title: Btk plays a crucial role in the amplification of Fc epsilonRI-mediated mast cell activation by kit.
abstract: Stem cell factor (SCF) acts in synergy with antigen to enhance the calcium signal, degranulation, activation of transcription factors, and cytokine production in human mast cells. However, the underlying mechanisms for this synergy remain unclear. Here we show, utilizing bone marrow-derived mast cells (BMMCs) from Btk and Lyn knock-out mice, that activation of Btk via Lyn plays a key role in promoting synergy. As in human mast cells, SCF enhanced degranulation and cytokine production in BMMCs. In Btk-/- BMMCs, in which there was a partial reduction in the capacity to degranulate in response to antigen, SCF was unable to enhance the residual antigen-mediated degranulation. Furthermore, as with antigen, the ability of SCF to promote cytokine production was abrogated in the Btk-/- BMMCs. The impairment of responses in Btk-/- cells correlated with an inability of SCF to augment phospholipase Cgamma1 activation and calcium mobilization, and to phosphorylate NFkappaB and NFAT for cytokine gene transcription in these cells. Similar studies with Lyn-/- and Btk-/-/Lyn-/- BMMCs indicated that Lyn was a regulator of Btk for these responses. These data demonstrate, for the first time, that Btk is a key regulator of a Kit-mediated amplification pathway that augments Fc epsilonRI-mediated mast cell activation.
authors.affiliation: Laboratory of Allergic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892-1881, USA.
authors.forename: Shoko
authors.initials: S
authors.lastname: Iwaki
authors.forename: Christine
authors.initials: C
authors.lastname: Tkaczyk
authors.forename: Anne B
authors.initials: AB
authors.lastname: Satterthwaite
authors.forename: Kristina
authors.initials: K
authors.lastname: Halcomb
authors.forename: Michael A
authors.initials: MA
authors.lastname: Beaven
authors.forename: Dean D
authors.initials: DD
authors.lastname: Metcalfe
authors.forename: Alasdair M
authors.initials: AM
authors.lastname: Gilfillan
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D000941:Antigens / Q000378:metabolism; D001854:Bone Marrow Cells / Q000166:cytology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D020935:MAP Kinase Signaling System; D008407:Mast Cells / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism; D051966:Phospholipase C gamma / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology*; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D017455:Receptors, IgE / Q000737:chemistry*; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D000941:Antigens; D016207:Cytokines; D016328:NF-kappa B; D017455:Receptors, IgE; D019089:Stem Cell Factor; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; D051966:Phospholipase C gamma; D002118:Calcium