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Shc products are substrates of erbB-2 kinase
Abstract:
The shc genes encodes three widely expressed proteins of 46, 52 and 66 kDa. Overexpression of p46shc and p52shc in NIH3T3 fibroblasts induces a tumorigenic phenotype. Shc products are phosphorylated on tyrosine by the activated epidermal growth factor receptor (EGFR) and become physically associated with EGFR via their SH2 domain. Thus Shc oncoproteins may play a role in mitogenic signal transduction. Here we report that Shc products are substrates also of the erbB-2 kinase and form complexes with the erbB-2 product in intact cells. In vitro, the bacterially expressed Shc SH2 domain is sufficient to reconstitute the high affinity Shc/erbB-2 interaction. The erbB-2 region required for Shc binding was narrowed down to the most COOH-terminal 179 residues of gp185erbB-2; within this region, phosphorylation of one or more of the erbB-2 autophosphorylation sites is required for Shc/gp185erbB-2 complex formation as well as optimal phosphorylation of Shc products by the erbB-2 kinase. Thus, Shc proteins may play a role in signal transduction by gp185erbB-2.
Insights
Shc proteins, involved in cell growth, interact with the erbB-2 kinase. This interaction is crucial for signal transduction pathways mediated by erbB-2, impacting cell proliferation and potentially cancer development.
Area of Science:
- Molecular Biology
- Cell Signaling
- Oncology
Background:
- The shc genes encode proteins (p46shc, p52shc, p66shc) involved in cell signaling.
- Overexpression of p46shc and p52shc can induce a tumorigenic phenotype in fibroblasts.
- Shc proteins associate with activated epidermal growth factor receptor (EGFR) via their SH2 domain, suggesting a role in mitogenic signal transduction.
Purpose of the Study:
- To investigate the interaction between Shc proteins and the erbB-2 kinase.
- To elucidate the molecular mechanisms underlying Shc/erbB-2 complex formation and Shc phosphorylation by erbB-2.
Main Methods:
- Co-immunoprecipitation assays to detect Shc/erbB-2 complex formation in intact cells.
- In vitro binding assays using bacterially expressed Shc SH2 domain.
- Site-directed mutagenesis to identify the erbB-2 binding region and phosphorylation sites.
Main Results:
- Shc proteins form complexes with the erbB-2 product in intact cells.
- The SH2 domain of Shc is sufficient for high-affinity interaction with erbB-2.
- A specific region within the COOH-terminal 179 residues of gp185erbB-2 is required for Shc binding.
- Phosphorylation of erbB-2 autophosphorylation sites is necessary for Shc/erbB-2 complex formation and optimal Shc phosphorylation by erbB-2 kinase.
Conclusions:
- Shc proteins are substrates of the erbB-2 kinase, in addition to EGFR.
- Shc proteins play a significant role in signal transduction pathways mediated by gp185erbB-2.
- The findings highlight Shc proteins as key mediators in erbB-2 signaling, with implications for understanding cancer biology.