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  • Title: ATF-1 mediates protease-activated receptor-1 but not receptor tyrosine kinase-induced DNA synthesis in vascular smooth muscle cells.
    Author: Ghosh SK, Gadiparthi L, Zeng ZZ, Bhanoori M, Tellez C, Bar-Eli M, Rao GN.
    Journal: J Biol Chem; 2002 Jun 14; 277(24):21325-31. PubMed ID: 11925444.
    Abstract:
    Previously we have demonstrated that activation of p38 mitogen-activated protein kinase (MAPK) and induction of DNA synthesis in response to receptor tyrosine kinase (RTK) and G protein-coupled receptor (GPCR) agonists require NADH/NADPH-like oxidase activity in vascular smooth muscle cells (VSMC). Here we tested the role of p38 MAPK in RTK and GPCR agonist-induced DNA synthesis in VSMC. Platelet-derived growth factor (PDGF)-BB and thrombin (RTK and GPCR agonists, respectively) activated p38 MAPK in a time-dependent manner in VSMC. Inhibition of p38 MAPK led to a 50% decrease in the DNA synthesis induced by thrombin but not PDGF-BB. ATF-1 was found to be the predominant member of the cyclic AMP response element (CRE)-DNA complex formed in VSMC in response to PDGF-BB and thrombin, and both agonists induced its phosphorylation. Regardless of this, inhibition of p38 MAPK reduced only thrombin- but not PDGF-BB-induced ATF-1 phosphorylation. Similarly, inhibition of p38 MAPK caused a 50% decrease in thrombin- but not PDGF-BB-induced CRE promoter-dependent transcription. Ectopic expression of an inhibitory anti-ATF-1 single-chain antibody fragment, ScFv, significantly interfered with DNA synthesis induced by thrombin but not PDGF-BB. Together, these results suggest the following conclusions. 1) Both RTK and GPCR agonists activate p38 MAPK and induce CRE promoter-dependent transcription; 2) both RTK and GPCR agonists induce ATF-1 phosphorylation, and ATF-1 is a predominant member in the CRE-DNA complexes formed in response to these agents; and 3) p38 MAPK-dependent ATF-1 phosphorylation and CRE promoter-mediated transcription are associated with GPCR agonist-induced VSMC growth.
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