Interaction of insulin receptor substrate-1 with the sigma3A subunit of the adaptor protein complex-3 in cultured adipocytes
Program in Molecular Medicine and the Department of Biochemistry and Molecular Biology
3T3 Cells; *Adaptor Protein Complex 3; Adaptor Protein Complex sigma Subunits; Adipocytes; Amino Acid Sequence; Animals; Base Sequence; Binding Sites; Carrier Proteins; Cells, Cultured; Humans; Insulin; Mice; Molecular Sequence Data; *Nerve Tissue Proteins; Phosphoproteins; Rats; Rats, Inbred F344; Recombinant Proteins; Signal Transduction
Life Sciences | Medicine and Health Sciences
Signaling through the insulin receptor tyrosine kinase involves its autophosphorylation in response to insulin and the subsequent tyrosine phosphorylation of substrate proteins such as insulin receptor substrate-1 (IRS-1). In basal 3T3-L1 adipocytes, IRS-1 is predominantly membrane-bound, and this localization may be important in targeting downstream signaling elements that mediate insulin action. Since IRS-1 localization to membranes may occur through its association with specific membrane proteins, a 3T3-F442A adipocyte cDNA expression library was screened with non-tyrosine-phosphorylated, baculovirus-expressed IRS-1 in order to identify potential IRS-1 receptors. A cDNA clone that encodes sigma3A, a small subunit of the AP-3 adaptor protein complex, was demonstrated to bind IRS-1 utilizing this cloning strategy. The specific interaction between IRS-1 and sigma3A was further verified by in vitro binding studies employing baculovirus-expressed IRS-1 and a glutathione S-transferase (GST)-sigma3A fusion protein. IRS-1 and sigma3A were found to co-fractionate in a detergent-resistant population of low density membranes isolated from basal 3T3-L1 adipocytes. Importantly, the addition of exogenous purified GST-sigma3A to low density membranes caused the release of virtually all of the IRS-1 bound to these membranes, while GST alone had no effect. These results are consistent with the hypothesis that sigma3A serves as an IRS-1 receptor that may dictate the subcellular localization and the signaling functions of IRS-1.
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Citation: J Biol Chem. 1998 Nov 6;273(45):29942-9.
The Journal of biological chemistry
VanRenterghem, Barbara; Morin, Michelle; Czech, Michael P.; and Heller-Harrison, Robin A., "Interaction of insulin receptor substrate-1 with the sigma3A subunit of the adaptor protein complex-3 in cultured adipocytes" (1998). Open Access Articles. 772.