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Zhang L, Wu X, Cao X, Rao K, Hong L. Trp207 regulation of voltage-dependent activation of human H v1 proton channel. J Biol Chem 2024; 300:105674. [PMID: 38272234 PMCID: PMC10875263 DOI: 10.1016/j.jbc.2024.105674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 01/08/2024] [Accepted: 01/13/2024] [Indexed: 01/27/2024] Open
Abstract
In voltage-gated Na+ and K+ channels, the hydrophobicity of noncharged residues in the S4 helix has been shown to regulate the S4 movement underlying the process of voltage-sensing domain (VSD) activation. In voltage-gated proton channel Hv1, there is a bulky noncharged tryptophan residue located at the S4 transmembrane segment. This tryptophan remains entirely conserved across all Hv1 members but is not seen in other voltage-gated ion channels, indicating that the tryptophan contributes different roles in VSD activation. The conserved tryptophan of human voltage-gated proton channel Hv1 is Trp207 (W207). Here, we showed that W207 modifies human Hv1 voltage-dependent activation, and small residues replacement at position 207 strongly perturbs Hv1 channel opening and closing, and the size of the side chain instead of the hydrophobic group of W207 regulates the transition between closed and open states of the channel. We conclude that the large side chain of tryptophan controls the energy barrier during the Hv1 VSD transition.
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Affiliation(s)
- Lu Zhang
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Xin Wu
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Xinyu Cao
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA; Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Khushi Rao
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA; Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA
| | - Liang Hong
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA; Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, Illinois, USA; Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, USA.
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2
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Tsai WH, Grauffel C, Huang MY, Postić S, Rupnik MS, Lim C, Yang SB. Allosteric coupling between transmembrane segment 4 and the selectivity filter of TALK1 potassium channels regulates their gating by extracellular pH. J Biol Chem 2022; 298:101998. [PMID: 35500647 PMCID: PMC9168622 DOI: 10.1016/j.jbc.2022.101998] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 04/19/2022] [Accepted: 04/27/2022] [Indexed: 11/28/2022] Open
Abstract
Opening of two-pore domain K+ channels (K2Ps) is regulated by various external cues, such as pH, membrane tension, or temperature, which allosterically modulate the selectivity filter (SF) gate. However, how these cues cause conformational changes in the SF of some K2P channels remains unclear. Herein, we investigate the mechanisms by which extracellular pH affects gating in an alkaline-activated K2P channel, TALK1, using electrophysiology and molecular dynamics (MD) simulations. We show that R233, located at the N-terminal end of transmembrane segment 4, is the primary pHo sensor. This residue distally regulates the orientation of the carbonyl group at the S1 potassium-binding site through an interacting network composed of residues on transmembrane segment 4, the pore helix domain 1, and the SF. Moreover, in the presence of divalent cations, we found the acidic pH-activated R233E mutant recapitulates the network interactions of protonated R233. Intriguingly, our data further suggested stochastic coupling between R233 and the SF gate, which can be described by an allosteric gating model. We propose that this allosteric model could predict the hybrid pH sensitivity in heterodimeric channels with alkaline-activated and acidic-activated K2P subunits.
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Affiliation(s)
- Wen-Hao Tsai
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan; Taiwan International Graduate Program in Molecular Medicine, National Yang Ming Chiao Tung University and Academia Sinica, Taipei, Taiwan
| | - Cédric Grauffel
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Ming-Yueh Huang
- Institute of Statistical Science, Academia Sinica, Taipei, Taiwan
| | - Sandra Postić
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Marjan Slak Rupnik
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria; Institute of Physiology, Faculty of Medicine, University of Maribor, Maribor, Slovenia; Alma Mater Europaea - European Center Maribor, Maribor, Slovenia
| | - Carmay Lim
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Shi-Bing Yang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan; Taiwan International Graduate Program in Molecular Medicine, National Yang Ming Chiao Tung University and Academia Sinica, Taipei, Taiwan.
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3
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Aisenberg WH, McCray BA, Sullivan JM, Diehl E, DeVine LR, Alevy J, Bagnell AM, Carr P, Donohue JK, Goretzki B, Cole RN, Hellmich UA, Sumner CJ. Multiubiquitination of TRPV4 reduces channel activity independent of surface localization. J Biol Chem 2022; 298:101826. [PMID: 35300980 PMCID: PMC9010760 DOI: 10.1016/j.jbc.2022.101826] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 02/19/2022] [Accepted: 02/21/2022] [Indexed: 02/06/2023] Open
Abstract
Ubiquitin (Ub)-mediated regulation of plasmalemmal ion channel activity canonically occurs via stimulation of endocytosis. Whether ubiquitination can modulate channel activity by alternative mechanisms remains unknown. Here, we show that the transient receptor potential vanilloid 4 (TRPV4) cation channel is multiubiquitinated within its cytosolic N-terminal and C-terminal intrinsically disordered regions (IDRs). Mutagenizing select lysine residues to block ubiquitination of the N-terminal but not C-terminal IDR resulted in a marked elevation of TRPV4-mediated intracellular calcium influx, without increasing cell surface expression levels. Conversely, enhancing TRPV4 ubiquitination via expression of an E3 Ub ligase reduced TRPV4 channel activity but did not decrease plasma membrane abundance. These results demonstrate Ub-dependent regulation of TRPV4 channel function independent of effects on plasma membrane localization. Consistent with ubiquitination playing a key negative modulatory role of the channel, gain-of-function neuropathy-causing mutations in the TRPV4 gene led to reduced channel ubiquitination in both cellular and Drosophila models of TRPV4 neuropathy, whereas increasing mutant TRPV4 ubiquitination partially suppressed channel overactivity. Together, these data reveal a novel mechanism via which ubiquitination of an intracellular flexible IDR domain modulates ion channel function independently of endocytic trafficking and identify a contributory role for this pathway in the dysregulation of TRPV4 channel activity by neuropathy-causing mutations.
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Affiliation(s)
- William H Aisenberg
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Brett A McCray
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jeremy M Sullivan
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Erika Diehl
- Department of Chemistry, Biochemistry Section, Johannes Gutenberg-Universität Mainz, Mainz, Germany
| | - Lauren R DeVine
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jonathan Alevy
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Anna M Bagnell
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Patrice Carr
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jack K Donohue
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Benedikt Goretzki
- Institute of Organic Chemistry and Macromolecular Chemistry, Cluster of Excellence 'Balance of the Microverse', Friedrich-Schiller-Universität, Jena, Germany; Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-Universität, Frankfurt am Main, Germany
| | - Robert N Cole
- Institute of Organic Chemistry and Macromolecular Chemistry, Cluster of Excellence 'Balance of the Microverse', Friedrich-Schiller-Universität, Jena, Germany
| | - Ute A Hellmich
- Institute of Organic Chemistry and Macromolecular Chemistry, Cluster of Excellence 'Balance of the Microverse', Friedrich-Schiller-Universität, Jena, Germany; Center for Biomolecular Magnetic Resonance (BMRZ), Goethe-Universität, Frankfurt am Main, Germany
| | - Charlotte J Sumner
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
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4
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Yang PL, Li XH, Wang J, Ma XF, Zhou BY, Jiao YF, Wang WH, Cao P, Zhu MX, Li PW, Xiao ZH, Li CZ, Guo CR, Lei YT, Yu Y. GSK1702934A and M085 directly activate TRPC6 via a mechanism of stimulating the extracellular cavity formed by the pore helix and transmembrane helix S6. J Biol Chem 2021; 297:101125. [PMID: 34461094 PMCID: PMC8458982 DOI: 10.1016/j.jbc.2021.101125] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 08/22/2021] [Accepted: 08/26/2021] [Indexed: 01/20/2023] Open
Abstract
Transient receptor potential canonical (TRPC) channels, as important membrane proteins regulating intracellular calcium (Ca2+i) signaling, are involved in a variety of physiological and pathological processes. Activation and regulation of TRPC are more dependent on membrane or intracellular signals. However, how extracellular signals regulate TRPC6 function remains to be further investigated. Here, we suggest that two distinct small molecules, M085 and GSK1702934A, directly activate TRPC6, both through a mechanism of stimulation of extracellular sites formed by the pore helix (PH) and transmembrane (TM) helix S6. In silico docking scanning of TRPC6 identified three extracellular sites that can bind small molecules, of which only mutations on residues of PH and S6 helix significantly reduced the apparent affinity of M085 and GSK1702934A and attenuated the maximal response of TRPC6 to these two chemicals by altering channel gating of TRPC6. Combing metadynamics, molecular dynamics simulations, and mutagenesis, we revealed that W679, E671, E672, and K675 in the PH and N701 and Y704 in the S6 helix constitute an orthosteric site for the recognition of these two agonists. The importance of this site was further confirmed by covalent modification of amino acid residing at the interface of the PH and S6 helix. Given that three structurally distinct agonists M085, GSK1702934A, and AM-0883, act at this site, as well as the occupancy of lipid molecules at this position found in other TRP subfamilies, it is suggested that the cavity formed by the PH and S6 has an important role in the regulation of TRP channel function by extracellular signals.
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Affiliation(s)
- Pei-Lin Yang
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Xing-Hua Li
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Jin Wang
- Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Xue-Fei Ma
- College of Bioscience and Biotechnology, Hunan Agricultural University, Changsha, China
| | - Bo-Ying Zhou
- Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Yuan-Feng Jiao
- Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Wen-Hui Wang
- Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Peng Cao
- Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, China
| | - Michael Xi Zhu
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Pei-Wang Li
- State Key Laboratory of Utilization of Woody Oil Resource, Hunan Academy of Forestry, Changsha, China
| | - Zhi-Hong Xiao
- State Key Laboratory of Utilization of Woody Oil Resource, Hunan Academy of Forestry, Changsha, China
| | - Chang-Zhu Li
- State Key Laboratory of Utilization of Woody Oil Resource, Hunan Academy of Forestry, Changsha, China
| | - Chang-Run Guo
- School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, China.
| | - Yun-Tao Lei
- School of Science, China Pharmaceutical University, Nanjing, China.
| | - Ye Yu
- Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China.
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5
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Deng YN, Kashtoh H, Wang Q, Zhen GX, Li QY, Tang LH, Gao HL, Zhang CR, Qin L, Su M, Li F, Huang XH, Wang YC, Xie Q, Clarke OB, Hendrickson WA, Chen YH. Structure and activity of SLAC1 channels for stomatal signaling in leaves. Proc Natl Acad Sci U S A 2021; 118:e2015151118. [PMID: 33926963 DOI: 10.1073/pnas.2015151118] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Stomata in leaves regulate gas exchange between the plant and its atmosphere. Various environmental stimuli elicit abscisic acid (ABA); ABA leads to phosphoactivation of slow anion channel 1 (SLAC1); SLAC1 activity reduces turgor pressure in aperture-defining guard cells; and stomatal closure ensues. We used electrophysiology for functional characterizations of Arabidopsis thaliana SLAC1 (AtSLAC1) and cryoelectron microscopy (cryo-EM) for structural analysis of Brachypodium distachyon SLAC1 (BdSLAC1), at 2.97-Å resolution. We identified 14 phosphorylation sites in AtSLAC1 and showed nearly 330-fold channel-activity enhancement with 4 to 6 of these phosphorylated. Seven SLAC1-conserved arginines are poised in BdSLAC1 for regulatory interaction with the N-terminal extension. This BdSLAC1 structure has its pores closed, in a basal state, spring loaded by phenylalanyl residues in high-energy conformations. SLAC1 phosphorylation fine-tunes an equilibrium between basal and activated SLAC1 trimers, thereby controlling the degree of stomatal opening.
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6
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Zhuang W, Yan Z. The S2-S3 Loop of Kv7.4 Channels Is Essential for Calmodulin Regulation of Channel Activation. Front Physiol 2021; 11:604134. [PMID: 33551832 PMCID: PMC7854705 DOI: 10.3389/fphys.2020.604134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 12/23/2020] [Indexed: 11/16/2022] Open
Abstract
Kv7.4 (KCNQ4) voltage-gated potassium channels control excitability in the inner ear and the central auditory pathway. Mutations in Kv7.4 channels result in inherited progressive deafness in humans. Calmodulin (CaM) is crucial for regulating Kv7 channels, but how CaM affects Kv7 activity has remained unclear. Here, based on electrophysiological recordings, we report that the third EF hand (EF3) of CaM controls the calcium-dependent regulation of Kv7.4 activation and that the S2–S3 loop of Kv7.4 is essential for the regulation mediated by CaM. Overexpression of the mutant CaM1234, which loses the calcium binding ability of all four EF hands, facilitates Kv7.4 activation by accelerating activation kinetics and shifting the voltage dependence of activation leftwards. The single mutant CaM3, which loses the calcium binding ability of the EF3, phenocopies facilitating effects of CaM1234 on Kv7.4 activation. Kv7.4 channels co-expressed with wild-type (WT) CaM show inhibited activation when intracellular calcium levels increase, while Kv7.4 channels co-expressed with CaM1234 or CaM3 are insensitive to calcium. Mutations C156A, C157A, C158V, R159, and R161A, which are located within the Kv7.4 S2–S3 loop, dramatically facilitate activation of Kv7.4 channels co-expressed with WT CaM but have no effect on activation of Kv7.4 channels co-expressed with CaM3, indicating that these five mutations decrease the inhibitory effect of Ca2+/CaM. The double mutation C156A/R159A decreases Ca2+/CaM binding and completely abolishes CaM-mediated calcium-dependent regulation of Kv7.4 activation. Taken together, our results provide mechanistic insights into CaM regulation of Kv7.4 activation and highlight the crucial role of the Kv7.4 S2–S3 loop in CaM regulation.
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Affiliation(s)
- Wenhui Zhuang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Physiology and Biophysics, School of Life Sciences, Human Phenome Institute, Fudan University, Shanghai, China
| | - Zhiqiang Yan
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Physiology and Biophysics, School of Life Sciences, Human Phenome Institute, Fudan University, Shanghai, China.,Shenzhen Bay Laboratory, Institute of Molecular Physiology, Shenzhen, China
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7
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Nosyreva ED, Thompson D, Syeda R. Identification and functional characterization of the Piezo1 channel pore domain. J Biol Chem 2021; 296:100225. [PMID: 33361157 PMCID: PMC7948955 DOI: 10.1074/jbc.ra120.015905] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 12/16/2020] [Accepted: 12/22/2020] [Indexed: 12/22/2022] Open
Abstract
Mechanotransduction is the process by which cells convert physical forces into electrochemical responses. On a molecular scale, these forces are detected by mechanically activated ion channels, which constitute the basis for hearing, touch, pain, cold, and heat sensation, among other physiological processes. Exciting high-resolution structural details of these channels are currently emerging that will eventually allow us to delineate the molecular determinants of gating and ion permeation. However, our structural-functional understanding across the family remains limited. Piezo1 is one of the largest and least understood of these channels, with various structurally identified features within its trimeric assembly. This study seeks to determine the modularity and function of Piezo1 channels by constructing deletion proteins guided by cryo EM structural knowledge. Our comprehensive functional study identified, for the first time, the minimal amino acid sequence of the full-length Piezo1 that can fold and function as the channel's pore domain between E2172 and the last residue E2547. While the addition of an anchor region has no effect on permeation properties. The Piezo1 pore domain is not pressure-sensitive and the appending of Piezo Repeat-A did not restore pressure-dependent gating, hence the sensing module must exist between residues 1 to 1952. Our efforts delineating the permeation and gating regions within this complex ion channel have implications in identifying small molecules that exclusively regulate the activity of the channel's pore module to influence mechanotransduction and downstream processes.
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Affiliation(s)
- Elena D Nosyreva
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - David Thompson
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Ruhma Syeda
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
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8
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Wang M, Gao M, Fang S, Zheng R, Peng D, Luo Q, Yu B. L51P, a novel mutation in the PAS domain of hERG channel, confers long QT syndrome by impairing channel activation. Am J Transl Res 2020; 12:8040-8049. [PMID: 33437379 PMCID: PMC7791479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 10/28/2020] [Indexed: 06/12/2023]
Abstract
The human ether-à-go-go-related gene (hERG) potassium channel mediates the repolarization of ventricular action potentials. Mutations in the KCNH2 cause long QT syndrome (LQTS) and are associated with cardiac arrhythmias and sudden death. Here, we functionally analyzed a mutation of hERG potassium channel (p.L51P), gaining novel insights into clinical genotype-phenotype relationships. Potassium currents were recorded by whole-cell patch clamping in HEK293 cells transiently transfected with wild-type and/or mutant hERG potassium channel. Immunofluorescence assay and confocal imaging were undertaken to study the effects of L51P mutation on channel trafficking. The models of the protein structure of hERG and its mutations are predicted by Amber16 software. Molecular dynamics (MD) of individual protein were performed with Particle Mesh Ewald (PME). The production of MD simulations of hERG-WT and hERG-Mut at constant pressure and temperature were carried out with SHAKE. L51 was a conservative amino acid, located in the Per-Arnt-Sim (PAS) domain of the amino terminus. L51P caused loss of function via impairing channel activation. L51P was predicted to destroy hydrophobic structure in the PAS domain, thus causing the failure of channel opening. In summary, the present study identifies L51P as a novel mutation of hERG potassium channel. L51P mutation mechanistically impairs channel activation, reducing channel functionality.
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Affiliation(s)
- Mi Wang
- Department of Cardiovascular Medicine, The Second Xiangya Hospital, Central South UniversityChangsha, Hunan, China
- Research Institute of Blood Lipid and Atherosclerosis, Central South UniversityChangsha, Hunan, China
| | - Min Gao
- Department of Pharmacy, The Sixth Affiliated Hospital, Sun Yat-sen UniversityGuangzhou, Guangdong, China
| | - Senbiao Fang
- School of Computer Science and Engineering, Central South UniversityChangsha, Hunan, China
| | - Ruoqian Zheng
- School of Computer Science and Engineering, Central South UniversityChangsha, Hunan, China
| | - Daoquan Peng
- Department of Cardiovascular Medicine, The Second Xiangya Hospital, Central South UniversityChangsha, Hunan, China
- Research Institute of Blood Lipid and Atherosclerosis, Central South UniversityChangsha, Hunan, China
| | - Qin Luo
- Department of Cardiovascular Medicine, The Second Xiangya Hospital, Central South UniversityChangsha, Hunan, China
- Research Institute of Blood Lipid and Atherosclerosis, Central South UniversityChangsha, Hunan, China
| | - Bilian Yu
- Department of Cardiovascular Medicine, The Second Xiangya Hospital, Central South UniversityChangsha, Hunan, China
- Research Institute of Blood Lipid and Atherosclerosis, Central South UniversityChangsha, Hunan, China
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9
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Du G, Tian Y, Yao Z, Vu S, Zheng J, Chai L, Wang K, Yang S. A specialized pore turret in the mammalian cation channel TRPV1 is responsible for distinct and species-specific heat activation thresholds. J Biol Chem 2020; 295:9641-9649. [PMID: 32461255 DOI: 10.1074/jbc.ra120.013037] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/20/2020] [Indexed: 11/06/2022] Open
Abstract
The transient receptor potential vanilloid 1 (TRPV1) channel is a heat-activated cation channel that plays a crucial role in ambient temperature detection and thermal homeostasis. Although several structural features of TRPV1 have been shown to be involved in heat-induced activation of the gating process, the physiological significance of only a few of these key elements has been evaluated in an evolutionary context. Here, using transient expression in HEK293 cells, electrophysiological recordings, and molecular modeling, we show that the pore turret contains both structural and functional determinants that set the heat activation thresholds of distinct TRPV1 orthologs in mammals whose body temperatures fluctuate widely. We found that TRPV1 from the bat Carollia brevicauda exhibits a lower threshold temperature of channel activation than does its human ortholog and three bat-specific amino acid substitutions located in the pore turret are sufficient to determine this threshold temperature. Furthermore, the structure of the TRPV1 pore turret appears to be of physiological and evolutionary significance for differentiating the heat-activated threshold among species-specific TRPV1 orthologs. These findings support a role for the TRPV1 pore turret in tuning the heat-activated threshold, and they suggest that its evolution was driven by adaption to specific physiological traits among mammals exposed to variable temperatures.
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Affiliation(s)
- Guangxu Du
- Department of Pharmacology, Qingdao University School of Pharmacy, Qingdao, Shandong, China
| | - Yuhua Tian
- Department of Pharmacology, Qingdao University School of Pharmacy, Qingdao, Shandong, China
| | - Zhihao Yao
- Department of Pharmacology, Qingdao University School of Pharmacy, Qingdao, Shandong, China.,Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of the Yunnan Province Kunming Institute of Zoology, Kunming, Yunnan China
| | - Simon Vu
- University of California Davis, School of Medicine, Davis, California, USA
| | - Jie Zheng
- University of California Davis, School of Medicine, Davis, California, USA
| | - Longhui Chai
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, China
| | - KeWei Wang
- Department of Pharmacology, Qingdao University School of Pharmacy, Qingdao, Shandong, China
| | - Shilong Yang
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, China
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10
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Chen JH. Protein kinase A phosphorylation potentiates cystic fibrosis transmembrane conductance regulator gating by relieving autoinhibition on the stimulatory C terminus of the regulatory domain. J Biol Chem 2020; 295:4577-4590. [PMID: 32102849 DOI: 10.1074/jbc.ra119.008427] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 02/25/2020] [Indexed: 01/12/2023] Open
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel activated by protein kinase A (PKA) phosphorylation on the regulatory (R) domain. Phosphorylation at several R domain residues stimulates ATP-dependent channel openings and closings, termed channel gating. To explore the protein segment responsible for channel potentiation and PKA-dependent activation, deletion mutations were constructed by removing one to three protein segments of the R domain including residues 708-759 (ΔR708-759), R760-783, and R784-835, each of which contains one or two PKA phosphorylation sites. Deletion of R708-759 or R760-783 had little effect on CFTR gating, whereas all mutations lacking R784-835 reduced CFTR activity by decreasing the mean burst duration and increasing the interburst interval (IBI). The data suggest that R784-835 plays a major role in stimulating CFTR gating. For ATP-associated regulation, ΔR784-835 had minor impact on gating potentiation by 2'dATP, CaATP, and pyrophosphate. Interestingly, introducing a phosphorylated peptide matching R809-835 shortened the IBI of ΔR708-835-CFTR. Consistently, ΔR815-835, but not ΔR784-814, enhanced IBI, whereas both reduced mean burst duration. These data suggest that the entirety of R784-835 is required for stabilizing the open state of CFTR; however, R815-835, through interactions with the channel, is dominant for enhancing the opening rate. Of note, PKA markedly decreased the IBI of ΔR708-783-CFTR. Conversely, the IBI of ΔR708-814-CFTR was short and PKA-independent. These data reveal that for stimulating CFTR gating, PKA phosphorylation may relieve R784-814-mediated autoinhibition that prevents IBI shortening by R815-835 This mechanism may elucidate how the R domain potentiates channel gating and may unveil CFTR stimulation by other protein kinases.
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Affiliation(s)
- Jeng-Haur Chen
- College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang Province 321004, China .,University of Hong Kong Shenzhen Institute of Research and Innovation, Shenzhen 518057, China .,Department of Internal Medicine and Howard Hughes Medical Institute, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
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11
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Balleza D, Rosas ME, Romero-Romero S. Voltage vs. Ligand I: Structural basis of the intrinsic flexibility of S3 segment and its significance in ion channel activation. Channels (Austin) 2019; 13:455-476. [PMID: 31647368 PMCID: PMC6833973 DOI: 10.1080/19336950.2019.1674242] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
We systematically predict the internal flexibility of the S3 segment, one of the most mobile elements in the voltage-sensor domain. By analyzing the primary amino acid sequences of V-sensor containing proteins, including Hv1, TPC channels and the voltage-sensing phosphatases, we established correlations between the local flexibility and modes of activation for different members of the VGIC superfamily. Taking advantage of the structural information available, we also assessed structural aspects to understand the role played by the flexibility of S3 during the gating of the pore. We found that S3 flexibility is mainly determined by two specific regions: (1) a short NxxD motif in the N-half portion of the helix (S3a), and (2) a short sequence at the beginning of the so-called paddle motif where the segment has a kink that, in some cases, divide S3 into two distinct helices (S3a and S3b). A good correlation between the flexibility of S3 and the reported sensitivity to temperature and mechanical stretch was found. Thus, if the channel exhibits high sensitivity to heat or membrane stretch, local S3 flexibility is low. On the other hand, high flexibility of S3 is preferentially associated to channels showing poor heat and mechanical sensitivities. In contrast, we did not find any apparent correlation between S3 flexibility and voltage or ligand dependence. Overall, our results provide valuable insights into the dynamics of channel-gating and its modulation.
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Affiliation(s)
- Daniel Balleza
- Departamento de Química ICET, Universidad Autónoma de Guadalajara , Zapopan Jalisco , Mexico
| | - Mario E Rosas
- Departamento de Química ICET, Universidad Autónoma de Guadalajara , Zapopan Jalisco , Mexico
| | - Sergio Romero-Romero
- Facultad de Medicina, Departamento de Bioquímica, Universidad Nacional Autónoma de México, 04510 Mexico City, Mexico. Current address: Department of Biochemistry, University of Bayreuth , Bayreuth , Germany
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12
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Li D, Jin T, Gazgalis D, Cui M, Logothetis DE. On the mechanism of GIRK2 channel gating by phosphatidylinositol bisphosphate, sodium, and the Gβγ dimer. J Biol Chem 2019; 294:18934-18948. [PMID: 31659119 DOI: 10.1074/jbc.ra119.010047] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 10/21/2019] [Indexed: 12/19/2022] Open
Abstract
G protein-gated inwardly rectifying K+ (GIRK) channels belong to the inward-rectifier K+ (Kir) family, are abundantly expressed in the heart and the brain, and require that phosphatidylinositol bisphosphate is present so that intracellular channel-gating regulators such as Gβγ and Na+ ions can maintain the channel-open state. However, despite high-resolution structures (GIRK2) and a large number of functional studies, we do not have a coherent picture of how Gβγ and Na+ ions control gating of GIRK2 channels. Here, we utilized computational modeling and all-atom microsecond-scale molecular dynamics simulations to determine which gates are controlled by Na+ and Gβγ and how each regulator uses the channel domain movements to control gate transitions. We found that Na+ ions control the cytosolic gate of the channel through an anti-clockwise rotation, whereas Gβγ stabilizes the transmembrane gate in the open state through a rocking movement of the cytosolic domain. Both effects alter the way in which the channel interacts with phosphatidylinositol bisphosphate and thereby stabilizes the open states of the respective gates. These studies of GIRK channel dynamics present for the first time a comprehensive structural model that is consistent with the great body of literature on GIRK channel function.
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Affiliation(s)
- Dailin Li
- Key Laboratory of Environmental Biotechnology, Fujian Province University, Xiamen University of Technology, Xiamen, 361024 China; Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115.
| | - Taihao Jin
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115
| | - Dimitris Gazgalis
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Bouve College of Health Sciences, Boston, Massachusetts 02115.
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13
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Talbot BE, Vandorpe DH, Stotter BR, Alper SL, Schlondorff JS. Transmembrane insertases and N-glycosylation critically determine synthesis, trafficking, and activity of the nonselective cation channel TRPC6. J Biol Chem 2019; 294:12655-12669. [PMID: 31266804 PMCID: PMC6709635 DOI: 10.1074/jbc.ra119.008299] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/28/2019] [Indexed: 12/12/2022] Open
Abstract
Transient receptor potential cation channel subfamily C member 6 (TRPC6) is a widely expressed ion channel. Gain-of-function mutations in the human TRPC6 channel cause autosomal-dominant focal segmental glomerulosclerosis, but the molecular components involved in disease development remain unclear. Here, we found that overexpression of gain-of-function TRPC6 channel variants is cytotoxic in cultured cells. Exploiting this phenotype in a genome-wide CRISPR/Cas screen for genes whose inactivation rescues cells from TRPC6-associated cytotoxicity, we identified several proteins essential for TRPC6 protein expression, including the endoplasmic reticulum (ER) membrane protein complex transmembrane insertase. We also identified transmembrane protein 208 (TMEM208), a putative component of a signal recognition particle-independent (SND) ER protein-targeting pathway, as being necessary for expression of TRPC6 and several other ion channels and transporters. TRPC6 expression was also diminished by loss of the previously uncharacterized WD repeat domain 83 opposite strand (WDR83OS), which interacted with both TRPC6 and TMEM208. Additionally enriched among the screen hits were genes involved in N-linked protein glycosylation. Deletion of the mannosyl (α-1,3-)-glycoprotein β-1,2-N-acetylglucosaminyltransferase (MGAT1), necessary for the generation of complex N-linked glycans, abrogated TRPC6 gain-of-function variant-mediated Ca2+ influx and extracellular signal-regulated kinase activation in HEK cells, but failed to diminish cytotoxicity in cultured podocytes. However, mutating the two TRPC6 N-glycosylation sites abrogated the cytotoxicity of mutant TRPC6 and reduced its surface expression. These results expand the targets of TMEM208-mediated ER translocation to include multipass transmembrane proteins and suggest that TRPC6 N-glycosylation plays multiple roles in modulating channel trafficking and activity.
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Affiliation(s)
- Brianna E Talbot
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
| | - David H Vandorpe
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
| | - Brian R Stotter
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
- Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Seth L Alper
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
| | - Johannes S Schlondorff
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
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14
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Li AQ, Sun ZP, Liu X, Yang JS, Jin F, Zhu L, Jia WH, De Vos S, Van Stappen G, Bossier P, Yang WJ. The chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) controls cellular quiescence by hyperpolarizing the cell membrane during diapause in the crustacean Artemia. J Biol Chem 2019; 294:6598-6611. [PMID: 30765604 DOI: 10.1074/jbc.ra118.005900] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 02/10/2019] [Indexed: 01/10/2023] Open
Abstract
Cellular quiescence, a reversible state in which growth, proliferation, and other cellular activities are arrested, is important for self-renewal, differentiation, development, regeneration, and stress resistance. However, the physiological mechanisms underlying cellular quiescence remain largely unknown. In the present study, we used embryos of the crustacean Artemia in the diapause stage, in which these embryos remain quiescent for prolonged periods, as a model to explore the relationship between cell-membrane potential (V mem) and quiescence. We found that V mem is hyperpolarized and that the intracellular chloride concentration is high in diapause embryos, whereas V mem is depolarized and intracellular chloride concentration is reduced in postdiapause embryos and during further embryonic development. We identified and characterized the chloride ion channel protein cystic fibrosis transmembrane conductance regulator (CFTR) of Artemia (Ar-CFTR) and found that its expression is silenced in quiescent cells of Artemia diapause embryos but remains constant in all other embryonic stages. Ar-CFTR knockdown and GlyH-101-mediated chemical inhibition of Ar-CFTR produced diapause embryos having a high V mem and intracellular chloride concentration, whereas control Artemia embryos released free-swimming nauplius larvae. Transcriptome analysis of embryos at different developmental stages revealed that proliferation, differentiation, and metabolism are suppressed in diapause embryos and restored in postdiapause embryos. Combined with RNA sequencing (RNA-Seq) of GlyH-101-treated MCF-7 breast cancer cells, these analyses revealed that CFTR inhibition down-regulates the Wnt and Aurora Kinase A (AURKA) signaling pathways and up-regulates the p53 signaling pathway. Our findings provide insight into CFTR-mediated regulation of cellular quiescence and V mem in the Artemia model.
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Affiliation(s)
- An-Qi Li
- From the College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Zhan-Peng Sun
- From the College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Xu Liu
- From the College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Jin-Shu Yang
- From the College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Feng Jin
- From the College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Lin Zhu
- From the College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Wen-Huan Jia
- From the College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Stephanie De Vos
- the Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, B-9000 Ghent, Belgium, and
| | - Gilbert Van Stappen
- the Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, B-9000 Ghent, Belgium, and
| | - Peter Bossier
- the Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, B-9000 Ghent, Belgium, and
| | - Wei-Jun Yang
- From the College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China, .,the Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266000, China
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15
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Morgan JLW, Evans EGB, Zagotta WN. Functional characterization and optimization of a bacterial cyclic nucleotide-gated channel. J Biol Chem 2019; 294:7503-7515. [PMID: 30885945 DOI: 10.1074/jbc.ra119.007699] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 03/15/2019] [Indexed: 02/01/2023] Open
Abstract
Cyclic nucleotide-gated (CNG) channels produce the initial electrical signal in mammalian vision and olfaction. They open in response to direct binding of cyclic nucleotide (cAMP or cGMP) to a cytoplasmic region of the channel. However, the conformational rearrangements occurring upon binding to produce pore opening (i.e. gating) are not well understood. SthK is a bacterial CNG channel that has the potential to serve as an ideal model for structure-function studies of gating but is currently limited by its toxicity, native cysteines, and low open probability (P o). Here, we expressed SthK in giant Escherichia coli spheroplasts and performed patch-clamp recordings to characterize SthK gating in a bacterial membrane. We demonstrated that the P o in cAMP is higher than has been previously published and that cGMP acts as a weak partial SthK agonist. Additionally, we determined that SthK expression is toxic to E. coli because of gating by cytoplasmic cAMP. We overcame this toxicity by developing an adenylate cyclase-knockout E. coli cell line. Finally, we generated a cysteine-free SthK construct and introduced mutations that further increase the P o in cAMP. We propose that this SthK model will help elucidate the gating mechanism of CNG channels.
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Affiliation(s)
- Jacob L W Morgan
- From the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195
| | - Eric G B Evans
- From the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195
| | - William N Zagotta
- From the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195
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16
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Absalom NL, Ahring PK, Liao VW, Balle T, Jiang T, Anderson LL, Arnold JC, McGregor IS, Bowen MT, Chebib M. Functional genomics of epilepsy-associated mutations in the GABA A receptor subunits reveal that one mutation impairs function and two are catastrophic. J Biol Chem 2019; 294:6157-6171. [PMID: 30728247 DOI: 10.1074/jbc.ra118.005697] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 01/30/2019] [Indexed: 12/29/2022] Open
Abstract
A number of epilepsy-causing mutations have recently been identified in the genes of the α1, β3, and γ2 subunits comprising the γ-aminobutyric acid type A (GABAA) receptor. These mutations are typically dominant, and in certain cases, such as the α1 and β3 subunits, they may lead to a mix of receptors at the cell surface that contain no mutant subunits, a single mutated subunit, or two mutated subunits. To determine the effects of mutations in a single subunit or in two subunits on receptor activation, we created a concatenated protein assembly that links all five subunits of the α1β3γ2 receptor and expresses them in the correct orientation. We created nine separate receptor variants with a single-mutant subunit and four receptors containing two subunits of the γ2R323Q, β3D120N, β3T157M, β3Y302C, and β3S254F epilepsy-causing mutations. We found that the singly mutated γ2R323Q subunit impairs GABA activation of the receptor by reducing GABA potency. A single β3D120N, β3T157M, or β3Y302C mutation also substantially impaired receptor activation, and two copies of these mutants within a receptor were catastrophic. Of note, an effect of the β3S254F mutation on GABA potency depended on the location of this mutant subunit within the receptor, possibly because of the membrane environment surrounding the transmembrane region of the receptor. Our results highlight that precise functional genomic analyses of GABAA receptor mutations using concatenated constructs can identify receptors with an intermediate phenotype that contribute to epileptic phenotypes and that are potential drug targets for precision medicine approaches.
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Affiliation(s)
- Nathan L Absalom
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; School of Pharmacy, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Philip K Ahring
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; School of Pharmacy, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Vivian W Liao
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; School of Pharmacy, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Thomas Balle
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; School of Pharmacy, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Tian Jiang
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; School of Pharmacy, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Lyndsey L Anderson
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; Discipline of Pharmacology, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia; Lambert Initiative for Cannabinoid Therapeutics, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia
| | - Jonathon C Arnold
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; Discipline of Pharmacology, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia; Lambert Initiative for Cannabinoid Therapeutics, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia
| | - Iain S McGregor
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; Lambert Initiative for Cannabinoid Therapeutics, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; the School of Psychology, Faculty of Science, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Michael T Bowen
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; Lambert Initiative for Cannabinoid Therapeutics, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; the School of Psychology, Faculty of Science, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Mary Chebib
- From the Brain and Mind Centre, University of Sydney, 94 Mallett Street, Camperdown, New South Wales 2050, Australia; School of Pharmacy, University of Sydney, Camperdown, New South Wales 2006, Australia.
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17
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Zhang XY, Bi RY, Zhang P, Gan YH. Veratridine modifies the gating of human voltage-gated sodium channel Nav1.7. Acta Pharmacol Sin 2018; 39:1716-1724. [PMID: 29950616 DOI: 10.1038/s41401-018-0065-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 06/05/2018] [Indexed: 01/22/2023] Open
Abstract
Veratridine is a lipid-soluble neurotoxin derived from plants in the family Liliaceae. It has been broadly investigated for its action as a sodium channel agonist. However, the effects of veratridine on subtypes of sodium channels, especially Nav1.7, remain to be studied. Here, we investigated the effects of veratridine on human Nav1.7 ectopically expressed in HEK293A cells and recorded Nav1.7 currents from the cells using whole-cell patch clamp technique. We found that veratridine exerted a dose-dependent inhibitory effect on the peak current of Nav1.7, with the half-maximal inhibition concentration (IC50) of 18.39 µM. Meanwhile, veratridine also elicited tail current (linearly) and sustained current [half-maximal concentration (EC50): 9.53 µM], also in a dose-dependent manner. Veratridine (75 µM) shifted the half-maximal activation voltage of the Nav1.7 activation curve in the hyperpolarized direction, from -21.64 ± 0.75 mV to -28.14 ± 0.66 mV, and shifted the half-inactivation voltage of the steady-state inactivation curve from -59.39 ± 0.39 mV to -73.78 ± 0.5 mV. An increased frequency of stimulation decreased the peak and tail currents of Nav1.7 for each pulse along with pulse number, and increased the accumulated tail current at the end of train stimulation. These findings reveal the different modulatory effects of veratridine on the Nav1.7 peak current and tail current.
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18
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Zhelay T, Wieczerzak KB, Beesetty P, Alter GM, Matsushita M, Kozak JA. Depletion of plasma membrane-associated phosphoinositides mimics inhibition of TRPM7 channels by cytosolic Mg 2+, spermine, and pH. J Biol Chem 2018; 293:18151-18167. [PMID: 30305398 PMCID: PMC6254349 DOI: 10.1074/jbc.ra118.004066] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 10/04/2018] [Indexed: 12/20/2022] Open
Abstract
Transient receptor potential cation channel subfamily M member 7 (TRPM7) is an ion channel/protein kinase belonging to the TRP melastatin and eEF2 kinase families. Under physiological conditions, most native TRPM7 channels are inhibited by cytoplasmic Mg2+, protons, and polyamines. Currents through these channels (ITRPM7) are robustly potentiated when the cell interior is exchanged with low Mg2+-containing buffers. ITRPM7 is also potentiated by phosphatidyl inositol bisphosphate (PI(4,5)P2) and suppressed by its hydrolysis. Here we characterized internal Mg2+- and pH-mediated inhibition of TRPM7 channels in HEK293 cells overexpressing WT voltage-sensing phospholipid phosphatase (VSP) or its catalytically inactive variant VSP-C363S. VSP-mediated depletion of membrane phosphoinositides significantly increased channel sensitivity to Mg2+ and pH. Proton concentrations that were too low to inhibit ITRPM7 when the VSP-C363S variant was expressed (pH 8.2) became inhibitory in WT VSP-expressing cells. At pH 6.5, protons inhibited ITRPM7 both in WT and VSP C363S-expressing cells but with a faster time course in the WT VSP-expressing cells. Inhibition by 150 μm Mg2+ was also significantly faster in the WT VSP-expressing cells. Cellular PI(4,5)P2 depletion increased the sensitivity of TRPM7 channels to the inhibitor 2-aminoethyl diphenyl borinate, which acidifies the cytosol. Single substitutions at Ser-1107 of TRPM7, reducing its sensitivity to Mg2+, also decreased its inhibition by spermine and acidic pH. Furthermore, these channel variants were markedly less sensitive to VSP-mediated PI(4,5)P2 depletion than the WT. We conclude that the internal Mg2+-, polyamine-, and pH-mediated inhibition of TRPM7 channels is not direct but, rather, reflects electrostatic screening and resultant disruption of PI(4,5)P2-channel interactions.
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Affiliation(s)
- Tetyana Zhelay
- From the Departments of Neuroscience, Cell Biology, and Physiology and
| | | | - Pavani Beesetty
- From the Departments of Neuroscience, Cell Biology, and Physiology and
| | - Gerald M Alter
- Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio 45435 and
| | - Masayuki Matsushita
- the Department of Molecular and Cellular Physiology, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan
| | - J Ashot Kozak
- From the Departments of Neuroscience, Cell Biology, and Physiology and.
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19
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Wang X, Tang S, Wen X, Hong L, Hong F, Li Y. Transmembrane TM3b of Mechanosensitive Channel MscS Interacts With Cytoplasmic Domain Cyto-Helix. Front Physiol 2018; 9:1389. [PMID: 30327617 PMCID: PMC6174206 DOI: 10.3389/fphys.2018.01389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 09/12/2018] [Indexed: 11/25/2022] Open
Abstract
The mechanosensitive channel MscS functions as an osmolyte emergency release-valve in the event of a sudden decrease in external environmental osmolarity. MscS has served as a paradigm for studying how channel proteins detect and respond to mechanical stimuli. However, the inter-domain interactions and structural rearrangements that occur in the MscS gating process remain largely unknown. Here, we determined the interactions between the transmembrane domain and cytoplasmic domain of MscS. Using in vivo cellular viability, single-channel electrophysiological recording, and cysteine disulfide trapping, we demonstrated that N117 of the TM3b helix and N167 of the Cyto-helix are critical residues that function at the TM3b-Cyto helix interface. In vivo downshock assays showed that double cysteine substitution at N117 and N167 failed to rescue the osmotic-lysis phenotype of cells in acute osmotic downshock. Single-channel recordings demonstrated that cysteine cross-linking of N117C and N167C led to a non-conductive channel. Consistently, coordination of the histidines of N117H and N167H caused a decrease in channel gating. Moreover, cross-linked N117 and N167 altered the gating of the severe gain-of-function mutant L109S. Our results demonstrate that N117–N167 interactions stabilize the inactivation state by an association of TM3b segments with β-domains of the cytoplasmic region, providing further insights into the gating mechanism of the MscS channel.
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Affiliation(s)
- Xiaomin Wang
- Children's Hospital and Department of Biophysics, National Health Commission and Chinese Academy of Medical Sciences Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Siyang Tang
- Children's Hospital and Department of Biophysics, National Health Commission and Chinese Academy of Medical Sciences Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Xiaoxu Wen
- Children's Hospital and Department of Biophysics, National Health Commission and Chinese Academy of Medical Sciences Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Lang Hong
- Children's Hospital and Department of Biophysics, National Health Commission and Chinese Academy of Medical Sciences Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Feifan Hong
- Children's Hospital and Department of Biophysics, National Health Commission and Chinese Academy of Medical Sciences Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
| | - Yuezhou Li
- Children's Hospital and Department of Biophysics, National Health Commission and Chinese Academy of Medical Sciences Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China
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20
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Basso E, Rigotto G, Zucchetti AE, Pozzan T. Slow activation of fast mitochondrial Ca 2+ uptake by cytosolic Ca 2. J Biol Chem 2018; 293:17081-17094. [PMID: 30228190 DOI: 10.1074/jbc.ra118.002332] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 09/06/2018] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial Ca2+ uptake through the mitochondrial Ca2+ uniporter (MCU) is a tightly controlled process that sustains cell functions mainly by fine-tuning oxidative metabolism to cellular needs. The kinetics of Ca2+ fluxes across the mitochondrial membranes have been studied both in vitro and in vivo for many years, and the discovery of the molecular components of the MCU has further clarified that this Ca2+ uptake mechanism is based on a complex system subject to elaborate layers of controls. Alterations in the speed or capacity of the in-and-out pathways can have detrimental consequences for both the organelle and the cell, impairing cellular metabolism and ultimately causing cell death. Here, we report that pretreatment of deenergized mitochondria with low-micromolar Ca2+ concentrations for a few minutes markedly increases the speed of mitochondrial Ca2+ uptake upon re-addition of an oxidizable substrate. We found that this phenomenon is sensitive to alterations in the level of the MCU modulator proteins mitochondrial calcium uptake 1 (MICU1) and 2 (MICU2), and is accompanied by changes in the association of MICU1-MICU2 complexes with MCU. This increased Ca2+ uptake capacity, occurring under conditions mimicking those during ischemia/reperfusion in vivo, could lead to a massive amount of Ca2+ entering the mitochondrial matrix even at relatively low levels of cytosolic Ca2+ We conclude that the phenomenon uncovered here represents a potential threat of mitochondrial Ca2+ overload to the cell.
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Affiliation(s)
- Emy Basso
- From the National Research Council, Department of Biomedical Science, Neuroscience Institute (Padua Section), 35131 Padua, Italy,
| | - Giulia Rigotto
- the Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy
| | - Andrés E Zucchetti
- the Institut Curie, PSL Research University, INSERM, U932, 26 rue d'Ulm, 75248 Paris Cedex 05, France, and
| | - Tullio Pozzan
- From the National Research Council, Department of Biomedical Science, Neuroscience Institute (Padua Section), 35131 Padua, Italy.,the Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy.,the Venetian Institute of Molecular Medicine, 35129 Padua, Italy
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21
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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: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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22
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Lasala M, Corradi J, Bruzzone A, Esandi MDC, Bouzat C. A human-specific, truncated α7 nicotinic receptor subunit assembles with full-length α7 and forms functional receptors with different stoichiometries. J Biol Chem 2018; 293:10707-10717. [PMID: 29784875 DOI: 10.1074/jbc.ra117.001698] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 05/15/2018] [Indexed: 11/06/2022] Open
Abstract
The cholinergic α7 nicotinic receptor gene, CHRNA7, encodes a subunit that forms the homopentameric α7 receptor, involved in learning and memory. In humans, exons 5-10 in CHRNA7 are duplicated and fused to the FAM7A genetic element, giving rise to the hybrid gene CHRFAM7A Its product, dupα7, is a truncated subunit lacking part of the N-terminal extracellular ligand-binding domain and is associated with neurological disorders, including schizophrenia, and immunomodulation. We combined dupα7 expression on mammalian cells with patch clamp recordings to understand its functional role. Transfected cells expressed dupα7 protein, but they exhibited neither surface binding of the α7 antagonist α-bungarotoxin nor responses to acetylcholine (ACh) or to an allosteric agonist that binds to the conserved transmembrane region. To determine whether dupα7 assembles with α7, we generated receptors comprising α7 and dupα7 subunits, one of which was tagged with conductance substitutions that report subunit stoichiometry and monitored ACh-elicited channel openings in the presence of a positive allosteric α7 modulator. We found that α7 and dupα7 subunits co-assemble into functional heteromeric receptors, which require at least two α7 subunits for channel opening, and that dupα7's presence in the pentameric arrangement does not affect the duration of the potentiated events compared with that of α7. Using an α7 subunit mutant, we found that activation of (α7)2(dupα7)3 receptors occurs through ACh binding at the α7/α7 interfacial binding site. Our study contributes to the understanding of the modulation of α7 function by the human specific, duplicated subunit, associated with human disorders.
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Affiliation(s)
- Matías Lasala
- From the Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina
| | - Jeremías Corradi
- From the Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina
| | - Ariana Bruzzone
- From the Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina
| | - María Del Carmen Esandi
- From the Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina
| | - Cecilia Bouzat
- From the Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina
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23
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Briot J, Mailhot O, Bourdin B, Tétreault MP, Najmanovich R, Parent L. A three-way inter-molecular network accounts for the Ca Vα2δ1-induced functional modulation of the pore-forming Ca V1.2 subunit. J Biol Chem 2018; 293:7176-7188. [PMID: 29588365 DOI: 10.1074/jbc.ra118.001902] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 03/09/2018] [Indexed: 12/17/2022] Open
Abstract
L-type CaV1.2 channels are essential for the excitation-contraction coupling in cardiomyocytes and are hetero-oligomers of a pore-forming CaVα1C assembled with CaVβ and CaVα2δ1 subunits. A direct interaction between CaVα2δ1 and Asp-181 in the first extracellular loop of CaVα1 reproduces the native properties of the channel. A 3D model of the von Willebrand factor type A (VWA) domain of CaVα2δ1 complexed with the voltage sensor domain of CaVα1C suggests that Ser-261 and Ser-263 residues in the metal ion-dependent adhesion site (MIDAS) motif are determinant in this interaction, but this hypothesis is untested. Here, coimmunoprecipitation assays and patch-clamp experiments of single-substitution variants revealed that CaVα2δ1 Asp-259 and Ser-261 are the two most important residues in regard to protein interactions and modulation of CaV1.2 currents. In contrast, mutating the side chains of CaVα2δ1 Ser-263, Thr-331, and Asp-363 with alanine did not completely prevent channel function. Molecular dynamics simulations indicated that the carboxylate side chain of CaVα2δ1 Asp-259 coordinates the divalent cation that is further stabilized by the oxygen atoms from the hydroxyl side chain of CaVα2δ1 Ser-261 and the carboxylate group of CaVα1C Asp-181. In return, the hydrogen atoms contributed by the side chain of Ser-261 and the main chain of Ser-263 bonded the oxygen atoms of CaV1.2 Asp-181. We propose that CaVα2δ1 Asp-259 promotes Ca2+ binding necessary to produce the conformation of the VWA domain that locks CaVα2δ1 Ser-261 and Ser-263 within atomic distance of CaVα1C Asp-181. This three-way network appears to account for the CaVα2δ1-induced modulation of CaV1.2 currents.
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Affiliation(s)
- Julie Briot
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Olivier Mailhot
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Biochimie et Médecine Moléculaire, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada
| | - Benoîte Bourdin
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Marie-Philippe Tétreault
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Rafael Najmanovich
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada
| | - Lucie Parent
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada.
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24
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Stakaitytė G, Nwogu N, Lippiat JD, Blair GE, Poterlowicz K, Boyne JR, Macdonald A, Mankouri J, Whitehouse A. The cellular chloride channels CLIC1 and CLIC4 contribute to virus-mediated cell motility. J Biol Chem 2018; 293:4582-4590. [PMID: 29462791 PMCID: PMC5868249 DOI: 10.1074/jbc.ra117.001343] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Indexed: 12/11/2022] Open
Abstract
Ion channels regulate many aspects of cell physiology, including cell proliferation, motility, and migration, and aberrant expression and activity of ion channels is associated with various stages of tumor development, with K+ and Cl− channels now being considered the most active during tumorigenesis. Accordingly, emerging in vitro and preclinical studies have revealed that pharmacological manipulation of ion channel activity offers protection against several cancers. Merkel cell polyomavirus (MCPyV) is a major cause of Merkel cell carcinoma (MCC), primarily because of the expression of two early regulatory proteins termed small and large tumor antigens (ST and LT, respectively). Several molecular mechanisms have been attributed to MCPyV-mediated cancer formation but, thus far, no studies have investigated any potential link to cellular ion channels. Here we demonstrate that Cl− channel modulation can reduce MCPyV ST-induced cell motility and invasiveness. Proteomic analysis revealed that MCPyV ST up-regulates two Cl− channels, CLIC1 and CLIC4, which when silenced, inhibit MCPyV ST-induced motility and invasiveness, implicating their function as critical to MCPyV-induced metastatic processes. Consistent with these data, we confirmed that CLIC1 and CLIC4 are up-regulated in primary MCPyV-positive MCC patient samples. We therefore, for the first time, implicate cellular ion channels as a key host cell factor contributing to virus-mediated cellular transformation. Given the intense interest in ion channel modulating drugs for human disease. This highlights CLIC1 and CLIC4 activity as potential targets for MCPyV-induced MCC.
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Affiliation(s)
- Gabrielė Stakaitytė
- From the School of Molecular and Cellular Biology.,Astbury Centre for Structural Molecular Biology
| | - Nnenna Nwogu
- From the School of Molecular and Cellular Biology.,Astbury Centre for Structural Molecular Biology
| | - Jonathan D Lippiat
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom and
| | - G Eric Blair
- From the School of Molecular and Cellular Biology
| | - Krzysztof Poterlowicz
- Centre for Skin Sciences, School of Chemistry and Biosciences, Faculty of Life Sciences, University of Bradford, Bradford BD7 1DP, United Kingdom
| | - James R Boyne
- Centre for Skin Sciences, School of Chemistry and Biosciences, Faculty of Life Sciences, University of Bradford, Bradford BD7 1DP, United Kingdom
| | - Andrew Macdonald
- From the School of Molecular and Cellular Biology.,Astbury Centre for Structural Molecular Biology
| | - Jamel Mankouri
- From the School of Molecular and Cellular Biology, .,Astbury Centre for Structural Molecular Biology
| | - Adrian Whitehouse
- From the School of Molecular and Cellular Biology, .,Astbury Centre for Structural Molecular Biology
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25
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Fan J, Gandini MA, Zhang FX, Chen L, Souza IA, Zamponi GW. Down-regulation of T-type Cav3.2 channels by hyperpolarization-activated cyclic nucleotide-gated channel 1 (HCN1): Evidence of a signaling complex. Channels (Austin) 2017; 11:434-443. [PMID: 28467171 DOI: 10.1080/19336950.2017.1326233] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Formation of complexes between ion channels is important for signal processing in the brain. Here we investigate the biochemical and biophysical interactions between HCN1 channels and Cav3.2 T-type channels. We found that HCN1 co-immunoprecipitated with Cav3.2 from lysates of either mouse brain or tsA-201 cells, with the HCN1 N-terminus associating with the Cav3.2 N-terminus. Cav3.2 channel activity appeared to be functionally regulated by HCN1. The expression of HCN1 induced a decrease in Cav3.2 Ba2+ influx (IBa2+) along with altered channel kinetics and a depolarizing shift in activation gating. However, a reciprocal regulation of HCN1 by Cav3.2 was not observed. This study highlights a regulatory role of HCN1 on Cav3.2 voltage-dependent properties, which are expected to affect physiologic functions such as synaptic transmission and cellular excitability.
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Affiliation(s)
- Jing Fan
- a Department of Physiology and Pharmacology , Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary , Calgary , Alberta , Canada
| | - Maria A Gandini
- a Department of Physiology and Pharmacology , Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary , Calgary , Alberta , Canada
| | - Fang-Xiong Zhang
- a Department of Physiology and Pharmacology , Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary , Calgary , Alberta , Canada
| | - Lina Chen
- a Department of Physiology and Pharmacology , Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary , Calgary , Alberta , Canada
| | - Ivana A Souza
- a Department of Physiology and Pharmacology , Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary , Calgary , Alberta , Canada
| | - Gerald W Zamponi
- a Department of Physiology and Pharmacology , Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary , Calgary , Alberta , Canada
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26
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Chen L, Bi D, Lu ZH, McClafferty H, Shipston MJ. Distinct domains of the β1-subunit cytosolic N terminus control surface expression and functional properties of large-conductance calcium-activated potassium (BK) channels. J Biol Chem 2017; 292:8694-8704. [PMID: 28373283 PMCID: PMC5448097 DOI: 10.1074/jbc.m116.769505] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 03/17/2017] [Indexed: 11/06/2022] Open
Abstract
The properties and function of large-conductance calcium- and voltage-activated potassium (BK) channels are modified by the tissue-specific expression of regulatory β1-subunits. Although the short cytosolic N-terminal domain of the β1-subunit is important for controlling both BK channel trafficking and function, whether the same, or different, regions of the N terminus control these distinct processes remains unknown. Here we demonstrate that the first six N-terminal residues including Lys-3, Lys-4, and Leu-5 are critical for controlling functional regulation, but not trafficking, of BK channels. This membrane-distal region has features of an amphipathic helix that is predicted to control the orientation of the first transmembrane-spanning domain (TM1) of the β1-subunit. In contrast, a membrane-proximal leucine residue (Leu-17) controls trafficking without affecting functional coupling, an effect that is in part dependent on controlling efficient endoplasmic reticulum exit of the pore-forming α-subunit. Thus cell surface trafficking and functional coupling with BK channels are controlled by distinct domains of the β1-subunit N terminus.
