title: Possible involvement of phosphatidylinositol 3-kinase in regulated exocytosis: studies in chromaffin cells with inhibitor LY294002.
abstract: Several lines of evidence suggest that phosphorylated products of phosphatidylinositol play critical functions in the regulation of membrane trafficking along the secretory pathway. To probe the possible involvement of phosphatidylinositol 3-kinase (PI 3-kinase) in regulated exocytosis, we have examined its subcellular distribution in cultured chromaffin cells by immunoreplica analysis and confocal immunofluorescence. We found that the PI 3-kinase heterodimer consisting of the regulatory and catalytic subunits was associated essentially with the subplasmalemmal cytoskeleton in both resting and nicotine-stimulated chromaffin cells. Attempts to immunoprecipitate PI 3-kinase with anti-phosphotyrosine antibodies failed, suggesting that the activity of PI 3-kinase was not modulated by tyrosine phosphorylation and/or physical interaction with SH2-containing proteins in stimulated chromaffin cells. LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one], a potent inhibitor of PI 3-kinase, produced a dose-dependent inhibition of catecholamine secretion evoked by various secretagogues. Furthermore, cytochemical experiments with rhodamine-labeled phalloidin revealed that LY294002 blocked the disassembly of cortical actin in chromaffin cells stimulated by a depolarizing concentration of potassium. Our results suggest that PI 3-kinase may be one of the important regulatory exocytotic components involved in the signaling cascade controlling actin rearrangements required for catecholamine secretion.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U-338, Biologie de la Communication Cellulaire, Strasbourg, France.
authors.forename: S
authors.initials: S
authors.lastname: Chasserot-Golaz
authors.forename: P
authors.initials: P
authors.lastname: Hubert
authors.forename: D
authors.initials: D
authors.lastname: Thiersé
authors.forename: S
authors.initials: S
authors.lastname: Dirrig
authors.forename: C J
authors.initials: CJ
authors.lastname: Vlahos
authors.forename: D
authors.initials: D
authors.lastname: Aunis
authors.forename: M F
authors.initials: MF
authors.lastname: Bader
mesh_terms: D000199:Actins / Q000648:ultrastructure; D000311:Adrenal Glands / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002458:Cell Fractionation; D019439:Chromaffin Cells / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure; D002867:Chromones / Q000494:pharmacology*; D003599:Cytoskeleton / Q000187:drug effects / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005089:Exocytosis / Q000187:drug effects*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D009025:Morpholines / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000648:ultrastructure; D000081082:Phosphoinositide-3 Kinase Inhibitors
chemical_list: D000199:Actins; D002118:Calcium; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D009638:Norepinephrine; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one