Gα _12/13 induction of CYR61 in association with arteriosclerotic intimal hyperplasia: Effect of sphingosine-1-phosphate

Objective- Gα _12/13 play a role in oncogenic transformation and tumor growth. Cysteine-rich protein 61 (CYR61) is a growth-factor-inducible angiogenic factor. In view of potential overlapping functions between Gα _12/13 and CYR61, this study investigated the role of these G proteins in CYR61 induction in association with hyperplastic vascular abnormality. Methods and Results- Overexpression of activated Gα12 or Gα13 induced CYR61 expression in vascular smooth muscle cells (VSMCs). Gene knockdown and knockout experiments revealed that sphingosine-1-phosphate (S1P) treatment induced CYR61 via Gα12/13. JunD/activator protein-1 (AP-1) was identified as a transcription factor required for CYR61 transactivation by S1P. Deficiencies in Gα12/13 abrogated AP-1 activation and AP-1-mediated CYR61 induction. c-Jun N-terminal kinase was responsible for CYR61 induction. Moreover, deficiencies of Gα _12/13 abolished c-Jun N-terminal kinase-dependent CYR61 induction by S1P. N-acetyl-l-cysteine or NADPH oxidase inhibitor treatment reversed CYR61 induction by S1P, indicating that reactive oxygen species are responsible for this process. The levels of Gα _12/13 were increased within thickened intimas and medias in wire-injured mouse femoral arteries, which was accompanied by simultaneous CYR61 induction. Moreover, Gα _12/13 and CYR61 were costained in the arteriosclerotic lesions immediately adjacent to human tumor tissues. Conclusion- Gα _12/13 regulate AP-1-dependent CYR61 induction in VSMCs and promote VSMC migration, and they are upregulated with CYR61 in arteriosclerotic lesions.