Physical and functional interaction between Hck tyrosine kinase and guanine nucleotide exchange factor C3G results in apoptosis, which is independent of C3G catalytic domain.

The hematopoietic cell kinase Hck is a Src family tyrosine kinase expressed in cells of myelomonocytic lineage, B lymphocytes, and embryonic stem cells. To study its role in signaling pathways we used the Hck-SH3 domain in protein interaction cloning and identified C3G, the guanine nucleotide exchange factor for Rap1 and ...
R-Ras, as a protein that associated with Hck. This interaction was direct and was mediated partly through the proline-rich region of C3G. C3G could be co-immunoprecipitated with Hck from Cos-1 cells transfected with Hck and C3G. C3G was phosphorylated on tyrosine 504 in cells when coexpressed with Hck but not with a catalytically inactive mutant of Hck. Phosphorylation of endogenous C3G at Tyr-504 was increased by treatment of human myelomonocytic THP-1 cells with mercuric chloride, which is known to activate Hck tyrosine kinase specifically. Coexpression of Hck with C3G induced a high level of apoptosis in many cell lines by 30-42 h of transfection. Induction of apoptosis was not dependent on Tyr-504 phosphorylation or the catalytic domain of C3G but required the catalytic activity of Hck. Using dominant negative constructs of caspases we found that caspase-1, -8, and -9 are involved in this apoptotic pathway. These results suggest that C3G and Hck interact physically and functionally in vivo to activate kinase-dependent and caspase-mediated apoptosis, which is independent of catalytic domain of C3G.
Mesh Terms:
Animals, Apoptosis, Blotting, Western, COS Cells, Caspase 1, Caspase 8, Caspase 9, Caspases, Catalysis, Catalytic Domain, Cell Line, Cell Line, Tumor, Electrophoresis, Polyacrylamide Gel, Genes, Dominant, Genetic Vectors, Glutathione Transferase, Guanine Nucleotide-Releasing Factor 2, Hela Cells, Humans, Mercuric Chloride, Microscopy, Fluorescence, Phosphorylation, Precipitin Tests, Protein Binding, Protein-Tyrosine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-hck, Signal Transduction, Time Factors, Transfection, Tyrosine, rap1 GTP-Binding Proteins, src Homology Domains
J. Biol. Chem.
Date: Dec. 26, 2003
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