Dissection of the growth versus metabolic effects of insulin and insulin-like growth factor-I in transfected cells expressing kinase-defective human insulin receptors.
We have recently reported that the expression of an in vitro mutated, kinase-defective insulin receptor (A/K1018) leads to cellular insulin resistance when expressed in Rat 1 fibroblasts. That is, despite the presence of normal numbers of activatable native insulin receptors in the host cell, the A/K1018 receptors prevent the normal receptors from phosphorylating endogenous substrates and from signalling insulin action, perhaps by competing for limiting amounts of these substrates. We report here that insulin-like growth factor I-stimulated phosphorylation of two endogenous substrate proteins, pp220 and pp170, is also inhibited in cells expressing A/K1018 receptors. Because insulin-like growth factor I stimulation of glucose uptake is not inhibited in cells with A/K1018 receptors while pp220 and pp170 phosphorylation is inhibited, it is unlikely that either pp220 or pp170 are involved in mediating the stimulation of glucose transport. In contrast, insulin-like growth factor I-mediated stimulation of mitogenesis is inhibited in cells with A/K1018 receptors. Thus, pp170 or pp220 could be involved in mitogenic signalling. We also report that both H2O2 and tetradecanoylphorbolacetate stimulate glucose transport normally in cells with A/K1018 receptors. Phorbol esters also lead to the phosphorylation of both normal and A/K1018 receptors on serine and/or threonine. This argues that phorbol esters or H2O2 bypass the normal proximal steps in signalling insulin action.
McClain
D A
DA
Veterans Administration Medical Center, Medical Research Service, San Diego, California 92161.
Maegawa
H
H
Thies
R S
RS
Olefsky
J M
JM
D000818:Animals; D002455:Cell Division; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D051381:Rats; D011972:Receptor, Insulin / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000378:metabolism; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000494:pharmacology*; D014162:Transfection
D003837:Deoxy Sugars; D007328:Insulin; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D003847:Deoxyglucose; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin