Angiotensin II reduces the surface abundance of K V 1.5 channels in arterial myocytes to stimulate vasoconstriction

Key points Several different voltage‐dependent K + (K V ) channel isoforms are expressed in arterial smooth muscle cells (myocytes). Vasoconstrictors inhibit K V currents, but the isoform selectivity and mechanisms involved are unclear. We show that angiotensin II (Ang II), a vasoconstrictor, stimulates degradation of K V 1.5, but not K V 2.1, channels through a protein kinase C‐ and lysosome‐dependent mechanism, reducing abundance at the surface of mesenteric artery myocytes. The Ang II‐induced decrease in cell surface K V 1.5 channels reduces whole‐cell K V 1.5 currents and attenuates K V 1.5 function in pressurized arteries. We describe a mechanism by which Ang II stimulates protein kinase C‐dependent K V 1.5 channel degradation, reducing the abundance of functional channels at the myocyte surface.Abstract Smooth muscle cells (myocytes) of resistance‐size arteries express several different voltage‐dependent K + (K V ) channels, including K V 1.5 and K V 2.1, which regulate contractility. Myocyte K V currents are inhibited by vasoconstrictors, including angiotensin II (Ang II), but the mechanisms involved are unclear. Here, we tested the hypothesis that Ang II inhibits K V currents by reducing the plasma membrane abundance of K V channels in myocytes. Angiotensin II (applied for 2 h) reduced surface and total K V 1.5 protein in rat mesenteric arteries. In contrast, Ang II did not alter total or surface K V 2.1, or K V 1.5 or K V 2.1 cellular distribution, measured as the percentage of total protein at the surface. Bisindolylmaleimide (BIM; a protein kinase C blocker), a protein kinase C inhibitory peptide or bafilomycin A (a lysosomal degradation inhibitor) each blocked the Ang II‐induced decrease in total and surface K V 1.5. Immunofluorescence also suggested that Ang II reduced surface K V 1.5 protein in isolated myocytes; an effect inhibited by BIM. Arteries were exposed to Ang II or Ang II plus BIM (for 2 h), after which these agents were removed and contractility measurements performed or myocytes isolated for patch‐clamp electrophysiology. Angiotensin II reduced both whole‐cell K V currents and currents inhibited by Psora‐4, a K V 1.5 channel blocker. Angiotensin II also reduced vasoconstriction stimulated by Psora‐4 or 4‐aminopyridine, another K V channel inhibitor. These data indicate that Ang II activates protein kinase C, which stimulates K V 1.5 channel degradation, leading to a decrease in surface K V 1.5, a reduction in whole‐cell K V 1.5 currents and a loss of functional K V 1.5 channels in myocytes of pressurized arteries.