A close relationship between EEA1 and internalized caveolae structure

概要

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Internalization of caveolae structure on the cell surface is promoted by oxidant stress or inhibitor of phosphatase (Aoki et al., Exp Cell Res 253, 629, 1999). The internalization is accompanied by phosphorylation of caveolin-1 , a marker protein of caveolae. Little is known about the significance of this internalization. Recently we showed that phosphorylated caveolin-1 forms a complex with Rab5 protein. The existence of Rab5-caveolin-1 complex suggests that internalized caveolac could be translocated to endosomes. To see whether early endosome marker protein EEA1 is related to caveolae, we examined internalized caveolae by immunofluorescence microscopy, cryoultrathin immunogold electron microscopy, immunoprecipitation. Immunofluorescence examination revealed that internalized caveolae colocalized with EEA1 in many area. By immunoprecipitation, both caveolin-1 antibody and phosphorylated caveolin-1 antibody precipitated EEA1 protein. When caveolae were internalized, EEA1 antibody effectively precipitated many phosphorylated caveolin-1 . On ultrathin cryosections of cultured endothelial cells and caveolae-rich fractions obtained by sucrose density-centrifugatioin method, we confirmed that EEA1 colocalized with caveolae structure. These results show a close relationship between EEA1 and caveolae structure.