The Ternary Complex Factor Net Regulates Cell Migration through Inhibition of PAI-1 Expression

Abstract

Net, Elk-1, and Sap-1 are members of the ternary complex factor (TCF) subfamily of Ets transcription factors. They form ternary complexes with serum response factor (SRF) on serum response elements of immediate early genes such as c-fos and egr-1 and mediate responses to growth factors and mitogen-activated protein kinase signaling. Although the TCFs have been extensively studied as intermediates in signaling cascades, surprisingly little is known about their different target genes and physiological functions. We report that Net homozygous mutant mouse embryonic fibroblasts have a defect in cell migration. This defect results at least in part from increased expression of plasminogen activator inhibitor type 1 (PAI-1), a serine protease inhibitor (serpin) that controls extracellular proteolysis and cell matrix adhesion. The defect in cell migration can be reverted by the addition of a PAI-1 blocking antibody. Net represses PAI-1 promoter activity and binds to a specific region of the promoter containing Ets binding sites in the absence of SRF. We conclude that Net is a negative regulator of PAI-1 expression and is thereby involved in cell migration.

ACKNOWLEDGMENTS

We thank Jean-Luc Vonesch, Marcel Boeglin, and Didier Hentsch from the IGBMC Microscopy and Imaging Centre for their support with time lapse microscopy and image analysis; Jens Frauenfeld for his contribution to Net silencing with antisense RNA; Christine Wasylyk for her contribution to the cDNA array and Q-RT-PCR analysis; the Wasylyk laboratory members for support and encouragement; and the IGBMC core facilities.

G.B. is the recipient of a Ligue contre le Cancer fellowship. C.G. is the recipient of postgraduate fellowship from the Ministère de la Recherche et Technologie. Our laboratory is supported by the Ligue Nationale Française contre le Cancer (Equipe labelisée), the Ligue Régionale (Haut-Rhin) contre le Cancer, the Ligue Régionale (Bas-Rhin) contre le Cancer, the Association pour la Recherche sur le Cancer, BioAvenir (Aventis, Rhone-Poulenc), the Centre National de la Recherche Scientifique, the Institut National de la Santé et de la Recherche Médicale, and the Hôpital Universitaire de Strasbourg.