Phosphorylation of Caveolin-1 Tyrosine 14 Leads to Caveolar Coat Destablilzation, Membrane Invagination and Endocytosis

Caveolin 1 (Cav-1) is a cholesterol-binding membrane-associated protein required for caveolae formation and transcytosis of macromolecules through the endothelial barrier. Studies from our lab showed that activation of Src via albumin-binding protein gp60, Gβγ or NO leads to phosphorylation of Cav-1 tyrosine 14 and an increase in Cav-1-mediated endocytosis. Here we show that Y14-Cav-1 phosphorylation leads to destabilization of high molecular weight (HMW) Cav-1 oligomers. Using cell fractionation we see a decrease in HMW Cav-1 (> 250 kD) and a corresponding increase in phosphorylated Cav-1 monomers (~ 25 kD) in cells stimulated with albumin or NO. A similar decrease was observed in cells with phospho-mimicking (Y14D), and abolished in cells with phospho-defective (Y14F) mutants of Cav-1. Also Y14D-Cav-1-GFP positive vesicles tracked by TIRF and spinning-disc confocal microscopy were greater in number, velocity and volume when compared to Y14F. When wt Cav-1-CFP- and -YFP were co-transfected in HEK cells, ...