title: Defective degranulation and calcium mobilization of bone-marrow derived mast cells from Xid and Btk-deficient mice.
abstract: Regulation of adhesion and degranulation of mast cells plays an important role in allergy and inflammation. We investigated a possible role of Bruton's tyrosine kinase (Btk) in the regulation of adhesion and degranulation by using bone marrow-derived mast cells from X-linked immunodeficiency (Xid) and Btk-deficient mice. Cross-linking of the high affinity IgE receptor (Fc epsilonRI) and steel factor (SLF) induced indistinguishable adhesive responses of mast cells to fibronectin in kinetics, and these adhesive responses were comparable among wild type, Xid, and Btk-deficient mast cells. Cross-linking of Fc epsilonRI, but not SLF triggered degranulation of bone marrow-derived mast cells. However, Fc epsilonRI-induced degranulation was impaired in Xid and Btk-deficient mast cells. Calcium influx induced by Fc epsilonRI cross-linking and SLF were also reduced in Xid and Btk-deficient mast cells. Degranulation and calcium influx were reduced more severely in Btk-deficient than in Xid mast cells. Consistently, cross-linking Fc epsilonRI and SLF augmented Btk kinase activities transiently. Inositol triphosphate (IP3) production was also severely reduced in Btk-deficient mast cells, indicating Btk play a critical role of Fc epsilonRI-induced IP3 production. The differential sensitivity of wortmannin on calcium influx in wild type and Xid mast cells suggested that the activation of phosphatidylinositol 3 kinase (PI 3-kinase) was required in calcium influx. Furthermore, abnormal secretory granules with translucent contents and variable in size were observed both in Xid and Btk-deficient mast cells. Our study demonstrated a critical role of Btk in regulating intracellular calcium and granule exocytosis.
authors.affiliation: Department of Immunology, Institute of Medical Science, The University of Tokyo, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Setoguchi
authors.forename: T
authors.initials: T
authors.lastname: Kinashi
authors.forename: H
authors.initials: H
authors.lastname: Sagara
authors.forename: K
authors.initials: K
authors.lastname: Hirosawa
authors.forename: K
authors.initials: K
authors.lastname: Takatsu
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D015550:Cell Degranulation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007153:Immunologic Deficiency Syndromes / Q000276:immunology*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008407:Mast Cells / Q000502:physiology* / Q000648:ultrastructure; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D017455:Receptors, IgE / Q000378:metabolism; D019089:Stem Cell Factor / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D004791:Enzyme Inhibitors; D017455:Receptors, IgE; D019089:Stem Cell Factor; D015544:Inositol 1,4,5-Trisphosphate; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625951:Btk protein, mouse; D002118:Calcium; D000077191:Wortmannin