This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Maggi, D. Articles by Cordera, R. Search for Related Content PubMed PubMed Citation Articles by Maggi, D. Articles by Cordera, R.

Cys⁸⁶⁰ in the Extracellular Domain of Insulin Receptor ß-Subunit Is Critical for Internalization and Signal Transduction¹

Department of Endocrinology and Metabolism, University of Genova, Genova, Italy; and the Department of Morphology, University of Geneva (J.-L.C.), Geneva, Switzerland

Address all correspondence and requests for reprints to: Dr. Renzo Cordera, Viale Benedetto XV 6, 16132 Genova, Italy. E-mail: record{at}unige.it

The C860S mutation (IR^C860S) in the extracellular domain of the insulin receptor ß-subunit has previously been shown to result in an inhibition of insulin receptor internalization. The present work aims at further dissecting the consequences of this mutation not only on insulin receptor internalization, but also on the signaling of the receptor. Following transfection of Chinese hamster ovary (CHO) cells with insulin receptors with the C860S mutation (CHO-IR^C860S) and quantitative electron microscopic analysis of [¹²⁵I]insulin localization in these cells, the inhibition of receptor internalization appears to be due to an inhibition of the lateral translocation of the receptor from microvilli to nonvillous domains of the cell surface. At 37 C, insulin-stimulated insulin receptor substrate-1 (IRS-1) phosphorylation is inhibited by 50% in CHO-IR^C860S, whereas Shc phosphorylation remains unaffected. The inhibition of IRS-1 phosphorylation is still present when experiments are conducted at 4 C, a temperature at which insulin receptor internalization is prevented, suggesting that the defect in IRS-1 phosphorylation is not due to the reduced internalization of the receptor. In terms of biological effects, the mutation has negative consequences on insulin-stimulated c-fos expression and DNA synthesis as well as on glycogen synthase activity. Eventually, the events observed are specific for Cys⁸⁶⁰, as individual substitution of the two more proximal Cys residues (795 and 872) to Ser is not accompanied by any change in either insulin-induced insulin receptor internalization or IRS-1 phosphorylation. Thus, the present analysis of CHO-IR^C860S 1) reveals that insulin receptor surface redistribution is not solely dependent on receptor autophosphorylation, 2) emphasizes that IRS-1 phosphorylation is not dependent on receptor internalization and can be triggered from microvilli, and 3) stresses divergent aspects between two of the major signaling pathways of the insulin receptor.

This article has been cited by other articles:

				K. Kabayama, T. Sato, F. Kitamura, S. Uemura, B. W. Kang, Y. Igarashi, and J.-i. Inokuchi TNF{alpha}-induced insulin resistance in adipocytes as a membrane microdomain disorder: involvement of ganglioside GM3 Glycobiology, January 1, 2005; 15(1): 21 - 29. [Abstract] [Full Text] [PDF]

				S. Boura-Halfon, H. Voliovitch, R. Feinstein, K. Paz, and Y. Zick Extracellular Matrix Proteins Modulate Endocytosis of the Insulin Receptor J. Biol. Chem., April 25, 2003; 278(18): 16397 - 16404. [Abstract] [Full Text] [PDF]