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Moldenhauer HJ, Tammen K, Meredith AL. Structural mapping of patient-associated KCNMA1 gene variants. Biophys J 2024; 123:1984-2000. [PMID: 38042986 PMCID: PMC11309989 DOI: 10.1016/j.bpj.2023.11.3404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [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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Li Q, Chen G, Yan J. Transmembrane determinants of voltage-gating differences between BK (Slo1) and Slo3 channels. Biophys J 2024; 123:2154-2166. [PMID: 38637987 PMCID: PMC11309983 DOI: 10.1016/j.bpj.2024.04.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 02/01/2024] [Accepted: 04/15/2024] [Indexed: 04/20/2024] Open
Abstract
Voltage-gated potassium channels are critical in modulating cellular excitability, with Slo (slowpoke) channels forming a unique family characterized by their large conductance and dual regulation by electrical signals and intracellular messengers. Despite their structural and evolutionary similarities, Slo1 and Slo3 channels exhibit significant differences in their voltage-gating properties. This study investigates the molecular determinants that differentiate the voltage-gating properties of human Slo1 and mouse Slo3 channels. Utilizing Slo1/Slo3 chimeras, we pinpointed the selectivity filter region as a key factor in the Slo3 channel's reduced conductance at negative voltages. The S6 transmembrane (TM) segment was identified as pivotal for the Slo3 channel's biphasic deactivation kinetics at these voltages. Additionally, the S4 and S6 TM segments were found to be responsible for the gradual slope in the Slo3 channel's conductance-voltage relationship, while multiple TM regions appear to be involved in the Slo3 channel's requirement of strong depolarization for activation. Mutations in the Slo1's S5 and S6 TM segments revealed three residues (I233, L302, and M304) that likely play a crucial role in the allosteric coupling between the voltage sensors and the pore gate.
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Affiliation(s)
- Qin Li
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas; Molecular & Translational Biology and Neuroscience Programs, MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, Texas
| | - Guanxing Chen
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas; Molecular & Translational Biology and Neuroscience Programs, MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, Texas
| | - Jiusheng Yan
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas; Molecular & Translational Biology and Neuroscience Programs, MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, Texas.
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3
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Meredith AL. BK Channelopathies and KCNMA1-Linked Disease Models. Annu Rev Physiol 2024; 86:277-300. [PMID: 37906945 DOI: 10.1146/annurev-physiol-030323-042845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Novel KCNMA1 variants, encoding the BK K+ channel, are associated with a debilitating dyskinesia and epilepsy syndrome. Neurodevelopmental delay, cognitive disability, and brain and structural malformations are also diagnosed at lower incidence. More than half of affected individuals present with a rare negative episodic motor disorder, paroxysmal nonkinesigenic dyskinesia (PNKD3). The mechanistic relationship of PNKD3 to epilepsy and the broader spectrum of KCNMA1-associated symptomology is unknown. This review summarizes patient-associated KCNMA1 variants within the BK channel structure, functional classifications, genotype-phenotype associations, disease models, and treatment. Patient and transgenic animal data suggest delineation of gain-of-function (GOF) and loss-of-function KCNMA1 neurogenetic disease, validating two heterozygous alleles encoding GOF BK channels (D434G and N999S) as causing seizure and PNKD3. This discovery led to a variant-defined therapeutic approach for PNKD3, providing initial insight into the neurological basis. A comprehensive clinical definition of monogenic KCNMA1-linked disease and the neuronal mechanisms currently remain priorities for continued investigation.
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Affiliation(s)
- Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA;
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4
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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: 1] [Impact Index Per Article: 1.0] [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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5
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Gao J, Yin H, Dong Y, Wang X, Liu Y, Wang K. A Novel Role of Uricosuric Agent Benzbromarone in BK Channel Activation and Reduction of Airway Smooth Muscle Contraction. Mol Pharmacol 2023; 103:241-254. [PMID: 36669879 DOI: 10.1124/molpharm.122.000638] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 11/28/2022] [Accepted: 12/19/2022] [Indexed: 01/21/2023] Open
Abstract
The uricosuric drug benzbromarone, widely used for treatment of gout, hyperpolarizes the membrane potential of airway smooth muscle cells, but how it works remains unknown. Here we show a novel role of benzbromarone in activation of large conductance calcium-activated K+ channels. Benzbromarone results in dose-dependent activation of macroscopic big potassium (BK) currents about 1.7- to 14.5-fold with an EC50 of 111 μM and shifts the voltage-dependent channel activation to a more hyperpolarizing direction about 10 to 54 mV in whole-cell patch clamp recordings. In single-channel recordings, benzbromarone decreases single BKα channel closed dwell time and increases the channel open probability. Coexpressing β1 subunit also enhances BK activation by benzbromarone with an EC50 of 67 μM and a leftward shift of conductance-voltage (G-V) curve about 44 to 138 mV. Site-directed mutagenesis reveals that a motif of three amino acids 329RKK331 in the cytoplasmic linker between S6 and C-terminal regulator of potassium conductance (RCK) gating ring mediates the pharmacological activation of BK channels by benzbromarone. Further ex vivo assay shows that benzbromarone causes reduction of tracheal strip contraction. Taken together, our findings demonstrate that uricosuric benzbromarone activates BK channels through molecular mechanism of action involving the channel RKK motif of S6-RCK linker. Pharmacological activation of BK channel by benzbromarone causes reduction of tracheal strip contraction, holding a repurposing potential for asthma and pulmonary arterial hypertension or BK channelopathies. SIGNIFICANCE STATEMENT: We describe a novel role of uricosuric agent benzbromarone in big potassium (BK) channel activation and relaxation of airway smooth muscle contraction. In this study, we find that benzbromarone is an activator of the large-conductance Ca2+- and voltage-activated K+ channel (BK channel), which serves numerous cellular functions, including control of smooth muscle contraction. Pharmacological activation of BK channel by the FDA-approved drug benzbromarone may hold repurposing potential for treatment of asthma and pulmonary arterial hypertension or BK channelopathies.
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Affiliation(s)
- Jian Gao
- Department of Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China (J.G., X.W.); Department of Pharmacology, School of Pharmacy, Qingdao University Medical College, Qingdao, China (H.Y., Y.D., Y.L., K.W.); and Institute of Innovative Drugs, Qingdao University, Qingdao, China (Y.L., K.W.)
| | - Hao Yin
- Department of Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China (J.G., X.W.); Department of Pharmacology, School of Pharmacy, Qingdao University Medical College, Qingdao, China (H.Y., Y.D., Y.L., K.W.); and Institute of Innovative Drugs, Qingdao University, Qingdao, China (Y.L., K.W.)
| | - Yanqun Dong
- Department of Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China (J.G., X.W.); Department of Pharmacology, School of Pharmacy, Qingdao University Medical College, Qingdao, China (H.Y., Y.D., Y.L., K.W.); and Institute of Innovative Drugs, Qingdao University, Qingdao, China (Y.L., K.W.)
| | - Xintong Wang
- Department of Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China (J.G., X.W.); Department of Pharmacology, School of Pharmacy, Qingdao University Medical College, Qingdao, China (H.Y., Y.D., Y.L., K.W.); and Institute of Innovative Drugs, Qingdao University, Qingdao, China (Y.L., K.W.)
| | - Yani Liu
- Department of Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China (J.G., X.W.); Department of Pharmacology, School of Pharmacy, Qingdao University Medical College, Qingdao, China (H.Y., Y.D., Y.L., K.W.); and Institute of Innovative Drugs, Qingdao University, Qingdao, China (Y.L., K.W.)
| | - KeWei Wang
- Department of Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, China (J.G., X.W.); Department of Pharmacology, School of Pharmacy, Qingdao University Medical College, Qingdao, China (H.Y., Y.D., Y.L., K.W.); and Institute of Innovative Drugs, Qingdao University, Qingdao, China (Y.L., K.W.)
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6
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Potassium channelopathies associated with epilepsy-related syndromes and directions for therapeutic intervention. Biochem Pharmacol 2023; 208:115413. [PMID: 36646291 DOI: 10.1016/j.bcp.2023.115413] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023]
Abstract
A number of mutations to members of several CNS potassium (K) channel families have been identified which result in rare forms of neonatal onset epilepsy, or syndromes of which one prominent characteristic is a form of epilepsy. Benign Familial Neonatal Convulsions or Seizures (BFNC or BFNS), also referred to as Self-Limited Familial Neonatal Epilepsy (SeLNE), results from mutations in 2 members of the KV7 family (KCNQ) of K channels; while generally self-resolving by about 15 weeks of age, these mutations significantly increase the probability of generalized seizure disorders in the adult, in some cases they result in more severe developmental syndromes. Epilepsy of Infancy with Migrating Focal Seizures (EIMSF), or Migrating Partial Seizures of Infancy (MMPSI), is a rare severe form of epilepsy linked primarily to gain of function mutations in a member of the sodium-dependent K channel family, KCNT1 or SLACK. Finally, KCNMA1 channelopathies, including Liang-Wang syndrome (LIWAS), are rare combinations of neurological symptoms including seizure, movement abnormalities, delayed development and intellectual disabilities, with Liang-Wang syndrome an extremely serious polymalformative syndrome with a number of neurological sequelae including epilepsy. These are caused by mutations in the pore-forming subunit of the large-conductance calcium-activated K channel (BK channel) KCNMA1. The identification of these rare but significant channelopathies has resulted in a resurgence of interest in their treatment by direct pharmacological or genetic modulation. We will briefly review the genetics, biophysics and pharmacology of these K channels, their linkage with the 3 syndromes described above, and efforts to more effectively target these syndromes.
