Distribution of caveolin-1 in bovine lens and redistribution in cultured bovine lens epithelial cells upon confluence

The distribution of caveolin-1 in the lens and lens epithelial cells was determined to assess possible roles in cholesterol trafficking, cell to cell communication and signal transduction. Bovine lenses and cultured bovine lens epithelial cells (BLEC) were divided into subcellular fractions and the distribution of proteins recognized by three different caveolin-1 antibodies determined. The immunolocalization of caveolin-1 in the lens epithelium and in subconfluent and confluent cultured BLEC was probed by fluorescence microscopy and laser scanning confocal microscopy. EGF induced phosphorylation of caveolin-1 was detected by Western blotting with an anti-phosphotyrosine antibody to immunoprecipitated caveolin-1 from BLEC and human cancer cells. Monomeric caveolin-1 of about 26 kDa was detected in the epithelial cell membrane of cultured BLEC and fresh epithelia and in the plasma membrane fraction of lens cortical fiber cells. Caveolin-1 of cultured BLEC redistributed from the cytoplasm to plasma membrane as the cells proceeded from subconfluent to confluent states. The apparent abundance of caveolin-1 in cortical fiber cell plasma membrane is consistent with possible roles in distribution of lens membrane cholesterol and membrane structure. The presence of caveolin-1 in the plasma membrane of epithelial cells at – but not before – confluency is consistent with a role of caveolin-1 in cell to cell communications. EGF stimulated phosphorylation of caveolin-1 in human A431 cells but not lens cells.