Overexpression of G protein-coupled receptor kinase-2 in smooth muscle cells attenuates mitogenic signaling via G protein-coupled and platelet-derived growth factor receptors

Background-Neointimal hyperplasia involves activation of smooth muscle cell s (SMCs) by several G protein-coupled receptor (GPCR) agonists, including e ndothelin-1, angiotensin II, thrombin, and thromboxane A(2). Signaling of m any GPCRs is diminished by GPCR kinase-2 (GRK2). We therefore tested whethe r overexpression of GRK2 in SMCs could diminish mitogenic signaling elicite d by agonists implicated in the pathogenesis of neointimal hyperplasia. Methods and Results-Overexpression of GRK2 was achieved in primary rabbit a ortic SMCs with a recombinant adenovirus. Control SMCs were infected with a n empty vector adenovirus. Inositol phosphate responses to endothelin-1, an giotensin II, thrombin agonist peptide, and platelet-derived growth factor (PDGF) were attenuated by 37% to 72% in GRK2-overexpressing cells (P<0.01), but the response to the thromboxane A(2) analogue U46619 was unaffected. G RK2 also inhibited SMC [H-3]thymidine incorporation stimulated not only by these agonists (by 30% to 60%, P<0.01) but also by 10% FBS (by 35%, P<0.05) , However, GRK2 overexpression had no effect on epidermal growth factor-ind uced [H-3]thymidine incorporation. Agonist-induced tyrosine phosphorylation of the PDGF-beta receptor, but not the epidermal growth factor receptor, w as reduced in GRK2-overexpressing SMCs. GRK2 overexpression also reduced SM C proliferation in response to endothelin-l, PDGF, and 10% FBS by 62%, 51%, and 29%, respectively (P<0.01), without any effect on SMC apoptosis. Conclusions-GRK2 overexpression diminishes SMC mitogenic signaling and prol iferation stimulated by PDGF or agonists for several GPCRs. Gene transfer o f GRK2 may therefore be therapeutically useful for neointimal hyperplasia.