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External Hemin as an Inhibitor of Mitochondrial Large-Conductance Calcium-Activated Potassium Channel Activity. Int J Mol Sci 2022; 23:ijms232113391. [DOI: 10.3390/ijms232113391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 10/26/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial large-conductance calcium-activated potassium channel (mitoBKCa) is located in the inner mitochondrial membrane and seems to play a crucial role in cytoprotection. The mitoBKCa channel is regulated by many modulators, including activators, such as calcium ions and inhibitors, such as heme and its oxidized form hemin. Heme/hemin binds to the heme-binding motif (CXXCH) located between two RCK domains present in the mitochondrial matrix. In the present study, we used the patch-clamp technique in the outside-out configuration to record the activity of mitoBKCa channels. This allowed for the application of channel modulators to the intermembrane-space side of the mitoBKCa. We found that hemin applied in this configuration inhibits the activity of mitoBKCa. In addition, we proved that the observed hemin effect is specific and it is not due to its interaction with the inner mitochondrial membrane. Our data suggest the existence of a new potential heme/hemin binding site in the structure of the mitoBKCa channel located on the mitochondrial intermembrane space side, which could constitute a new way for the regulation of mitoBKCa channel activity.
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González-Cota AL, Santana-Calvo C, Servín-Vences R, Orta G, Balderas E. Regulatory mechanisms of mitochondrial BK Ca channels. Channels (Austin) 2021; 15:424-437. [PMID: 33955332 PMCID: PMC8117780 DOI: 10.1080/19336950.2021.1919463] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/05/2021] [Accepted: 04/05/2021] [Indexed: 02/06/2023] Open
Abstract
The mitochondrial BKCa channel (mitoBKCa) is a splice variant of plasma membrane BKCa (Maxi-K, BKCa, Slo1, KCa1.1). While a high-resolution structure of mitoBKCa is not available yet, functional and structural studies of the plasma membrane BKCa have provided important clues on the gating of the channel by voltage and Ca2+, as well as the interaction with auxiliary subunits. To date, we know that the control of expression of mitoBKCa, targeting and voltage-sensitivity strongly depends on its association with its regulatory β1-subunit, which overall participate in the control of mitochondrial Ca2+-overload in cardiac myocytes. Moreover, novel regulatory mechanisms of mitoBKCa such as β-subunits and amyloid-β have recently been proposed. However, major basic questions including how the regulatory BKCa-β1-subunit reaches mitochondria and the mechanism through which amyloid-β impairs mitoBKCa channel function remain to be addressed.
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Affiliation(s)
- Ana L. González-Cota
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, UNAM. Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Carmen Santana-Calvo
- Instituto Gulbenkian de Ciência. Rua da Quinta Grande 6, Oeiras, Portugal
- Instituto de Tecnologia Química e Biológica, Universida de Nova de Lisboa. Av. da República, Oeiras, Portugal
| | - Rocío Servín-Vences
- Department of Neuroscience, The Scripps Research Institute. 10550 North Torrey Pines Road, La Jolla, CA, USA
| | - Gerardo Orta
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, UNAM. Av. Universidad 2001, Cuernavaca, Morelos, México
| | - Enrique Balderas
- Nora Eccles Harrison Cardiovascular Research & Training Institute, University of Utah, Salt Lake City, UT, USA
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Cui J. BK Channel Gating Mechanisms: Progresses Toward a Better Understanding of Variants Linked Neurological Diseases. Front Physiol 2021; 12:762175. [PMID: 34744799 PMCID: PMC8567085 DOI: 10.3389/fphys.2021.762175] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 10/01/2021] [Indexed: 12/21/2022] Open
Abstract
The large conductance Ca2+-activated potassium (BK) channel is activated by both membrane potential depolarization and intracellular Ca2+ with distinct mechanisms. Neural physiology is sensitive to the function of BK channels, which is shown by the discoveries of neurological disorders that are associated with BK channel mutations. This article reviews the molecular mechanisms of BK channel activation in response to voltage and Ca2+ binding, including the recent progress since the publication of the atomistic structure of the whole BK channel protein, and the neurological disorders associated with BK channel mutations. These results demonstrate the unique mechanisms of BK channel activation and that these mechanisms are important factors in linking BK channel mutations to neurological disorders.
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Affiliation(s)
- Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO, United States
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10
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Wu T, Yin N, Chen X, Huang H, Liao Y. Functional coupling between BKCa and SOC channels. Tissue Cell 2020; 66:101394. [DOI: 10.1016/j.tice.2020.101394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 05/31/2020] [Accepted: 05/31/2020] [Indexed: 01/13/2023]
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A Calcium Sensor Discovered in Bluetongue Virus Nonstructural Protein 2 Is Critical for Virus Replication. J Virol 2020; 94:JVI.01099-20. [PMID: 32759321 PMCID: PMC7527055 DOI: 10.1128/jvi.01099-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 07/29/2020] [Indexed: 12/20/2022] Open
Abstract
After entering the host cells, viruses use cellular host factors to ensure a successful virus replication process. For replication in infected cells, members of the Reoviridae family form inclusion body-like structures known as viral inclusion bodies (VIB) or viral factories. Bluetongue virus (BTV) forms VIBs in infected cells through nonstructural protein 2 (NS2), a phosphoprotein. An important regulatory factor critical for VIB formation is phosphorylation of NS2. In our study, we discovered a characteristic calcium-binding EF-hand-like motif in NS2 and found that the calcium binding preferentially affects phosphorylation level of the NS2 and has a role in regulating VIB assembly. Many viruses use specific viral proteins to bind calcium ions (Ca2+) for stability or to modify host cell pathways; however, to date, no Ca2+ binding protein has been reported in bluetongue virus (BTV), the causative agent of bluetongue disease in livestock. Here, using a comprehensive bioinformatics screening, we identified a putative EF-hand-like Ca2+ binding motif in the carboxyl terminal region of BTV nonstructural phosphoprotein 2 (NS2). Subsequently, using a recombinant NS2, we demonstrated that NS2 binds Ca2+ efficiently and that Ca2+ binding was perturbed when the Asp and Glu residues in the motif were substituted by alanine. Using circular dichroism analysis, we found that Ca2+ binding by NS2 triggered a helix-to-coil secondary structure transition. Further, cryo-electron microscopy in the presence of Ca2+ revealed that NS2 forms helical oligomers which, when aligned with the N-terminal domain crystal structure, suggest an N-terminal domain that wraps around the C-terminal domain in the oligomer. Further, an in vitro kinase assay demonstrated that Ca2+ enhanced the phosphorylation of NS2 significantly. Importantly, mutations introduced at the Ca2+ binding site in the viral genome by reverse genetics failed to allow recovery of viable virus, and the NS2 phosphorylation level and assembly of viral inclusion bodies (VIBs) were reduced. Together, our data suggest that NS2 is a dedicated Ca2+ binding protein and that calcium sensing acts as a trigger for VIB assembly, which in turn facilitates virus replication and assembly. IMPORTANCE After entering the host cells, viruses use cellular host factors to ensure a successful virus replication process. For replication in infected cells, members of the Reoviridae family form inclusion body-like structures known as viral inclusion bodies (VIB) or viral factories. Bluetongue virus (BTV) forms VIBs in infected cells through nonstructural protein 2 (NS2), a phosphoprotein. An important regulatory factor critical for VIB formation is phosphorylation of NS2. In our study, we discovered a characteristic calcium-binding EF-hand-like motif in NS2 and found that the calcium binding preferentially affects phosphorylation level of the NS2 and has a role in regulating VIB assembly.
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12
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Gessner G, Rühl P, Westerhausen M, Hoshi T, Heinemann SH. Fe 2+-Mediated Activation of BK Ca Channels by Rapid Photolysis of CORM-S1 Releasing CO and Fe 2. ACS Chem Biol 2020; 15:2098-2106. [PMID: 32667185 DOI: 10.1021/acschembio.0c00282] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Heme catabolism by heme oxygenase (HO) with a decrease in intracellular heme concentration and a concomitant local release of CO and Fe2+ has the potential to regulate BKCa channels. Here, we show that the iron-based photolabile CO-releasing molecule CORM-S1 [dicarbonyl-bis(cysteamine)iron(II)] coreleases CO and Fe2+, making it a suitable light-triggered source of these downstream products of HO activity. To investigate the impact of CO, iron, and cysteamine on BKCa channel activation, human Slo1 (hSlo1) was expressed in HEK293T cells and studied with electrophysiological methods. Whereas hSlo1 channels are activated by CO and even more strongly by Fe2+, Fe3+ and cysteamine possess only marginal activating potency. Investigation of hSlo1 mutants revealed that Fe2+ modulates the channels mainly through the Mg2+-dependent activation mechanism. Flash photolysis of CORM-S1 suits for rapid and precise delivery of Fe2+ and CO in biological settings.
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Affiliation(s)
- Guido Gessner
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, Hans-Knöll-Str. 2, D-07745 Jena, Germany
| | - Philipp Rühl
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, Hans-Knöll-Str. 2, D-07745 Jena, Germany
| | - Matthias Westerhausen
- Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, D-07740 Jena, Germany
| | - Toshinori Hoshi
- Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania United States
| | - Stefan H. Heinemann
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, Hans-Knöll-Str. 2, D-07745 Jena, Germany
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From Local to Global Modeling for Characterizing Calcium Dynamics and Their Effects on Electrical Activity and Exocytosis in Excitable Cells. Int J Mol Sci 2019; 20:ijms20236057. [PMID: 31801305 PMCID: PMC6928823 DOI: 10.3390/ijms20236057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/27/2019] [Accepted: 11/27/2019] [Indexed: 12/25/2022] Open
Abstract
Electrical activity in neurons and other excitable cells is a result of complex interactions between the system of ion channels, involving both global coupling (e.g., via voltage or bulk cytosolic Ca2+ concentration) of the channels, and local coupling in ion channel complexes (e.g., via local Ca2+ concentration surrounding Ca2+ channels (CaVs), the so-called Ca2+ nanodomains). We recently devised a model of large-conductance BKCa potassium currents, and hence BKCa–CaV complexes controlled locally by CaVs via Ca2+ nanodomains. We showed how different CaV types and BKCa–CaV stoichiometries affect whole-cell electrical behavior. Ca2+ nanodomains are also important for triggering exocytosis of hormone-containing granules, and in this regard, we implemented a strategy to characterize the local interactions between granules and CaVs. In this study, we coupled electrical and exocytosis models respecting the local effects via Ca2+ nanodomains. By simulating scenarios with BKCa–CaV complexes with different stoichiometries in pituitary cells, we achieved two main electrophysiological responses (continuous spiking or bursting) and investigated their effects on the downstream exocytosis process. By varying the number and distance of CaVs coupled with the granules, we found that bursting promotes exocytosis with faster rates than spiking. However, by normalizing to Ca2+ influx, we found that bursting is only slightly more efficient than spiking when CaVs are far away from granules, whereas no difference in efficiency between bursting and spiking is observed with close granule-CaV coupling.
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Martinez GQ, Gordon SE. Multimerization of Homo sapiens TRPA1 ion channel cytoplasmic domains. PLoS One 2019; 14:e0207835. [PMID: 30794546 PMCID: PMC6386368 DOI: 10.1371/journal.pone.0207835] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 01/23/2019] [Indexed: 11/19/2022] Open
Abstract
The transient receptor potential Ankyrin-1 (TRPA1) ion channel is modulated by myriad noxious stimuli that interact with multiple regions of the channel, including cysteine-reactive natural extracts from onion and garlic which modify residues in the cytoplasmic domains. The way in which TRPA1 cytoplasmic domain modification is coupled to opening of the ion-conducting pore has yet to be elucidated. The cryo-EM structure of TRPA1 revealed a tetrameric C-terminal coiled-coil surrounded by N-terminal ankyrin repeat domains (ARDs), an architecture shared with the canonical transient receptor potential (TRPC) ion channel family. Similarly, structures of the TRP melastatin (TRPM) ion channel family also showed a C-terminal coiled-coil surrounded by N-terminal cytoplasmic domains. This conserved architecture may indicate a common gating mechanism by which modification of cytoplasmic domains can transduce conformational changes to open the ion-conducting pore. We developed an in vitro system in which N-terminal ARDs and C-terminal coiled-coil domains can be expressed in bacteria and maintain the ability to interact. We tested three gating regulators: temperature; the polyphosphate compound IP6; and the covalent modifier allyl isothiocyanate to determine whether they alter N- and C-terminal interactions. We found that none of the modifiers tested abolished ARD-coiled-coil interactions, though there was a significant reduction at 37˚C. We found that coiled-coils tetramerize in a concentration dependent manner, with monomers and trimers observed at lower concentrations. Our system provides a method for examining the mechanism of oligomerization of TRPA1 cytoplasmic domains as well as a system to study the transmission of conformational changes resulting from covalent modification.
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Affiliation(s)
- Gilbert Q. Martinez
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
| | - Sharona E. Gordon
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
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15
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Kshatri AS, Gonzalez-Hernandez A, Giraldez T. Physiological Roles and Therapeutic Potential of Ca 2+ Activated Potassium Channels in the Nervous System. Front Mol Neurosci 2018; 11:258. [PMID: 30104956 PMCID: PMC6077210 DOI: 10.3389/fnmol.2018.00258] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 07/06/2018] [Indexed: 12/21/2022] Open
Abstract
Within the potassium ion channel family, calcium activated potassium (KCa) channels are unique in their ability to couple intracellular Ca2+ signals to membrane potential variations. KCa channels are diversely distributed throughout the central nervous system and play fundamental roles ranging from regulating neuronal excitability to controlling neurotransmitter release. The physiological versatility of KCa channels is enhanced by alternative splicing and co-assembly with auxiliary subunits, leading to fundamental differences in distribution, subunit composition and pharmacological profiles. Thus, understanding specific KCa channels’ mechanisms in neuronal function is challenging. Based on their single channel conductance, KCa channels are divided into three subtypes: small (SK, 4–14 pS), intermediate (IK, 32–39 pS) and big potassium (BK, 200–300 pS) channels. This review describes the biophysical characteristics of these KCa channels, as well as their physiological roles and pathological implications. In addition, we also discuss the current pharmacological strategies and challenges to target KCa channels for the treatment of various neurological and psychiatric disorders.
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Affiliation(s)
- Aravind S Kshatri
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Alberto Gonzalez-Hernandez
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Teresa Giraldez
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
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16
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Sclip A, Acuna C, Luo F, Südhof TC. RIM-binding proteins recruit BK-channels to presynaptic release sites adjacent to voltage-gated Ca 2+-channels. EMBO J 2018; 37:embj.201798637. [PMID: 29967030 PMCID: PMC6092624 DOI: 10.15252/embj.201798637] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 06/01/2018] [Accepted: 06/04/2018] [Indexed: 12/31/2022] Open
Abstract
The active zone of presynaptic nerve terminals organizes the neurotransmitter release machinery, thereby enabling fast Ca2+-triggered synaptic vesicle exocytosis. BK-channels are Ca2+-activated large-conductance K+-channels that require close proximity to Ca2+-channels for activation and control Ca2+-triggered neurotransmitter release by accelerating membrane repolarization during action potential firing. How BK-channels are recruited to presynaptic Ca2+-channels, however, is unknown. Here, we show that RBPs (for RIM-binding proteins), which are evolutionarily conserved active zone proteins containing SH3- and FN3-domains, directly bind to BK-channels. We find that RBPs interact with RIMs and Ca2+-channels via their SH3-domains, but to BK-channels via their FN3-domains. Deletion of RBPs in calyx of Held synapses decreased and decelerated presynaptic BK-currents and depleted BK-channels from active zones. Our data suggest that RBPs recruit BK-channels into a RIM-based macromolecular active zone complex that includes Ca2+-channels, synaptic vesicles, and the membrane fusion machinery, thereby enabling tight spatio-temporal coupling of Ca2+-influx to Ca2+-triggered neurotransmitter release in a presynaptic terminal.
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Affiliation(s)
- Alessandra Sclip
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Claudio Acuna
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA.,CH Schaller Foundation and Institute of Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Fujun Luo
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA.,School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Thomas C Südhof
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA
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17
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Luo Y, Yu X, Ma C, Luo J, Yang W. Identification of a Novel EF-Loop in the N-terminus of TRPM2 Channel Involved in Calcium Sensitivity. Front Pharmacol 2018; 9:581. [PMID: 29915540 PMCID: PMC5994415 DOI: 10.3389/fphar.2018.00581] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 05/15/2018] [Indexed: 01/10/2023] Open
Abstract
As an oxidative stress sensor, transient receptor potential melastatin 2 (TRPM2) channel is involved in many physiological and pathological processes including warmth sensing, ischemia injury, inflammatory diseases and diabetes. Intracellular calcium is critical for TRPM2 channel activation and the IQ-like motif in the N-terminus has been shown to be important by mediating calmodulin binding. Sequence analysis predicted two potential EF-loops in the N-terminus of TRPM2. Site-directed mutagenesis combining with functional assay showed that substitution with alanine of several residues, most of which are conserved in the typical EF-loop, including D267, D278, D288, and E298 dramatically reduced TRPM2 channel currents. By further changing the charges or side chain length of these conserved residues, our results indicate that the negative charge of D267 and the side chain length of D278 are critical for calcium-induced TRPM2 channel activation. G272I mutation also dramatically reduced the channel currents, suggesting that this site is critical for calcium-induced TRPM2 channel activation. Furthermore, D267A mutant dramatically reduced the currents induced by calcium alone compared with that by ADPR, indicating that D267 residue in D267–D278 motif is the most important site for calcium sensitivity of TRPM2. In addition, inside-out recordings showed that mutations at D267, G272, D278, and E298 had no effect on single-channel conductance. Taken together, our data indicate that D267–D278 motif in the N-terminus as a novel EF-loop is critical for calcium-induced TRPM2 channel activation.
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Affiliation(s)
- Yuhuan Luo
- Department of Neurobiology, Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Xiafei Yu
- Department of Neurobiology, Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Cheng Ma
- Co-facility Center, Zhejiang University School of Medicine, Hangzhou, China
| | - Jianhong Luo
- Department of Neurobiology, Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Wei Yang
- Department of Neurobiology, Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
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18
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Zhu Y, Ye P, Chen SL, Zhang DM. Functional regulation of large conductance Ca 2+-activated K + channels in vascular diseases. Metabolism 2018; 83:75-80. [PMID: 29373813 DOI: 10.1016/j.metabol.2018.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Revised: 01/03/2018] [Accepted: 01/18/2018] [Indexed: 12/17/2022]
Abstract
The large conductance Ca2+-activated potassium channels, the BK channels, is widely expressed in various tissues and activated in a Ca2+- and voltage-dependent manner. The activation of BK channels hyperpolarizes vascular smooth muscle cell membrane potential, resulting in vasodilation. Under pathophysiological conditions, such as diabetes mellitus and hypertension, impaired BK channel function exacerbates vascular vasodilation and leads to organ ischemia. The vascular BK channel is composed of 4 pore-forming subunits, BK-α together with 4 auxiliary subunits: β1 subunits (BK-β1) or γ1 subunits (BK-γ1). Recent studies have shown that down-regulation of the BK β1 subunit in diabetes mellitus induced vascular dysfunction; however, the molecular mechanism of these vascular diseases is not well understood. In this review, we summarize the potential mechanisms regarding BK channelopathy and the potential therapeutic targets of BK channels for vascular diseases.
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Affiliation(s)
- Yanrong Zhu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Peng Ye
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Shao-Liang Chen
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Dai-Min Zhang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China.
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19
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Molecular determinants of Ca 2+ sensitivity at the intersubunit interface of the BK channel gating ring. Sci Rep 2018; 8:509. [PMID: 29323236 PMCID: PMC5765161 DOI: 10.1038/s41598-017-19029-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 12/19/2017] [Indexed: 12/31/2022] Open
Abstract
The large-conductance calcium-activated K+ (BK) channel contains two intracellular tandem Ca2+-sensing RCK domains (RCK1 and RCK2), which tetramerize into a Ca2+ gating ring that regulates channel opening by conformational expansion in response to Ca2+ binding. Interestingly, the gating ring’s intersubunit assembly interface harbors the RCK2 Ca2+-binding site, known as the Ca2+ bowl. The gating ring’s assembly interface is made in part by intersubunit coordination of a Ca2+ ion between the Ca2+ bowl and an RCK1 Asn residue, N449, and by apparent intersubunit electrostatic interactions between E955 in RCK2 and R786 and R790 in the RCK2 of the adjacent subunit. To understand the role of the intersubunit assembly interface in Ca2+ gating, we performed mutational analyses of these putative interacting residues in human BK channels. We found that N449, despite its role in Ca2+ coordination, does not set the channel’s Ca2+ sensitivity, whereas E955 is a determinant of Ca2+ sensitivity, likely through intersubunit electrostatic interactions. Our findings provide evidence that the intersubunit assembly interface contains molecular determinants of Ca2+-sensitivity in BK channels.
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20
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Giraldez T, Rothberg BS. Understanding the conformational motions of RCK gating rings. J Gen Physiol 2017; 149:431-441. [PMID: 28246116 PMCID: PMC5379921 DOI: 10.1085/jgp.201611726] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 01/17/2017] [Indexed: 12/16/2022] Open
Abstract
A timely review of the structural basis of Ca2+-activated K+ channel modulation by regulator of conduction of K+ (RCK) domains Regulator of conduction of K+ (RCK) domains are ubiquitous regulators of channel and transporter activity in prokaryotes and eukaryotes. In humans, RCK domains form an integral component of large-conductance calcium-activated K channels (BK channels), key modulators of nerve, muscle, and endocrine cell function. In this review, we explore how the study of RCK domains in bacterial and human channels has contributed to our understanding of the structural basis of channel function. This knowledge will be critical in identifying mechanisms that underlie BK channelopathies that lead to epilepsy and other diseases, as well as regions of the channel that might be successfully targeted to treat such diseases.
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Affiliation(s)
- Teresa Giraldez
- Department of Basic Medical Sciences, Institute of Biomedical Technologies and Centre for Biomedical Research of the Canary Islands, Universidad de La Laguna, La Laguna 38071, Spain
| | - Brad S Rothberg
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA 19140
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21
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Latorre R, Castillo K, Carrasquel-Ursulaez W, Sepulveda RV, Gonzalez-Nilo F, Gonzalez C, Alvarez O. Molecular Determinants of BK Channel Functional Diversity and Functioning. Physiol Rev 2017; 97:39-87. [DOI: 10.1152/physrev.00001.2016] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Large-conductance Ca2+- and voltage-activated K+ (BK) channels play many physiological roles ranging from the maintenance of smooth muscle tone to hearing and neurosecretion. BK channels are tetramers in which the pore-forming α subunit is coded by a single gene ( Slowpoke, KCNMA1). In this review, we first highlight the physiological importance of this ubiquitous channel, emphasizing the role that BK channels play in different channelopathies. We next discuss the modular nature of BK channel-forming protein, in which the different modules (the voltage sensor and the Ca2+ binding sites) communicate with the pore gates allosterically. In this regard, we review in detail the allosteric models proposed to explain channel activation and how the models are related to channel structure. Considering their extremely large conductance and unique selectivity to K+, we also offer an account of how these two apparently paradoxical characteristics can be understood consistently in unison, and what we have learned about the conduction system and the activation gates using ions, blockers, and toxins. Attention is paid here to the molecular nature of the voltage sensor and the Ca2+ binding sites that are located in a gating ring of known crystal structure and constituted by four COOH termini. Despite the fact that BK channels are coded by a single gene, diversity is obtained by means of alternative splicing and modulatory β and γ subunits. We finish this review by describing how the association of the α subunit with β or with γ subunits can change the BK channel phenotype and pharmacology.
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Affiliation(s)
- Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Willy Carrasquel-Ursulaez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Romina V. Sepulveda
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Fernando Gonzalez-Nilo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Carlos Gonzalez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Osvaldo Alvarez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
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22
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A large-conductance calcium-regulated K+ channel in human dermal fibroblast mitochondria. Biochem J 2016; 473:4457-4471. [PMID: 27729542 DOI: 10.1042/bcj20160732] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 09/23/2016] [Accepted: 10/10/2016] [Indexed: 02/06/2023]
Abstract
Potassium channels have been found in the inner mitochondrial membrane of various cells. These channels regulate the mitochondrial membrane potential, respiration and production of reactive oxygen species. In the present study, we identified the activity of a mitochondrial large-conductance Ca2+-regulated potassium channel (mitoBKCa channel) in mitoplasts isolated from a primary human dermal fibroblast cell line. A potassium selective current was recorded with a mean conductance of 280 ± 2 pS in a symmetrical 150 mM KCl solution. The mitoBKCa channel was activated by the Ca2+ and by potassium channel opener NS1619. The channel activity was irreversibly inhibited by paxilline, a selective inhibitor of the BKCa channels. In isolated fibroblast mitochondria NS1619 depolarized the mitochondrial membrane potential, stimulated nonphosphorylating respiration and decreased superoxide formation. Additionally, the α- and β-subunits (predominantly the β3-form) of the BKCa channels were identified in fibroblast mitochondria. Our findings indicate, for the first time, the presence of a large-conductance Ca2+-regulated potassium channel in the inner mitochondrial membrane of human dermal fibroblasts.
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23
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Diaz-Franulic I, Poblete H, Miño-Galaz G, González C, Latorre R. Allosterism and Structure in Thermally Activated Transient Receptor Potential Channels. Annu Rev Biophys 2016; 45:371-98. [DOI: 10.1146/annurev-biophys-062215-011034] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ignacio Diaz-Franulic
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago 8370146, Chile
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103, Chile; ,
- Fraunhofer Chile Research, Las Condes 7550296, Santiago, Chile
| | - Horacio Poblete
- Institute of Computational Comparative Medicine, Nanotechnology Innovation Center of Kansas State, Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas 66506-5802
| | - Germán Miño-Galaz
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago 8370146, Chile
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103, Chile; ,
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103, Chile; ,
| | - Ramón Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2366103, Chile; ,
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Cox DH. Modeling a Ca(2+) channel/BKCa channel complex at the single-complex level. Biophys J 2016; 107:2797-2814. [PMID: 25517147 DOI: 10.1016/j.bpj.2014.10.069] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/26/2014] [Accepted: 10/23/2014] [Indexed: 11/18/2022] Open
Abstract
BKCa-channel activity often affects the firing properties of neurons, the shapes of neuronal action potentials (APs), and in some cases the extent of neurotransmitter release. It has become clear that BKCa channels often form complexes with voltage-gated Ca(2+) channels (CaV channels) such that when a CaV channel is activated, the ensuing influx of Ca(2+) activates its closely associated BKCa channel. Thus, in modeling the electrical properties of neurons, it would be useful to have quantitative models of CaV/BKCa complexes. Furthermore, in a population of CaV/BKCa complexes, all BKCa channels are not exposed to the same Ca(2+) concentration at the same time. Thus, stochastic rather than deterministic models are required. To date, however, no such models have been described. Here, however, I present a stochastic model of a CaV2.1/BKCa(α-only) complex, as might be found in a central nerve terminal. The CaV2.1/BKCa model is based on kinetic modeling of its two component channels at physiological temperature. Surprisingly, The CaV2.1/BKCa model predicts that although the CaV channel will open nearly every time during a typical cortical AP, its associated BKCa channel is expected to open in only 30% of trials, and this percentage is very sensitive to the duration of the AP, the distance between the two channels in the complex, and the presence of fast internal Ca(2+) buffers. Also, the model predicts that the kinetics of the BKCa currents of a population of CaV2.1/BKCa complexes will not be limited by the kinetics of the CaV2.1 channel, and during a train of APs, the current response of the complex is expected to faithfully follow even very rapid trains. Aside from providing insight into how these complexes are likely to behave in vivo, the models presented here could also be of use more generally as components of higher-level models of neural function.
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Affiliation(s)
- Daniel H Cox
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts.
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25
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Hoshi T, Heinemann SH. Modulation of BK Channels by Small Endogenous Molecules and Pharmaceutical Channel Openers. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:193-237. [PMID: 27238265 DOI: 10.1016/bs.irn.2016.03.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Voltage- and Ca(2+)-activated K(+) channels of big conductance (BK channels) are abundantly found in various organs and their relevance for smooth muscle tone and neuronal signaling is well documented. Dysfunction of BK channels is implicated in an array of human diseases involving many organs including the nervous, pulmonary, cardiovascular, renal, and urinary systems. In humans a single gene (KCNMA1) encodes the pore-forming α subunit (Slo1) of BK channels, but the channel properties are variable because of alternative splicing, tissue- and subcellular-specific auxiliary subunits (β, γ), posttranslational modifications, and a multitude of endogenous signaling molecules directly affecting the channel function. Initiatives to develop drugs capable of activating BK channels (channel openers) therefore need to consider the tissue-specific variability of BK channel structure and the potential interference with endogenously produced regulatory factors. The atomic structural basis of BK channel function is only beginning to be revealed. However, building on detailed knowledge of BK channel function, including its single-channel characteristics, voltage- and Ca(2+) dependence of channel gating, and modulation by diffusible messengers, a multi-tier allosteric model of BK channel gating (Horrigan and Aldrich (HA) model) has become a valuable tool in studying modulation of the channel. Using the conceptual framework of the HA model, we here review the functional impact of endogenous modulatory factors and select small synthetic compounds that regulate BK channel activity. Furthermore, we devise experimental approaches for studying BK channel-drug interactions with the aim to classify BK-modulating substances according to their molecular mode of action.
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Affiliation(s)
- T Hoshi
- University of Pennsylvania, Philadelphia, PA, United States.
| | - S H Heinemann
- Friedrich Schiller University Jena & Jena University Hospital, Jena, Germany
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26
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Abstract
BK channels are universal regulators of cell excitability, given their exceptional unitary conductance selective for K(+), joint activation mechanism by membrane depolarization and intracellular [Ca(2+)] elevation, and broad expression pattern. In this chapter, we discuss the structural basis and operational principles of their activation, or gating, by membrane potential and calcium. We also discuss how the two activation mechanisms interact to culminate in channel opening. As members of the voltage-gated potassium channel superfamily, BK channels are discussed in the context of archetypal family members, in terms of similarities that help us understand their function, but also seminal structural and biophysical differences that confer unique functional properties.
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Affiliation(s)
- A Pantazis
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, United States
| | - R Olcese
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, United States.
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27
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Modulation of BK Channel Function by Auxiliary Beta and Gamma Subunits. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:51-90. [PMID: 27238261 DOI: 10.1016/bs.irn.2016.03.015] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The large-conductance, Ca(2+)- and voltage-activated K(+) (BK) channel is ubiquitously expressed in mammalian tissues and displays diverse biophysical or pharmacological characteristics. This diversity is in part conferred by channel modulation with different regulatory auxiliary subunits. To date, two distinct classes of BK channel auxiliary subunits have been identified: β subunits and γ subunits. Modulation of BK channels by the four auxiliary β (β1-β4) subunits has been well established and intensively investigated over the past two decades. The auxiliary γ subunits, however, were identified only very recently, which adds a new dimension to BK channel regulation and improves our understanding of the physiological functions of BK channels in various tissues and cell types. This chapter will review the current understanding of BK channel modulation by auxiliary β and γ subunits, especially the latest findings.
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28
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Abstract
SIGNIFICANCE Oxygen plays a key role in cellular metabolism and function. Oxygen delivery to cells is crucial, and a lack of oxygen such as that which occurs during myocardial infarction can be lethal. Cells should, therefore, be able to respond to changes in oxygen tension. RECENT ADVANCES Since the first studies examining the acute cellular effect of hypoxia on activation of transmitter release from glomus or type I chemoreceptor cells, it is now known that virtually all cells are able to respond to changes in oxygen tension. CRITICAL ISSUES Despite advances made in characterizing hypoxic responses, the identity of the "oxygen sensor" remains debated. Recently, more evidence has evolved as to how cardiac myocytes sense acute changes in oxygen. This review will examine the available evidence in support of acute oxygen-sensing mechanisms providing a brief historical perspective and then more detailed insights into the heart and the role of cardiac ion channels in hypoxic responses. FUTURE DIRECTIONS A further understanding of these cellular processes should result in interventions that assist in preventing the deleterious effects of acute changes in oxygen tension such as alterations in contractile function and cardiac arrhythmia.
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Affiliation(s)
- Livia C Hool
- School of Anatomy, Physiology, and Human Biology, The University of Western Australia , Crawley, Australia
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29
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González C, Baez-Nieto D, Valencia I, Oyarzún I, Rojas P, Naranjo D, Latorre R. K(+) channels: function-structural overview. Compr Physiol 2013; 2:2087-149. [PMID: 23723034 DOI: 10.1002/cphy.c110047] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Potassium channels are particularly important in determining the shape and duration of the action potential, controlling the membrane potential, modulating hormone secretion, epithelial function and, in the case of those K(+) channels activated by Ca(2+), damping excitatory signals. The multiplicity of roles played by K(+) channels is only possible to their mammoth diversity that includes at present 70 K(+) channels encoding genes in mammals. Today, thanks to the use of cloning, mutagenesis, and the more recent structural studies using x-ray crystallography, we are in a unique position to understand the origins of the enormous diversity of this superfamily of ion channels, the roles they play in different cell types, and the relations that exist between structure and function. With the exception of two-pore K(+) channels that are dimers, voltage-dependent K(+) channels are tetrameric assemblies and share an extremely well conserved pore region, in which the ion-selectivity filter resides. In the present overview, we discuss in the function, localization, and the relations between function and structure of the five different subfamilies of K(+) channels: (a) inward rectifiers, Kir; (b) four transmembrane segments-2 pores, K2P; (c) voltage-gated, Kv; (d) the Slo family; and (e) Ca(2+)-activated SK family, SKCa.
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Affiliation(s)
- Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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30
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Bosch Calero C, Selga E, Brugada R, Scornik FS, Pérez GJ. The smooth muscle-type β1 subunit potentiates activation by DiBAC4(3) in recombinant BK channels. Channels (Austin) 2013; 8:95-102. [PMID: 24299688 DOI: 10.4161/chan.27212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Large-conductance Ca(2+)-activated (BK) channels, expressed in a variety of tissues, play a fundamental role in regulating and maintaining arterial tone. We recently demonstrated that the slow voltage indicator DiBAC4(3) does not depend, as initially proposed, on the β 1 or β 4 subunits to activate native arterial smooth muscle BK channels. Using recombinant mslo BK channels, we now show that the β 1 subunit is not essential to this activation but exerts a large potentiating effect. DiBAC4(3) promotes concentration-dependent activation of BK channels and slows deactivation kinetics, changes that are independent of Ca(2+). Kd values for BK channel activation by DiBAC4(3) in 0 mM Ca(2+) are approximately 20 μM (α) and 5 μM (α+β 1), and G-V curves shift up to -40 mV and -110 mV, respectively. β1 to β2 mutations R11A and C18E do not interfere with the potentiating effect of the subunit. Our findings should help refine the role of the β 1 subunit in cardiovascular pharmacology.
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Affiliation(s)
- Cristina Bosch Calero
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
| | - Elisabet Selga
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
| | - Ramon Brugada
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
| | - Fabiana S Scornik
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
| | - Guillermo J Pérez
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
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31
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Hoshi T, Pantazis A, Olcese R. Transduction of voltage and Ca2+ signals by Slo1 BK channels. Physiology (Bethesda) 2013; 28:172-89. [PMID: 23636263 DOI: 10.1152/physiol.00055.2012] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Large-conductance Ca2+ -and voltage-gated K+ channels are activated by an increase in intracellular Ca2+ concentration and/or depolarization. The channel activation mechanism is well described by an allosteric model encompassing the gate, voltage sensors, and Ca2+ sensors, and the model is an excellent framework to understand the influences of auxiliary β and γ subunits and regulatory factors such as Mg2+. Recent advances permit elucidation of structural correlates of the biophysical mechanism.
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Affiliation(s)
- T Hoshi
- Department of Physiology, The University of Pennsylvania, Philadelphia, Pennsylvania, USA
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32
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Choi SH, Lee BH, Kim HJ, Hwang SH, Lee SM, Nah SY. Activation of lysophosphatidic Acid receptor is coupled to enhancement of ca(2+)-activated potassium channel currents. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2013; 17:223-8. [PMID: 23776399 PMCID: PMC3682083 DOI: 10.4196/kjpp.2013.17.3.223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 05/07/2013] [Accepted: 05/22/2013] [Indexed: 11/15/2022]
Abstract
The calcium-activated K(+) (BKCa) channel is one of the potassium-selective ion channels that are present in the nervous and vascular systems. Ca(2+) is the main regulator of BKCa channel activation. The BKCa channel contains two high affinity Ca(2+) binding sites, namely, regulators of K(+) conductance, RCK1 and the Ca(2+) bowl. Lysophosphatidic acid (LPA, 1-radyl-2-hydroxy-sn-glycero-3-phosphate) is one of the neurolipids. LPA affects diverse cellular functions on many cell types through G protein-coupled LPA receptor subtypes. The activation of LPA receptors induces transient elevation of intracellular Ca(2+) levels through diverse G proteins such as Gαq/11, Gαi, Gα12/13, and Gαs and the related signal transduction pathway. In the present study, we examined LPA effects on BKCa channel activity expressed in Xenopus oocytes, which are known to endogenously express the LPA receptor. Treatment with LPA induced a large outward current in a reversible and concentration-dependent manner. However, repeated treatment with LPA induced a rapid desensitization, and the LPA receptor antagonist Ki16425 blocked LPA action. LPA-mediated BKCa channel activation was also attenuated by the PLC inhibitor U-73122, IP3 inhibitor 2-APB, Ca(2+) chelator BAPTA, or PKC inhibitor calphostin. In addition, mutations in RCK1 and RCK2 also attenuated LPA-mediated BKCa channel activation. The present study indicates that LPA-mediated activation of the BKCa channel is achieved through the PLC, IP3, Ca(2+), and PKC pathway and that LPA-mediated activation of the BKCa channel could be one of the biological effects of LPA in the nervous and vascular systems.
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Affiliation(s)
- Sun-Hye Choi
- Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
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Liu J, Bukiya AN, Kuntamallappanavar G, Singh AK, Dopico AM. Distinct sensitivity of slo1 channel proteins to ethanol. Mol Pharmacol 2012; 83:235-44. [PMID: 23093494 DOI: 10.1124/mol.112.081240] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Ethanol levels reached in circulation during moderate-to-heavy alcohol intoxication (50-100 mM) modify Ca(2+)- and voltage-gated K(+) (BK) channel steady-state activity, eventually altering both physiology and behavior. Ethanol action on BK steady-state activity solely requires the channel-forming subunit slo1 within a bare lipid environment. To identify the protein regions that confer ethanol sensitivity to slo1, we tested the ethanol sensitivity of heterologously expressed slo1 and structurally related channels. Ethanol (50 mM) increased the steady-state activities of mslo1 and Ca(2+)-gated MthK, the latter after channel reconstitution into phospholipid bilayers. In contrast, 50-100 mM ethanol failed to alter the steady-state activities of Na(+)/Cl(-)-gated rslo2, H(+)-gated mslo3, and an mslo1/3 chimera engineered by joining the mslo1 region encompassing the N terminus to S6 with the mslo3 cytosolic tail domain (CTD). Collectively, data indicate that the slo family canonical design, which combines a transmembrane 6 (TM6) voltage-gated K(+) channel (K(V)) core with CTDs that empower the channel with ion-sensing, does not necessarily render ethanol sensitivity. In addition, the region encompassing the N terminus to the S0-S1 cytosolic loop (missing in MthK) is not necessary for ethanol action. Moreover, incorporation of both this region and an ion-sensing CTD to TM6 K(V) cores (a design common to mslo1, mslo3, and the mslo1/mslo3 chimera) is not sufficient for ethanol sensitivity. Rather, a CTD containing Ca(2+)-sensing regulator of conductance for K(+) domains seems to be critical to bestow K(V) structures, whether of TM2 (MthK) or TM6 (slo1), with sensitivity to intoxicating ethanol levels.
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Affiliation(s)
- Jianxi Liu
- University of Tennessee Health Science Center, College of Medicine, Department of Pharmacology, 874 Union Avenue, Memphis, TN 38163, USA
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34
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Pantazis A, Olcese R. Relative transmembrane segment rearrangements during BK channel activation resolved by structurally assigned fluorophore-quencher pairing. ACTA ACUST UNITED AC 2012; 140:207-18. [PMID: 22802360 PMCID: PMC3409098 DOI: 10.1085/jgp.201210807] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Voltage-activated proteins can sense, and respond to, changes in the electric field pervading the cell membrane by virtue of a transmembrane helix bundle, the voltage-sensing domain (VSD). Canonical VSDs consist of four transmembrane helices (S1-S4) of which S4 is considered a principal component because it possesses charged residues immersed in the electric field. Membrane depolarization compels the charges, and by extension S4, to rearrange with respect to the field. The VSD of large-conductance voltage- and Ca-activated K(+) (BK) channels exhibits two salient inconsistencies from the canonical VSD model: (1) the BK channel VSD possesses an additional nonconserved transmembrane helix (S0); and (2) it exhibits a "decentralized" distribution of voltage-sensing charges, in helices S2 and S3, in addition to S4. Considering these unique features, the voltage-dependent rearrangements of the BK VSD could differ significantly from the standard model of VSD operation. To understand the mode of operation of this unique VSD, we have optically tracked the relative motions of the BK VSD transmembrane helices during activation, by manipulating the quenching environment of site-directed fluorescent labels with native and introduced Trp residues. Having previously reported that S0 and S4 diverge during activation, in this work we demonstrate that S4 also diverges from S1 and S2, whereas S2, compelled by its voltage-sensing charged residues, moves closer to S1. This information contributes spatial constraints for understanding the BK channel voltage-sensing process, revealing the structural rearrangements in a non-canonical VSD.
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Affiliation(s)
- Antonios Pantazis
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90075, USA
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35
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Barium ions selectively activate BK channels via the Ca2+-bowl site. Proc Natl Acad Sci U S A 2012; 109:11413-8. [PMID: 22733762 DOI: 10.1073/pnas.1204444109] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Activation of Ca(2+)-dependent BK channels is increased via binding of micromolar Ca(2+) to two distinct high-affinity sites per BK α-subunit. One site, termed the Ca(2+) bowl, is embedded within the second RCK domain (RCK2; regulator of conductance for potassium) of each α-subunit, while oxygen-containing residues in the first RCK domain (RCK1) have been linked to a separate Ca(2+) ligation site. Although both sites are activated by Ca(2+) and Sr(2+), Cd(2+) selectively favors activation via the RCK1 site. Divalent cations of larger ionic radius than Sr(2+) are thought to be ineffective at activating BK channels. Here we show that Ba(2+), better known as a blocker of K(+) channels, activates BK channels and that this effect arises exclusively from binding at the Ca(2+)-bowl site. Compared with previous estimates for Ca(2+) bowl-mediated activation by Ca(2+), the affinity of Ba(2+) to the Ca(2+) bowl is reduced about fivefold, and coupling of binding to activation is reduced from ∼3.6 for Ca(2+) to about ∼2.8 for Ba(2+). These results support the idea that ionic radius is an important determinant of selectivity differences among different divalent cations observed for each Ca(2+)-binding site.
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36
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Savalli N, Pantazis A, Yusifov T, Sigg D, Olcese R. The contribution of RCK domains to human BK channel allosteric activation. J Biol Chem 2012; 287:21741-50. [PMID: 22556415 PMCID: PMC3381136 DOI: 10.1074/jbc.m112.346171] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 04/10/2012] [Indexed: 11/06/2022] Open
Abstract
Large conductance voltage- and Ca(2+)-activated K(+) (BK) channels are potent regulators of cellular processes including neuronal firing, synaptic transmission, cochlear hair cell tuning, insulin release, and smooth muscle tone. Their unique activation pathway relies on structurally distinct regulatory domains including one transmembrane voltage-sensing domain (VSD) and two intracellular high affinity Ca(2+)-sensing sites per subunit (located in the RCK1 and RCK2 domains). Four pairs of RCK1 and RCK2 domains form a Ca(2+)-sensing apparatus known as the "gating ring." The allosteric interplay between voltage- and Ca(2+)-sensing apparati is a fundamental mechanism of BK channel function. Using voltage-clamp fluorometry and UV photolysis of intracellular caged Ca(2+), we optically resolved VSD activation prompted by Ca(2+) binding to the gating ring. The sudden increase of intracellular Ca(2+) concentration ([Ca(2+)](i)) induced a hyperpolarizing shift in the voltage dependence of both channel opening and VSD activation, reported by a fluorophore labeling position 202, located in the upper side of the S4 transmembrane segment. The neutralization of the Ca(2+) sensor located in the RCK2 domain abolished the effect of [Ca(2+)](i) increase on the VSD rearrangements. On the other hand, the mutation of RCK1 residues involved in Ca(2+) sensing did not prevent the effect of Ca(2+) release on the VSD, revealing a functionally distinct interaction between RCK1 and RCK2 and the VSD. A statistical-mechanical model quantifies the complex thermodynamics interplay between Ca(2+) association in two distinct sites, voltage sensor activation, and BK channel opening.
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Affiliation(s)
- Nicoletta Savalli
- From the Department of Anesthesiology, Division of Molecular Medicine
| | - Antonios Pantazis
- From the Department of Anesthesiology, Division of Molecular Medicine
| | - Taleh Yusifov
- From the Department of Anesthesiology, Division of Molecular Medicine
| | - Daniel Sigg
- From the Department of Anesthesiology, Division of Molecular Medicine
| | - Riccardo Olcese
- From the Department of Anesthesiology, Division of Molecular Medicine
- the Brain Research Institute, and
- the Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90075
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37
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On the simple random-walk models of ion-channel gate dynamics reflecting long-term memory. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 41:505-26. [PMID: 22484857 PMCID: PMC3359465 DOI: 10.1007/s00249-012-0806-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 03/06/2012] [Accepted: 03/13/2012] [Indexed: 01/21/2023]
Abstract
Several approaches to ion-channel gating modelling have been proposed. Although many models describe the dwell-time distributions correctly, they are incapable of predicting and explaining the long-term correlations between the lengths of adjacent openings and closings of a channel. In this paper we propose two simple random-walk models of the gating dynamics of voltage and Ca(2+)-activated potassium channels which qualitatively reproduce the dwell-time distributions, and describe the experimentally observed long-term memory quite well. Biological interpretation of both models is presented. In particular, the origin of the correlations is associated with fluctuations of channel mass density. The long-term memory effect, as measured by Hurst R/S analysis of experimental single-channel patch-clamp recordings, is close to the behaviour predicted by our models. The flexibility of the models enables their use as templates for other types of ion channel.
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Prole DL, Marrion NV. Identification of putative potassium channel homologues in pathogenic protozoa. PLoS One 2012; 7:e32264. [PMID: 22363819 PMCID: PMC3283738 DOI: 10.1371/journal.pone.0032264] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Accepted: 01/24/2012] [Indexed: 12/21/2022] Open
Abstract
K+ channels play a vital homeostatic role in cells and abnormal activity of these channels can dramatically alter cell function and survival, suggesting that they might be attractive drug targets in pathogenic organisms. Pathogenic protozoa lead to diseases such as malaria, leishmaniasis, trypanosomiasis and dysentery that are responsible for millions of deaths each year worldwide. The genomes of many protozoan parasites have recently been sequenced, allowing rational design of targeted therapies. We analyzed the genomes of pathogenic protozoa and show the existence within them of genes encoding putative homologues of K+ channels. These protozoan K+ channel homologues represent novel targets for anti-parasitic drugs. Differences in the sequences and diversity of human and parasite proteins may allow pathogen-specific targeting of these K+ channel homologues.
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Affiliation(s)
- David L Prole
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom.
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39
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Abstract
Large-conductance voltage- and Ca(2+)-activated K(+) (Slo1 BK) channels serve numerous cellular functions, and their dysregulation is implicated in various diseases. Drugs activating BK channels therefore bear substantial therapeutic potential, but their deployment has been hindered in part because the mode of action remains obscure. Here we provide mechanistic insight into how the dehydroabietic acid derivative Cym04 activates BK channels. As a representative of NS1619-like BK openers, Cym04 reversibly left-shifts the half-activation voltage of Slo1 BK channels. Using an established allosteric BK gating model, the Cym04 effect can be simulated by a shift of the voltage sensor and the ion conduction gate equilibria toward the activated and open state, respectively. BK activation by Cym04 occurs in a splice variant-specific manner; it does not occur in such Slo1 BK channels using an alternative neuronal exon 9, which codes for the linker connecting the transmembrane segment S6 and the cytosolic RCK1 domain--the S6/RCK linker. In addition, Cym04 does not affect Slo1 BK channels with a two-residue deletion within this linker. Mutagenesis and model-based gating analysis revealed that BK openers, such as Cym04 and NS1619 but not mallotoxin, activate BK channels by functionally interacting with the S6/RCK linker, mimicking site-specific shortening of this purported passive spring, which transmits force from the cytosolic gating ring structure to open the channel's gate.
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Abstract
INTRODUCTION Epilepsies are disorders of neuronal excitability characterized by spontaneous and recurrent seizures. Ion channels are critical for regulating neuronal excitability and, therefore, can contribute significantly to epilepsy pathophysiology. In particular, large conductance, Ca2+-activated K+ (BKCa) channels play an important role in seizure etiology. These channels are activated by both membrane depolarization and increased intracellular Ca2+. This unique coupling of Ca2+ signaling to membrane depolarization is important in controlling neuronal hyperexcitability, as outward K+ current through BKCa channels hyperpolarizes neurons. AREAS COVERED BKCa channel structure-function and the role of these channels in epilepsy pathophysiology. EXPERT OPINION Loss-of-function BKCa channel mutations contribute to neuronal hyperexcitability that can lead to temporal lobe epilepsy, tonic-clonic seizures and alcohol withdrawal seizures. Similarly, BKCa channel blockade can trigger seizures and status epilepticus. Paradoxically, some mutations in BKCa channel subunit can give rise to channel gain-of-function that leads to development of idiopathic epilepsy (primarily absence epilepsy). Seizures themselves also enhance BKCa channel currents associated with neuronal hyperexcitability, and blocking BKCa channels suppresses generalized tonic-clonic seizures. Thus, both loss-of-function and gain-of-function BKCa channels might serve as molecular targets for drugs to suppress certain seizure phenotypes including temporal lobe seizures and absence seizures, respectively.
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Affiliation(s)
- Prosper N'Gouemo
- Georgetown University Medical Center, Interdisciplinary Program in Neuroscience and Department of Pediatrics, Washington, DC 20057, USA.
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41
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Sakai Y, Harvey M, Sokolowski B. Identification and quantification of full-length BK channel variants in the developing mouse cochlea. J Neurosci Res 2011; 89:1747-60. [PMID: 21800349 DOI: 10.1002/jnr.22713] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 04/28/2011] [Accepted: 05/12/2011] [Indexed: 01/03/2023]
Abstract
Maxi-K(+) (BK) channel diversity is attributed to alternative splicing in the kcnma1 gene. The resultant variants manifest themselves in different cell types, tissues, and functions, such as excitation, metabolism, and signaling. Immunoelectron microscopy revealed immunogold particle labeling of BK in apical and basal regions of inner and outer hair cells, respectively. Additional labeling occurs in Deiters' cells and the inner mitochondrial membrane. Identification of full-length sequences reveals 27 BK variants from embryonic and postnatal mouse inner ear, per classification by tail motif, VYR, DEC, and ERL, and by exon usage. Three predicted start codons are found encoding MAN, MSS, and MDA, of which MDA shows the greatest expression through all stages in development, whereas MAN is undetectable. Complex splice sites occur between exons 9 and 10 and between 21 and 23. Spliced-in/out exons between 8 and 10 reveal a short fragment composed of exons 8 + 10, detectable on postnatal day (PD) 14 and PD30, and a longer fragment composed of exons 8 + 9 + 10 that is upregulated on embryonic day (ED) 14. Spliced-in exons 22 or 23 are expressed on ED14 but decrease over time; however, exon 22 increases again on PD34. Using tail-specific primers, qRT-PCR from ED14, PD4, -14, and -30 shows that BK-VYR and -ERL dominate expression on ED14, whereas DEC dominates after birth in all cochlear regions. The localization of BK and the changes in expression of its exons and tail types, by alternative splicing during development, may contribute to cochlear organization, acquisition of hearing, and intracellular signaling.
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Affiliation(s)
- Yoshihisa Sakai
- Department of Otolaryngology-Head and Neck Surgery, University of South Florida, Tampa, Florida 33612, USA
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Félétou M. The Endothelium, Part I: Multiple Functions of the Endothelial Cells -- Focus on Endothelium-Derived Vasoactive Mediators. ACTA ACUST UNITED AC 2011. [DOI: 10.4199/c00031ed1v01y201105isp019] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Javaherian AD, Yusifov T, Pantazis A, Franklin S, Gandhi CS, Olcese R. Metal-driven operation of the human large-conductance voltage- and Ca2+-dependent potassium channel (BK) gating ring apparatus. J Biol Chem 2011; 286:20701-9. [PMID: 21471215 DOI: 10.1074/jbc.m111.235234] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Large-conductance voltage- and Ca(2+)-dependent K(+) (BK, also known as MaxiK) channels are homo-tetrameric proteins with a broad expression pattern that potently regulate cellular excitability and Ca(2+) homeostasis. Their activation results from the complex synergy between the transmembrane voltage sensors and a large (>300 kDa) C-terminal, cytoplasmic complex (the "gating ring"), which confers sensitivity to intracellular Ca(2+) and other ligands. However, the molecular and biophysical operation of the gating ring remains unclear. We have used spectroscopic and particle-scale optical approaches to probe the metal-sensing properties of the human BK gating ring under physiologically relevant conditions. This functional molecular sensor undergoes Ca(2+)- and Mg(2+)-dependent conformational changes at physiologically relevant concentrations, detected by time-resolved and steady-state fluorescence spectroscopy. The lack of detectable Ba(2+)-evoked structural changes defined the metal selectivity of the gating ring. Neutralization of a high-affinity Ca(2+)-binding site (the "calcium bowl") reduced the Ca(2+) and abolished the Mg(2+) dependence of structural rearrangements. In congruence with electrophysiological investigations, these findings provide biochemical evidence that the gating ring possesses an additional high-affinity Ca(2+)-binding site and that Mg(2+) can bind to the calcium bowl with less affinity than Ca(2+). Dynamic light scattering analysis revealed a reversible Ca(2+)-dependent decrease of the hydrodynamic radius of the gating ring, consistent with a more compact overall shape. These structural changes, resolved under physiologically relevant conditions, likely represent the molecular transitions that initiate the ligand-induced activation of the human BK channel.
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Affiliation(s)
- Anoosh D Javaherian
- Division of Molecular Medicine, Department of Anesthesiology, David Geffen School of Medicine, UCLA, Los Angeles, California 90095-7115, USA
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45
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Tao J, Shi J, Yan L, Chen Y, Duan YH, Ye P, Feng Q, Zhang JW, Shu XQ, Ji YH. Enhancement effects of martentoxin on glioma BK channel and BK channel (α+β1) subtypes. PLoS One 2011; 6:e15896. [PMID: 21445248 PMCID: PMC3060806 DOI: 10.1371/journal.pone.0015896] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 11/30/2010] [Indexed: 12/20/2022] Open
Abstract
Background BK channels are usually activated by membrane depolarization and cytoplasmic Ca2+. Especially,the activity of BK channel (α+β4) can be modulated by martentoxin, a 37 residues peptide, with Ca2+-dependent manner. gBK channel (glioma BK channel) and BK channel (α+β1) possessed higher Ca2+ sensitivity than other known BK channel subtypes. Methodology and Principal Findings The present study investigated the modulatory characteristics of martentoxin on these two BK channel subtypes by electrophysiological recordings, cell proliferation and Ca2+ imaging. In the presence of cytoplasmic Ca2+, martentoxin could enhance the activities of both gBK and BK channel (α+β1) subtypes in dose-dependent manner with EC50 of 46.7 nM and 495 nM respectively, while not shift the steady-state activation of these channels. The enhancement ratio of martentoxin on gBK and BK channel (α+β1) was unrelated to the quantitive change of cytoplasmic Ca2+ concentrations though the interaction between martentoxin and BK channel (α+β1) was accelerated under higher cytoplasmic Ca2+. The selective BK pore blocker iberiotoxin could fully abolish the enhancement of these two BK subtypes induced by martentoxin, suggesting that the auxiliary β subunit might contribute to the docking for martentoxin. However, in the absence of cytoplasmic Ca2+, the activity of gBK channel would be surprisingly inhibited by martentoxin while BK channel (α+β1) couldn't be affected by the toxin. Conclusions and Significance Thus, the results shown here provide the novel evidence that martentoxin could increase the two Ca2+-hypersensitive BK channel subtypes activities in a new manner and indicate that β subunit of these BK channels plays a vital role in this enhancement by martentoxin.
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Affiliation(s)
- Jie Tao
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Jian Shi
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Li Yan
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Ying Chen
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Yan Hong Duan
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Pin Ye
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Qi Feng
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Jian Wei Zhang
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Xue Qin Shu
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Yong Hua Ji
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
- * E-mail:
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46
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Abstract
This review focuses on thiol/disulfide redox switches that regulate heme binding to proteins and modulate their activities. The importance of redox switches in metabolic regulation and the general mechanism by which redox switches modulate activity are discussed. Methods are described to characterize heme-binding sites and to assess their physiological relevance. For thiol/disulfide interconversion to regulate activity of a system, the redox process must be reversible at the ambient redox potentials found within the cell; thus, methods (and their limitations) are discussed that can address the physiological relevance of a redox switch. We review recent results that define a mechanism for how thiol/disulfide redox switches that control heme binding can regulate the activities of an enzyme, heme oxygenase-2, and an ion channel, the BK potassium channel. The redox switches on these proteins are composed of different types of Cys-containing motifs that have opposite effects on heme affinity, yet have complementary effects on hypoxia sensing. Finally, a model is proposed to describe how the redox switches on heme oxygenase-2 and the BK channel form an interconnected system that is poised to sense oxygen levels in the bloodstream and to elicit the hypoxic response when oxygen levels drop below a threshold value.
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Affiliation(s)
- Stephen W Ragsdale
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA.
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47
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Abstract
The BK channel is a Ca²+- and voltage-gated potassium channel with many important physiological functions. To identify proteins important to its function in vivo, we screened for Caenorhabditis elegans mutants that suppressed a lethargic phenotype caused by expressing a gain-of-function (gf) isoform of the BK channel α-subunit SLO-1. BKIP-1 (for BK channel interacting protein), a small peptide with no significant homology to any previously characterized molecules, was thus identified. BKIP-1 and SLO-1 showed similar expression and subcellular localization patterns and appeared to interact physically through discrete domains. bkip-1 loss-of-function (lf) mutants phenocopied slo-1(lf) mutants in behavior and synaptic transmission and suppressed the lethargy, egg-laying defect, and deficient neurotransmitter release caused by SLO-1(gf). In heterologous expression systems, BKIP-1 decreased the activation rate and shifted the conductance-voltage relationship of SLO-1 in a Ca²+-dependent manner and increased SLO-1 surface expression. Thus, BKIP-1 is a novel auxiliary subunit critical to SLO-1 function in vivo.
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48
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Pantazis A, Kohanteb AP, Olcese R. Relative motion of transmembrane segments S0 and S4 during voltage sensor activation in the human BK(Ca) channel. J Gen Physiol 2010; 136:645-57. [PMID: 21078868 PMCID: PMC2995153 DOI: 10.1085/jgp.201010503] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Accepted: 11/01/2010] [Indexed: 01/06/2023] Open
Abstract
Large-conductance voltage- and Ca(2+)-activated K(+) (BK(Ca)) channel α subunits possess a unique transmembrane helix referred to as S0 at their N terminus, which is absent in other members of the voltage-gated channel superfamily. Recently, S0 was found to pack close to transmembrane segments S3 and S4, which are important components of the BK(Ca) voltage-sensing apparatus. To assess the role of S0 in voltage sensitivity, we optically tracked protein conformational rearrangements from its extracellular flank by site-specific labeling with an environment-sensitive fluorophore, tetramethylrhodamine maleimide (TMRM). The structural transitions resolved from the S0 region exhibited voltage dependence similar to that of charge-bearing transmembrane domains S2 and S4. The molecular determinant of the fluorescence changes was identified in W203 at the extracellular tip of S4: at hyperpolarized potential, W203 quenches the fluorescence of TMRM labeling positions at the N-terminal flank of S0. We provide evidence that upon depolarization, W203 (in S4) moves away from the extracellular region of S0, lifting its quenching effect on TMRM fluorescence. We suggest that S0 acts as a pivot component against which the voltage-sensitive S4 moves upon depolarization to facilitate channel activation.
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Affiliation(s)
- Antonios Pantazis
- Department of Anesthesiology, Division of Molecular Medicine, Brain Research Institute, and Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90075
| | - Azadeh P. Kohanteb
- Department of Anesthesiology, Division of Molecular Medicine, Brain Research Institute, and Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90075
| | - Riccardo Olcese
- Department of Anesthesiology, Division of Molecular Medicine, Brain Research Institute, and Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90075
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49
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Lee US, Cui J. BK channel activation: structural and functional insights. Trends Neurosci 2010; 33:415-23. [PMID: 20663573 DOI: 10.1016/j.tins.2010.06.004] [Citation(s) in RCA: 183] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2010] [Revised: 06/22/2010] [Accepted: 06/22/2010] [Indexed: 01/26/2023]
Abstract
The voltage- and Ca(2+)-activated K(+) (BK) channels are involved in the regulation of neurotransmitter release and neuronal excitability. Structurally, BK channels are homologous to voltage- and ligand-gated K(+) channels, having a voltage sensor and pore as the membrane-spanning domain and a cytosolic domain containing metal binding sites. Recently published electron cryomicroscopy (cryo-EM) and X-ray crystallographic structures of the BK channel provided the first glimpse into the assembly of these domains, corroborating the close interactions among these domains during channel gating that have been suggested by functional studies. This review discusses these latest findings and an emerging new understanding about BK channel gating and implications for diseases such as epilepsy, in which mutations in BK channel genes have been associated.
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Affiliation(s)
- Urvi S Lee
- Department of Biomedical Engineering and Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
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50
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Wu RS, Marx SO. The BK potassium channel in the vascular smooth muscle and kidney: α- and β-subunits. Kidney Int 2010; 78:963-74. [DOI: 10.1038/ki.2010.325] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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