Tob, a novel protein that interacts with p185erbB2, is associated with anti-proliferative activity

Area of Science:

• Molecular biology
• Cell signaling
• Oncology

Background:

• The c-erbB-2 proto-oncogene product p185erbB2 is a receptor-type tyrosine kinase implicated in cell growth and cancer.
• Understanding proteins that interact with p185erbB2 is crucial for elucidating cell growth regulation.
• The anti-proliferative gene BTG-1 shares homology with novel proteins.

Purpose of the Study:

• To identify and characterize novel proteins interacting with the c-erbB-2 gene product p185erbB2.
• To investigate the functional role of the novel protein Tob (Transducer of ErbB-2) in cell growth regulation.
• To determine the interaction domains and regulatory mechanisms between Tob and p185erbB2.

Main Methods:

• Molecular cloning and nucleotide sequencing of Tob cDNA.
• Expression of recombinant Tob protein and analysis of its effect on NIH3T3 cell proliferation.
• Co-immunoprecipitation assays to confirm the interaction between Tob and p185erbB2.
• Analysis of Tob mRNA expression in various cell types.

Main Results:

• A novel protein, Tob (Transducer of ErbB-2), was cloned and characterized. Tob is 45 kDa, homologous to BTG-1 in its N-terminal half, and interacts with p185erbB2 via its C-terminal half.
• Exogenous Tob expression suppressed NIH3T3 cell growth, an effect diminished by kinase-active p185erbB2.
• Co-immunoprecipitation confirmed the physical interaction between Tob and p185erbB2.
• Tob mRNA expression was detected in various cell types and was not correlated with c-erbB-2 expression.

Conclusions:

• p185erbB2 negatively regulates the Tob-mediated anti-proliferative pathway through direct interaction, potentially leading to growth stimulation.
• The carboxyl-terminal half of Tob is essential for its interaction with p185erbB2.
• Tob's regulation of cell growth may involve other receptor-type protein-tyrosine kinases besides c-erbB-2.