title: Phosphatidylinositol-3-kinase regulates mast cell ion channel activity.
abstract: Stimulation of the mast cell IgE-receptor (FcepsilonRI) by antigen leads to stimulation of Ca(2+) entry with subsequent mast cell degranulation and release of inflammatory mediators. Ca(2+) further activates Ca(2+)-activated K(+) channels, which in turn provide the electrical driving force for Ca(2+) entry. Since phosphatidylinositol (PI)-3-kinase has previously been shown to be required for mast cell activation and degranulation, we explored, whether mast cell Ca(2+) and Ca(2+)-activated K(+) channels may be sensitive to PI3-kinase activity. Whole-cell patch clamp experiments and Fura-2 fluorescence measurements for determination of cytosolic Ca(2+) concentration were performed in mouse bone marrow-derived mast cells either treated or untreated with the PI3-kinase inhibitors LY-294002 (10 muM) and wortmannin (100 nM). Antigen-stimulated Ca(2+) entry but not Ca(2+) release from the intracellular stores was dramatically reduced upon PI3-kinase inhibition. Ca(2+) entry was further inhibited by TRPV blocker ruthenium red (10 muM). Ca(2+) entry following readdition after Ca(+)-store depletion with thapsigargin was again decreased by LY-294002, pointing to inhibition of store-operated channels (SOCs). Moreover, inhibition of PI3-kinase abrogated IgE-stimulated, but not ionomycin-induced stimulation of Ca(2+)-activated K(+) channels. These observations disclose PI3-kinase-dependent regulation of Ca(2+) entry and Ca(2+)-activated K(+)-channels, which in turn participate in triggering mast cell degranulation.
authors.affiliation: Department of Physiology, University of Tübingen, Germany.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Lam
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Shumilina
authors.forename: Nicole
authors.initials: N
authors.lastname: Matzner
authors.forename: Irina M
authors.initials: IM
authors.lastname: Zemtsova
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Sobiesiak
authors.forename: Camelia
authors.initials: C
authors.lastname: Lang
authors.forename: Edward
authors.initials: E
authors.lastname: Felder
authors.forename: Paul
authors.initials: P
authors.lastname: Dietl
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Huber
authors.forename: Florian
authors.initials: F
authors.lastname: Lang