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Affiliation(s)
- Lie Chen
- From the Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom.,PAPRSB Institute of Health Sciences, Universiti Brunei Darussalam, Jalan Tungku Link BE1410, Brunei Darussalam
| | - Danlei Bi
- From the Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom.,Neurodegenerative Disease Research Center, School of Life Sciences, University of Science and Technology of China, Hefei 230026, China,and
| | - Zen Huat Lu
- PAPRSB Institute of Health Sciences, Universiti Brunei Darussalam, Jalan Tungku Link BE1410, Brunei Darussalam.,Division of Genetics and Genomics, The Roslin Institute, University of Edinburgh, Edinburgh EH25 9RG, Scotland, United Kingdom
| | - Heather McClafferty
- From the Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Michael J Shipston
- From the Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom,
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27
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Phan K, Ng CA, David E, Shishmarev D, Kuchel PW, Vandenberg JI, Perry MD. The S1 helix critically regulates the finely tuned gating of Kv11.1 channels. J Biol Chem 2017; 292:7688-7705. [PMID: 28280240 DOI: 10.1074/jbc.m117.779298] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 02/26/2017] [Indexed: 11/06/2022] Open
Abstract
Congenital mutations in the cardiac Kv11.1 channel can cause long QT syndrome type 2 (LQTS2), a heart rhythm disorder associated with sudden cardiac death. Mutations act either by reducing protein expression at the membrane and/or by perturbing the intricate gating properties of Kv11.1 channels. A number of clinical LQTS2-associated mutations have been reported in the first transmembrane segment (S1) of Kv11.1 channels, but the role of this region of the channel is largely unexplored. In part, this is due to problems defining the extent of the S1 helix, as a consequence of its low sequence homology with other Kv family members. Here, we used NMR spectroscopy and electrophysiological characterization to show that the S1 of Kv11.1 channels extends seven helical turns, from Pro-405 to Phe-431, and is flanked by unstructured loops. Functional analysis suggests that pre-S1 loop residues His-402 and Tyr-403 play an important role in regulating the kinetics and voltage dependence of channel activation and deactivation. Multiple residues within the S1 helix also play an important role in fine-tuning the voltage dependence of activation, regulating slow deactivation, and modulating C-type inactivation of Kv11.1 channels. Analyses of LQTS2-associated mutations in the pre-S1 loop or S1 helix of Kv11.1 channels demonstrate perturbations to both protein expression and most gating transitions. Thus, S1 region mutations would reduce both the action potential repolarizing current passed by Kv11.1 channels in cardiac myocytes, as well as the current passed in response to premature depolarizations that normally helps protect against the formation of ectopic beats.
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Affiliation(s)
- Kevin Phan
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010.,the St. Vincent's Clinical School, University of New South Wales, New South Wales 2052, and
| | - Chai Ann Ng
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010.,the St. Vincent's Clinical School, University of New South Wales, New South Wales 2052, and
| | - Erikka David
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010
| | - Dmitry Shishmarev
- the School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Philip W Kuchel
- the School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Jamie I Vandenberg
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010.,the St. Vincent's Clinical School, University of New South Wales, New South Wales 2052, and
| | - Matthew D Perry
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, .,the St. Vincent's Clinical School, University of New South Wales, New South Wales 2052, and
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28
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Lynagh T, Komnatnyy VV, Pless SA. Unique Contributions of an Arginine Side Chain to Ligand Recognition in a Glutamate-gated Chloride Channel. J Biol Chem 2017; 292:3940-3946. [PMID: 28096462 PMCID: PMC5339774 DOI: 10.1074/jbc.m116.772939] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/11/2017] [Indexed: 11/06/2022] Open
Abstract
Glutamate recognition by neurotransmitter receptors often relies on Arg residues in the binding site, leading to the assumption that charge-charge interactions underlie ligand recognition. However, assessing the precise chemical contribution of Arg side chains to protein function and pharmacology has proven to be exceedingly difficult in such large and complex proteins. Using the in vivo nonsense suppression approach, we report the first successful incorporation of the isosteric, titratable Arg analog, canavanine, into a neurotransmitter receptor in a living cell, utilizing a glutamate-gated chloride channel from the nematode Haemonchus contortus Our data unveil a surprisingly small contribution of charge at a conserved arginine side chain previously suggested to form a salt bridge with the ligand, glutamate. Instead, our data show that Arg contributes crucially to ligand sensitivity via a hydrogen bond network, where Arg interacts both with agonist and with a conserved Thr side chain within the receptor. Together, the data provide a new explanation for the reliance of neurotransmitter receptors on Arg side chains and highlight the exceptional capacity of unnatural amino acid incorporation for increasing our understanding of ligand recognition.
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Affiliation(s)
- Timothy Lynagh
- From the Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, 2100 H Copenhagen, Denmark
| | - Vitaly V Komnatnyy
- From the Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, 2100 H Copenhagen, Denmark
| | - Stephan A Pless
- From the Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, 2100 H Copenhagen, Denmark
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29
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Jain A, Kuryatov A, Wang J, Kamenecka TM, Lindstrom J. Unorthodox Acetylcholine Binding Sites Formed by α5 and β3 Accessory Subunits in α4β2* Nicotinic Acetylcholine Receptors. J Biol Chem 2016; 291:23452-23463. [PMID: 27645992 DOI: 10.1074/jbc.m116.749150] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Indexed: 11/06/2022] Open
Abstract
All nicotinic acetylcholine receptors (nAChRs) evolved from homomeric nAChRs in which all five subunits are involved in forming acetylcholine (ACh) binding sites at their interfaces. Heteromeric α4β2* nAChRs typically have two ACh binding sites at α4/β2 interfaces and a fifth accessory subunit surrounding the central cation channel. β2 accessory subunits do not form ACh binding sites, but α4 accessory subunits do at the α4/α4 interface in (α4β2)2α4 nAChRs. α5 and β3 are closely related subunits that had been thought to act only as accessory subunits and not take part in forming ACh binding sites. The effect of agonists at various subunit interfaces was determined by blocking homologous sites at these interfaces using the thioreactive agent 2-((trimethylammonium)ethyl) methanethiosulfonate (MTSET). We found that α5/α4 and β3/α4 interfaces formed ACh binding sites in (α4β2)2α5 and (α4β2)2β3 nAChRs. The α4/α5 interface in (β2α4)2α5 nAChRs also formed an ACh binding site. Blocking of these sites with MTSET reduced the maximal ACh evoked responses of these nAChRs by 30-50%. However, site-selective agonists NS9283 (for the α4/α4 site) and sazetidine-A (for the α4/β2 site) did not act on the ACh sites formed by the α5/α4 or β3/α4 interfaces. This suggests that unorthodox sites formed by α5 and β3 subunits have unique ligand selectivity. Agonists or antagonists for these unorthodox sites might be selective and effective drugs for modulating nAChR function to treat nicotine addiction and other disorders.
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Affiliation(s)
- Akansha Jain
- From the Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Alexander Kuryatov
- From the Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Jingyi Wang
- the Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, and
| | - Theodore M Kamenecka
- the Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, Florida 33458
| | - Jon Lindstrom
- From the Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104,
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30
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Syeda R, Santos JS, Montal M. The Sensorless Pore Module of Voltage-gated K+ Channel Family 7 Embodies the Target Site for the Anticonvulsant Retigabine. J Biol Chem 2015; 291:2931-7. [PMID: 26627826 DOI: 10.1074/jbc.m115.683185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Indexed: 01/03/2023] Open
Abstract
KCNQ (voltage-gated K(+) channel family 7 (Kv7)) channels control cellular excitability and underlie the K(+) current sensitive to muscarinic receptor signaling (the M current) in sympathetic neurons. Here we show that the novel anti-epileptic drug retigabine (RTG) modulates channel function of pore-only modules (PMs) of the human Kv7.2 and Kv7.3 homomeric channels and of Kv7.2/3 heteromeric channels by prolonging the residence time in the open state. In addition, the Kv7 channel PMs are shown to recapitulate the single-channel permeation and pharmacological specificity characteristics of the corresponding full-length proteins in their native cellular context. A mutation (W265L) in the reconstituted Kv7.3 PM renders the channel insensitive to RTG and favors the conductive conformation of the PM, in agreement to what is observed when the Kv7.3 mutant is heterologously expressed. On the basis of the new findings and homology models of the closed and open conformations of the Kv7.3 PM, we propose a structural mechanism for the gating of the Kv7.3 PM and for the site of action of RTG as a Kv7.2/Kv7.3 K(+) current activator. The results validate the modular design of human Kv channels and highlight the PM as a high-fidelity target for drug screening of Kv channels.
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Affiliation(s)
- Ruhma Syeda
- From the Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California 92093
| | - Jose S Santos
- From the Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California 92093
| | - Mauricio Montal
- From the Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California 92093
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31
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Ehrhardt A, Chung WJ, Pyle LC, Wang W, Nowotarski K, Mulvihill CM, Ramjeesingh M, Hong J, Velu SE, Lewis HA, Atwell S, Aller S, Bear CE, Lukacs GL, Kirk KL, Sorscher EJ. Channel Gating Regulation by the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) First Cytosolic Loop. J Biol Chem 2015; 291:1854-1865. [PMID: 26627831 DOI: 10.1074/jbc.m115.704809] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Indexed: 11/06/2022] Open
Abstract
In this study, we present data indicating a robust and specific domain interaction between the cystic fibrosis transmembrane conductance regulator (CFTR) first cytosolic loop (CL1) and nucleotide binding domain 1 (NBD1) that allows ion transport to proceed in a regulated fashion. We used co-precipitation and ELISA to establish the molecular contact and showed that binding kinetics were not altered by the common clinical mutation F508del. Both intrinsic ATPase activity and CFTR channel gating were inhibited severely by CL1 peptide, suggesting that NBD1/CL1 binding is a crucial requirement for ATP hydrolysis and channel function. In addition to cystic fibrosis, CFTR dysregulation has been implicated in the pathogenesis of prevalent diseases such as chronic obstructive pulmonary disease, acquired rhinosinusitis, pancreatitis, and lethal secretory diarrhea (e.g. cholera). On the basis of clinical relevance of the CFTR as a therapeutic target, a cell-free drug screen was established to identify modulators of NBD1/CL1 channel activity independent of F508del CFTR and pharmacologic rescue. Our findings support a targetable mechanism of CFTR regulation in which conformational changes in the NBDs cause reorientation of transmembrane domains via interactions with CL1 and result in channel gating.
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Affiliation(s)
- Annette Ehrhardt
- From the Gregory Fleming James Cystic Fibrosis Research Center and; the Department of Pediatrics, Emory University, Atlanta, Georgia 30322
| | - W Joon Chung
- From the Gregory Fleming James Cystic Fibrosis Research Center and; Departments of Neurobiology
| | - Louise C Pyle
- From the Gregory Fleming James Cystic Fibrosis Research Center and
| | - Wei Wang
- Cellular, Integrative, and Developmental Biology
| | | | - Cory M Mulvihill
- the Hospital for Sick Children Research Institute, Toronto M5G 1X8, Canada
| | | | - Jeong Hong
- From the Gregory Fleming James Cystic Fibrosis Research Center and; Cellular, Integrative, and Developmental Biology
| | - Sadanandan E Velu
- Chemistry, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Hal A Lewis
- Bristol-Myers Squibb, Princeton, New Jersey 08543
| | | | - Steve Aller
- From the Gregory Fleming James Cystic Fibrosis Research Center and; Pharmacology, and
| | - Christine E Bear
- the Hospital for Sick Children Research Institute, Toronto M5G 1X8, Canada,; the Departments of Biochemistry and; Physiology, University of Toronto, Toronto M5G 1X8, Canada, and
| | - Gergely L Lukacs
- the Department of Physiology, McGill University, Montreal H3G 1Y6, Canada
| | - Kevin L Kirk
- From the Gregory Fleming James Cystic Fibrosis Research Center and; Cellular, Integrative, and Developmental Biology
| | - Eric J Sorscher
- the Department of Pediatrics, Emory University, Atlanta, Georgia 30322,.
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32
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Riquelme MA, Burra S, Kar R, Lampe PD, Jiang JX. Mitogen-activated Protein Kinase (MAPK) Activated by Prostaglandin E2 Phosphorylates Connexin 43 and Closes Osteocytic Hemichannels in Response to Continuous Flow Shear Stress. J Biol Chem 2015; 290:28321-28328. [PMID: 26442583 DOI: 10.1074/jbc.m115.683417] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Indexed: 01/04/2023] Open
Abstract
Cx43 hemichannels serve as a portal for the release of prostaglandins, a critical process in mediating biological responses of mechanical loading on bone formation and remodeling. We have previously observed that fluid flow shear stress (FFSS) opens hemichannels; however, sustained FFSS results in hemichannel closure, as continuous opening of hemichannels is detrimental to cell viability and bone remodeling. However, the mechanism that regulates the closure of the hemichannels is unknown. Here, we show that activation of p44/42 ERK upon continuous FFSS leads to Cx43 phosphorylation at Ser(279)-Ser(282), sites known to be phosphorylated sites by p44/42 MAPK. Incubation of osteocytic MLO-Y4 cells with conditioned media (CM) collected after continuous FFSS increased MAPK-dependent phosphorylation of Cx43. CM treatment inhibited hemichannel opening and this inhibition was reversed when cells were pretreated with the MAPK pathway inhibitor. We found that prostaglandin E2 (PGE2) accumulates in the CM in a time-dependent manner. Treatment with PGE2 increased phospho-p44/42 ERK levels and also Cx43 phosphorylation at Ser(279)-Ser(282) sites. Depletion of PGE2 from CM, and pre-treatment with a p44/42 ERK pathway-specific inhibitor, resulted in a complete inhibition of ERK-dependent Cx43 phosphorylation and attenuated the inhibition of hemichannels by CM and PGE2. Consistently, the opening of hemichannels by FFSS was blocked by PGE2 and CM and this blockage was reversed by U0126 and the CM depleted of PGE2. A similar observation was also obtained in isolated primary osteocytes. Together, results from this study suggest that extracellular PGE2 accumulated after continuous FFSS is responsible for activation of p44/42 ERK signaling and subsequently, direct Cx43 phosphorylation by activated ERK leads to hemichannel closure.
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Affiliation(s)
- Manuel A Riquelme
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900
| | - Sirisha Burra
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900
| | - Rekha Kar
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900
| | - Paul D Lampe
- Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109
| | - Jean X Jiang
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900.
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33
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Bagriantsev SN, Chatelain FC, Clark KA, Alagem N, Reuveny E, Minor DL. Tethered protein display identifies a novel Kir3.2 (GIRK2) regulator from protein scaffold libraries. ACS Chem Neurosci 2014; 5:812-22. [PMID: 25028803 PMCID: PMC4176385 DOI: 10.1021/cn5000698] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
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Use of randomized peptide libraries
to evolve molecules with new
functions provides a means for developing novel regulators of protein
activity. Despite the demonstrated power of such approaches for soluble
targets, application of this strategy to membrane systems, such as
ion channels, remains challenging. Here, we have combined libraries
of a tethered protein scaffold with functional selection in yeast
to develop a novel activator of the G-protein-coupled mammalian inwardly
rectifying potassium channel Kir3.2 (GIRK2). We show that the novel
regulator, denoted N5, increases Kir3.2 (GIRK2) basal activity by
inhibiting clearance of the channel from the cellular surface rather
than affecting the core biophysical properties of the channel. These
studies establish the tethered protein display strategy as a means
to create new channel modulators and highlight the power of approaches
that couple randomized libraries with direct selections for functional
effects. Our results further underscore the possibility for the development
of modulators that influence channel function by altering cell surface
expression densities rather than by direct action on channel biophysical
parameters. The use of tethered library selection strategies coupled
with functional selection bypasses the need for a purified target
and is likely to be applicable to a range of membrane protein systems.
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Affiliation(s)
| | | | | | - Noga Alagem
- Department
of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eitan Reuveny
- Department
of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Daniel L. Minor
- Physical
Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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34
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Stary A, Kudrnac M, Beyl S, Hohaus A, Timin EN, Wolschann P, Guy HR, Hering S. Molecular dynamics and mutational analysis of a channelopathy mutation in the IIS6 helix of Ca V 1.2. Channels (Austin) 2008; 2:216-23. [PMID: 18836301 PMCID: PMC3196984 DOI: 10.4161/chan.2.3.6160] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
A channelopathy mutation in segment IIS6 of Ca(V)1.4 (I745T) has been shown to cause severe visual impairment by shifting the activation and inactivation curves to more hyperpolarized voltages and slowing activation and inactivation kinetics. A similar gating phenotype is caused by the corresponding mutation, I781T, in Ca(V)1.2 (midpoint of activation curve (V(0.5)) shifted to -37.7 +/- 1.2 mV). We show here that wild-type gating can partially be restored by a helix stabilizing rescue mutation N785A. V(0.5) of I781T/N785A (V(0.5) = -21.5 +/- 0.6 mV) was shifted back towards wild-type (V(0.5) = -9.9 +/- 1.1 mV). Homology models developed in our group (see accompanying article for details) were used to perform Molecular Dynamics-simulations (MD-simulations) on wild-type and mutant channels. Systematic changes in segment IIIS6 (M1187-F1194) and in helix IIS6 (N785-L786) were studied. The simulated structural changes in S6 segments of I781T/N785A were less pronounced than in I781T. A delicate balance between helix flexibility and stability enabling the formation of hydrophobic seals at the inner channel mouth appears to be important for wild-type Ca(V)1.2 gating. Our study illustrates that effects of mutations in the lower part of IIS6 may not be localized to the residue or even segment being mutated, but may affect conformations of interacting segments.
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Affiliation(s)
- Anna Stary
- Institute for Theoretical Chemistry; University of Vienna; Vienna, Austria
| | - Michaela Kudrnac
- Institute of Pharmacology and Toxicology; University of Vienna; Vienna, Austria
| | - Stanislav Beyl
- Institute of Pharmacology and Toxicology; University of Vienna; Vienna, Austria
| | - Annette Hohaus
- Institute of Pharmacology and Toxicology; University of Vienna; Vienna, Austria
| | - Eugen N. Timin
- Institute of Pharmacology and Toxicology; University of Vienna; Vienna, Austria
| | - Peter Wolschann
- Institute for Theoretical Chemistry; University of Vienna; Vienna, Austria
| | - H. Robert Guy
- Laboratory of Cell Biology; National Cancer Institute; National Institutes of Health; Bethesda, Maryland, USA
| | - Steffen Hering
- Institute of Pharmacology and Toxicology; University of Vienna; Vienna, Austria
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35
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Ren D, Xu H, Eberl DF, Chopra M, Hall LM. A mutation affecting dihydropyridine-sensitive current levels and activation kinetics in Drosophila muscle and mammalian heart calcium channels. J Neurosci 1998; 18:2335-41. [PMID: 9502794 PMCID: PMC6793086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/1997] [Revised: 01/06/1998] [Accepted: 01/09/1998] [Indexed: 02/06/2023] Open
Abstract
The Dmca1D gene encodes a Drosophila calcium channel alpha1 subunit. We describe the first functional characterization of a mutation in this gene. This alpha1 subunit mediates the dihydropyridine-sensitive calcium channel current in larval muscle but does not contribute to the amiloride-sensitive current in that tissue. A mutation, which changes a highly conserved Cys to Tyr in transmembrane domain IS1, identifies a residue important for channel function not only in Drosophila muscle but also in mammalian cardiac channels. In both cases, mutations in this Cys residue slow channel activation and reduce expressed currents. Amino acid substitutions at this Cys position in the cardiac alpha1 subunit show that the size of the side chain, rather than its ability to form disulfide bonds, affects channel activation.
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Affiliation(s)
- D Ren
- Department of Biochemical Pharmacology, State University of New York at Buffalo, Buffalo, New York 14260-1200, USA
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