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Identification of epidermal growth factor receptor- Grb2-associated binder-1-SHP-2 complex formation and its
H Kameda1, J I Risinger, B B Han
1Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, North Carolina 27709, USA.
Abstract:
The adaptor protein Grb2-associated binder-1 (Gab1) is known to bind to the SHP-2 tyrosine phosphatase on epidermal growth factor (EGF) receptor stimulation. To clarify the roles of these two proteins in EGF receptor (EGFR) signaling and determine their possible alteration during neoplastic cell progression, we studied these proteins in a Syrian hamster embryo (SHE) cell line model of neoplastic progression. Specifically, we used asbestos-transformed SHE fibroblasts: the 10W+8 clone, which is immortal but nontumorigenic; and the 10W2T clone, which is tumorigenic. Gab1 was detected, and the EGF-dependent formation of the EGFR-Gab1-SHP-2 complex was observed in 10W+8 cells. After cloning hamster Gab1 cDNA, exogenous expression of Gab1 significantly enhanced EGF-dependent mitogenic activity in 10W+8 cells. On the other hand, Gab1 was not detected in 10W2T cells, and the EGF-dependent association of SHP-2 with EGFR was also absent. Exogenous Gab1 expression in transfected 10W2T cells restored the EGF-dependent association of SHP-2 with EGFR, although it only showed a marginal effect on EGF-dependent mitogenic activity. Thus, Gab1 plays a pivotal role in the EGFR signaling pathway via the formation of the EGFR-Gab1-SHP-2 complex, and alteration in the expression and function of Gab1 is implicated in the neoplastic progression of SHE cells.
Insights
Grb2-associated binder-1 (Gab1) protein is crucial for epidermal growth factor receptor (EGFR) signaling. Its absence in tumorigenic cells suggests Gab1 alteration contributes to neoplastic progression.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- The adaptor protein Grb2-associated binder-1 (Gab1) interacts with SHP-2 phosphatase upon epidermal growth factor (EGF) receptor stimulation.
- Understanding the roles of Gab1 and SHP-2 in EGF receptor (EGFR) signaling is vital, especially concerning their potential alterations during neoplastic cell progression.
Purpose of the Study:
- To investigate the roles of Gab1 and SHP-2 in EGFR signaling.
- To determine if Gab1 and SHP-2 expression and function are altered during neoplastic progression using a Syrian hamster embryo (SHE) cell line model.
Main Methods:
- Utilized asbestos-transformed SHE fibroblasts (immortal, nontumorigenic 10W+8 clone; tumorigenic 10W2T clone).
- Cloned hamster Gab1 cDNA and performed exogenous expression studies.
- Analyzed EGF-dependent EGFR-Gab1-SHP-2 complex formation and mitogenic activity.
Main Results:
- EGF-dependent EGFR-Gab1-SHP-2 complex formation and enhanced mitogenic activity were observed in 10W+8 cells.
- Gab1 was undetectable in 10W2T cells, with absent EGF-dependent SHP-2/EGFR association.
- Exogenous Gab1 in 10W2T cells restored SHP-2/EGFR association but had minimal impact on mitogenic activity.
Conclusions:
- Gab1 is essential for EGFR signaling through the EGFR-Gab1-SHP-2 complex.
- Altered Gab1 expression and function are implicated in the neoplastic progression of SHE cells.