β3A-integrin downregulates the urokinase-type plasminogen activator receptor (u-PAR) through a PEA3/ets transcriptional silencing element in the u-PAR promoter

Migration of cells requires interactions with the extracellular matrix mediated, in part, by integrins, proteases, and their receptors. Previous studies have shown that beta (3)-integrin interacts with the urokinase-type plasminogen activator receptor (u-PAR) at the cell surface. Since integrins mediate signaling into the cell, the current study,vas undertaken to determine if in addition beta (3)-integrin regulates u PAR expression. Overexpression of beta (3)-integrin in CHO cells, which are avid expressers of the receptor, downregulated u-PAR protein and mRNA expression. The u-PAR promoter (-1,469 bp) that is normally constitutively active in CHO cells was downregulated by induced beta (3)-integrin expression. A region between -398 and -197 bp of the u-PAR promoter was critical for beta (3)-integrin-induced downregulation of u-PAR promoter activity. Deletion of the PEA3/ets motif at -248 bp substantially impaired the ability of beta (3)-integrin to downregulate the u-PAR promoter, suggesting that the PEA3/ets site acts as a silencing element. An expression vector encoding the transcription factor PEA3 caused inhibition of the wild-type but not the PEA3/ets-deleted u-PAR promoter. The PEA3/ets site bound nuclear factors from CHO cells specifically, but binding mas enhanced when beta (3)-integrin was overexpressed. A PEA3 antibody inhibited DNA-protein complex formation, indicating the presence of PEA3. Downregulation of the u-PAR promoter mas achieved by the beta (3)-integrin isoform but not by other beta (3)-integrin isoforms and required the cytoplasmic membrane NITY759 motif. Moreover, overexpression of the short but not the long isoform of the beta (3)-integrin adapter protein beta (3)-endonexin blocked u-PAR promoter activity through the PEA3/els binding site. Thus, besides the physical interaction of beta (3)-integrin and u-PAR at the cell surface, beta (3) signaling is implicated in the regulation of u-PAR gene transcription, suggesting a mutual regulation of adhesion and prateolysis receptors.