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Moldenhauer HJ, Tammen K, Meredith AL. Structural mapping of patient-associated KCNMA1 gene variants. Biophys J 2023:S0006-3495(23)04120-6. [PMID: 38042986 DOI: 10.1016/j.bpj.2023.11.3404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 11/30/2023] [Accepted: 11/30/2023] [Indexed: 12/04/2023] Open
Abstract
KCNMA1-linked channelopathy is a neurological disorder characterized by seizures, motor abnormalities, and neurodevelopmental disabilities. The disease mechanisms are predicted to result from alterations in KCNMA1-encoded BK K+ channel activity; however, only a subset of the patient-associated variants have been functionally studied. The localization of these variants within the tertiary structure or evaluation by pathogenicity algorithms has not been systematically assessed. In this study, 82 nonsynonymous patient-associated KCNMA1 variants were mapped within the BK channel protein. Fifty-three variants localized within cryoelectron microscopy-resolved structures, including 21 classified as either gain of function (GOF) or loss of function (LOF) in BK channel activity. Clusters of LOF variants were identified in the pore, the AC region (RCK1), and near the Ca2+ bowl (RCK2), overlapping with sites of pharmacological or endogenous modulation. However, no clustering was found for GOF variants. To further understand variants of uncertain significance (VUSs), assessments by multiple standard pathogenicity algorithms were compared, and new thresholds for sensitivity and specificity were established from confirmed GOF and LOF variants. An ensemble algorithm was constructed (KCNMA1 meta score (KMS)), consisting of a weighted summation of this trained dataset combined with a structural component derived from the Ca2+-bound and unbound BK channels. KMS assessment differed from the highest-performing individual algorithm (REVEL) at 10 VUS residues, and a subset were studied further by electrophysiology in HEK293 cells. M578T, E656A, and D965V (KMS+;REVEL-) were confirmed to alter BK channel properties in voltage-clamp recordings, and D800Y (KMS-;REVEL+) was assessed as benign under the test conditions. However, KMS failed to accurately assess K457E. These combined results reveal the distribution of potentially disease-causing KCNMA1 variants within BK channel functional domains and pathogenicity evaluation for VUSs, suggesting strategies for improving channel-level predictions in future studies by building on ensemble algorithms such as KMS.
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Affiliation(s)
- Hans J Moldenhauer
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Kelly Tammen
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland.
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2
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Moldenhauer HJ, Tammen K, Meredith AL. Structural mapping of patient-associated KCNMA1 gene variants. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.27.550850. [PMID: 37546746 PMCID: PMC10402178 DOI: 10.1101/2023.07.27.550850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
KCNMA1-linked channelopathy is a neurological disorder characterized by seizures, motor abnormalities, and neurodevelopmental disabilities. The disease mechanisms are predicted to result from alterations in KCNMA1-encoded BK K+ channel activity; however, only a subset of the patient-associated variants have been functionally studied. The localization of these variants within the tertiary structure or evaluation by pathogenicity algorithms has not been systematically assessed. In this study, 82 nonsynonymous patient-associated KCNMA1 variants were mapped within the BK channel protein. Fifty-three variants localized within cryo-EM resolved structures, including 21 classified as either gain-of-function (GOF) or loss-of-function (LOF) in BK channel activity. Clusters of LOF variants were identified in the pore, the AC region (RCK1), and near the Ca 2+ bowl (RCK2), overlapping with sites of pharmacological or endogenous modulation. However, no clustering was found for GOF variants. To further understand variants of uncertain significance (VUS), assessments by multiple standard pathogenicity algorithms were compared, and new thresholds for sensitivity and specificity were established from confirmed GOF and LOF variants. An ensemble algorithm was constructed (KCNMA1 Meta Score), consisting of a weighted summation of this trained dataset combined with a structural component derived from the Ca 2+ bound and unbound BK channels. KMS assessment differed from the highest performing individual algorithm (REVEL) at 10 VUS residues, and a subset were studied further by electrophysiology in HEK293 cells. M578T, E656A, and D965V (KMS+;REVEL-) were confirmed to alter BK channel properties in voltage-clamp recordings, and D800Y (KMS-;REVEL+) was assessed as benign under the test conditions. However, KMS failed to accurately assess K457E. These combined results reveal the distribution of potentially disease-causing KCNMA1 variants within BK channel functional domains and pathogenicity evaluation for VUS, suggesting strategies for improving channel-level predictions in future studies by building on ensemble algorithms such as KMS.
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3
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Mukherjee S, Sikdar SK. Intracellular activation of full-length human TREK-1 channel by hypoxia, high lactate, and low pH denotes polymodal integration by ischemic factors. Pflugers Arch 2020; 473:167-183. [PMID: 33025137 DOI: 10.1007/s00424-020-02471-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 09/18/2020] [Accepted: 09/30/2020] [Indexed: 10/23/2022]
Abstract
TREK-1, a two-pore domain potassium channel, responds to ischemic levels of intracellular lactate and acidic pH to provide neuroprotection. There are two splice variants of hTREK1: the shorter splice variant having a shorter N-terminus compared with the full-length hTREK1 with similar C-terminus sequence that is widely expressed in the brain. The shorter variant was reported to be irresponsive to hypoxia-a condition attributed to ischemia, which has put the neuroprotective role of hTREK-1 channel into question. Since interaction between N- and C-terminus of different ion channels shapes their gating, we re-examined the sensitivity of the full-length as well as the shorter hTREK-1 channel to intracellular hypoxia along with lactate. Single-channel data obtained from the excised inside-out patches of the full-length channel expressed in HEK293 cells indicated an increase in activity as opposed to a decrease in activity in the shorter isoform. However, both the isoforms showed an increase in activity under combined hypoxia, 20mM lactate, and low pH 6 condition, albeit with subtle differences in their individual actions, confirming the neuroprotective role played by hTREK-1 irrespective of the differences in the N-terminus among the splice variants. Furthermore, E321A mutant that disrupts the interaction of the C-terminus with the membrane showed a decrease in activity with hypoxia indicating the importance of the C-terminus in the hypoxic response of the full-length hTREK-1. We propose an increase in activity of both the splice variants of hTREK-1 in combined hypoxia, high lactate, and low pH conditions typically associated with ischemia provides neuroprotection.
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Affiliation(s)
- Sourajit Mukherjee
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Sujit Kumar Sikdar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, 560012, India.
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4
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Guo F, Sun Y, Wang X, Wang H, Wang J, Gong T, Chen X, Zhang P, Su L, Fu G, Su J, Yang S, Lai R, Jiang C, Liang P. Patient-Specific and Gene-Corrected Induced Pluripotent Stem Cell-Derived Cardiomyocytes Elucidate Single-Cell Phenotype of Short QT Syndrome. Circ Res 2019; 124:66-78. [PMID: 30582453 DOI: 10.1161/circresaha.118.313518] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RATIONALE Short QT syndrome (SQT) is a rare but arrhythmogenic disorder featured by shortened ventricular repolarization and a propensity toward life-threatening ventricular arrhythmias and sudden cardiac death. OBJECTIVE This study aimed to investigate the single-cell mechanism of SQT using patient-specific and gene-corrected induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). METHODS AND RESULTS One SQT patient carrying missense mutation T618I in potassium voltage-gated channel subfamily H member 2 ( KCNH2) was recruited as well as 2 healthy control subjects in this study. Control and SQT patient-specific iPSCs were generated from skin fibroblasts using nonintegrated Sendai virus. The KCNH2 T618I mutation was corrected by genome editing in SQT iPSC lines to generate isogenic controls. All iPSCs were differentiated into iPSC-CMs using monolayer-based differentiation protocol. SQT iPSC-CMs exhibited abnormal action potential phenotype featured by shortened action potential duration and increased beat-beat interval variability, when compared with control and gene-corrected iPSC-CMs. Furthermore, SQT iPSC-CMs showed KCNH2 gain-of-function with increased rapid delayed rectifying potassium current (IKr) density and enhanced membrane expression. Gene expression profiling of iPSC-CMs exhibited a differential cardiac ion-channel gene expression profile of SQT. Moreover, QTc of SQT patient and action potential durations of SQT iPSC-CMs were both normalized by quinidine, indicating that quinidine is beneficial to KCNH2 T618I of SQT. Importantly, shortened action potential duration phenotype observed in SQT iPSC-CMs was effectively rescued by a short-peptide scorpion toxin BmKKx2 with a mechanism of targeting KCNH2. CONCLUSIONS We demonstrate that patient-specific and gene-corrected iPSC-CMs are able to recapitulate single-cell phenotype of SQT, which is caused by the gain-of-function mutation KCNH2 T618I. These findings will help elucidate the mechanisms underlying SQT and discover therapeutic drugs for treating the disease by using peptide toxins as lead compounds.
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Affiliation(s)
- Fengfeng Guo
- From the Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health, the First Affiliated Hospital (F.G., X.W., J.W., T.G., J.S., P.L.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Yaxun Sun
- Department of Cardiology (Y.S., C.J.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Xiaochen Wang
- From the Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health, the First Affiliated Hospital (F.G., X.W., J.W., T.G., J.S., P.L.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.,Institute of Translational Medicine, Zhejiang University, Hangzhou, China (F.G., X.W., J.W., J.S., P.L.)
| | - Hao Wang
- Department of Prenatal Diagnosis (Screening) Center, Hangzhou Women's Hospital (Hangzhou Maternity and Child Health Care Hospital), China (H.W.)
| | - Jue Wang
- From the Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health, the First Affiliated Hospital (F.G., X.W., J.W., T.G., J.S., P.L.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.,Institute of Translational Medicine, Zhejiang University, Hangzhou, China (F.G., X.W., J.W., J.S., P.L.)
| | - Tingyu Gong
- From the Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health, the First Affiliated Hospital (F.G., X.W., J.W., T.G., J.S., P.L.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Xianzhen Chen
- Department of Dermatology and Venerology (X.C.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Ping Zhang
- Department of Cardiology, Beijing Tsinghua Changgeng Hospital, China (P.Z.)
| | - Lan Su
- Cardiovascular Medicine Department, The First Affiliated Hospital of Wenzhou Medical University, China (L.S.)
| | - Guosheng Fu
- Institute of Translational Medicine, Zhejiang University, Hangzhou, China (F.G., X.W., J.W., J.S., P.L.)
| | - Jun Su
- From the Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health, the First Affiliated Hospital (F.G., X.W., J.W., T.G., J.S., P.L.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.,Institute of Translational Medicine, Zhejiang University, Hangzhou, China (F.G., X.W., J.W., J.S., P.L.).,Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences (S.Y., L.R.), Kunming Institute of Zoology, China
| | - Shilong Yang
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences (S.Y., L.R.), Kunming Institute of Zoology, China.,Key Laboratory of Bioactive Peptides of Yunnan Province (S.Y., L.R.), Kunming Institute of Zoology, China
| | - Ren Lai
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences (S.Y., L.R.), Kunming Institute of Zoology, China.,Key Laboratory of Bioactive Peptides of Yunnan Province (S.Y., L.R.), Kunming Institute of Zoology, China
| | - Chenyang Jiang
- Department of Cardiology (Y.S., C.J.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Ping Liang
- From the Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health, the First Affiliated Hospital (F.G., X.W., J.W., T.G., J.S., P.L.), Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China.,Institute of Translational Medicine, Zhejiang University, Hangzhou, China (F.G., X.W., J.W., J.S., P.L.)
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5
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Eisenach C, Baetz U, Huck NV, Zhang J, De Angeli A, Beckers GJM, Martinoia E. ABA-Induced Stomatal Closure Involves ALMT4, a Phosphorylation-Dependent Vacuolar Anion Channel of Arabidopsis. THE PLANT CELL 2017; 29:2552-2569. [PMID: 28874508 DOI: 10.1105/tpc.1117.00452] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 08/09/2017] [Accepted: 08/31/2017] [Indexed: 05/24/2023]
Abstract
Stomatal pores are formed between a pair of guard cells and allow plant uptake of CO2 and water evaporation. Their aperture depends on changes in osmolyte concentration of guard cell vacuoles, specifically of K+ and Mal2- Efflux of Mal2- from the vacuole is required for stomatal closure; however, it is not clear how the anion is released. Here, we report the identification of ALMT4 (ALUMINUM ACTIVATED MALATE TRANSPORTER4) as an Arabidopsis thaliana ion channel that can mediate Mal2- release from the vacuole and is required for stomatal closure in response to abscisic acid (ABA). Knockout mutants showed impaired stomatal closure in response to the drought stress hormone ABA and increased whole-plant wilting in response to drought and ABA. Electrophysiological data show that ALMT4 can mediate Mal2- efflux and that the channel activity is dependent on a phosphorylatable C-terminal serine. Dephosphomimetic mutants of ALMT4 S382 showed increased channel activity and Mal2- efflux. Reconstituting the active channel in almt4 mutants impaired growth and stomatal opening. Phosphomimetic mutants were electrically inactive and phenocopied the almt4 mutants. Surprisingly, S382 can be phosphorylated by mitogen-activated protein kinases in vitro. In brief, ALMT4 likely mediates Mal2- efflux during ABA-induced stomatal closure and its activity depends on phosphorylation.
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Affiliation(s)
- Cornelia Eisenach
- Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland
| | - Ulrike Baetz
- Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland
| | - Nicola V Huck
- Department of Plant Physiology, Aachen Biology and Biotechnology, RWTH Aachen University, Aachen 52056, Germany
| | - Jingbo Zhang
- Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland
| | - Alexis De Angeli
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Gerold J M Beckers
- Department of Plant Physiology, Aachen Biology and Biotechnology, RWTH Aachen University, Aachen 52056, Germany
| | - Enrico Martinoia
- Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland
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6
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Eisenach C, Baetz U, Huck NV, Zhang J, De Angeli A, Beckers GJM, Martinoia E. ABA-Induced Stomatal Closure Involves ALMT4, a Phosphorylation-Dependent Vacuolar Anion Channel of Arabidopsis. THE PLANT CELL 2017; 29:2552-2569. [PMID: 28874508 PMCID: PMC5774580 DOI: 10.1105/tpc.17.00452] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 08/09/2017] [Accepted: 08/31/2017] [Indexed: 05/18/2023]
Abstract
Stomatal pores are formed between a pair of guard cells and allow plant uptake of CO2 and water evaporation. Their aperture depends on changes in osmolyte concentration of guard cell vacuoles, specifically of K+ and Mal2- Efflux of Mal2- from the vacuole is required for stomatal closure; however, it is not clear how the anion is released. Here, we report the identification of ALMT4 (ALUMINUM ACTIVATED MALATE TRANSPORTER4) as an Arabidopsis thaliana ion channel that can mediate Mal2- release from the vacuole and is required for stomatal closure in response to abscisic acid (ABA). Knockout mutants showed impaired stomatal closure in response to the drought stress hormone ABA and increased whole-plant wilting in response to drought and ABA. Electrophysiological data show that ALMT4 can mediate Mal2- efflux and that the channel activity is dependent on a phosphorylatable C-terminal serine. Dephosphomimetic mutants of ALMT4 S382 showed increased channel activity and Mal2- efflux. Reconstituting the active channel in almt4 mutants impaired growth and stomatal opening. Phosphomimetic mutants were electrically inactive and phenocopied the almt4 mutants. Surprisingly, S382 can be phosphorylated by mitogen-activated protein kinases in vitro. In brief, ALMT4 likely mediates Mal2- efflux during ABA-induced stomatal closure and its activity depends on phosphorylation.
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Affiliation(s)
- Cornelia Eisenach
- Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland
| | - Ulrike Baetz
- Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland
| | - Nicola V Huck
- Department of Plant Physiology, Aachen Biology and Biotechnology, RWTH Aachen University, Aachen 52056, Germany
| | - Jingbo Zhang
- Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland
| | - Alexis De Angeli
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Gerold J M Beckers
- Department of Plant Physiology, Aachen Biology and Biotechnology, RWTH Aachen University, Aachen 52056, Germany
| | - Enrico Martinoia
- Department of Plant and Microbial Biology, University of Zurich, CH-8008 Zurich, Switzerland
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7
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Benmocha Guggenheimer A, Almagor L, Tsemakhovich V, Tripathy DR, Hirsch JA, Dascal N. Interactions between N and C termini of α1C subunit regulate inactivation of CaV1.2 L-type Ca(2+) channel. Channels (Austin) 2016; 10:55-68. [PMID: 26577286 DOI: 10.1080/19336950.2015.1108499] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The modulation and regulation of voltage-gated Ca(2+) channels is affected by the pore-forming segments, the cytosolic parts of the channel, and interacting intracellular proteins. In this study we demonstrate a direct physical interaction between the N terminus (NT) and C terminus (CT) of the main subunit of the L-type Ca(2+) channel CaV1.2, α1C, and explore the importance of this interaction for the regulation of the channel. We used biochemistry to measure the strength of the interaction and to map the location of the interaction sites, and electrophysiology to investigate the functional impact of the interaction. We show that the full-length NT (amino acids 1-154) and the proximal (close to the plasma membrane) part of the CT, pCT (amino acids 1508-1669) interact with sub-micromolar to low-micromolar affinity. Calmodulin (CaM) is not essential for the binding. The results further suggest that the NT-CT interaction regulates the channel's inactivation, and that Ca(2+), presumably through binding to calmodulin (CaM), reduces the strength of NT-CT interaction. We propose a molecular mechanism in which NT and CT of the channel serve as levers whose movements regulate inactivation by promoting changes in the transmembrane core of the channel via S1 (NT) or S6 (pCT) segments of domains I and IV, accordingly, and not as a kind of pore blocker. We hypothesize that Ca(2+)-CaM-induced changes in NT-CT interaction may, in part, underlie the acceleration of CaV1.2 inactivation induced by Ca(2+) entry into the cell.
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Affiliation(s)
- Adva Benmocha Guggenheimer
- a Department of Physiology and Pharmacology ; Sackler School of Medicine; Sagol School of Neuroscience ; Tel Aviv , Israel
| | - Lior Almagor
- b Department of Biochemistry & Molecular Biology ; Institute of Structural Biology, George S Weiss Faculty of Life Sciences; Sagol School of Neuroscience; Tel Aviv University ; Tel Aviv , Israel.,c Present address: Department of Structural Biology , Stanford University, School of Medicine ; Stanford , CA USA
| | - Vladimir Tsemakhovich
- a Department of Physiology and Pharmacology ; Sackler School of Medicine; Sagol School of Neuroscience ; Tel Aviv , Israel
| | - Debi Ranjan Tripathy
- b Department of Biochemistry & Molecular Biology ; Institute of Structural Biology, George S Weiss Faculty of Life Sciences; Sagol School of Neuroscience; Tel Aviv University ; Tel Aviv , Israel
| | - Joel A Hirsch
- b Department of Biochemistry & Molecular Biology ; Institute of Structural Biology, George S Weiss Faculty of Life Sciences; Sagol School of Neuroscience; Tel Aviv University ; Tel Aviv , Israel
| | - Nathan Dascal
- a Department of Physiology and Pharmacology ; Sackler School of Medicine; Sagol School of Neuroscience ; Tel Aviv , Israel
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8
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Paul F. Cranefield Award to Matthew Trudeau. J Gen Physiol 2015; 145:3-4. [PMID: 25512597 PMCID: PMC4278183 DOI: 10.1085/jgp.201411331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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9
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Ma L, Yang F, Zheng J. Application of fluorescence resonance energy transfer in protein studies. J Mol Struct 2014; 1077:87-100. [PMID: 25368432 DOI: 10.1016/j.molstruc.2013.12.071] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Since the physical process of fluorescence resonance energy transfer (FRET) was elucidated more than six decades ago, this peculiar fluorescence phenomenon has turned into a powerful tool for biomedical research due to its compatibility in scale with biological molecules as well as rapid developments in novel fluorophores and optical detection techniques. A wide variety of FRET approaches have been devised, each with its own advantages and drawbacks. Especially in the last decade or so, we are witnessing a flourish of FRET applications in biological investigations, many of which exemplify clever experimental design and rigorous analysis. Here we review the current stage of FRET methods development with the main focus on its applications in protein studies in biological systems, by summarizing the basic components of FRET techniques, most established quantification methods, as well as potential pitfalls, illustrated by example applications.
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Affiliation(s)
- Linlin Ma
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA 95616, USA ; Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Fan Yang
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA 95616, USA
| | - Jie Zheng
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA 95616, USA
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10
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Insight into the molecular interaction between the cyclic nucleotide-binding homology domain and the eag domain of the hERG channel. FEBS Lett 2014; 588:2782-8. [PMID: 24931372 DOI: 10.1016/j.febslet.2014.05.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 05/14/2014] [Accepted: 05/27/2014] [Indexed: 12/18/2022]
Abstract
The gating of the hERG channel is regulated by its eag domain through molecular interaction with either the cyclic nucleotide-binding homology domain (CNBHD) or the linker between transmembrane segments 4 and 5. Our NMR study on the purified CNBHD demonstrated that it contains nine β-strands and does not bind cAMP. We show that the eag domain binds to the CBND through an interface containing several disease-associated mutations. The N-terminal cap domain and R56 in the eag domain are important for the interaction with the CNBHD. Residues from the CNBHD that were affected by the interaction with the eag domain were also identified. A R56Q mutation does not cause major structural changes in the eag domain and showed reduced interaction with the CNBHD.
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11
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Li Q, Ng HQ, Yoon HS, Kang C. Solution structure of the cyclic-nucleotide binding homology domain of a KCNH channel. J Struct Biol 2014; 186:68-74. [PMID: 24632450 DOI: 10.1016/j.jsb.2014.03.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Revised: 03/03/2014] [Accepted: 03/10/2014] [Indexed: 12/28/2022]
Abstract
The carboxy-terminal region of the KCNH family of potassium channels contains a cyclic-nucleotide binding homology domain (CNBHD) that is important for channel gating and trafficking. The solution structure of the CNBHD of the KCNH potassium of zebrafish was determined using solution NMR spectroscopy. This domain exists as a monomer under solution conditions and adopts a similar fold to that determined by X-ray crystallography. The CNBHD does not bind cAMP because residue Y740 blocks the entry of cyclic-nucleotide to the binding pocket. Relaxation results show that the CNBHD is rigid except that some residues in the loop between β6 and β7 are flexible. Our results will be useful to understand the gating mechanism of KCNH family members through the CNBHD.
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Affiliation(s)
- Qingxin Li
- Institute of Chemical & Engineering Sciences, Agency for Science, Technology and Research (A∗STAR), Singapore 627833, Singapore
| | - Hui Qi Ng
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A∗STAR), Singapore 138669, Singapore
| | - Ho Sup Yoon
- Division of Structural Biology and Biochemistry, School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637511, Singapore
| | - Congbao Kang
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A∗STAR), Singapore 138669, Singapore.
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12
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Yang F, Ma L, Cao X, Wang K, Zheng J. Divalent cations activate TRPV1 through promoting conformational change of the extracellular region. ACTA ACUST UNITED AC 2013; 143:91-103. [PMID: 24344245 PMCID: PMC3874565 DOI: 10.1085/jgp.201311024] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Divalent cations Mg2+ and Ba2+ selectively and directly potentiate transient receptor potential vanilloid type 1 heat activation by lowering the activation threshold into the room temperature range. We found that Mg2+ potentiates channel activation only from the extracellular side; on the intracellular side, Mg2+ inhibits channel current. By dividing the extracellularly accessible region of the channel protein into small segments and perturbing the structure of each segment with sequence replacement mutations, we observed that the S1–S2 linker, the S3–S4 linker, and the pore turret are all required for Mg2+ potentiation. Sequence replacements at these regions substantially reduced or eliminated Mg2+-induced activation at room temperature while sparing capsaicin activation. Heat activation was affected by many, but not all, of these structural alternations. These observations indicate that extracellular linkers and the turret may interact with each other. Site-directed fluorescence resonance energy transfer measurements further revealed that, like heat, Mg2+ also induces structural changes in the pore turret. Interestingly, turret movement induced by Mg2+ precedes channel activation, suggesting that Mg2+-induced conformational change in the extracellular region most likely serves as the cause of channel activation instead of a coincidental or accommodating structural adjustment.
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Affiliation(s)
- Fan Yang
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, Davis, CA 95616
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