SH2-Balpha is an insulin-receptor adapter protein and substrate that interacts with the activation loop of the insulin-receptor kinase.
We identified SH2-Balpha as an insulin-receptor-binding protein based on interaction screening in yeast hybrid systems and co-precipitation in cells. SH2-Balpha contains pleckstrin-homology ('PH') and Src homology 2 (SH2) domains and is closely related to APS (adapter protein with a PH domain and an SH2 domain) and lnk, adapter proteins first identified in lymphocytes. SH2-Balpha is ubiquitously expressed and is present in rat epididymal adipose tissue, liver and skeletal muscle, physiological sites of insulin action. On SDS/PAGE, SH2-Balpha migrates at a molecular mass of 98 kDa, although the predicted size of SH2-Balpha is 79.6 kDa. Insulin causes an electrophoretic mobility shift. SH2-Balpha can be immunoprecipitated using anti-(insulin receptor) antibody from insulin-stimulated cells. Anti-phosphotyrosine antibody or the growth factor receptor-binding protein 2 (Grb2) SH2 domain precipitate SH2-Balpha after insulin stimulation, suggesting that SH2-Balpha is tyrosine-phosphorylated and may be a substrate for the insulin receptor. The SH2-Balpha SH2 domain did not interact with insulin-receptor substrate (IRS) proteins or epidermal-growth-factor receptor. Mutation of the juxtamembrane and C-terminus of the insulin receptor did not abolish the interaction with the SH2 domain. This was further confirmed using a panel of activation-loop single point mutants where mutation of Tyr1158, Tyr1162 and Tyr1163 abolished interaction. Thus SH2-Balpha is a likely component in the insulin-signalling pathway and may function as an alternative signalling protein by interacting with the activation loop of the insulin-receptor cytoplasmic domain.
Kotani
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K
Cell Signalling Laboratory, Department of Metabolic Medicine, Imperial College School of Medicine-Hammersmith Campus, 150 Du Cane Road, London W12 0NN, UK.
Wilden
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Pillay
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D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism*; D006224:Cricetinae; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D051380:GRB2 Adaptor Protein; D047908:Intracellular Signaling Peptides and Proteins; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D015398:Signal Transduction; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D051380:GRB2 Adaptor Protein; C495950:Grb2 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; C518910:SH2B1 protein, human; C492010:SH2B1 protein, rat; C488161:Sh2b2 protein, mouse; C488162:Sh2b2 protein, rat; D011972:Receptor, Insulin