title: Fyn kinase controls FcepsilonRI receptor-operated calcium entry necessary for full degranulation in mast cells.
abstract: IgE-antigen-dependent crosslinking of the high affinity IgE receptor (FcepsilonRI) on mast cells leads to degranulation, leukotriene synthesis and cytokine production. Calcium (Ca(2+)) mobilization is a sine qua non requisite for degranulation, allowing the rapid secretion of stored pro-inflammatory mediators responsible for allergy symptoms. Fyn is a Src-family kinase that positively controls FcepsilonRI-induced mast cell degranulation. However, our understanding of the mechanism connecting Fyn activation to secretion of pre-synthesized mediators is very limited. We analyzed FcepsilonRI-dependent Ca(2+) mobilization in bone marrow-derived mast cells (BMMCs) differentiated from WT and Fyn -/- knock out mice. Fyn -/- BMMCs showed a marked defect in extracellular Ca(2+) influx after FcepsilonRI crosslinking but not after thapsigargin addition. High concentrations of Gadolinium (Gd(3+)) partially blocked FcepsilonRI-induced Ca(2+) influx in WT cells but, in contrast, completely inhibited Ca(2+) mobilization in Fyn -/- cells. Low concentrations of an inhibitor of the canonical transient receptor potential (TRPC) Ca(2+) channels (2-aminoethoxyphenyl-borane, 2-APB) blocked FcepsilonRI-induced maximal Ca(2+) rise in WT but not in Fyn -/- cells. Ca(2+) entry through Fyn-controlled, 2-APB sensitive channels was found to be important for full degranulation and IL-2 mRNA accumulation in WT cells. Immunoprecipitation assays showed that Fyn kinase interacts with TRPC 3/6/7 channels after IgE-antigen stimulation, but its association is not related to protein tyrosine phosphorylation. Results indicate Fyn kinase mediates the receptor-dependent activation of TRPC channels that contribute to degranulation in FcepsilonRI-stimulated mast cells.
authors.affiliation: Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados, Sede Sur, Calzada de los Tenorios 235, Col Granjas Coapa, CP 14330 Mexico City, Mexico.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Sanchez-Miranda
authors.forename: Alfredo
authors.initials: A
authors.lastname: Ibarra-Sanchez
authors.forename: Claudia
authors.initials: C
authors.lastname: Gonzalez-Espinosa
mesh_terms: D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015550:Cell Degranulation; D008407:Mast Cells / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D011493:Protein Kinase C / Q000378:metabolism; D064546:Protein Kinase C beta; D051076:Proto-Oncogene Proteins c-fyn / Q000235:genetics / Q000378:metabolism*; D017455:Receptors, IgE / Q000378:metabolism*; D050052:TRPC Cation Channels / Q000378:metabolism; D000074287:TRPC6 Cation Channel
chemical_list: D001896:Boron Compounds; D017455:Receptors, IgE; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; D000074287:TRPC6 Cation Channel; C492146:Trpc6 protein, mouse; C498502:Trpc7 protein, mouse; C109986:2-aminoethoxydiphenyl borate; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D002118:Calcium