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The Function of GRB2 in Linking the Insulin Receptor to Ras Signaling Pathways

E. Y. Skolnik, A. Batzer, N. Li, C.-H. Lee, E. Lowenstein, M. Mohammadi, B. Margolis and J. Schlessinger
Science
New Series, Vol. 260, No. 5116 (Jun. 25, 1993), pp. 1953-1955
Stable URL: http://www.jstor.org/stable/2881425
Page Count: 3
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Abstract

Insulin-induced activation of extracellular signal-regulated kinases [ERKs, also known as mitogen-activated protein (MAP) kinases] is mediated by Ras. Insulin activates Ras primarily by increasing the rate of guanine nucleotide-releasing activity. Here, we show that insulin-induced activation of ERKs was enhanced by stable overexpression of growth factor receptor-bound protein 2 (GRB2) but not by overexpression of GRB2 proteins with point mutations in the Src homology 2 and 3 domains. Moreover, a dominant negative form of Ras (with Ser$^{17}$ substituted with Asn) blocked insulin-induced activation of ERKs in cells that overexpressed GRB2. GRB2 overexpression led to increased formation of a complex between the guanine nucleotide-releasing factor Sos (the product of the mammalian homolog of son of sevenless gene) and GRB2. In response to insulin stimulation, this complex bound to tyrosine-phosphorylated IRS-1 (insulin receptor substrate-1) and Shc. In contrast to the activated epidermal growth factor receptor that binds the GRB2-Sos complex directly, activation of the insulin receptor results in the interaction of GRB2-Sos with IRS-1 and Shc, thus linking the insulin receptor to Ras signaling pathways.

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