beta(3)A-integrin downregulates the urokinase-type plasminogen activator receptor (u-PAR) through a PEA3/ets transcriptional silencing element in the u-PAR promoter
2118 - 2132
MOL CELL BIOL
MetadataShow full item record
Migration of cells requires interactions with the extracellular matrix mediated, in part, by integrins, proteases, and their receptors. Previous studies have shown that b3-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 was undertaken to determine if in addition b3-integrin regulates u-PAR expression. Overexpression of b3-integrin in CHO cells, which are avid expressers of the receptor, downregulated u-PAR protein and mRNA expression. The u-PAR promoter (21,469 bp) that is normally constitutively active in CHO cells was downregulated by induced b3-integrin expression. A region between 2398 and 2197 bp of the u-PAR promoter was critical for b3-integrin-induced downregulation of u-PAR promoter activity. Deletion of the PEA3/ets motif at 2248 bp substantially impaired the ability of b3-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 was enhanced when b3-integrin was overexpressed. A PEA3 antibody inhibited DNA-protein complex formation, indicating the presence of PEA3. Downregulation of the u-PAR promoter was achieved by the b3A-integrin isoform but not by other b3-integrin isoforms and required the cytoplasmic membrane NITY759 motif. Moreover, overexpression of the short but not the long isoform of the b3-integrin adapter protein b3-endonexin blocked u-PAR promoter activity through the PEA3/ets binding site. Thus, besides the physical interaction of b3-integrin and u-PAR at the cell surface, b3 signaling is implicated in the regulation of u-PAR gene transcription, suggesting a mutual regulation of adhesion and proteolysis receptors.