The
platelet-derived growth factor (PDGF) family of
ligands (composed of A-, B-, C-, and D-chains), potent
mitogens, and
chemoattractants for cells of mesenchymal origin has been implicated in numerous vascular pathologies involving smooth muscle cell (SMC)
hyperplasia. Understanding the molecular mechanisms mediating PDGF transcription would provide new insights into strategies to control PDGF-dependent pathophysiologic processes. We demonstrated previously that
PDGF-A expression is under the positive regulatory influence of Sp1, Sp3, and Egr-1 and is negatively controlled by GCF2, NF-1(X), and WT-1. In this article, we demonstrate that Ets-1 induces
PDGF-A expression in primary rat aortic SMCs at the level of transcription and
mRNA expression. Electrophoretic mobility shift, supershift, and mutational analyses revealed a functional role for the (-555)TTCC(-552) motif in the
PDGF-A promoter that binds endogenous Ets-1.
Chromatin immunoprecipitation analysis showed the interaction of endogenous and exogenous Ets-1 or
glutathione S-transferase-tagged Ets-1, bearing only the
DNA-binding domain with the authentic
PDGF-A promoter. Conversely, dominant-negative mutant of Ets-1 blocked the promoter interaction of endogenous Ets-1. Overexpression of Ets-1 but not the mutant form of Ets-1 activates the
PDGF-A promoter cooperatively with Sp1. Sp1, which interacts with Ets-1, failed to induce
PDGF-A promoter-dependent expression if the promoter contained a site-specific mutation in this novel Ets-binding site.
Small interfering RNA to Ets-1 and Sp1 blocked
PDGF-BB- and serum-inducible
PDGF-A expression. SMC growth was stimulated by Ets-1 and Sp1 separately and further increased by both factors together. Ets-1-inducible mitogenesis is blocked by
antibodies neutralizing PDGF-A and involves activation of the
PDGF alpha-receptor, which binds
PDGF-A. These findings identify a functional cis-acting
element for Ets-1 in the
PDGF-A promoter and demonstrate that Sp1 and Ets-1 cooperatively activate
PDGF-A transcription in vascular SMCs.