The role of the tyrosine kinase domain of the insulin-like growth factor- I receptor in intracellular signaling, cellular proliferation, and tumorigenesis

C. Hernandez-Sanchez, V. Blakesley, T. Kalebic, L. Helman, D. LeRoith

Research output: Contribution to journalArticlepeer-review

Abstract

Insulin and insulin-like growth factor (IGF-I) receptors are heterotetrameric proteins consisting of two α- and two β-subunits and members of the transmembrane tyrosine kinase receptors. Specific ligand binding to the receptor triggers a cascade of intracellular events, which begins with autophosphorylation of several tyrosine residues of the β- subunit of the receptor. The triple cluster in the tyrosine kinase domain of the β-subunit is the earliest and major autophosphorylation site. Previous studies have shown that substitutions of these three tyrosines by phenylalanines of both insulin and IGF-I receptors practically abolish any activation of cellular signaling pathways. We have studied the effect of double tyrosine mutations on IGF-I-induced receptor autophosphorylation, activation of Shc and IRS-1 pathways, and cell proliferation and tumorigenicity. Substitution of tyrosines 1131/1135 blocks any detectable autophosphorylation, whereas substitution of tyrosines 1131/1136 or 1135/1136 only reduces autophosphorylation levels in some clones by 50%. Nevertheless, all the cells expressing IGF-I receptors with double tyrosine substitutions demonstrated markedly reduced signaling through Shc and IRS-1 pathways. In addition, they were unable to respond to IGF-I-stimulated cell growth in culture, and tumor formation in nude mice was abrogated. These data suggest that the presence of tyrosine 1131 or 1135 essential for receptor autophosphorylation, whereas the presence of each of these tyrosines is necessary for a fully functional receptor.

Original languageEnglish (US)
Pages (from-to)29176-29181
Number of pages6
JournalJournal of Biological Chemistry
Volume270
Issue number49
DOIs
StatePublished - 1995

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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