title: P2Y6 nucleotide receptor activates PKC to protect 1321N1 astrocytoma cells against tumor necrosis factor-induced apoptosis.
abstract: 1. We recently reported that the activation by UDP of rat P2Y6 nucleotide receptors expressed in 1321N1 astrocytoma cells protected them from TNFalpha-induced apoptosis by suppressing activation of caspase 3 and 8. This study aims to characterize the involvement of intracellular signaling pathways, including kinases involved in the antiapoptotic effect of UDP. 2. Cell death was induced in 1321N1 astrocytoma cells permanently expressing the rat P2Y6 receptor by exposure to TNFalpha in the presence of cycloheximide. The apoptotic fraction was analyzed using flow cytometry. 3. The activation of P2Y6 receptors by UDP both protected the astrocytes from TNF-alpha induced apoptosis and activated protein kinase C (PKC) isotypes. The phorbol ester PMA also activated PKC and protected the cells from TNFalpha-induced cell death. The alpha- and epsilon-isotypes of PKC were both activated in a persistent fashion upon 5-min exposure to either UDP (10 microM) or the phorbol ester PMA (100 nM). The PKCzeta isotype was markedly activated upon UDP treatment. 4. The addition of PKC inhibitors, GF109203X or Gö6976, partially antagonized the protective effect of UDP and reduced the UDP-induced phosphorylation of extracellular signal-regulated protein kinases (Erk). The inhibitors of Erk, PD98,059 or U0126, antagonized UDP-induced protection. 5. The antiapoptotic protein, Akt, was not affected by P2Y6 receptor activation. Incubation of the astrocytes with calcium modifiers BAPTA-AM or dantrolene, did not affect the UDP-induced protection from apoptosis. 6. The addition of phospholipase C (PLC) inhibitors, D609 or U73122, partially antagonized both UDP-induced protection and PKC activation.
authors.affiliation: Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0810, USA.
authors.forename: Seong G
authors.initials: SG
authors.lastname: Kim
authors.forename: Zhan-Guo
authors.initials: ZG
authors.lastname: Gao
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Soltysiak
authors.forename: Tong-Shin
authors.initials: TS
authors.lastname: Chang
authors.forename: Chaya
authors.initials: C
authors.lastname: Brodie
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Jacobson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001254:Astrocytoma; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004347:Drug Interactions / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D020033:Protein Isoforms / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D014530:Uridine Diphosphate / Q000378:metabolism / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D018048:Receptors, Purinergic P2; D014409:Tumor Necrosis Factor-alpha; C099845:purinoceptor P2Y6; D014530:Uridine Diphosphate; C494918:AKT1 protein, human; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate