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Chen H, Chatelain FC, Lesage F. Altered and dynamic ion selectivity of K+ channels in cell development and excitability. Trends Pharmacol Sci 2014; 35:461-9. [PMID: 25023607 DOI: 10.1016/j.tips.2014.06.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 06/11/2014] [Accepted: 06/12/2014] [Indexed: 12/21/2022]
Abstract
K(+) channels play a key role in regulating cellular excitability. It was thought that the strong K(+) selectivity of these channels was static, only altered by mutations in their selectivity filter, which can cause severe genetic disorders. Recent studies demonstrate that selectivity of K(+) channels can also exhibit dynamic changes. Under acidic conditions or in low extracellular K(+) concentrations, the two-pore domain K(+) channel (K2P) TWIK1 becomes permeable to Na(+), shifting from an inhibitory role to an excitatory role. This phenomenon is responsible for the paradoxical depolarization of human cardiomyocytes in pathological hypokalemia, and therefore may contribute to cardiac arrhythmias. In other cell types, TWIK1 produces depolarizing leak currents under physiological conditions. Dynamic ion selectivity also occurs in other K2P channels. Here we review evidence that dynamic selectivity of K2P channels constitutes a new regulatory mechanism of cellular excitability, whose significance is only now becoming appreciated.
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Amer MS, McKeown L, Tumova S, Liu R, Seymour VAL, Wilson LA, Naylor J, Greenhalgh K, Hou B, Majeed Y, Turner P, Sedo A, O'Regan DJ, Li J, Bon RS, Porter KE, Beech DJ. Inhibition of endothelial cell Ca²⁺ entry and transient receptor potential channels by Sigma-1 receptor ligands. Br J Pharmacol 2013; 168:1445-55. [PMID: 23121507 PMCID: PMC3596649 DOI: 10.1111/bph.12041] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [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: 09/27/2012] [Accepted: 10/10/2012] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE The Sigma-1 receptor (Sig1R) impacts on calcium ion signalling and has a plethora of ligands. This study investigated Sig1R and its ligands in relation to endogenous calcium events of endothelial cells and transient receptor potential (TRP) channels. EXPERIMENTAL APPROACH Intracellular calcium and patch clamp measurements were made from human saphenous vein endothelial cells and HEK 293 cells expressing exogenous human TRPC5, TRPM2 or TRPM3. Sig1R ligands were applied and short interfering RNA was used to deplete Sig1R. TRP channels tagged with fluorescent proteins were used for subcellular localization studies. KEY RESULTS In endothelial cells, 10-100 μM of the Sig1R antagonist BD1063 inhibited sustained but not transient calcium responses evoked by histamine. The Sig1R agonist 4-IBP and related antagonist BD1047 were also inhibitory. The Sig1R agonist SKF10047 had no effect. Sustained calcium entry evoked by VEGF or hydrogen peroxide was also inhibited by BD1063, BD1047 or 4-IBP, but not SKF10047. 4-IBP, BD1047 and BD1063 inhibited TRPC5 or TRPM3, but not TRPM2. Inhibitory effects of BD1047 were rapid in onset and readily reversed on washout. SKF10047 inhibited TRPC5 but not TRPM3 or TRPM2. Depletion of Sig1R did not prevent the inhibitory actions of BD1063 or BD1047 and Sig1R did not co-localize with TRPC5 or TRPM3. CONCLUSIONS AND IMPLICATIONS The data suggest that two types of Sig1R ligand (BD1047/BD1063 and 4-IBP) are inhibitors of receptor- or chemically activated calcium entry channels, acting relatively directly and independently of the Sig1R. Chemical foundations for TRP channel inhibitors are suggested.
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Affiliation(s)
- Mohamed S Amer
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
- Clinical Physiology Department, Faculty of Medicine, Menoufiya UniversityMenoufiya, Egypt
| | - Lynn McKeown
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Sarka Tumova
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Ruifeng Liu
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Victoria AL Seymour
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Lesley A Wilson
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Jacqueline Naylor
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Katriona Greenhalgh
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Bing Hou
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Yasser Majeed
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Paul Turner
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Alicia Sedo
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - David J O'Regan
- Department of Cardiac Surgery, Leeds General InfirmaryLeeds, UK
| | - Jing Li
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - Robin S Bon
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- School of Chemistry, University of LeedsLeeds, UK
| | - Karen E Porter
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Medicine and Health, University of LeedsLeeds, UK
| | - David J Beech
- Multidisciplinary Cardiovascular Research Centre, University of LeedsLeeds, UK
- Faculty of Biological Sciences, University of LeedsLeeds, UK
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