β3A-Integrin Downregulates the Urokinase-Type Plasminogen Activator Receptor (u-PAR) through aPEA3/ets Transcriptional Silencing Element in the u-PAR …

S Hapke, M Gawaz, K Dehne, J Köhler… - … and cellular biology, 2001 - Am Soc Microbiol
S Hapke, M Gawaz, K Dehne, J Köhler, JF Marshall, H Graeff, M Schmitt, U Reuning…
Molecular and cellular biology, 2001Am Soc Microbiol
Migration of cells requires interactions with the extracellular matrix mediated, in part, by
integrins, proteases, and their receptors. Previous studies have shown that β 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 was undertaken to
determine if in addition β 3-integrin regulates u-PAR expression. Overexpression of β 3-
integrin in CHO cells, which are avid expressers of the receptor, downregulated u-PAR …
Abstract
Migration of cells requires interactions with the extracellular matrix mediated, in part, by integrins, proteases, and their receptors. Previous studies have shown that β 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 was undertaken to determine if in addition β 3-integrin regulates u-PAR expression. Overexpression of β 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 β 3-integrin expression. A region between− 398 and− 197 bp of the u-PAR promoter was critical for β 3-integrin-induced downregulation of u-PAR promoter activity. Deletion of the PEA3/ets motif at− 248 bp substantially impaired the ability of β 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 was enhanced when β 3-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 β 3 A-integrin isoform but not by other β 3-integrin isoforms and required the cytoplasmic membrane NITY 759 motif. Moreover, overexpression of the short but not the long isoform of the β 3-integrin adapter protein β 3-endonexin blocked u-PAR promoter activity through the PEA3/etsbinding site. Thus, besides the physical interaction of β 3-integrin and u-PAR at the cell surface, β 3 signaling is implicated in the regulation of u-PAR gene transcription, suggesting a mutual regulation of adhesion and proteolysis receptors.
American Society for Microbiology