FLT3 signaling in hematopoietic cells involves CBL, SHC and an unknown P115 as prominent tyrosine-phosphorylated substrates.
Proliferation and survival of hematopoietic progenitors are partially dependent on the interaction between the FLT3 receptor tyrosine kinase (RTK) and its ligand, FL. This biological function depends primarily on tyrosine phosphorylation of cellular targets that initiate several transduction cascades. These events return to their basal levels upon activation of specific phosphatases. We analyzed tyrosine phosphorylation events in response to FL, in human cell lines of different hematopoietic origins that express endogenous FLT3, namely the myelomonocytic, monocytic, pre-B and pro-B lineages. This study aimed at determining (1) the identity of FLT3 downstream substrates in physiologically relevant cells and (2) distinct substrate involvement in myeloid or early B cells. The two prominent tyrosine-phosphorylated proteins are p52SHC and p115CBL in myeloid cell lines and p52SHC and an uncharacterized p115 in early B cell lines. Following FL stimulation, a concomitant increase in both CBL phosphorylation and complex formation with p85 subunit of phosphatidylinositol 3' kinase is observed. In contrast, the GRB2/CBL association observed in unstimulated cells is not modified after stimulation, and SHC is never detected in anti-CBL immunoprecipitates. FL-inducible binding of CBL to the CRKII adaptor molecule is also demonstrated. This study presents a picture of the signaling events triggered by activation of endogenous FLT3 receptor in human hematopoietic cells, including the existence of a B cell-specific FLT3 substrate.
Lavagna-Sévenier
C
C
Laboratory of Molecular Oncology, INSERM U119, Marseille, France.
Marchetto
S
S
Birnbaum
D
D
Rosnet
O
O
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D001402:B-Lymphocytes; D002460:Cell Line; D051380:GRB2 Adaptor Protein; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology*; D006801:Humans; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000032:analysis; D011494:Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013379:Substrate Specificity; D014162:Transfection; D014407:Tumor Cells, Cultured; D051941:fms-Like Tyrosine Kinase 3; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C111405:P11 (CBL); D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D011994:Recombinant Proteins; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D019000:Phosphotyrosine; D011494:Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; C497970:FLT3 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3