Role of IRS-1-GRB-2 complexes in insulin signaling.

• DOI: 10.1128/mcb.14.6.3577
• Publication Date: 2015-10-06T00:40:01Z
• Authors: M G Myers; L M Wang; X J Sun; Y Zhang; L Yenush; J Schlessinger; J H Pierce; M F White
• Keywords: 0301 basic medicine; Base Sequence; Cells; Molecular Sequence Data; Gene Expression; CHO Cells; Hematopoietic Stem Cells; Phosphoproteins; Models, Biological; ErbB Receptors; Kinetics; 03 medical and health sciences; Cricetinae; Calcium-Calmodulin-Dependent Protein Kinases; Insulin Receptor Substrate Proteins; Mutagenesis, Site-Directed; Animals; Insulin; Cell Division; Adaptor Proteins, Signal Transducing; DNA Primers; GRB2 Adaptor Protein

GRB-2 is a small SH2- and SH3 domain-containing adapter protein that associates with the mammalian SOS homolog to regulate p21ras during growth factor signaling. During insulin stimulation, GRB-2 binds to the phosphorylated Y895VNI motif of IRS-1. Substitution of Tyr-895 with phenylalanine (IRS-1F-895) prevented the IRS-1-GRB-2 association in vivo and in vitro. The myeloid progenitor cell line, 32-D, is insensitive to insulin because it contains few insulin receptors and no IRS-1. Coexpression of IRS-1 or IRS-1F-895 with the insulin receptor was required for insulin-stimulated mitogenesis in 32-D cells, while expression of the insulin receptor alone was sufficient to mediate insulin-stimulated tyrosine phosphorylation of Shc and activation of p21ras and mitogen-activated protein (MAP) kinase. The Shc-GRB-2 complex formed during insulin stimulation is a possible mediator of p21ras and MAP kinase activation in IRS-1-deficient 32-D cells. Interestingly, IRS-1, but not IRS-1F-895, enhanced the stimulation of MAP kinase by insulin in 32-D cells expressing insulin receptors. Thus, IRS-1 contributes to the stimulation of MAP kinase by insulin, probably through formation of the IRS-1-GRB-2 complex at Tyr-895. Our results suggest that the Shc-GRB-2 complex and the activation of p21ras-dependent signaling pathways, including MAP kinase, are insufficient for insulin-stimulated mitogenesis and that the essential function(s) of IRS-1 in proliferative signaling is largely unrelated to IRS-1-GRB-2 complex formation.