Coupling between p210bcr-abl and Shc and Grb2 adaptor proteins in hematopoietic cells permits growth factor receptor-independent link to ras activation pathway.
Enforced expression of p210bcr-abl transforms interleukin 3 (IL-3)-dependent hematopoietic cell lines to growth factor-independent proliferation. It has been demonstrated that nonreceptor tyrosine kinase oncogenes may couple to the p21ras pathway to exert their transforming effect. In particular, p210bcr-abl was recently found to effect p21ras activation in hematopoietic cells. In this context, experiments were performed to evaluate a protein signaling pathway by which p210bcr-abl might regulate p21ras. It was asked whether Shc p46/p52, a protein containing a src-homology region 2 (SH2) domain, and known to function upstream from p21ras, might form specific complexes with p210bcr-abl and thus, possibly alter p21ras activity by coupling to the guanine nucleotide exchange factor (Sos/CDC25) through the Grb2 protein-Sos complex. This latter complex has been previously demonstrated to occur ubiquitously. We found that p210bcr-abl formed a specific complex with Shc and with Grb2 in three different murine cell lines transfected with a p210bcr-abl expression vector. There appeared to be a higher order complex containing Shc, Grb2, and bcr-abl proteins. In contrast to p210bcr-abl transformed cells, in which there was constitutive tight association between Grb2 and Shc, binding between Grb2 and Shc was Steel factor (SLF)-dependent in a SLF-responsive, nontransformed parental cell line. The SLF-dependent association between Grb2 and Shc in nontransformed cells involved formation of a complex of Grb2 with c-kit receptor after SLF treatment. Thus, p210bcr-abl appears to function in a hematopoietic p21ras activation pathway to allow growth factor-independent coupling between Grb2, which exists in a complex with the guanine nucleotide exchange factor (Sos), and p21ras. Shc may not be required for Grb2-c-kit interaction, because it fails to bind strongly to c-kit.
Tauchi
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T
Department of Medicine (Hematology/Oncology), Indiana University School of Medicine, Indianapolis 46202.
Boswell
H S
HS
Leibowitz
D
D
Broxmeyer
H E
HE
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D001854:Bone Marrow Cells; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D066246:ErbB Receptors / Q000378:metabolism*; D016044:Fusion Proteins, bcr-abl / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D016298:Hematopoietic Cell Growth Factors / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D051379:Mice; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D016184:Receptors, Colony-Stimulating Factor / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D019089:Stem Cell Factor; D014443:Tyrosine / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D016298:Hematopoietic Cell Growth Factors; D011506:Proteins; D011518:Proto-Oncogene Proteins; D016184:Receptors, Colony-Stimulating Factor; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D019089:Stem Cell Factor; D014443:Tyrosine; D066246:ErbB Receptors; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl; D015689:Oncogene Protein p21(ras)