The insulin receptor C-terminus is involved in regulation of the receptor kinase activity.
During the insulin receptor activation process, ligand binding and autophosphorylation induce two distinct conformational changes in the C-terminal domain of the receptor beta-subunit. To analyze the role of this domain and the involvement of the C-terminal autophosphorylation sites (Tyr1316 and Tyr1322) in receptor activation, we used (i) antipeptide antibodies against three different C-terminal sequences (1270-1281, 1294-1317, and 1309-1326) and (ii) an insulin receptor mutant (Y/F2) where Tyr1316 and Tyr1322 have been replaced by Phe. We show that the autophosphorylation-induced C-terminal conformational change is preserved in the Y/F2 receptor, indicating that this change is not induced by phosphorylation of the C-terminal sites but most likely by phosphorylation of the major sites in the kinase domain (Tyr1146, Tyr1150, and Tyr1151). Binding of antipeptide antibodies to the C-terminal domain modulated (activated or inhibited) both mutant and wild-type receptor-mediated phosphorylation of poly(Glu/Tyr). In contrast to the wild-type receptor, Y/F2 exhibited the same C-terminal configuration before and after insulin binding, evidencing that mutation of Tyr1316 and Tyr1322 introduced conformational changes in the C-terminus. Finally, the mutant receptor was 2-fold more active than the wild-type receptor for poly(Glu/Tyr) phosphorylation. In conclusion, the whole C-terminal region of the insulin receptor beta-subunit is likely to exert a regulatory influence on the receptor kinase activity. Perturbations of the C-terminal region, such as binding of antipeptides or mutation of Tyr1316 and Tyr1322, provoke alterations at the receptor kinase level, leading to activation or inhibition of the enzymic activity.
Kaliman
P
P
INSERM U145, Faculté de Médecine, Nice, France.
Baron
V
V
Alengrin
F
F
Takata
Y
Y
Webster
N J
NJ
Olefsky
J M
JM
Van Obberghen
E
E
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003593:Cytoplasm / Q000502:physiology; D006801:Humans; D007158:Immunologic Techniques; D066298:In Vitro Techniques; D019000:Phosphotyrosine; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D014162:Transfection; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry
D011994:Recombinant Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D000255:Adenosine Triphosphate; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin