Biologic activities of naturally occurring human insulin receptor mutations. Evidence that metabolic effects of insulin can be mediated by a kinase-deficient insulin receptor mutant.
We have studied insulin receptor-mediated signaling in Chinese hamster ovary (CHO) cell transfectants that expressed either of two naturally occurring mutant human insulin receptors: Trp1200----Ser1200 and Ala1134----Thr1134. Compared with overexpressed normal human insulin receptors, both mutant receptors displayed normal processing and normal binding affinity; however, neither was capable of detectable insulin-stimulated autophosphorylation or tyrosine kinase activity toward endogenous (pp185) or exogenous substrates. Several biologic actions of insulin were evaluated in transfected cells. Compared with neomycin-only transfected CHO cells (CHO-NEO), cells expressing normal receptors demonstrated increased insulin sensitivity for 2-deoxyglucose uptake, [14C]glucose incorporation into glycogen, [3H]thymidine incorporation into DNA, and specific gene expression (accumulation of glucose transporter GLUT-1 mRNA). Cells expressing either Ser1200 or Thr1134 receptors showed no increase in insulin-stimulated thymidine incorporation or GLUT-1 mRNA accumulation compared with CHO-NEO. Surprisingly, cells expressing Ser1200 receptors showed increased insulin stimulation of 2-deoxyglucose uptake and glucose incorporation into glycogen compared with CHO-NEO, whereas Thr1134 receptors failed to signal these metabolic responses. We conclude that 1) transfected kinase-deficient insulin receptor mutants derived from insulin-resistant patients have distinct defects in the ability to mediate insulin action in vitro; 2) divergence of insulin signaling pathways may occur at the level of the receptor; and 3) normal activation of the receptor tyrosine kinase by insulin is not necessarily required for signaling of certain important biologic actions.
Moller
D E
DE
Charles A. Dana Research Institute, Beth Israel Hospital, Boston, Massachusetts 02215.
Benecke
H
H
Flier
J S
JS
D000818:Animals; D002460:Cell Line; D004261:DNA Replication / Q000187:drug effects; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000096:biosynthesis; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D011972:Receptor, Insulin / Q000235:genetics* / Q000378:metabolism; D014162:Transfection
D007328:Insulin; D009004:Monosaccharide Transport Proteins; D006003:Glycogen; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D005947:Glucose