Insulin receptor-induced phosphorylation of cellular and synthetic substrates is regulated by the receptor beta-subunit C-terminus.

The transmembrane beta-subunits of the insulin receptor possess hormone-sensitive tyrosine kinase activity. To study the role of the C-terminus domain, a rabbit antipeptide antibody directed to the 1294-1317 domain was produced. The antipeptide antibody inhibited the receptor-induced phosphorylation of poly (Glu, Tyr) and synthetic peptides corresponding to the receptor autophosphorylation sites. In contrast, the same antibody did not inhibit receptor autophosphorylation. The kinetic parameters of the poly(Glu, Tyr) phosphorylation reaction indicated that the antibody interfered with the receptor enzymatic site. Concerning the insulin receptor cellular substrates, the anti-(1294-1317) antibody inhibited Src homology/collagen and IRS-1 phosphorylation. The extent of inhibition was 52% for Src homology/collagen phosphorylation and 30% for IRS-1 phosphorylation. From our data, we conclude that a similar regulation of insulin receptor-induced phosphorylation of artificial and cellular insulin receptor substrates can be generated at the level of the receptor beta-subunit C-terminus.