title: Fyn kinase acts upstream of Shp2 and p38 mitogen-activated protein kinase to promote chemotaxis of mast cells towards stem cell factor.
abstract: The c-Kit receptor protein-tyrosine kinase plays a critical role in the differentiation, growth and survival of mast cells. Binding of its ligand stem cell factor (SCF), induces c-Kit dimerization, autophosphorylation, and recruitment of signaling proteins. The juxtamembrane sequence of c-Kit contains recruitment sites for the Src family kinases Fyn and Lyn, as well as Shp1 and Shp2 protein-tyrosine phosphatases. To characterize the role of Fyn in c-Kit signaling, we generated bone marrow-derived mast cells (BMMCs) from wild-type and Fyn knock-out mice. In contrast with previous studies of Lyn-deficient BMMCs, SCF treatment of Fyn-deficient BMMCs revealed no overt defects in the overall pattern of tyrosine phosphorylation, phosphatidylinositol 3' kinase recruitment to c-Kit, or phosphorylation of Stat3 transcription factor. However, Fyn-deficient mast cells showed a significant reduction in phosphorylation of Shp2 phosphatase and p38 mitogen-activated protein kinase. Defects in Shp2 and p38 phosphorylation were restored in Fyn-deficient mast cells transduced with a Fyn-expressing retrovirus (Fyn-rescue). Fyn-deficient BMMCs displayed reduced chemotaxis towards SCF, and this defect was corrected in Fyn-rescue cells. This study provides evidence that recruitment of both Shp2 and Fyn to juxtamembrane sites in c-Kit results in Shp2 phosphorylation, downstream signaling to p38 mitogen-activated protein kinase, and enhanced chemotaxis of mast cells.
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, ON, Canada K7L 3N6.
authors.forename: Lionel A
authors.initials: LA
authors.lastname: Samayawardhena
authors.forename: Jinghui
authors.initials: J
authors.lastname: Hu
authors.forename: Paul L
authors.initials: PL
authors.lastname: Stein
authors.forename: Andrew W B
authors.initials: AW
authors.lastname: Craig
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism; D002633:Chemotaxis / Q000502:physiology*; D004789:Enzyme Activation; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008407:Mast Cells / Q000166:cytology / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D048056:Mitogen-Activated Protein Kinase 9 / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn / Q000235:genetics / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D019089:Stem Cell Factor / Q000378:metabolism*; D013234:Stem Cells; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D019089:Stem Cell Factor; D019869:Phosphatidylinositol 3-Kinases; D048056:Mitogen-Activated Protein Kinase 9; D019009:Proto-Oncogene Proteins c-kit; D051076:Proto-Oncogene Proteins c-fyn; D048051:p38 Mitogen-Activated Protein Kinases; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse