S1928 Phosphorylation Tunes Vascular L‐type Channel Ca V 1.2 and Arterial Function during Angiotensin II Signaling and Hypertension

Abstract

The L-type channel CaV1.2 is essential for vascular smooth muscle contraction and arterial tone. Increased vascular CaV1.2 expression and function are related to high smooth muscle contractility and enhanced arterial tone during hypertension, which is characterized by enhanced angiotensin II (angII) signaling. Several pathways have been proposed to account for increased CaV1.2 expression during hypertension, including increased CaV1.2 trafficking. However, mechanisms underlying enhanced CaV1.2 function during angII signaling and hypertension remain a subject of intense investigation. In this study, we hypothesize that CaV1.2 phosphorylation at the S1928 site is a key event that mediates increased channel activity and vascular reactivity during angII signaling and hypertension. Initial experiments found increased S1928 phosphorylation in angII-treated wild type arterial lysates. This was associated with elevated vascular smooth muscle whole-cell L-type channel currents, global intracellular Ca2+, and contraction. Similarly, ex vivo and in vivo experiments in mesenteric arteries reveal an increased arterial tone and decreased mesenteric blood flow from wild type mice. Moreover, smooth muscle cells treated with angII showed a redistribution of CaV1.2 into larger clusters. These functional changes were prevented or significantly ameliorated in arteries or cells from a knockin mouse expressing a mutant CaV1.2 in which serine was replaced with alanine at position 1928 (S1928A mouse) and by protein kinase C inhibition. In angII-induced hypertensive mice, increased CaV1.2 clusters size and channel activity, enhanced arterial tone, and mean arterial pressure in wild type mice were prevented or significantly reduce in S1928A mice. Altogether, these results suggest a key role for phosphorylation of CaV1.2 at S1928 in regulating CaV1.2 distribution, activity, and vascular function during angII signaling and hypertension. Phosphorylation of this single vascular CaV1.2 amino acid could be an essential regulatory mechanism that could be exploited for therapeutic intervention.