| Title | Rapid insulin-dependent endocytosis of the insulin receptor by caveolae in primary adipocytes. | | Author(s) | Fagerholm S, Ortegren U, Karlsson M, Ruishalme I, Strålfors P | | Institution | Division of Cell Biology, Department of Clinical and Experimental Medicine and Diabetes Research Centre, University of Linköping, Linköping, Sweden. | | Source | PLoS One 2009; 4(6):e5985. | | Abstract | BACKGROUND: The insulin receptor is localized in caveolae and is dependent on caveolae or cholesterol for signaling in adipocytes. When stimulated with insulin, the receptor is internalized.
METHODOLOGY/PRINCIPAL FINDINGS: We examined primary rat adipocytes by subcellular fractionation to examine if the insulin receptor was internalized in a caveolae-mediated process. Insulin induced a rapid, t(1/2)<3 min, endocytosis of the insulin receptor in parallel with receptor tyrosine autophosphorylation. Concomitantly, caveolin-1 was phosphorylated at tyrosine(14) and endocytosed. Vanadate increased the phosphorylation of caveolin-1 without affecting insulin receptor phosphorylation or endocytosis. Immunocapture of endosomal vesicles with antibodies against the insulin receptor co-captured caveolin-1 and immunocapture with antibodies against tyrosine(14)-phosphorylated caveolin-1 co-captured the insulin receptor, demonstrating that the insulin receptor was endocytosed together with tyrosine(14)-phosphorylated caveolin-1. By immunogold electron microscopy the insulin receptor and caveolin-1 were colocalized in endosome vesicles that resembled caveosomes. Clathrin was not endocytosed with the insulin receptor and the inhibitor of clathrin-coated pit-mediated endocytosis, chlorpromazine, did not inhibit internalization of the insulin receptor, while transferrin receptor internalization was inhibited.
CONCLUSION: It is concluded that in response to insulin stimulation the autophosphorylated insulin receptor in primary adipocytes is rapidly endocytosed in a caveolae-mediated process, involving tyrosine phosphorylation of caveolin-1. | | Language | eng | | Pub Type(s) | Journal Article
| | PubMed ID | 19543529 |
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