title: Pertussis toxin- and PMA-insensitive calcium mobilization by sphingosine in CFPAC-1 cells: evidence for a phosphatidic acid-dependent mechanism.
abstract: In a pancreatic duct adenocarcinoma cell line (CFPAC-1) sphingosine (10 microM) induced both mobilization of intracellular Ca2+ and stimulation of inositol phosphates accumulation. Whereas this latter effect was significantly inhibited by treatment with pertussis toxin or by short-term incubation with phorbol 12-myristate 13-acetate, Ca2+ mobilization was completely insensitive to both treatments. Experiments with permeabilized cells showed that sphingosine or the sphingosine metabolites sphingosine-1-phosphate and sphingosylphosphorylcholine were unable to directly release Ca2+ from internal stores, whereas phosphatidic acid, but not arachidonic acid, was effective. Phosphatidic acid formation was markedly enhanced (2.9-fold over control) by sphingosine, this effect being significantly reduced by preincubation with the diacylglycerol kinase inhibitor R59022. Ca2+ mobilization by sphingosine was also cut down by preincubation with R59022. In conclusion, the results suggest that sphingosine activates phospholipase C through a mechanism functionally coupled through a G protein and under control of PKC. Mobilization of [Ca2+]i by sphingosine is independent of phospholipase C stimulation and likely due to elevation of phosphatidic acid generated by stimulation of diacylglycerol kinase activity.
authors.affiliation: Dipart. di Biologia Ev. Sp. Università di Bologna, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Orlati
authors.forename: S
authors.initials: S
authors.lastname: Hrelia
authors.forename: M
authors.initials: M
authors.lastname: Rugolo
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line / Q000187:drug effects; D006801:Humans; D007295:Inositol Phosphates / Q000032:analysis; D008246:Lysophospholipids; D037342:Pertussis Toxin; D010712:Phosphatidic Acids / Q000378:metabolism* / Q000494:pharmacology; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D007295:Inositol Phosphates; D008246:Lysophospholipids; D010712:Phosphatidic Acids; D010566:Virulence Factors, Bordetella; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; C060506:sphingosine 1-phosphate; D016718:Arachidonic Acid; D000255:Adenosine Triphosphate; D037342:Pertussis Toxin; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium