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Balderas E, Lee SH, Shankar TS, Yin X, Balynas AM, Kyriakopoulos CP, Selzman CH, Drakos SG, Chaudhuri D. Mitochondria possess a large, non-selective ionic current that is enhanced during cardiac injury. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.15.567241. [PMID: 38014208 PMCID: PMC10680780 DOI: 10.1101/2023.11.15.567241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Mitochondrial ion channels are essential for energy production and cell survival. To avoid depleting the electrochemical gradient used for ATP synthesis, channels so far described in the mitochondrial inner membrane open only briefly, are highly ion-selective, have restricted tissue distributions, or have small currents. Here, we identify a mitochondrial inner membrane conductance that has strikingly different behavior from previously described channels. It is expressed ubiquitously, and transports cations non-selectively, producing a large, up to nanoampere-level, current. The channel does not lead to inner membrane uncoupling during normal physiology because it only becomes active at depolarized voltages. It is inhibited by external Ca2+, corresponding to the intermembrane space, as well as amiloride. This large, ubiquitous, non-selective, amiloride-sensitive (LUNA) current appears most active when expression of the mitochondrial calcium uniporter is minimal, such as in the heart. In this organ, we find that LUNA current magnitude increases two- to threefold in multiple mouse models of injury, an effect also seen in cardiac mitochondria from human patients with heart failure with reduced ejection fraction. Taken together, these features lead us to speculate that LUNA current may arise from an essential protein that acts as a transporter under physiological conditions, but becomes a channel under conditions of mitochondrial stress and depolarization.
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Affiliation(s)
- Enrique Balderas
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Sandra H.J. Lee
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Thirupura S. Shankar
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Xue Yin
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Anthony M. Balynas
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Christos P. Kyriakopoulos
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Craig H. Selzman
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
- Department of Surgery, Division of Cardiothoracic Surgery, University of Utah, Salt Lake City, UT
- U.T.A.H. (Utah Transplant Affiliated Hospitals) Cardiac Transplant Program: University of Utah Healthcare and School of Medicine, Intermountain Medical Center, Salt Lake Veterans Affairs Health Care System, Salt Lake City, UT
| | - Stavros G. Drakos
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
- U.T.A.H. (Utah Transplant Affiliated Hospitals) Cardiac Transplant Program: University of Utah Healthcare and School of Medicine, Intermountain Medical Center, Salt Lake Veterans Affairs Health Care System, Salt Lake City, UT
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT
| | - Dipayan Chaudhuri
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
- U.T.A.H. (Utah Transplant Affiliated Hospitals) Cardiac Transplant Program: University of Utah Healthcare and School of Medicine, Intermountain Medical Center, Salt Lake Veterans Affairs Health Care System, Salt Lake City, UT
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT
- Departments of Biochemistry, Biomedical Engineering, University of Utah, Salt Lake City, UT
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2
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Zhang B, Zhang S, Polovitskaya MM, Yi J, Ye B, Li R, Huang X, Yin J, Neuens S, Balfroid T, Soblet J, Vens D, Aeby A, Li X, Cai J, Song Y, Li Y, Tartaglia M, Li Y, Jentsch TJ, Yang M, Liu Z. Molecular basis of ClC-6 function and its impairment in human disease. SCIENCE ADVANCES 2023; 9:eadg4479. [PMID: 37831762 PMCID: PMC10575590 DOI: 10.1126/sciadv.adg4479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2022] [Accepted: 09/08/2023] [Indexed: 10/15/2023]
Abstract
ClC-6 is a late endosomal voltage-gated chloride-proton exchanger that is predominantly expressed in the nervous system. Mutated forms of ClC-6 are associated with severe neurological disease. However, the mechanistic role of ClC-6 in normal and pathological states remains largely unknown. Here, we present cryo-EM structures of ClC-6 that guided subsequent functional studies. Previously unrecognized ATP binding to cytosolic ClC-6 domains enhanced ion transport activity. Guided by a disease-causing mutation (p.Y553C), we identified an interaction network formed by Y553/F317/T520 as potential hotspot for disease-causing mutations. This was validated by the identification of a patient with a de novo pathogenic variant p.T520A. Extending these findings, we found contacts between intramembrane helices and connecting loops that modulate the voltage dependence of ClC-6 gating and constitute additional candidate regions for disease-associated gain-of-function mutations. Besides providing insights into the structure, function, and regulation of ClC-6, our work correctly predicts hotspots for CLCN6 mutations in neurodegenerative disorders.
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Affiliation(s)
- Bing Zhang
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai Institute of Maternal-Fetal Medicine and Gynecologic Oncology, Department of Anesthesiology, Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, 201204 Shanghai, China
| | - Sensen Zhang
- Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Maya M. Polovitskaya
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
- Max-Delbrück-Centrum für Molekulare Medizin (MDC), 13125 Berlin, Germany
| | - Jingbo Yi
- Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Binglu Ye
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai Institute of Maternal-Fetal Medicine and Gynecologic Oncology, Department of Anesthesiology, Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, 201204 Shanghai, China
| | - Ruochong Li
- Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Xueying Huang
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai Institute of Maternal-Fetal Medicine and Gynecologic Oncology, Department of Anesthesiology, Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, 201204 Shanghai, China
| | - Jian Yin
- Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Sebastian Neuens
- Department of Genetics, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Tom Balfroid
- Department of Pediatric Neurology, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Julie Soblet
- Department of Genetics, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Brussels, Belgium
- Department of Genetics, Hôpital Erasme, Université Libre de Bruxelles (ULB), Brussels, Belgium
- Interuniversity Institute of Bioinformatics in Brussels, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Daphné Vens
- Pediatric Intensive Care Unit, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Alec Aeby
- Department of Pediatric Neurology, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Xiaoling Li
- Wuya College of Innovation, Shenyang Pharmaceutical University, 110016 Shenyang, China
| | - Jinjin Cai
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 201203 Shanghai, China
| | - Yingcai Song
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai Institute of Maternal-Fetal Medicine and Gynecologic Oncology, Department of Anesthesiology, Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, 201204 Shanghai, China
| | - Yuanxi Li
- Institute for Cognitive Neurodynamics, School of Mathematics, East China University of Science and Technology, 200237 Shanghai, China
| | - Marco Tartaglia
- Molecular Genetics and Functional Genomics, Ospedale Pediatrico Bambino Gesù, IRCCS, 00146 Rome, Italy
| | - Yang Li
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 201203 Shanghai, China
- National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Thomas J. Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
- Max-Delbrück-Centrum für Molekulare Medizin (MDC), 13125 Berlin, Germany
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Maojun Yang
- Ministry of Education Key Laboratory of Protein Science, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, 100084 Beijing, China
- Cryo-EM Facility Center, Southern University of Science & Technology, 518055 Shenzhen, Guangdong, China
| | - Zhiqiang Liu
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai Institute of Maternal-Fetal Medicine and Gynecologic Oncology, Department of Anesthesiology, Clinical and Translational Research Center, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, 201204 Shanghai, China
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Wang Y, Zeng W, Lin B, Yao Y, Li C, Hu W, Wu H, Huang J, Zhang M, Xue T, Ren D, Qu L, Cang C. CLN7 is an organellar chloride channel regulating lysosomal function. SCIENCE ADVANCES 2021; 7:eabj9608. [PMID: 34910516 PMCID: PMC8673761 DOI: 10.1126/sciadv.abj9608] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Neuronal ceroid lipofuscinoses (NCLs) are a group of autosomal recessive lysosomal storage diseases. One variant form of late-infantile NCL (vLINCL) is caused by mutations of a lysosomal membrane protein CLN7, the function of which has remained unknown. Here, we identified CLN7 as a novel endolysosomal chloride channel. Overexpression of CLN7 increases endolysosomal chloride currents and enlarges endolysosomes through a Ca2+/calmodulin-dependent way. Human CLN7 and its yeast homolog exhibit characteristics of chloride channels and are sensitive to chloride channel blockers. Moreover, CLN7 regulates lysosomal chloride conductance, luminal pH, and lysosomal membrane potential and promotes the release of lysosomal Ca2+ through transient receptor potential mucolipin 1 (TRPML1). Knocking out CLN7 causes pathological features that are similar to those of patients with vLINCL, including retinal degeneration and autofluorescent lipofuscin. The pathogenic mutations in CLN7 lead to a decrease in chloride permeability, suggesting that reconstitution of lysosomal Cl− homeostasis may be an effective strategy for the treatment of vLINCL.
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Affiliation(s)
- Yayu Wang
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wenping Zeng
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Bingqian Lin
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yichuan Yao
- CAS Key Laboratory of Brain Function and Disease, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Canjun Li
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wenqi Hu
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Haotian Wu
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jiamin Huang
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Mei Zhang
- CAS Key Laboratory of Brain Function and Disease, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Tian Xue
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Key Laboratory of Brain Function and Disease, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Dejian Ren
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Lili Qu
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
- Corresponding author. (L.Q.); (C.C.)
| | - Chunlei Cang
- Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
- Corresponding author. (L.Q.); (C.C.)
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Liu C, Zhao Y, Zhao X, Dong J, Yuan Z. Genome-wide identification and expression analysis of the CLC gene family in pomegranate (Punica granatum) reveals its roles in salt resistance. BMC PLANT BIOLOGY 2020; 20:560. [PMID: 33308157 PMCID: PMC7733266 DOI: 10.1186/s12870-020-02771-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 12/02/2020] [Indexed: 06/09/2023]
Abstract
BACKGROUNDS Pomegranate (Punica granatum L.) is an important commercial fruit tree, with moderate tolerance to salinity. The balance of Cl- and other anions in pomegranate tissues are affected by salinity, however, the accumulation patterns of anions are poorly understood. The chloride channel (CLC) gene family is involved in conducting Cl-, NO3-, HCO3- and I-, but its characteristics have not been reported on pomegranate. RESULTS In this study, we identified seven PgCLC genes, consisting of four antiporters and three channels, based on the presence of the gating glutamate (E) and the proton glutamate (E). Phylogenetic analysis revealed that seven PgCLCs were divided into two clades, with clade I containing the typical conserved regions GxGIPE (I), GKxGPxxH (II) and PxxGxLF (III), whereas clade II not. Multiple sequence alignment revealed that PgCLC-B had a P [proline, Pro] residue in region I, which was suspected to be a NO3-/H+ exchanger, while PgCLC-C1, PgCLC-C2, PgCLC-D and PgCLC-G contained a S [serine, Ser] residue, with a high affinity to Cl-. We determined the content of Cl-, NO3-, H2PO4-, and SO42- in pomegranate tissues after 18 days of salt treatments (0, 100, 200 and 300 mM NaCl). Compared with control, the Cl- content increased sharply in pomegranate tissues. Salinity inhibited the uptake of NO3- and SO42-, but accelerated H2PO4- uptake. The results of real-time reverse transcription PCR (qRT-PCR) revealed that PgCLC genes had tissue-specific expression patterns. The high expression levels of three antiporters PgCLC-C1, PgCLC-C2 and PgCLC-D in leaves might be contributed to sequestrating Cl- into the vacuoles. However, the low expression levels of PgCLCs in roots might be associated with the exclusion of Cl- from root cells. Also, the up-regulated PgCLC-B in leaves indicated that more NO3- was transported into leaves to mitigate the nitrogen deficiency. CONCLUSIONS Our findings suggested that the PgCLC genes played important roles in balancing of Cl- and NO3- in pomegranate tissues under salt stress. This study established a theoretical foundation for the further functional characterization of the CLC genes in pomegranate.
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Affiliation(s)
- Cuiyu Liu
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
- College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Yujie Zhao
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
- College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Xueqing Zhao
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
- College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Jianmei Dong
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
- College of Forestry, Nanjing Forestry University, Nanjing, 210037, China
| | - Zhaohe Yuan
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China.
- College of Forestry, Nanjing Forestry University, Nanjing, 210037, China.
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McKiernan KA, Koster AK, Maduke M, Pande VS. Dynamical model of the CLC-2 ion channel reveals conformational changes associated with selectivity-filter gating. PLoS Comput Biol 2020; 16:e1007530. [PMID: 32226009 PMCID: PMC7145265 DOI: 10.1371/journal.pcbi.1007530] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 04/09/2020] [Accepted: 11/05/2019] [Indexed: 12/18/2022] Open
Abstract
This work reports a dynamical Markov state model of CLC-2 "fast" (pore) gating, based on 600 microseconds of molecular dynamics (MD) simulation. In the starting conformation of our CLC-2 model, both outer and inner channel gates are closed. The first conformational change in our dataset involves rotation of the inner-gate backbone along residues S168-G169-I170. This change is strikingly similar to that observed in the cryo-EM structure of the bovine CLC-K channel, though the volume of the intracellular (inner) region of the ion conduction pathway is further expanded in our model. From this state (inner gate open and outer gate closed), two additional states are observed, each involving a unique rotameric flip of the outer-gate residue GLUex. Both additional states involve conformational changes that orient GLUex away from the extracellular (outer) region of the ion conduction pathway. In the first additional state, the rotameric flip of GLUex results in an open, or near-open, channel pore. The equilibrium population of this state is low (∼1%), consistent with the low open probability of CLC-2 observed experimentally in the absence of a membrane potential stimulus (0 mV). In the second additional state, GLUex rotates to occlude the channel pore. This state, which has a low equilibrium population (∼1%), is only accessible when GLUex is protonated. Together, these pathways model the opening of both an inner and outer gate within the CLC-2 selectivity filter, as a function of GLUex protonation. Collectively, our findings are consistent with published experimental analyses of CLC-2 gating and provide a high-resolution structural model to guide future investigations.
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Affiliation(s)
- Keri A. McKiernan
- Department of Chemistry, Stanford University, Stanford, California, United States of America
| | - Anna K. Koster
- Department of Chemistry, Stanford University, Stanford, California, United States of America
- Department of Molecular & Cellular Physiology, Stanford University, Stanford, California, United States of America
| | - Merritt Maduke
- Department of Molecular & Cellular Physiology, Stanford University, Stanford, California, United States of America
| | - Vijay S. Pande
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
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Liao Q, Zhou T, Yao JY, Han QF, Song HX, Guan CY, Hua YP, Zhang ZH. Genome-scale characterization of the vacuole nitrate transporter Chloride Channel (CLC) genes and their transcriptional responses to diverse nutrient stresses in allotetraploid rapeseed. PLoS One 2018; 13:e0208648. [PMID: 30571734 PMCID: PMC6301700 DOI: 10.1371/journal.pone.0208648] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Accepted: 11/20/2018] [Indexed: 12/18/2022] Open
Abstract
The Chloride Channel (CLC) gene family is reported to be involved in vacuolar nitrate (NO3-) transport. Nitrate distribution to the cytoplasm is beneficial for enhancing NO3- assimilation and plays an important role in the regulation of nitrogen (N) use efficiency (NUE). In this study, genomic information, high-throughput transcriptional profiles, and gene co-expression analysis were integrated to identify the CLCs (BnaCLCs) in Brassica napus. The decreased NO3- concentration in the clca-2 mutant up-regulated the activities of nitrate reductase and glutamine synthetase, contributing to increase N assimilation and higher NUE in Arabidopsis thaliana. The genome-wide identification of 22BnaCLC genes experienced strong purifying selection. Segmental duplication was the major driving force in the expansion of the BnaCLC gene family. The most abundant cis-acting regulatory elements in the gene promoters, including DNA-binding One Zinc Finger, W-box, MYB, and GATA-box, might be involved in the transcriptional regulation of BnaCLCs expression. High-throughput transcriptional profiles and quantitative real-time PCR results showed that BnaCLCs responded differentially to distinct NO3- regimes. Transcriptomics-assisted gene co-expression network analysis identified BnaA7.CLCa-3 as the core member of the BnaCLC family, and this gene might play a central role in vacuolar NO3- transport in crops. The BnaCLC members also showed distinct expression patterns under phosphate depletion and cadmium toxicity. Taken together, our results provide comprehensive insights into the vacuolar BnaCLCs and establish baseline information for future studies on BnaCLCs-mediated vacuolar NO3- storage and its effect on NUE.
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Affiliation(s)
- Qiong Liao
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
| | - Ting Zhou
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
| | - Jun-yue Yao
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
| | - Qing-fen Han
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
| | - Hai-xing Song
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
| | - Chun-yun Guan
- National Center of Oilseed Crops Improvement, Hunan Branch, Changsha, China
| | - Ying-peng Hua
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- * E-mail: (ZHZ); (YPH)
| | - Zhen-hua Zhang
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- * E-mail: (ZHZ); (YPH)
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Jentsch TJ, Pusch M. CLC Chloride Channels and Transporters: Structure, Function, Physiology, and Disease. Physiol Rev 2018; 98:1493-1590. [DOI: 10.1152/physrev.00047.2017] [Citation(s) in RCA: 214] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CLC anion transporters are found in all phyla and form a gene family of eight members in mammals. Two CLC proteins, each of which completely contains an ion translocation parthway, assemble to homo- or heteromeric dimers that sometimes require accessory β-subunits for function. CLC proteins come in two flavors: anion channels and anion/proton exchangers. Structures of these two CLC protein classes are surprisingly similar. Extensive structure-function analysis identified residues involved in ion permeation, anion-proton coupling and gating and led to attractive biophysical models. In mammals, ClC-1, -2, -Ka/-Kb are plasma membrane Cl−channels, whereas ClC-3 through ClC-7 are 2Cl−/H+-exchangers in endolysosomal membranes. Biological roles of CLCs were mostly studied in mammals, but also in plants and model organisms like yeast and Caenorhabditis elegans. CLC Cl−channels have roles in the control of electrical excitability, extra- and intracellular ion homeostasis, and transepithelial transport, whereas anion/proton exchangers influence vesicular ion composition and impinge on endocytosis and lysosomal function. The surprisingly diverse roles of CLCs are highlighted by human and mouse disorders elicited by mutations in their genes. These pathologies include neurodegeneration, leukodystrophy, mental retardation, deafness, blindness, myotonia, hyperaldosteronism, renal salt loss, proteinuria, kidney stones, male infertility, and osteopetrosis. In this review, emphasis is laid on biophysical structure-function analysis and on the cell biological and organismal roles of mammalian CLCs and their role in disease.
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Affiliation(s)
- Thomas J. Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; and Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Michael Pusch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; and Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy
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Poroca DR, Pelis RM, Chappe VM. ClC Channels and Transporters: Structure, Physiological Functions, and Implications in Human Chloride Channelopathies. Front Pharmacol 2017; 8:151. [PMID: 28386229 PMCID: PMC5362633 DOI: 10.3389/fphar.2017.00151] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/09/2017] [Indexed: 02/04/2023] Open
Abstract
The discovery of ClC proteins at the beginning of the 1990s was important for the development of the Cl- transport research field. ClCs form a large family of proteins that mediate voltage-dependent transport of Cl- ions across cell membranes. They are expressed in both plasma and intracellular membranes of cells from almost all living organisms. ClC proteins form transmembrane dimers, in which each monomer displays independent ion conductance. Eukaryotic members also possess a large cytoplasmic domain containing two CBS domains, which are involved in transport modulation. ClC proteins function as either Cl- channels or Cl-/H+ exchangers, although all ClC proteins share the same basic architecture. ClC channels have two gating mechanisms: a relatively well-studied fast gating mechanism, and a slow gating mechanism, which is poorly defined. ClCs are involved in a wide range of physiological processes, including regulation of resting membrane potential in skeletal muscle, facilitation of transepithelial Cl- reabsorption in kidneys, and control of pH and Cl- concentration in intracellular compartments through coupled Cl-/H+ exchange mechanisms. Several inherited diseases result from C1C gene mutations, including myotonia congenita, Bartter's syndrome (types 3 and 4), Dent's disease, osteopetrosis, retinal degeneration, and lysosomal storage diseases. This review summarizes general features, known or suspected, of ClC structure, gating and physiological functions. We also discuss biophysical properties of mammalian ClCs that are directly involved in the pathophysiology of several human inherited disorders, or that induce interesting phenotypes in animal models.
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Affiliation(s)
- Diogo R Poroca
- Department of Physiology and Biophysics, Dalhousie University, Halifax NS, Canada
| | - Ryan M Pelis
- Department of Pharmacology, Dalhousie University, Halifax NS, Canada
| | - Valérie M Chappe
- Department of Physiology and Biophysics, Dalhousie University, Halifax NS, Canada
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Zhan T, Lin M, Wu L, Zhang X, Zhang L, Zhao X, Zhang K. Proton-anion Ion-pair Recognition by a Hexaazatriphenylene-Hexaurea Receptor. CHINESE J CHEM 2017. [DOI: 10.1002/cjoc.201600843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Tianguang Zhan
- College of Chemistry and Life Science; Zhejiang Normal University, 688 Yingbin Road; Jinhua Zhejiang 321004 China
| | - Mengdi Lin
- College of Chemistry and Life Science; Zhejiang Normal University, 688 Yingbin Road; Jinhua Zhejiang 321004 China
| | - Lin Wu
- College of Chemistry and Life Science; Zhejiang Normal University, 688 Yingbin Road; Jinhua Zhejiang 321004 China
| | - Xiang Zhang
- Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry; Chinese Academy of Sciences; Shanghai 200032 China
- School of Chemical Engineering; Hunan Chemical Vocational Technology College; Zhuzhou Hunan 412000 China
| | - Liang Zhang
- Department of Chemistry; Fudan University; Shanghai 200433 China
| | - Xin Zhao
- Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry; Chinese Academy of Sciences; Shanghai 200032 China
| | - Kangda Zhang
- College of Chemistry and Life Science; Zhejiang Normal University, 688 Yingbin Road; Jinhua Zhejiang 321004 China
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Seong JY, Ha K, Hong C, Myeong J, Lim HH, Yang D, So I. Helix O modulates voltage dependency of CLC-1. Pflugers Arch 2016; 469:183-193. [PMID: 27921211 DOI: 10.1007/s00424-016-1907-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 10/14/2016] [Accepted: 11/14/2016] [Indexed: 11/25/2022]
Abstract
The chloride channel (CLC) family of proteins consists of channels and transporters that share similarities in architecture and play essential roles in physiological functions. Among the CLC family, CLC-1 channels have the representative homodimeric double-barreled structure carrying two gating processes. One is protopore gating that acts on each pore independently by glutamate residue (Eext). The other is common gating that closes both pores simultaneously in association with large conformational changes across each subunit. In skeletal muscle, CLC-1 is associated with maintaining normal sarcolemmal excitability, and a number of myotonic mutants were reported to modify the channel gating of CLC-1. In this study, we characterized highly conserved helix O as a key determinant of structural stability in CLC-1. Supporting this hypothesis, myotonic mutant (G523D) at N-terminal of helix O showed the activation at hyperpolarizing membrane potentials with a reversed voltage dependency. However, introducing glutamate at serine residue (S537) at the C-terminal of the helix O on G523D restored WT-like voltage dependency of the common gate and showed proton insensitive voltage dependency. To further validate this significant site, site-specific mutagenesis experiments was performed on V292 that is highly conserved as glutamate in antiporter and closely located to S537 and showed that this area is essential for channel function. Taken together, the results of our study suggest the importance of helix O as the main contributor for stable structure of evolutionary conserved CLC proteins and its key role in voltage dependency of the CLC-1. Furthermore, the C-terminal of the helix O can offer a clue for possible proton involvement in CLC-1 channel.
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Affiliation(s)
- Ju Yong Seong
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Kotdaji Ha
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Chansik Hong
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Jongyun Myeong
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Hyun-Ho Lim
- Korea Brain Research Institute (KBRI), Daegu, 41068, Republic of Korea
| | - Dongki Yang
- Department of Physiology, College of Medicine, Gachon University, Incheon, 461-701, Republic of Korea
| | - Insuk So
- Department of Physiology, Seoul National University, College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, Republic of Korea.
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Abraham SJ, Cheng RC, Chew TA, Khantwal CM, Liu CW, Gong S, Nakamoto RK, Maduke M. 13C NMR detects conformational change in the 100-kD membrane transporter ClC-ec1. JOURNAL OF BIOMOLECULAR NMR 2015; 61:209-26. [PMID: 25631353 PMCID: PMC4398623 DOI: 10.1007/s10858-015-9898-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 01/13/2015] [Indexed: 05/03/2023]
Abstract
CLC transporters catalyze the exchange of Cl(-) for H(+) across cellular membranes. To do so, they must couple Cl(-) and H(+) binding and unbinding to protein conformational change. However, the sole conformational changes distinguished crystallographically are small movements of a glutamate side chain that locally gates the ion-transport pathways. Therefore, our understanding of whether and how global protein dynamics contribute to the exchange mechanism has been severely limited. To overcome the limitations of crystallography, we used solution-state (13)C-methyl NMR with labels on methionine, lysine, and engineered cysteine residues to investigate substrate (H(+)) dependent conformational change outside the restraints of crystallization. We show that methyl labels in several regions report H(+)-dependent spectral changes. We identify one of these regions as Helix R, a helix that extends from the center of the protein, where it forms the part of the inner gate to the Cl(-)-permeation pathway, to the extracellular solution. The H(+)-dependent spectral change does not occur when a label is positioned just beyond Helix R, on the unstructured C-terminus of the protein. Together, the results suggest that H(+) binding is mechanistically coupled to closing of the intracellular access-pathway for Cl(-).
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Affiliation(s)
- Sherwin J. Abraham
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive West, Stanford, CA 94035
| | - Ricky C. Cheng
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive West, Stanford, CA 94035
| | - Thomas A. Chew
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive West, Stanford, CA 94035
| | - Chandra M. Khantwal
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive West, Stanford, CA 94035
| | - Corey W. Liu
- Stanford Magnetic Resonance Laboratory, Stanford University School of Medicine, 299 Campus Drive West, D105 Fairchild Science Building, Stanford, CA 94305
| | - Shimei Gong
- Department of Molecular Physiology and Biological Physics, University of Virginia, PO Box 10011, Charlottesville, VA 22906-0011
| | - Robert K. Nakamoto
- Department of Molecular Physiology and Biological Physics, University of Virginia, PO Box 10011, Charlottesville, VA 22906-0011
| | - Merritt Maduke
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive West, Stanford, CA 94035
- corresponding author, , tel (650)-723-9075, fax (650)-725-8021
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Krapp A, David LC, Chardin C, Girin T, Marmagne A, Leprince AS, Chaillou S, Ferrario-Méry S, Meyer C, Daniel-Vedele F. Nitrate transport and signalling in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:789-98. [PMID: 24532451 DOI: 10.1093/jxb/eru001] [Citation(s) in RCA: 251] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Plants have developed adaptive responses allowing them to cope with nitrogen (N) fluctuation in the soil and maintain growth despite changes in external N availability. Nitrate is the most important N form in temperate soils. Nitrate uptake by roots and its transport at the whole-plant level involves a large panoply of transporters and impacts plant performance. Four families of nitrate-transporting proteins have been identified so far: nitrate transporter 1/peptide transporter family (NPF), nitrate transporter 2 family (NRT2), the chloride channel family (CLC), and slow anion channel-associated homologues (SLAC/SLAH). Nitrate transporters are also involved in the sensing of nitrate. It is now well established that plants are able to sense external nitrate availability, and hence that nitrate also acts as a signal molecule that regulates many aspects of plant intake, metabolism, and gene expression. This review will focus on a global picture of the nitrate transporters so far identified and the recent advances in the molecular knowledge of the so-called primary nitrate response, the rapid regulation of gene expression in response to nitrate. The recent discovery of the NIN-like proteins as master regulators for nitrate signalling has led to a new understanding of the regulation cascade.
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Affiliation(s)
- Anne Krapp
- Institut National de la Recherche Agronomique (INRA), UMR1318, Institut Jean-Pierre Bourgin, Saclay Plant Sciences, RD10, F-78000 Versailles, France
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A Microscopic View of the Mechanisms of Active Transport Across the Cellular Membrane. ANNUAL REPORTS IN COMPUTATIONAL CHEMISTRY 2014. [DOI: 10.1016/b978-0-444-63378-1.00004-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Stauber T, Weinert S, Jentsch TJ. Cell biology and physiology of CLC chloride channels and transporters. Compr Physiol 2013; 2:1701-44. [PMID: 23723021 DOI: 10.1002/cphy.c110038] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Proteins of the CLC gene family assemble to homo- or sometimes heterodimers and either function as Cl(-) channels or as Cl(-)/H(+)-exchangers. CLC proteins are present in all phyla. Detailed structural information is available from crystal structures of bacterial and algal CLCs. Mammals express nine CLC genes, four of which encode Cl(-) channels and five 2Cl(-)/H(+)-exchangers. Two accessory β-subunits are known: (1) barttin and (2) Ostm1. ClC-Ka and ClC-Kb Cl(-) channels need barttin, whereas Ostm1 is required for the function of the lysosomal ClC-7 2Cl(-)/H(+)-exchanger. ClC-1, -2, -Ka and -Kb Cl(-) channels reside in the plasma membrane and function in the control of electrical excitability of muscles or neurons, in extra- and intracellular ion homeostasis, and in transepithelial transport. The mainly endosomal/lysosomal Cl(-)/H(+)-exchangers ClC-3 to ClC-7 may facilitate vesicular acidification by shunting currents of proton pumps and increase vesicular Cl(-) concentration. ClC-3 is also present on synaptic vesicles, whereas ClC-4 and -5 can reach the plasma membrane to some extent. ClC-7/Ostm1 is coinserted with the vesicular H(+)-ATPase into the acid-secreting ruffled border membrane of osteoclasts. Mice or humans lacking ClC-7 or Ostm1 display osteopetrosis and lysosomal storage disease. Disruption of the endosomal ClC-5 Cl(-)/H(+)-exchanger leads to proteinuria and Dent's disease. Mouse models in which ClC-5 or ClC-7 is converted to uncoupled Cl(-) conductors suggest an important role of vesicular Cl(-) accumulation in these pathologies. The important functions of CLC Cl(-) channels were also revealed by human diseases and mouse models, with phenotypes including myotonia, renal loss of salt and water, deafness, blindness, leukodystrophy, and male infertility.
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Affiliation(s)
- Tobias Stauber
- Leibniz-Institut für Molekulare Pharmakologie FMP and Max-Delbrück-Centrum für Molekulare Medizin MDC, Berlin, Germany
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Molecular determinants of common gating of a ClC chloride channel. Nat Commun 2013; 4:2507. [DOI: 10.1038/ncomms3507] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 08/27/2013] [Indexed: 11/08/2022] Open
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Brown LS. A thin line between channels and pumps. Biophys J 2013; 104:739-40. [PMID: 23442949 DOI: 10.1016/j.bpj.2012.12.050] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 12/07/2012] [Accepted: 12/11/2012] [Indexed: 11/18/2022] Open
Affiliation(s)
- Leonid S Brown
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Ontario, Canada.
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17
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Abstract
The lack of small-molecule inhibitors for anion-selective transporters and channels has impeded our understanding of the complex mechanisms that underlie ion passage. The ubiquitous CLC "Chloride Channel" family represents a unique target for biophysical and biochemical studies because its distinctive protein fold supports both passive chloride channels and secondary-active chloride-proton transporters. Here, we describe the synthesis and characterization of a specific small-molecule inhibitor directed against a CLC antiporter (ClC-ec1). This compound, 4,4'-octanamidostilbene-2,2'-disulfonate (OADS), inhibits ClC-ec1 with low micromolar affinity and has no specific effect on a CLC channel (ClC-1). Inhibition of ClC-ec1 occurs by binding to two distinct intracellular sites. The location of these sites and the lipid dependence of inhibition suggest potential mechanisms of action. This compound will empower research to elucidate differences between antiporter and channel mechanisms and to develop treatments for CLC-mediated disorders.
