title: Angiotensin II reduces the surface abundance of KV1.5 channels in arterial myocytes to stimulate vasoconstriction.
abstract: Several different voltage-dependent K+(KV) channel isoforms are expressed in arterial smooth muscle cells (myocytes). Vasoconstrictors inhibit KVcurrents, but the isoform selectivity and mechanisms involved are unclear. We show that angiotensin II (Ang II), a vasoconstrictor, stimulates degradation of KV1.5, but not KV2.1, 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 KV1.5 channels reduces whole-cell KV1.5 currents and attenuates KV1.5 function in pressurized arteries. We describe a mechanism by which Ang II stimulates protein kinase C-dependent KV1.5 channel degradation, reducing the abundance of functional channels at the myocyte surface.
  
  
  
  Smooth muscle cells (myocytes) of resistance-size arteries express several different voltage-dependent K+(KV) channels, including KV1.5 and KV2.1, which regulate contractility. Myocyte KVcurrents are inhibited by vasoconstrictors, including angiotensin II (Ang II), but the mechanisms involved are unclear. Here, we tested the hypothesis that Ang II inhibits KVcurrents by reducing the plasma membrane abundance of KVchannels in myocytes. Angiotensin II (applied for 2 h) reduced surface and total KV1.5 protein in rat mesenteric arteries. In contrast, Ang II did not alter total or surface KV2.1, or KV1.5 or KV2.1 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 KV1.5. Immunofluorescence also suggested that Ang II reduced surface KV1.5 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 KVcurrents and currents inhibited by Psora-4, a KV1.5 channel blocker. Angiotensin II also reduced vasoconstriction stimulated by Psora-4 or 4-aminopyridine, another KVchannel inhibitor. These data indicate that Ang II activates protein kinase C, which stimulates KV1.5 channel degradation, leading to a decrease in surface KV1.5, a reduction in whole-cell KV1.5 currents and a loss of functional KV1.5 channels in myocytes of pressurized arteries.
authors.affiliation: University of Tennessee Health Science Center, Memphis, TN, 38163, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Kidd
authors.affiliation: University of Tennessee Health Science Center, Memphis, TN, 38163, USA.
authors.forename: Simon
authors.initials: S
authors.lastname: Bulley
authors.affiliation: University of Tennessee Health Science Center, Memphis, TN, 38163, USA.
authors.forename: Jonathan H
authors.identifier: 0000-0003-1505-3335
authors.initials: JH
authors.lastname: Jaggar
mesh_terms: D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D051666:Kv1.5 Potassium Channel / Q000502:physiology*; D008297:Male; D008638:Mesenteric Arteries / Q000166:cytology / Q000502:physiology*; D032342:Muscle Cells / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D051669:Shab Potassium Channels / Q000502:physiology; D014661:Vasoconstriction
chemical_list: C496991:Kcnb1 protein, rat; D051666:Kv1.5 Potassium Channel; D051669:Shab Potassium Channels; D000804:Angiotensin II
keywords: KV channel; angiotensin II; smooth muscle; vasoconstriction