Tumorigenic and Mitogenic Capacities Are Reduced in Transfected Fibroblasts Expressing Mutant Insulin-Like Growth Factor (IGF)-I Receptors. The Role of Tyrosine Residues 1250, 1251, and 1316 in the Carboxy-Terminus of the IGF-I Receptor

Vicky A. Blakesley, Thea Kalebic, Lee J. Helman, Bethel Stannard, Teresa N. Faria, Charles Roberts, Derek Leroith

Research output: Contribution to journalArticle

68 Citations (Scopus)

Abstract

Regulation of ligand-mediated signal transduction through transmembrane tyrosine kinase growth factor receptors involves phosphorylation of tyrosine residues in the intracellular domain of the receptor. The insulin-like growth factor-I (IGF-I) receptor contains three tyrosine residues in the carboxy-terminal domain at positions 1250, 1251, and 1316. Of these, only the tyrosine at position 1316 is conserved in the homologous position of the insulin receptor. Mutational analysis was used to study the role of these tyrosines in specific outcomes of IGF-I-mediated signal transduction. Mutations in the human IGF-I receptor were either replacement of tyrosines 1250 and 1251 with phenylalanine and histidine (yyFH), respectively, or replacement of the conserved distal tyrosine (position 1316) with phenylalanine (yCF). The yyFH mutation results in an IGF-I receptor with the amino acids found in the homologous position of the human insulin receptor. Cells overexpressing mutated IGF-I receptors were compared with cells expressing only endogenous IGF-I receptors or overexpressing wild-type IGF-I receptors. The ability of yyFH mutant IGF-I receptors to autophosphorylate the β-subunit or phosphorylate insulin receptor substrate-1 was not significantly different from wild-type IGF-I receptors. However, one or both of the proximal tyrosine residues (positions 1250 and 1251) in the carboxy-terminus of the IGF-I receptor are essential for IGF-I-stimulation of mitogenic and tumorigenic pathways. IGF-I-induced mitogenesis, measured as thymidine incorporation and cellular proliferation, was abrogated in cells overexpressing mutant IGF-I receptors with replacement of the proximal double tyrosines (positions 1250 and 1251). Fibroblasts expressing this mutant IGF-I receptor formed fewer tumors than the negative control cells, whereas cells expressing wild-type IGF-I receptors formed large tumors in all recipient mice injected. Conversely, cells expressing mutant IGF-I receptors with only the conserved distal tyrosine (position 1316) replaced had slightly reduced IGF-I-stimulated β-subunit autophosphorylation, thymidine incorporation, and cellular proliferation when compared with cells expressing wild-type receptors. Phosphorylation of insulin receptor substrate-1 by the yCF mutant receptors was not impaired. Despite the ability of these mutant receptors to stimulate mitogenic growth, fibroblasts expressing this mutant receptor were also incapable of forming tumors in recipient nude mice. The distal tyrosine (position 1316) of the IGF-I receptor is crucial for tumor formation but is not essential for IGF-I stimulated mitogenesis. Thus, the tyrosine moieties in the carboxy-terminus of the IGF-I receptor participate in the signal transduction pathways that affect the mitogenic and tumorigenic potentials of cells expressing mutant IGF-I receptors.

Original languageEnglish (US)
Pages (from-to)410-417
Number of pages8
JournalEndocrinology
Volume137
Issue number2
StatePublished - 1996
Externally publishedYes

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IGF Type 1 Receptor
Tyrosine
Fibroblasts
Insulin-Like Growth Factor I
Insulin Receptor Substrate Proteins
Signal Transduction
Phenylalanine
Thymidine
Neoplasms
Phosphorylation
Cell Proliferation
Mutation
Growth Factor Receptors
Insulin Receptor

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Tumorigenic and Mitogenic Capacities Are Reduced in Transfected Fibroblasts Expressing Mutant Insulin-Like Growth Factor (IGF)-I Receptors. The Role of Tyrosine Residues 1250, 1251, and 1316 in the Carboxy-Terminus of the IGF-I Receptor. / Blakesley, Vicky A.; Kalebic, Thea; Helman, Lee J.; Stannard, Bethel; Faria, Teresa N.; Roberts, Charles; Leroith, Derek.

In: Endocrinology, Vol. 137, No. 2, 1996, p. 410-417.

Research output: Contribution to journalArticle

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title = "Tumorigenic and Mitogenic Capacities Are Reduced in Transfected Fibroblasts Expressing Mutant Insulin-Like Growth Factor (IGF)-I Receptors. The Role of Tyrosine Residues 1250, 1251, and 1316 in the Carboxy-Terminus of the IGF-I Receptor",
abstract = "Regulation of ligand-mediated signal transduction through transmembrane tyrosine kinase growth factor receptors involves phosphorylation of tyrosine residues in the intracellular domain of the receptor. The insulin-like growth factor-I (IGF-I) receptor contains three tyrosine residues in the carboxy-terminal domain at positions 1250, 1251, and 1316. Of these, only the tyrosine at position 1316 is conserved in the homologous position of the insulin receptor. Mutational analysis was used to study the role of these tyrosines in specific outcomes of IGF-I-mediated signal transduction. Mutations in the human IGF-I receptor were either replacement of tyrosines 1250 and 1251 with phenylalanine and histidine (yyFH), respectively, or replacement of the conserved distal tyrosine (position 1316) with phenylalanine (yCF). The yyFH mutation results in an IGF-I receptor with the amino acids found in the homologous position of the human insulin receptor. Cells overexpressing mutated IGF-I receptors were compared with cells expressing only endogenous IGF-I receptors or overexpressing wild-type IGF-I receptors. The ability of yyFH mutant IGF-I receptors to autophosphorylate the β-subunit or phosphorylate insulin receptor substrate-1 was not significantly different from wild-type IGF-I receptors. However, one or both of the proximal tyrosine residues (positions 1250 and 1251) in the carboxy-terminus of the IGF-I receptor are essential for IGF-I-stimulation of mitogenic and tumorigenic pathways. IGF-I-induced mitogenesis, measured as thymidine incorporation and cellular proliferation, was abrogated in cells overexpressing mutant IGF-I receptors with replacement of the proximal double tyrosines (positions 1250 and 1251). Fibroblasts expressing this mutant IGF-I receptor formed fewer tumors than the negative control cells, whereas cells expressing wild-type IGF-I receptors formed large tumors in all recipient mice injected. Conversely, cells expressing mutant IGF-I receptors with only the conserved distal tyrosine (position 1316) replaced had slightly reduced IGF-I-stimulated β-subunit autophosphorylation, thymidine incorporation, and cellular proliferation when compared with cells expressing wild-type receptors. Phosphorylation of insulin receptor substrate-1 by the yCF mutant receptors was not impaired. Despite the ability of these mutant receptors to stimulate mitogenic growth, fibroblasts expressing this mutant receptor were also incapable of forming tumors in recipient nude mice. The distal tyrosine (position 1316) of the IGF-I receptor is crucial for tumor formation but is not essential for IGF-I stimulated mitogenesis. Thus, the tyrosine moieties in the carboxy-terminus of the IGF-I receptor participate in the signal transduction pathways that affect the mitogenic and tumorigenic potentials of cells expressing mutant IGF-I receptors.",
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