A peptide-based protein-tyrosine phosphatase inhibitor specifically enhances insulin receptor function in intact cells.
3S-peptide-I is a synthetic tris-sulfotyrosyl dodecapeptide corresponding to the major site of insulin receptor autophosphorylation that potently inhibits dephosphorylation of the insulin receptor in a cell-free system and in digitonin-permeabilized Chinese hamster ovary (CHO) cells overexpressing the human insulin receptors (CHO/HIRc cells) (Liotta, A. S., Kole, H. K., Fales, H. M., Roth, J., and Bernier, M. (1994) J. Biol. Chem. 269, 22996-23001). In the present study, we found that 3S-peptide-I was not capable of inhibiting dephosphorylation of the epidermal growth factor (EGF) receptors in digitonin-permeabilized CHO cells that overexpress human EGF receptors (CHO/EGF-R cells). Moreover, the addition of a N-stearyl derivative of 3S-peptide-I to intact CHO/HIRc cells caused a concentration-dependent increase in insulin-stimulated phosphorylation of the insulin receptor, with a maximum effect (approximately 2.7-fold) at 50 microM. In contrast, ligand-stimulated EGF receptor phosphorylation in CHO/EGF-R cells was not affected by the presence of stearyl 3S-peptide-I. Furthermore, treatment of CHO/HIRc cells with this N-stearyl peptide led to a significant enhancement of the insulin-induced association of phosphatidylinositol (PI) 3-kinase activity with insulin receptor substrate 1 and the activation of mitogen-activated protein kinase. However, stearyl 3S-peptide-I had no effect on the EGF-stimulated activation of PI-3-kinase and mitogen-activated protein kinase in CHO/EGF-R cells. These data indicate that this tris-sulfotyrosyl dodecapeptide selectively enhances insulin signal transduction by specifically inhibiting dephosphorylation of the insulin receptor in intact cells.
Kole
H K
HK
Diabetes Section, Laboratory of Clinical Physiology, NIA, National Institutes of Health, Baltimore, Maryland 21224, USA.
Garant
M J
MJ
Kole
S
S
Bernier
M
M
D000595:Amino Acid Sequence; D000704:Analysis of Variance; D000818:Animals; D016466:CHO Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D006224:Cricetinae; D004072:Digitonin; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000494:pharmacology*; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D011972:Receptor, Insulin / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection
D004791:Enzyme Inhibitors; D009842:Oligopeptides; D011994:Recombinant Proteins; D066246:ErbB Receptors; D011972:Receptor, Insulin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D017027:Protein Tyrosine Phosphatases; D004072:Digitonin