Gab1 is required for cell cycle transition, cell proliferation, and transformation induced by an oncogenic met...

Area of Science:

• Cell Biology
• Molecular Biology
• Oncology

Background:

• The oncogenic Met receptor Tpr-Met signals through Grb2 or Shc to promote cell cycle progression in Xenopus oocytes.
• Direct adaptor binding to Tpr-Met is not required, suggesting an intermediary binding partner is involved.

Purpose of the Study:

• To investigate the role of Grb2-associated binder 1 (Gab1) as a Met receptor binding partner in cell cycle control and oncogenic transformation.
• To identify key Gab1 functional domains and signaling pathways required for Tpr-Met-mediated cellular responses.

Main Methods:

• Overexpression of Gab1 in Xenopus oocytes with Tpr-Met.
• Analysis of Gab1 functional domains, including Met-binding motif, pleckstrin homology domain, and binding sites for PI3K and SHP-2.
• Assessment of Gab1's role in Tpr-Met and fibroblast growth factor receptor signaling, and progesterone-induced cell cycle transition.
• Evaluation of Gab1's necessity for Tpr-Met-induced fibroblast transformation and proliferation.

Main Results:

• Gab1 overexpression promotes cell cycle progression when Tpr-Met is at suboptimal levels.
• Gab1 requires its Met-binding motif, PH domain, and PI3K/SHP-2 binding sites, but not Grb2/CrkII/PLCgamma sites, for this function.
• Gab1 signaling is critical for oncogenic Met and FGF receptor-driven cell cycle transition, but not progesterone-induced transition.
• Gab1 is essential for Tpr-Met-mediated fibroblast morphological transformation and proliferation.

Conclusions:

• Gab1 is a key Met receptor binding partner that induces cell cycle progression, proliferation, and oncogenic transformation.
• Gab1 and its associated signaling pathways are potential therapeutic targets for cancers with deregulated Met receptors.