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The ability of a cell to move requires the asymmetrical organization of cellular activities. To investigate polarized cellular activity in moving endothelial cells, human endothelial cells were incubated in a Dunn chamber to allow migration towards VEGF. Immunofluorescent staining with a specific antibody against caveolin-1 revealed that caveolin-1 was concentrated at the rear of moving cells. Similarly, monolayer scraping to induce cell random walk resulted in relocation of caveolin-1 to the cell rear. These results suggest that posterior polarization of caveolin-1 is a common feature both for chemotaxis and chemokinesis. Dual immunofluorescent labeling showed that, during cell spreading, caveolin-1 was located compactly in the cell center and excluded from nascent focal contacts along the circular lamellipodium revealed by integrin β1 and FAK staining. When cells were migrating, integrin β1 and FAK appeared at polarized lamellipodia, whereas caveolin-1 was found at the posterior of moving cells. Notably, wherever caveolin-1 was polarized, there was a conspicuous absence of both focal contacts and lamellipod extension. Transmission electron microscopy showed that caveolae, like their marker caveolin-1, were located at the cell center during cell spreading or at the cell rear during cell migration. In contrast to its unphosphorylated form, tyrosine-phosphorylated caveolin-1 upon fibronectin stimulation was associated with the focal complex molecule phospho-paxillin along the lamellipodia of moving cells. Importantly, loss of caveolin-1 polarity prevented cell polarization and migration. Our present results suggest a potential role of caveolin in lamellipod extension and cell migration. (This work was supported in part by grants from the American Heart Association and National Institutes of Health RR 16440).

[Proc Amer Assoc Cancer Res, Volume 46, 2005]