Catalysis of serine and tyrosine autophosphorylation by the human insulin receptor
Program in Molecular Medicine; Department of Biochemistry and Molecular Pharmacology
Amino Acid Sequence; Humans; Molecular Sequence Data; Phosphorylation; Phosphoserine; Phosphotyrosine; Protein-Tyrosine Kinases; Receptor, Insulin; Recombinant Proteins; Time Factors; Tyrosine
Life Sciences | Medicine and Health Sciences
The protein kinase activity of human insulin receptors purified from Sf9 insect cells after infection with a recombinant baculovirus was evaluated. The following experimental observations led to the unexpected conclusion that this receptor protein catalyzes both serine and tyrosine autophosphorylation at significant stoichiometries. (i) Phosphorylation of lectin-purified insulin receptors with [gamma-32P]ATP resulted in rapid receptor tyrosine phosphorylation (7 mol of P per high-affinity binding site) and the delayed onset of insulin-stimulated receptor serine phosphorylation (about 7% of total phosphorylation). The tyrosine kinase inhibitor (hydroxy-2-naphthalenylmethyl)phosphonic acid (HNMPA), which has no effect on protein kinase C or cyclic AMP-dependent protein kinase activities, inhibited both the receptor serine and tyrosine phosphorylation. (ii) Phosphorylation of a synthetic peptide substrate composed of insulin receptor residues 1290-1319 on serines-1305/1306 by partially purified insulin receptors was also inhibited by HNMPA. (iii) Insulin receptors sequentially affinity-purified on immobilized wheat germ agglutinin and immobilized insulin showed no apparent contaminant proteins on silver-stained SDS/polyacrylamide gels yet catalyzed autophosphorylation on receptor serine and tyrosine residues when incubated with [gamma-32P]ATP. These results suggest that the catalytic site of the insulin receptor tyrosine kinase also recognizes receptor serine residues as substrates for the phosphotransfer reaction. Furthermore, insulin-stimulated receptor serine phosphorylation in intact cells may occur in part by an autophosphorylation mechanism subsequent to tyrosine phosphorylation of the insulin receptor.
Proc Natl Acad Sci U S A. 1992 Sep 1;89(17):7885-9.
Proceedings of the National Academy of Sciences of the United States of America
Baltensperger K, Lewis RE, Woon C, Vissavajjhala P, Ross AH, Czech MP. (1992). Catalysis of serine and tyrosine autophosphorylation by the human insulin receptor. Open Access Articles. Retrieved from https://escholarship.umassmed.edu/oapubs/1821