Vasodilator-mediated activation of GPCRs, such as β-adrenoceptors, can lead to Gα s-mediated adenylyl cyclase (AC) activation, cAMP production and activation of PKA, leading to hyperpolarization and vasodilation. Moreover, K v channel activity recorded in inside-out patches of mesenteric artery smooth muscle cells is increased following application of the catalytic subunit of PKA. In addition to the PKC pathway, inhibition of cyclic AMP-dependent protein kinase (PKA) has also been shown to be a component of the attenuation of K ATP and K v current of mesenteric smooth muscle by Ang-II, suggesting a certain level of tonic activation of K + channels by PKA. We and others have shown that the vasoconstrictors angiotensin II (Ang-II) and endothelin-1 (ET-1) inhibit both K ATP and K v currents of rat mesenteric artery smooth muscle (MASMC), through activation of PKC. K + channel modulation via intracellular signalling pathways is well established. Several types of K + channels are expressed in arterial smooth muscle, including ATP-dependent K + (K ATP) channels, inward-rectifier K + channels, large-conductance, Ca 2+-activated K + (BK Ca) channels and voltage-gated K + (K v) channels, and all are involved in regulating the membrane potential. Activation of K + channels results in hyperpolarization, a decrease in i and vasodilation, while their inhibition leads to depolarization, an increase in i and vasoconstriction. K + channels play an important role in regulating the membrane potential of vascular smooth muscle cells. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedĭata Availability: All relevant data are within the paper.įunding: This study was funded by a British Heart Foundation grant (RG06/008/22062) to JMW, RAJC and NWD. Received: AugAccepted: JanuPublished: March 20, 2015Ĭopyright: © 2015 Brignell et al. Shapiro, University of Texas Health Science Center, UNITED STATES These findings highlight a novel, caveolae-dependent, tonic modulatory role of PKA on K v channels providing new insight into mechanisms and the potential for pharmacological manipulation of vascular tone.Ĭitation: Brignell JL, Perry MD, Nelson CP, Willets JM, Challiss RAJ, Davies NW (2015) Steady-State Modulation of Voltage-Gated K + Channels in Rat Arterial Smooth Muscle by Cyclic AMP-Dependent Protein Kinase and Protein Phosphatase 2B. Pre-treatment of the cells with methyl-β-cyclodextrin to deplete cellular cholesterol, or adding caveolin-scaffolding domain peptide to the pipette solution to disrupt caveolae-dependent signalling each attenuated PKA-mediated modulation of the K v current. Finally, we demonstrate that tonic PKA-mediated modulation of K v requires intact caveolae. PKA-dependent inhibition of K v by KT5720 can be abrogated by pre-treatment with the PP2B inhibitor cyclosporin A, or inclusion of a PP2B auto-inhibitory peptide in the pipette solution. We also show that this modulation of K v by PKA can be reversed by protein phosphatase 2B/calcineurin (PP2B). Tonic PKA-mediated activation of K v appears maximal as application of isoprenaline (a β-adrenoceptor agonist) or dibutyryl-cAMP failed to enhance K v currents. Application of PKA inhibitors, KT5720 or H89, caused a significant inhibition of K v currents. Whole-cell recording was used to assess the effect of manipulating PKA signalling on K v and ATP-dependent K+ channels of rat mesenteric artery smooth muscle cells. Here, we demonstrate that K v channel activity is maintained by tonic activity of PKA. Previous work indicates that K v channels can be modulated by receptor-driven alterations of cyclic AMP-dependent protein kinase (PKA) activity. Voltage-gated potassium channels (K v) are important regulators of membrane potential in vascular smooth muscle cells, which is integral to controlling intracellular Ca2+ concentration and regulating vascular tone.
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