The ubiquitously expressed Syp phosphatase interacts with c-kit and Grb2 in hematopoietic cells.
The c-kit proto-oncogene encodes a transmembrane tyrosine kinase receptor, which is important for the normal development of hematopoietic cells, melanoblasts, and germ cells. Autophosphorylation of c-kit receptor on tyrosine creates binding sites for cellular src homology 2 (SH2)-containing signaling molecules. The discovery of phosphotyrosine phosphatases that contain SH2 domains suggests roles for these molecules in growth factor signaling pathways. We found that Syp, a phosphotyrosine phosphatase widely expressed in all the tissues in mammals, associates with c-kit receptor after activation with its ligand, steel factor, in the factor-dependent cell line, M07e. Both NH2-terminal and COOH-terminal SH2 domains of Syp, made as glutathione S-transferase fusion proteins, were able to bind to the activated c-kit receptor in vitro. Furthermore, Syp became marginally phosphorylated on tyrosine upon c-kit receptor activation, and tyrosine-phosphorylated Syp was found to be complexed with Grb2 in steel factor-stimulated M07e cells. Direct binding between Syp and Grb2 was also observed in vitro. Last, Ras and Raf interacts in vitro as a result of steel factor-stimulated Ras activation. These results suggest that Syp may be an important signaling component downstream of the c-kit receptor and involved in activation of the Ras signaling pathway in hematopoietic cells.
Tauchi
T
T
Department of Medicine (Hematology/Oncology), Indiana University School of Medicine, Indianapolis 46202.
Feng
G S
GS
Marshall
M S
MS
Shen
R
R
Mantel
C
C
Pawson
T
T
Broxmeyer
H E
HE
D048868:Adaptor Proteins, Signal Transducing; D002460:Cell Line; D051380:GRB2 Adaptor Protein; D016298:Hematopoietic Cell Growth Factors / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit; D019908:Proto-Oncogene Proteins c-raf; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D016184:Receptors, Colony-Stimulating Factor / Q000378:metabolism*; D015398:Signal Transduction; D019089:Stem Cell Factor
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D016298:Hematopoietic Cell Growth Factors; D047908:Intracellular Signaling Peptides and Proteins; C000715470:MAS1 protein, human; D011506:Proteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D016184:Receptors, Colony-Stimulating Factor; D019089:Stem Cell Factor; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)