Involvement of Src-homology/collagen (SHC) Proteins in Signaling Through the Insulin Receptor and the insulin-like-growth-factor-I-receptor

Eur J Biochem. 1994 Jul 1;223(1):195-202. doi: 10.1111/j.1432-1033.1994.tb18983.x.

Abstract

Src homology/collagen (SHC) proteins are thought to participate in signaling through both receptor tyrosine kinases, such as the insulin receptor and the EGF (epidermal growth factor) receptor, and cytoplasmic tyrosine kinases, such as v-src and v-fps. Here we approached the insulin-induced and the insulin-like-growth-factor-I-induced (IGF-I-induced) phosphorylation of SHC proteins, and the possible role of these proteins in insulin and IGF-I signaling. First, we showed that SHC proteins are phosphorylated on tyrosine residues upon insulin and IGF-I treatment of fibroblasts transfected with a SHC cDNA construct. More important, ligand-activated insulin and IGF-I receptors phosphorylate SHC proteins in vitro, indicating that SHC proteins could be direct substrates for insulin and IGF-I receptors. Further, insulin or IGF-I treatment of SHC-transfected fibroblasts leads to immunoprecipitation of SHC proteins with insulin-receptor substrate 1 (IRS-1). We next looked at the possible effect of SHC proteins on biological responses in SHC-transfected fibroblasts. We found that the expression of exogenous SHC proteins results in an increased basal MEK (MAPK/ERK-activating kinase) activity. Further, neither the basal nor the insulin-induced or IGF-I-induced PtdIns-3-kinase activity were modified by expression of exogenous SHC proteins. These results illustrate that SHC proteins are implicated in the MAP (mitogen-activated protein)-kinase pathway, but not in that of PtdIns-3-kinase. Finally, we show that SHC-transfected cells, unlike control cells, are able to advance into the early phases of the cell cycle, and are more sensitive to the growth-promoting effect of insulin. In conclusion, SHC proteins are substrates for insulin and IGF-I receptors, and would appear to function as early post-receptor signaling components.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Cell Division / genetics
  • Collagen / metabolism*
  • Enzyme Activation
  • Fibroblasts / metabolism
  • Insulin-Like Growth Factor I / metabolism*
  • MAP Kinase Kinase 1
  • Mice
  • Mitogen-Activated Protein Kinase Kinases*
  • Oncogene Protein pp60(v-src) / metabolism*
  • Phosphatidylinositol 3-Kinases
  • Phosphorylation
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism
  • Protein-Serine-Threonine Kinases / metabolism
  • Protein-Tyrosine Kinases / metabolism
  • Receptor, Insulin / metabolism*
  • Receptors, Somatomedin / metabolism*
  • Signal Transduction*
  • Transfection
  • Tyrosine / metabolism

Substances

  • Receptors, Somatomedin
  • Tyrosine
  • Insulin-Like Growth Factor I
  • Collagen
  • Phosphatidylinositol 3-Kinases
  • Phosphotransferases (Alcohol Group Acceptor)
  • Protein-Tyrosine Kinases
  • Receptor, Insulin
  • Oncogene Protein pp60(v-src)
  • Protein-Serine-Threonine Kinases
  • MAP Kinase Kinase 1
  • Map2k1 protein, mouse
  • Mitogen-Activated Protein Kinase Kinases