Caveolin-1 polarization in transmigrating endothelial cells requires binding to intermediate filaments.

Caveolin-1 influences cell migration through multiple signaling pathways. In a previous report, we have shown that caveolin-1 is polarized in three-dimensional migrating endothelial cells (EC), and that caveolin-1 accumulation at the front of transmigrating cells requires the phosphorylatable Tyr(14) residue of caveolin-1. Immuno-electron microscopy further indicated that caveolin-1 was distributed along cytoskeletal structures in the anterior of transmigrating EC [Parat MO, Anand-Apte B, Fox PL (Mol Biol Cell 14:3156-3168, 2003)]. In the present study, we investigate whether caveolin-1 interacts with intermediate filaments (IF) and whether this interaction is required for caveolin-1 polarization in transmigrating cells. The distribution of vimentin is polarized in cells traversing a filter pore and overlaps with the distribution of caveolin-1, which accumulates in the cell front. In vivo sprouting EC also exhibit an anterior polarization of these two proteins. Furthermore, caveolin-1 co-purifies with intermediate filaments, suggesting an interaction between caveolin-1 and IF. Vimentin-deficient SW13 cells exhibit a dramatically altered polarization of caveolin-1-GFP, which no longer accumulates in the protruding cell extension. In addition, the Tyr(14) residue of caveolin-1 is required for co-purification of the protein with IF. Taken together, our results show that caveolin-1 Tyr(14) is necessary for binding to intermediate filaments, which in turn is required for anterior polarization of caveolin-1 in transmigrating cells.