VEGF-induced endothelial cell migration requires urokinase receptor (uPAR)-dependent integrin redistribution.
Alexander, Revu Ann 1,+; Prager, Gerald W. 1,2,+; Mihaly-Bison, Judit 1; Uhrin, Pavel 1; Sunzenauer, Stefan 3; Binder, Bernd R. 1,++; Schutz, Gerhard J. 3; Freissmuth, Michael 4; Breuss, Johannes M. 1,*
[Article] Cardiovascular Research. 94(1):125-135, April 1, 2012.

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Aims: Vascular endothelial growth factor (VEGF)-initiated angiogenesis requires coordinated proteolytic degradation of extracellular matrix provided by the urokinase plasminogen activator/urokinase receptor (uPA/uPAR) system and regulation of cell migration provided by integrin-matrix interaction. In this study, we investigated the mechanisms underlying the uPAR-dependent modulation of VEGF-induced endothelial migration.

Methods and results: We used flow cytometry to quantify integrins at the cell surface. Stimulation of human and murine endothelial cells with VEGF resulted in internalization of [alpha]5[beta]1-integrins. Micropatterning and immunocytochemistry revealed co-clustering of uPAR and [alpha]5[beta]1-integrins and retrieval via clathrin-coated vesicles. It was also contingent on receptors of the low-density lipoprotein receptor (LDL-R) family. VEGF-induced integrin redistribution was inhibited by elimination of uPAR from the endothelial cell surface or by inhibitory peptides that block the uPAR-integrin interaction. Under these conditions, the migratory response of endothelial cells upon VEGF stimulation was impaired both in vitro and in vivo.

Conclusions: The observations indicate that uPAR is an essential component of the network through which VEGF controls endothelial cell migration. uPAR is a bottleneck through which the VEGF-induced signal must be funnelled for both focused proteolytic activity at the leading edge and for redistribution of integrins.

(C) Copyright Oxford University Press 2012.