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Intermolecular transphosphorylation between insulin receptors and EGF‐insulin receptor chimerae.
Author(s) -
Ballotti R.,
Lammers R.,
Scimeca J.C.,
Dull T.,
Schlessinger J.,
Ullrich A.,
Van Obberghen E.
Publication year - 1989
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1989.tb08491.x
Subject(s) - biology , insulin receptor , receptor , insulin , endocrinology , medicine , insulin receptor substrate , intermolecular force , insulin resistance , biochemistry , physics , quantum mechanics , molecule
The insulin receptor, a glycoprotein consisting of two extracellular alpha‐ and two transmembrane beta‐subunits, is thought to mediate hormone action by means of its tyrosine‐specific protein kinase activity. To explore the mechanism of insulin receptor phosphorylation we have used NIH3T3 cells transfected with two receptor constructs: one encoding a chimeric receptor composed of the extracellular domain of the human EGF receptor and the cytosolic domain of the human insulin receptor beta‐subunit, and a second construct encoding a kinase‐defiecient human insulin receptor. Stimulation of these cells with EGF induced tyrosine autophosphorylation of the EGF‐insulin receptor chimera (150 kd) and tyrosine phosphorylation of the beta‐subunit of the kinase‐deficient insulin receptor (95 kd). The phosphopeptides of the autophosphorylated cytoplasmic domain of the EGF‐insulin receptor chimera were comparable to those of the transphosphorylated beta‐subunit of the kinase‐deficient insulin receptor and of the wild‐type human insulin receptor. When immunoaffinity purified EGF‐insulin receptor hybrids and kinase‐deficient insulin receptors were used in a cell lysate phosphorylation assay, it was found that addition of EGF produced 32P‐labeling of both receptor species. We conclude that EGF acting directly through the EGF‐insulin receptor chimera causes transphosphorylation of the kinase‐deficient insulin receptor. These data support the notion that autophosphorylation of the insulin receptor may proceed by an intermolecular mechanism.