Reduced β 3-endonexin levels are associated with enhanced urokinase-type plasminogen activator receptor expression in ApoE −/− mice

Abstract

Proteolysis of extracellular matrix components is required for cell migration occurring in atherosclerotic lesion formation. In the present study, gene expression of the urokinase plasmingen activator receptor (uPAR) and underlying mechanisms were analyzed during the development of atherosclerosis in the aorta of apolipoprotein E-deficient mice (apoE −/−). A significant increase of uPAR expression was detected in the atherosclerotic tissue with advancing plaque-dimension. As uPAR gene transcription involves the transcription factor nuclear factor-κB (NF-κB), we analyzed nuclear NF-κB activity in vascular tissue of apoE-deficient mice. Congruent to uPAR, we could detect an increase in NF-κB activity, which underlines the chronic inflammatory component of the disease. Recently we reported that β 3-endonexin, a protein that modulates β 3-integrins, regulates uPAR expression through direct interaction with subunits of the NF-κB-complex. Herein we could show that β 3-endonexin protein is expressed in aortic tissue of mice. Moreover, in contrast to uPAR or NF-κB, the expression of β 3-endonexin was reduced in extracts of advanced atherosclerotic aortic tissue. The cytoplasmic protein β 3-endonexin regulates function of β 3-integrins. We revealed that integrin stimulation of endothelial cells led to an enhanced NF-κB activity and secretion of the NF-κB dependent chemokine monocyte chemoattractant protein-1 (MCP-1). The β 3-integrin dependent increase in MCP-1 was notedly reduced in cells that overexpressed β 3-endonexin. These results provide strong evidence that β 3-endonexin acts as a regulating factor in the integrin-mediated signal transduction and the present findings imply a pathophysiological role of β 3-endonexin in atherogenesis.