Src-dependence and pertussis toxin sensitivity of urokinase receptor-dependent chemotaxis and cytoskeleton reorganization in rat smooth muscle cells

The catalytically inactive precursor of urokinase-type plasminogen activato r (pro-u-PA) induced a chemotactic response in rat smooth muscle cells (RSM C) through binding to the membrane receptor of urokinase (U-PA receptor [u- PAR]). A soluble form of U-PAR activated by chymotrypsin cleavage as well a s a peptide located between domain 1 and 2 of u-PAR reproduced the effect o f pro-u-PA on cell migration. The chemotactic pro-u-PA effect correlates wi th a dramatic reorganization of actin cytoskeleton, of adhesion plaques, an d with major cell shape changes in RSMC, Pro-u-PA induced a decrease in str ess fiber content, membrane ruffling, actin ring formation, and disruption leading to the characteristic elongated cell shape of motile cells with an actin semi-ring located close to the leading edge of cells, u-PAR effects o n both chemotaxis and cytoskeleton were sensitive to pertussis toxin and, h ence, possibly require G proteins, u-PAR effects are accompanied by a reloc ation of u-PAR, vitronectin receptor (VNR) alpha v beta 3, beta 1 integrin subunit, and Src tyrosine kinase to the leading membrane of migrating cells . In conclusion, our data show that pro-u-PA, via binding to u-PAR, control s a signaling pathway, regulated by tyrosine kinases and possibly G protein s, leading to cell cytoskeleton reorganization and cell migration. (C) 1999 by The American Society of Hematology.