Interaction of Ras and Raf in intact mammalian cells upon extracellular stimulation.

It has recently been shown that Ras proteins interact directly with Raf serine/threonine kinases in vitro and in the yeast two-hybrid system, leading to speculation that Raf proteins function as effectors for Ras. Here it is demonstrated that the endogenous Raf-1 protein co-immunoprecipitates with Ras from mammalian cells when the non-neutralizing anti-Ras monoclonal antibody Y13-238 is used. The formation of a Ras-Raf complex is absolutely dependent on prior treatment of the cells with a stimulus that activates Ras: phorbol ester or anti-T cell receptor antibody in the case of human peripheral blood T lymphoblasts, or epidermal growth factor in the case of Rat-1 fibroblasts. Up to 3% of cellular Raf-1 can be found in association with Ras. The association is not competed by addition of exogenous GST-Raf to the cell lysates and is therefore unlikely to be due to Ras-Raf binding after cell lysis. Specific interaction of Ras and Raf therefore occurs in intact mammalian cells in response to stimuli that cause Ras to become GTP-bound.
Mesh Terms:
Animals, Cells, Cultured, Epidermal Growth Factor, ErbB Receptors, Guanosine Triphosphate, Humans, In Vitro Techniques, Lymphocyte Activation, Protein Binding, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-raf, Proto-Oncogene Proteins p21(ras), Rats, T-Lymphocytes
J. Biol. Chem. Feb. 11, 1994; 269(6);3913-6 [PUBMED:8307946]
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