Kv7.5 Potassium Channel Subunits Are the Primary Targets for PKA-Dependent Enhancement of Vascular Smooth Muscle Kv7 Currents Journal Article

Authors: Mani, B. K.; Robakowski, C.; Brueggemann, L. I.; Cribbs, L. L.; Tripathi, A; Majetschak, M; Byron, K. L.
Article Title: Kv7.5 Potassium Channel Subunits Are the Primary Targets for PKA-Dependent Enhancement of Vascular Smooth Muscle Kv7 Currents
Abstract: Kv7 (KCNQ) channels, formed as homo- or heterotetramers of Kv7.4 and Kv7.5 alpha-subunits, are important regulators of vascular smooth muscle cell (VSMC) membrane voltage. Recent studies demonstrate that direct pharmacological modulation of VSMC Kv7 channel activity can influence blood vessel contractility and diameter. However, the physiologic regulation of Kv7 channel activity is still poorly understood. Here, we study the effect of cAMP/protein kinase A (PKA) activation on whole cell K(+) currents through endogenous Kv7.5 channels in A7r5 rat aortic smooth muscle cells or through Kv7.4/Kv7.5 heteromeric channels natively expressed in rat mesenteric artery smooth muscle cells. The contributions of specific alpha-subunits are further dissected using exogenously expressed human Kv7.4 and Kv7.5 homo- or heterotetrameric channels in A7r5 cells. Stimulation of Galphas-coupled beta-adrenergic receptors with isoproterenol induced PKA-dependent activation of endogenous Kv7.5 currents in A7r5 cells. The receptor-mediated enhancement of Kv7.5 currents was mimicked by pharmacological agents that increase [cAMP] (forskolin, rolipram, 3-isobutyl-1-methylxanthine, and papaverine) or mimic cAMP (8-bromo-cAMP); the 2- to 4-fold PKA-dependent enhancement of currents was also observed with exogenously expressed Kv7.5 channels. In contrast, exogenously-expressed heterotetrameric Kv7.4/7.5 channels in A7r5 cells or native mesenteric artery smooth muscle Kv7.4/7.5 channels were only modestly enhanced, and homo-tetrameric Kv7.4 channels were insensitive to this regulatory pathway. Correspondingly, proximity ligation assays indicated that isoproterenol induced PKA-dependent phosphorylation of exogenously expressed Kv7.5 channel subunits, but not of Kv7.4 subunits. These results suggest that signal transduction-mediated responsiveness of vascular smooth muscle Kv7 channel subunits to cAMP/PKA activation follows the order of Kv7.5 >> Kv7.4/Kv7.5 > Kv7.4.
Journal Title: Molecular pharmacology
Volume: 89
Issue: 3
ISSN: 1521-0111; 0026-895X
Publisher: by The American Society for Pharmacology and Experimental Therapeutics  
Journal Place: United States
Date Published: 2016
Start Page: 323
End Page: 334
Language: eng
Notes: LR: 20160309; CI: Copyright (c) 2016; JID: 0035623; OID: NLM: PMC4767407 [Available on 03/01/17]; PMCR: 2017/03/01 00:00; 2015/09/11 [received]; 2015/12/18 [accepted]; 2015/12/23 [aheadofprint]; ppublish