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J. Biol. Chem., Vol. 280, Issue 14, 13483-13486, April 8, 2005

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Dissociation of Insulin Receptor Expression and Signaling from Caveolin-1 Expression^*

Jonathan Wharton, Tova Meshulamy, Gino Vallega, and Paul Pilch

From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118

The presence of cell surface caveolin/caveolae has been postulated to influence the localization, expression levels, and kinase activity of numerous receptors, including the insulin receptor. However, there are conflicting data concerning the effects of caveolin on insulin receptor expression and function. To help clarify this issue, we created a gain of function situation by expressing caveolin-1 at various levels in HEK-293 cells where the endogenous level of caveolin-1 is very low. We generated four permanent lines of this cell expressing amounts of caveolin-1 ranging from 10 to 40 times that of parental cells. The amount of caveolin-1 in the human embryonic kidney cells expressing the highest caveolin levels is comparable with that of adipocytes, cells that naturally express one of the highest levels of caveolin-1. We measured insulin receptor amount and insulin-dependent receptor autophosphorylation as well as insulin receptor substrate 1 (IRS1) tyrosine phosphorylation as an index of insulin signaling. We found that the insulin receptor level was essentially the same in the parental and all four derived cell lines. Likewise, we determined that insulin-dependent insulin receptor and IRS1 tyrosine phosphorylation was not significantly different in the four cell lines representing parental, low, medium, and high levels of caveolin-1 expression. We conclude that insulin receptor expression and ligand-dependent signaling is independent of caveolin-1 expression.

Received for publication, December 9, 2004 , and in revised form, January 20, 2005.

^* This work was supported by National Institutes of Health Grant DK-56935 and a grant from the American Diabetes Association (both to P. P.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

These authors made equal contributions to the manuscript.

To whom correspondence should be addressed: Dept. of Biochemistry, Boston University School of Medicine, 715 Albany St., Boston, MA 02118. Tel.: 617-638-4004; E-mail: ppilch{at}bu.edu.

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