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Thompson E, Eldstrom J, Westhoff M, McAfee D, Balse E, Fedida D. cAMP-dependent regulation of IKs single-channel kinetics. J Gen Physiol 2017; 149:781-798. [PMID: 28687606 PMCID: PMC5560775 DOI: 10.1085/jgp.201611734] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 06/20/2017] [Indexed: 02/06/2023] Open
Abstract
The delayed potassium rectifier current, IKs , is composed of KCNQ1 and KCNE1 subunits and plays an important role in cardiac action potential repolarization. During β-adrenergic stimulation, 3'-5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) phosphorylates KCNQ1, producing an increase in IKs current and a shortening of the action potential. Here, using cell-attached macropatches and single-channel recordings, we investigate the microscopic mechanisms underlying the cAMP-dependent increase in IKs current. A membrane-permeable cAMP analog, 8-(4-chlorophenylthio)-cAMP (8-CPT-cAMP), causes a marked leftward shift of the conductance-voltage relation in macropatches, with or without an increase in current size. Single channels exhibit fewer silent sweeps, reduced first latency to opening (control, 1.61 ± 0.13 s; cAMP, 1.06 ± 0.11 s), and increased higher-subconductance-level occupancy in the presence of cAMP. The E160R/R237E and S209F KCNQ1 mutants, which show fixed and enhanced voltage sensor activation, respectively, largely abolish the effect of cAMP. The phosphomimetic KCNQ1 mutations, S27D and S27D/S92D, are much less and not at all responsive, respectively, to the effects of PKA phosphorylation (first latency of S27D + KCNE1 channels: control, 1.81 ± 0.1 s; 8-CPT-cAMP, 1.44 ± 0.1 s, P < 0.05; latency of S27D/S92D + KCNE1: control, 1.62 ± 0.1 s; cAMP, 1.43 ± 0.1 s, nonsignificant). Using total internal reflection fluorescence microscopy, we find no overall increase in surface expression of the channel during exposure to 8-CPT-cAMP. Our data suggest that the cAMP-dependent increase in IKs current is caused by an increase in the likelihood of channel opening, combined with faster openings and greater occupancy of higher subconductance levels, and is mediated by enhanced voltage sensor activation.
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Affiliation(s)
- Emely Thompson
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Donald McAfee
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - Elise Balse
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMR_S 1166, Unité de recherche sur les maladies cardiovasculaires, le métabolisme et la nutrition, Faculté de Médecine, Site Pitié-Salpêtrière, Paris, France
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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Berkowicz SR, Giousoh A, Bird PI. Neurodevelopmental MACPFs: The vertebrate astrotactins and BRINPs. Semin Cell Dev Biol 2017; 72:171-181. [PMID: 28506896 DOI: 10.1016/j.semcdb.2017.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 04/27/2017] [Accepted: 05/11/2017] [Indexed: 02/06/2023]
Abstract
Astrotactins (ASTNs) and Bone morphogenetic protein/retinoic acid inducible neural-specific proteins (BRINPs) are two groups of Membrane Attack Complex/Perforin (MACPF) superfamily proteins that show overlapping expression in the developing and mature vertebrate nervous system. ASTN(1-2) and BRINP(1-3) genes are found at conserved loci in humans that have been implicated in neurodevelopmental disorders (NDDs). Here we review the tissue distribution and cellular localization of these proteins, and discuss recent studies that provide insight into their structure and interactions. We highlight the genetic relationships and co-expression of Brinps and Astns; and review recent knock-out mouse phenotypes that indicate a possible overlap in protein function between ASTNs and BRINPs.
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Affiliation(s)
- Susan R Berkowicz
- Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, 3800, Australia.
| | - Aminah Giousoh
- Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, 3800, Australia
| | - Phillip I Bird
- Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, 3800, Australia
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