU ZASSHI 2012; 132:1037-43. [PMID: 23023421 DOI: 10.1248/yakushi.132.1037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
TRIC (trimeric intracellular cation) channel subtypes, namely TRIC-A and TRIC-B, are intracellular monovalent cation channels postulated to mediate counter-ion movements facilitating physiological Ca²⁺ release from intracellular stores. Tric-a-knockout mice developed hypertension during the daytime due to enhanced myogenic tone in resistance arteries. There are two Ca²⁺ release mechanisms in vascular smooth muscle cells (VSMCs); incidental opening of ryanodine receptors (RyRs) generates local Ca²⁺ sparks to induce hyperpolarization, while agonist-induced activation of inositol trisphosphate receptors (IP₃Rs) evokes global Ca²⁺ transients causing contraction. Tric-a gene ablation inhibited RyR-mediated hyperpolarization signaling to stimulate voltage-dependent Ca²⁺ influx, and adversely enhanced IP₃R-mediated Ca²⁺ transients by overloading Ca²⁺ stores in VSMCs. Therefore, TRIC-A channels contribute to maintaining blood pressure in vascular smooth muscles.
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Affiliation(s)
- Daiju Yamazaki
- Department of Biological Chemistry, Graduate School of Phamaceutical Sciences, Kyoto University, Japan.
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35
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Yamazaki D, Tabara Y, Kita S, Hanada H, Komazaki S, Naitou D, Mishima A, Nishi M, Yamamura H, Yamamoto S, Kakizawa S, Miyachi H, Yamamoto S, Miyata T, Kawano Y, Kamide K, Ogihara T, Hata A, Umemura S, Soma M, Takahashi N, Imaizumi Y, Miki T, Iwamoto T, Takeshima H. TRIC-A channels in vascular smooth muscle contribute to blood pressure maintenance. Cell Metab 2011; 14:231-41. [PMID: 21803293 DOI: 10.1016/j.cmet.2011.05.011] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 04/09/2011] [Accepted: 05/12/2011] [Indexed: 01/11/2023]
Abstract
TRIC channel subtypes, namely TRIC-A and TRIC-B, are intracellular monovalent cation channels postulated to mediate counter-ion movements facilitating physiological Ca(2+) release from internal stores. Tric-a-knockout mice developed hypertension during the daytime due to enhanced myogenic tone in resistance arteries. There are two Ca(2+) release mechanisms in vascular smooth muscle cells (VSMCs); incidental opening of ryanodine receptors (RyRs) generates local Ca(2+) sparks to induce hyperpolarization, while agonist-induced activation of inositol trisphosphate receptors (IP(3)Rs) evokes global Ca(2+) transients causing contraction. Tric-a gene ablation inhibited RyR-mediated hyperpolarization signaling to stimulate voltage-dependent Ca(2+) influx, and adversely enhanced IP(3)R-mediated Ca(2+) transients by overloading Ca(2+) stores in VSMCs. Moreover, association analysis identified single-nucleotide polymorphisms (SNPs) around the human TRIC-A gene that increase hypertension risk and restrict the efficiency of antihypertensive drugs. Therefore, TRIC-A channels contribute to maintaining blood pressure, while TRIC-A SNPs could provide biomarkers for constitutional diagnosis and personalized medical treatment of essential hypertension.
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Affiliation(s)
- Daiju Yamazaki
- Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
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36
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Silverio ALF, Saier MH. Bioinformatic characterization of the trimeric intracellular cation-specific channel protein family. J Membr Biol 2011; 241:77-101. [PMID: 21519847 DOI: 10.1007/s00232-011-9364-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 03/26/2011] [Indexed: 12/29/2022]
Abstract
Trimeric intracellular cation-specific (TRIC) channels are integral to muscle excitation-contraction coupling. TRIC channels provide counter-ionic flux when calcium is rapidly transported from intracellular stores to the cell cytoplasm. Until recently, knowledge of the presence of these proteins was limited to animals. We analyzed the TRIC family and identified a profusion of prokaryotic family members with topologies and motifs similar to those of their eukaryotic counterparts. Prokaryotic members far outnumber eukaryotic members, and although none has been functionally characterized, the evidence suggests that they function as secondary carriers. The presence of fused N- or C-terminal domains of known biochemical functions as well as genomic context analyses provide clues about the functions of these prokaryotic homologs. They are proposed to function in metabolite (e.g., amino acid/nucleotide) efflux. Phylogenetic analysis revealed that TRIC channel homologs diverged relatively early during evolutionary history and that horizontal gene transfer was frequent in prokaryotes but not in eukaryotes. Topological analyses of TRIC channels revealed that these proteins possess seven putative transmembrane segments (TMSs), which arose by intragenic duplication of a three-TMS polypeptide-encoding genetic element followed by addition of a seventh TMS at the C terminus to give the precursor of all current TRIC family homologs. We propose that this family arose in prokaryotes.
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Affiliation(s)
- Abe L F Silverio
- Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
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37
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Venturi E, Mio K, Nishi M, Ogura T, Moriya T, Pitt SJ, Okuda K, Kakizawa S, Sitsapesan R, Sato C, Takeshima H. Mitsugumin 23 forms a massive bowl-shaped assembly and cation-conducting channel. Biochemistry 2011; 50:2623-32. [PMID: 21381722 PMCID: PMC3065873 DOI: 10.1021/bi1019447] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mitsugumin 23 (MG23) is a 23 kDa transmembrane protein localized to the sarcoplasmic/endoplasmic reticulum and nuclear membranes in a wide variety of cells. Although the characteristics imply the participation in a fundamental function in intracellular membrane systems, the physiological role of MG23 is unknown. Here we report the biochemical and biophysical characterization of MG23. Hydropathicity profile and limited proteolytic analysis proposed three transmembrane segments in the MG23 primary structure. Chemical cross-linking analysis suggested a homo-oligomeric assembly of MG23. Ultrastructural observations detected a large symmetrical particle as the predominant component and a small asymmetric assembly as the second major component in highly purified MG23 preparations. Single-particle three-dimensional reconstruction revealed that MG23 forms a large bowl-shaped complex equipped with a putative central pore, which is considered an assembly of the small asymmetric subunit. After reconstitution into planar phospholipid bilayers, purified MG23 behaved as a voltage-dependent, cation-conducting channel, permeable to both K(+) and Ca(2+). A feature of MG23 gating was that multiple channels always appeared to be gating together in the bilayer. Our observations suggest that the bowl-shaped MG23 can transiently assemble and disassemble. These building transitions may underlie the unusual channel gating behavior of MG23 and allow rapid cationic flux across intracellular membrane systems.
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Affiliation(s)
- Elisa Venturi
- School of Physiology and Pharmacology, Bristol Heart Institute and Centre for Nanoscience and Quantum Information, University of Bristol, Bristol, United Kingdom
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