Caveolins and caveolae, roles in insulin signalling and diabetes.

Much data in the scientific literature demonstrate a fundamental involvement of caveolae in insulin action, although particular aspects remain matters of debate. The insulin receptor and part of the downstream signalling mediators are localized in or recruited to caveolae. Moreover, as part of the signalling, insulin receptors are rapidly endocytosed by caveolae in response to the hormone. The insulin regulated glucose transporter GLUT4 appears to localize to caveolae after insulin-stimulated translocation to the plasma membrane, while the endocytosis of GLUT4 may involve a clathrin-mediated process. Insulin resistance due to dysfunction of insulin signalling in target tissues is a primary cornerstone of Type 2 diabetes. Lack of caveolae makes animals and human beings insulin resistant, but there is presently no evidence that caveolae play a role in the pathogenesis of insulin resistance in obesity and Type 2 diabetes.