PDGF-induced migration of synthetic vascular smooth muscle cells through c-Src-activated L-type Ca²⁺ channels with full-length Ca_V1.2 C-terminus

Abstract

Platelet-derived growth factor (PDGF) potently induces migration of vascular smooth muscle cells (VSMC); however, molecular mechanism underlying this phenomenon remains unclear. The migration of rat aorta-derived synthetic VSMCs, A7r5, in response to PDGF was potently inhibited by a Ca_V1.2 channel inhibitor, nifedipine, and a Src family tyrosine kinase inhibitor, bosutinib, in a less-than-additive manner. In contractile VSMCs, the C-terminus of Ca_V1.2 is proteolytically cleaved into proximal and distal C-termini (PCT and DCT, respectively). Clipped DCT is noncovalently reassociated with PCT to autoinhibit the channel activity. Conversely, in synthetic A7r5 cells, full-length Ca_V1.2 (Ca_V1.2FL) is expressed much more abundantly than truncated Ca_V1.2. In a heterologous expression system, c-Src was bound to, phosphorylated Tyr1709 and Tyr1758 in PCT and activated Ca_V1.2 channels composed of Ca_V1.2FL significantly more efficiently than Ca_V1.2 (Ca_V1.2delta1763) or Ca_V1.2delta1763 plus clipped DCT. Therefore, in atherosclerotic lesions, phenotypic switching of VSMCs may facilitate pro-migratory effects of PDGF on VSMCs by suppressing posttranslational Ca_V1.2 modifications.