Inhibition of insulin receptor catalytic activity by the molecular adapter Grb14.
Grb14 belongs to the Grb7 family of adapters and was recently identified as a partner of the insulin receptor (IR). Here we show that Grb14 inhibits in vitro IR substrate phosphorylation. Grb14 does not alter the K(m) for ATP and behaves as an uncompetitive inhibitor for the IR substrate. Similar experiments performed with other members of the Grb7 family, Grb7 and Grb10, and with IGF-1 receptor argue in favor of a specific inhibition of the IR catalytic activity by Grb14. The IR-interacting domain of Grb14, the PIR, is sufficient for the inhibitory effect of Grb14, whereas the SH2 domain has no effect on IR catalytic activity. In Chinese hamster ovary (CHO) cells overexpressing both IR and Grb14, Grb14 binds to the IR as early as 1 min after insulin stimulation, and the two proteins remain associated. When interacting with Grb14, the IR is protected against tyrosine phosphatases action and therefore maintained under a phosphorylated state. However, the binding of Grb14 to the IR induces an early delay in the activation of Akt and ERK1/2 in CHO-IR cells, and ERK1/2 are less efficiently phosphorylated. These findings show that Grb14 is a direct inhibitor of the IR catalytic activity and could be considered as a modulator of insulin signaling.
Béréziat
Veronique
V
Endocrinologie et Métabolisme, CNRS UPR 1524 Institut Cochin de Genetique Moleculaire, 24 rue du Faubourg Saint-Jacques, 75674 Paris Cedex 14, France.
Kasus-Jacobi
Anne
A
Perdereau
Dominique
D
Cariou
Bertrand
B
Girard
Jean
J
Burnol
Anne-Françoise
AF
D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002384:Catalysis; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D051383:GRB10 Adaptor Protein; D051382:GRB7 Adaptor Protein; D005982:Glutathione Transferase / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011972:Receptor, Insulin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors
D007328:Insulin; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D051382:GRB7 Adaptor Protein; D051383:GRB10 Adaptor Protein; D005982:Glutathione Transferase; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases