Induction of smooth muscle alpha-actin in vascular smooth muscle cells by arginine vasopressin is mediated by c-Jun amino-terminal kinases and p38 mitogen-activated protein kinase

Exposure of vascular smooth muscle cells to arginine vasopressin (AVP) incr eases smooth muscle alpha-actin (SM-alpha-actin) expression through activat ion of the SM- alpha-actin promoter. The goal of this study was to determin e the role of the mitogen-activated protein kinase (MAP kinase) family in r egulation of SM-alpha-actin expression. AVP activated all three MAP kinase family members: ERKs, JNKs, and p38 MAP kinase, Inhibition of JNKs or p38 d ecreased AVP-stimulated SM-alpha-actin promoter activity, whereas inhibitio n of ERKs had no effect. A 150-base pair region of the promoter containing two CArG boxes was sufficient to mediate regulation by vasoconstrictors, Mu tations in either CArG box decreased AVP-stimulated promoter activity. Elec trophoretic mobility shift assays using oligonucleotides corresponding to e ither CArG box resulted in a complex of similar mobility whose intensity wa s increased by AVP, Antibodies against serum response factor (SRF) complete ly supershifted this complex, indicating that SRF binds to both CArG boxes. Overexpression of SRF increased basal promoter activity, but activity was still stimulated by AVP, AVP stimulation rapidly increased SRF phosphorylat ion, These data indicate that both JNKs and p38 participate in regulation o f SM- alpha-actin expression. SRF, which binds to two critical CArG boxes i n the promoter, represents a potential target of these kinases.