title: Differential effects of lysophospholipids on exocytosis  in rat PC12 cells.
abstract: Secretory phospholipase A2 (sPLA2) activity is present in the CNS and the sPLA2-IIA isoform has been shown to induce exocytosis in cultured hippocampal neurons. However, little is known about possible contributions of various lysophospholipid species to exocytosis in neuroendocrine cells. This study was therefore carried out to examine the effects of several lysophospholipid species on exocytosis on rat pheochromocytoma-12 (PC12) cells. An increase in vesicle fusion, indicating exocytosis, was observed in PC12 cells after external infusion of lysophosphatidylinositol (LPI), but not lysophosphatidylcholine or lysophosphatidylserine by total internal reflection microscopy. Similarly, external infusion of LPI induced significant increases in capacitance, or number of spikes detected at amperometry, indicating exocytosis. Depletion of cholesterol by pre-incubation of cells with methyl beta cyclodextrin and depletion of Ca2+ by thapsigargin and incubation in zero external Ca2+ resulted in attenuation of LPI induced exocytosis, indicating that exocytosis was dependent on the integrity of lipid rafts and intracellular Ca2+. Moreover, LPI induced a rise in intracellular Ca2+ suggesting that this could be the trigger for exocytosis. It is postulated that LPI may be an active participant in sPLA2-mediated exocytosis in the CNS.
authors.affiliation: Department of Oral and Maxillofacial Surgery, National University of Singapore, Singapore, Singapore.
authors.forename: May-Thu
authors.initials: MT
authors.lastname: Ma
authors.forename: Jin-Fei
authors.initials: JF
authors.lastname: Yeo
authors.forename: Akhlaq A
authors.initials: AA
authors.lastname: Farooqui
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Peng
authors.initials: P
authors.lastname: Chen
authors.forename: Wei-Yi
authors.initials: WY
authors.lastname: Ong
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000502:physiology; D025802:Electric Capacitance; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D000960:Hypolipidemic Agents / Q000494:pharmacology; D042541:Intracellular Space / Q000187:drug effects / Q000502:physiology; D008244:Lysophosphatidylcholines / Q000378:metabolism*; D008246:Lysophospholipids / Q000378:metabolism*; D021962:Membrane Microdomains / Q000187:drug effects / Q000502:physiology; D016716:PC12 Cells; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D000960:Hypolipidemic Agents; D008244:Lysophosphatidylcholines; D008246:Lysophospholipids; D047392:beta-Cyclodextrins; C025449:lysophosphatidylinositol; C025059:lysophosphatidylserine; C108732:methyl-beta-cyclodextrin; D019284:Thapsigargin; D002784:Cholesterol; D002118:Calcium