Taxol induces tyrosine phosphorylation of Shc and its association with Grb2 in murine RAW 264.7 cells.
Taxol, a natural product with significant anti-tumor activity, stabilizes microtubules and arrests cells in the G2/M phase of the cell cycle. It has been reported that taxol has additional effects in cells, including an increase in tyrosine phosphorylation of proteins and activation of MAP kinase. We investigated a possible effect of taxol on tyrosine phosphorylation of Shc and on formation of the Shc/Grb-2 complex in the murine macrophage-like cell line RAW 264.7. Shc, an SH2 domain containing adaptor protein, was immunoprecipitated from lysates of taxol-treated cells with anti-phosphotyrosine antibody and its identity determined by Western blotting with anti-Shc antibody. Non-denatured Shc containing protein complexes were immunoprecipitated with anti-Shc antibody, and analysis with an anti-Grb2 antibody revealed the presence of the 24-kDa Grb2 protein. Taxol also activated Raf-1 kinase and ERK1/ERK2 MAP kinases in these cells. These results demonstrate that taxol affects tyrosine phosphorylation of Shc and this may result in the activation of the Raf-1/MAPK cascade.
Wolfson
M
M
Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Yang
C P
CP
Horwitz
S B
SB
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D051380:GRB2 Adaptor Protein; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009363:Neoplasm Proteins / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014443:Tyrosine / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000972:Antineoplastic Agents, Phytogenic; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D009363:Neoplasm Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D019000:Phosphotyrosine; D014443:Tyrosine; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D017239:Paclitaxel