Protein kinase C δ activated adhesion regulates vascular smooth muscle cell migration

Background. Vascular smooth muscle cell (VSMC) migration, fundamental in the pathophysiology of atherogenesis and restenosis, is a coordinated process governed by the formation and disassembly of focal adhesions. Previous studies have demonstrated that VSMC migration is regulated via a signaling network involving protein kinase C delta (PKC delta). In these studies, we test the hypothesis that PKC delta regulates VSMC migration through modulation of cell adhesion. Materials and methods. Using primary VSMCs isolated from PKC delta wild type (+/+) and knock-out (-/-) mice, the effects of PKC delta on VSMC migration and adhesion were assessed by chemotaxis and cell adhesion. Results. In evaluating cell migration, we found a decrease in platelet-derived growth factor-BB (PDGF-BB; 5 ng/mL x 6 h) stimulated migration of PKC delta-/-VSMCs as compared to PKC delta+/+VSMCs, by 59.4 +/- 5.9% (P < 0.01). A similar reduction in migration of PKC delta-/-VSMCs (66.5 +/- 5.7%, P < 0.01) was also observed on collagen-coated (COL) membranes. Next, we examined cell attachment, a critical step of migration. PKC delta-/-VSMCs exhibited significantly reduced adherence by 50.3 +/- 1.8% (P < 0.01). A similar defect of PKC delta-/-VSMCs was also observed on the COL surface, 30.7 +/- 2.3% (P < 0.01). Interestingly, PDGF-BB did not stimulate attachment of VSMCs of either genotype. Consistent with these results, Rottlerin (2 mu M), a selective inhibitor of PKC delta, blocked migration and attachment of VSMCs by 56.8 +/- 3.4% (P < 0.01) and 37.7 +/- 1.9% (P < 0.01), respectively. Conclusions. Taken together, our data indicate that PKC delta activation is necessary for VSMC adhesion, which could, at least in part, contribute to the regulatory function of this kinase in cell migration thus pathogenesis of vascular lesions. (C) 2007 Elsevier Inc. All rights reserved.