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Abstract
Mutagenesis, functional analysis, and crystal structures identify a watery tunnel through which protons enter the interior of a Cl−/H+ antiport protein involved in acid resistance of enteric bacteria. Chloride-transporting membrane proteins of the CLC family appear in two distinct mechanistic flavors: H+-gated Cl− channels and Cl−/H+ antiporters. Transmembrane H+ movement is an essential feature of both types of CLC. X-ray crystal structures of CLC antiporters show the Cl− ion pathway through these proteins, but the H+ pathway is known only inferentially by two conserved glutamate residues that act as way-stations for H+ in its path through the protein. The extracellular-facing H+ transfer glutamate becomes directly exposed to aqueous solution during the transport cycle, but the intracellular glutamate E203, Gluin, is buried within the protein. Two regions, denoted “polar” and “interfacial,” at the intracellular surface of the bacterial antiporter CLC-ec1 are examined here as possible pathways by which intracellular aqueous protons gain access to Gluin. Mutations at multiple residues of the polar region have little effect on antiport rates. In contrast, mutation of E202, a conserved glutamate at the protein–water boundary of the interfacial region, leads to severe slowing of the Cl−/H+ antiport rate. An X-ray crystal structure of E202Y, the most strongly inhibited of these substitutions, shows an aqueous portal leading to Gluin physically blocked by cross-subunit interactions; moreover, this mutation has only minimal effect on a monomeric CLC variant, which necessarily lacks such interactions. The several lines of experiments presented argue that E202 acts as a water-organizer that creates a proton conduit connecting intracellular solvent with Gluin. Chloride-proton antiport proteins of the “CLC” superfamily are transmembrane proteins that form homodimers and are used for myriad physiological purposes, all requiring the coordinated movements of Cl− anions and H+ cations in opposite directions across biological membranes. While the pathway for Cl− ions through CLC antiporters is known, we currently have only indirect glimpses of how protons navigate their way through these membrane-embedded proteins. By combining mechanistic and structural approaches, we identify a proton-access pathway in a bacterial Cl−/H+ antiporter that allows intracellular protons to enter the protein interior and engage in the coupled antiport mechanism. We conclude that E202, a highly conserved glutamate residue, serves to organize water molecules and guide protons to the adjacent glutamate E203 (known as “Gluin”), a critical residue for the antiport mechanism.
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Barbier-Brygoo H, De Angeli A, Filleur S, Frachisse JM, Gambale F, Thomine S, Wege S. Anion channels/transporters in plants: from molecular bases to regulatory networks. ANNUAL REVIEW OF PLANT BIOLOGY 2011; 62:25-51. [PMID: 21275645 DOI: 10.1146/annurev-arplant-042110-103741] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Anion channels/transporters are key to a wide spectrum of physiological functions in plants, such as osmoregulation, cell signaling, plant nutrition and compartmentalization of metabolites, and metal tolerance. The recent identification of gene families encoding some of these transport systems opened the way for gene expression studies, structure-function analyses of the corresponding proteins, and functional genomics approaches toward further understanding of their integrated roles in planta. This review, based on a few selected examples, illustrates that the members of a given gene family exhibit a diversity of substrate specificity, regulation, and intracellular localization, and are involved in a wide range of physiological functions. It also shows that post-translational modifications of transport proteins play a key role in the regulation of anion transport activity. Key questions arising from the increasing complexity of networks controlling anion transport in plant cells (the existence of redundancy, cross talk, and coordination between various pathways and compartments) are also addressed.
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20
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Duran C, Thompson CH, Xiao Q, Hartzell HC. Chloride channels: often enigmatic, rarely predictable. Annu Rev Physiol 2010; 72:95-121. [PMID: 19827947 DOI: 10.1146/annurev-physiol-021909-135811] [Citation(s) in RCA: 241] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Until recently, anion (Cl(-)) channels have received considerably less attention than cation channels. One reason for this may be that many Cl(-) channels perform functions that might be considered cell-biological, like fluid secretion and cell volume regulation, whereas cation channels have historically been associated with cellular excitability, which typically happens more rapidly. In this review, we discuss the recent explosion of interest in Cl(-) channels, with special emphasis on new and often surprising developments over the past five years. This is exemplified by the findings that more than half of the ClC family members are antiporters, and not channels, as was previously thought, and that bestrophins, previously prime candidates for Ca(2+)-activated Cl(-) channels, have been supplanted by the newly discovered anoctamins and now hold a tenuous position in the Cl(-) channel world.
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Affiliation(s)
- Charity Duran
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
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21
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A single amino acid change converts the sugar sensor SGLT3 into a sugar transporter. PLoS One 2010; 5:e10241. [PMID: 20421923 PMCID: PMC2857651 DOI: 10.1371/journal.pone.0010241] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Accepted: 03/29/2010] [Indexed: 01/08/2023] Open
Abstract
Background Sodium-glucose cotransporter proteins (SGLT) belong to the SLC5A family, characterized by the cotransport of Na+ with solute. SGLT1 is responsible for intestinal glucose absorption. Until recently the only role described for SGLT proteins was to transport sugar with Na+. However, human SGLT3 (hSGLT3) does not transport sugar but causes depolarization of the plasma membrane when expressed in Xenopus oocytes. For this reason SGLT3 was suggested to be a sugar sensor rather than a transporter. Despite 70% amino acid identity between hSGLT3 and hSGLT1, their sugar transport, apparent sugar affinities, and sugar specificity differ greatly. Residue 457 is important for the function of SGLT1 and mutation at this position in hSGLT1 causes glucose-galactose malabsorption. Moreover, the crystal structure of vibrio SGLT reveals that the residue corresponding to 457 interacts directly with the sugar molecule. We thus wondered if this residue could account for some of the functional differences between SGLT1 and SGLT3. Methodology/Principal Findings We mutated the glutamate at position 457 in hSGLT3 to glutamine, the amino acid present in all SGLT1 proteins, and characterized the mutant. Surprisingly, we found that E457Q-hSGLT3 transported sugar, had the same stoichiometry as SGLT1, and that the sugar specificity and apparent affinities for most sugars were similar to hSGLT1. We also show that SGLT3 functions as a sugar sensor in a living organism. We expressed hSGLT3 and E457Q-hSGLT3 in C. elegans sensory neurons and found that animals sensed glucose in an hSGLT3-dependent manner. Conclusions/Significance In summary, we demonstrate that hSGLT3 functions as a sugar sensor in vivo and that mutating a single amino acid converts this sugar sensor into a sugar transporter similar to SGLT1.
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Miloshevsky GV, Hassanein A, Jordan PC. Antiport mechanism for Cl(-)/H(+) in ClC-ec1 from normal-mode analysis. Biophys J 2010; 98:999-1008. [PMID: 20303857 PMCID: PMC2849085 DOI: 10.1016/j.bpj.2009.11.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 11/06/2009] [Accepted: 11/17/2009] [Indexed: 01/24/2023] Open
Abstract
ClC chloride channels and transporters play major roles in cellular excitability, epithelial salt transport, volume, pH, and blood pressure regulation. One family member, ClC-ec1 from Escherichia coli, has been structurally resolved crystallographically and subjected to intensive mutagenetic, crystallographic, and electrophysiological studies. It functions as a Cl(-)/H(+) antiporter, not a Cl(-) channel; however, the molecular mechanism for Cl(-)/H(+) exchange is largely unknown. Using all-atom normal-mode analysis to explore possible mechanisms for this antiport, we propose that Cl(-)/H(+) exchange involves a conformational cycle of alternating exposure of Cl(-) and H(+) binding sites of both ClC pores to the two sides of the membrane. Both pores switch simultaneously from facing outward to facing inward, reminiscent of the standard alternating-access mechanism, which may have direct implications for eukaryotic Cl(-)/H(+) transporters and Cl(-) channels.
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Affiliation(s)
| | - Ahmed Hassanein
- School of Nuclear Engineering, Purdue University, West Lafayette, Indiana
| | - Peter C. Jordan
- Department of Chemistry, Brandeis University, Waltham, Massachusetts
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Accardi A, Picollo A. CLC channels and transporters: proteins with borderline personalities. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1457-64. [PMID: 20188062 DOI: 10.1016/j.bbamem.2010.02.022] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 02/12/2010] [Accepted: 02/18/2010] [Indexed: 11/19/2022]
Abstract
Controlled chloride movement across membranes is essential for a variety of physiological processes ranging from salt homeostasis in the kidneys to acidification of cellular compartments. The CLC family is formed by two, not so distinct, sub-classes of membrane transport proteins: Cl(-) channels and H(+)/Cl(-) exchangers. All CLC's are homodimers with each monomer forming an individual Cl- permeation pathway which appears to be largely unaltered in the two CLC sub-classes. Key residues for ion binding and selectivity are also highly conserved. Most CLC's have large cytosolic carboxy-terminal domains containing two cystathionine beta-synthetase (CBS) domains. The C-termini are critical regulators of protein trafficking and directly modulate Cl- by binding intracellular ATP, H+ or oxidizing compounds. This review focuses on the recent mechanistic insights on the how the structural similarities between CLC channels and transporters translate in unexpected mechanistic analogies between these two sub-classes.
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Affiliation(s)
- Alessio Accardi
- Department of Molecular Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
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Matsuda JJ, Filali MS, Collins MM, Volk KA, Lamb FS. The ClC-3 Cl-/H+ antiporter becomes uncoupled at low extracellular pH. J Biol Chem 2009; 285:2569-79. [PMID: 19926787 DOI: 10.1074/jbc.m109.018002] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adenovirus expressing ClC-3 (Ad-ClC-3) induces Cl(-)/H(+) antiport current (I(ClC-3)) in HEK293 cells. The outward rectification and time dependence of I(ClC-3) closely resemble an endogenous HEK293 cell acid-activated Cl(-) current (ICl(acid)) seen at extracellular pH <or= 5.5. ICl(acid) was present in smooth muscle cells from wild-type but not ClC-3 null mice. We therefore sought to determine whether these currents were related. ICl(acid) was larger in cells expressing Ad-ClC-3. Protons shifted the reversal potential (E(rev)) of I(ClC-3) between pH 8.2 and 6.2, but not pH 6.2 and 5.2, suggesting that Cl(-) and H(+) transport become uncoupled at low pH. At pH 4.0 E(rev) was completely Cl(-) dependent (55.8 +/- 2.3 mV/decade). Several findings linked ClC-3 with native ICl(acid); 1) RNA interference directed at ClC-3 message reduced native ICl(acid); 2) removal of the extracellular "fast gate" (E224A) produced large currents that were pH-insensitive; and 3) wild-type I(ClC-3) and ICl(acid) were both inhibited by (2-sulfonatoethyl)methanethiosulfonate (MTSES; 10-500 microm)-induced alkanethiolation at exposed cysteine residues. However, a ClC-3 mutant lacking four extracellular cysteine residues (C103_P130del) was completely resistant to MTSES. C103_P130del currents were still acid-activated, but could be distinguished from wild-type I(ClC-3) and from native ICl(acid) by a much slower response to low pH. Thus, ClC-3 currents are activated by protons and ClC-3 protein may account for native ICl(acid). Low pH uncouples Cl(-)/H(+) transport so that at pH 4.0 ClC-3 behaves as an anion-selective channel. These findings have important implications for the biology of Cl(-)/H(+) antiporters and perhaps for pH regulation in highly acidic intracellular compartments.
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Affiliation(s)
- James J Matsuda
- Department of Pediatrics, University of Iowa Children's Hospital, Iowa City, Iowa 52242, USA
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Ashcroft F, Gadsby D, Miller C. Introduction. The blurred boundary between channels and transporters. Philos Trans R Soc Lond B Biol Sci 2009; 364:145-7. [PMID: 18957372 DOI: 10.1098/rstb.2008.0245] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Frances Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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