title: Role of Ca2+-independent phospholipase A2 in exocytosis of amylase from parotid acinar cells.
abstract: We evaluated the role of cytosolic phospholipase A2 (PLA2) in the exocytosis of amylase from parotid acinar cells. The exocytosis stimulated by isoproterenol was dose-dependently inhibited by bromoenol lactone (BEL), a potent suicide inhibitor of Ca2+-independent cytosolic PLA2. The IC50 value of BEL was approximately 7 microM. AACOCF3, a selective inhibitor of Ca2+-dependent cytosolic PLA2, did not inhibit the exocytosis at least up to 30 microM. BEL also inhibited amylase release evoked by forskolin and membrane-permeable cAMP, but it did not inhibit cAMP-dependent protein kinase activity. PLA2 activity in parotid acinar cells was found to be predominantly Ca2+-independent, and was strongly inhibited by BEL, whose IC50 value was approximately 2 microM when it was applied to intact acini. Although isoproterenol scarcely enhanced [3H]arachidonic acid release from intact acinar cells, BEL dose-dependently decreased the basal arachidonic acid release to approximately one half of the control value. These results suggest that the cytosolic Ca2+-independent PLA2 activity plays a role in the membrane fusion process of exocytosis in parotid acinar cells.
authors.affiliation: Department of Oral Biochemistry, School of Dentistry, Health Sciences University of Hokkaido, Tobetsu. takuma@hucc.hokudai.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Takuma
authors.forename: T
authors.initials: T
authors.lastname: Ichida
mesh_terms: D000681:Amylases / Q000378:metabolism*; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D005089:Exocytosis / Q000502:physiology*; D054522:Group VI Phospholipases A2; D007545:Isoproterenol / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010306:Parotid Gland / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000502:physiology*; D054467:Phospholipases A2; D011753:Pyrones / Q000494:pharmacology; D051381:Rats
chemical_list: D009281:Naphthalenes; D010726:Phosphodiesterase Inhibitors; D011753:Pyrones; D016718:Arachidonic Acid; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; D054467:Phospholipases A2; D000681:Amylases; D007545:Isoproterenol