title: Insulin promotes diacylglycerol kinase activation by different mechanisms in rat cerebral cortex synaptosomes.
abstract: The mechanism by which insulin increases diacylglycerol kinase (DAGK) activity has been studied in cerebral cortex (CC) synaptosomes from adult (3-4 months of age) rats. The purpose of this study was to identify the role of phospholipases C and D (PLC and PLD) in DAGK activation by insulin. Neomycin, an inhibitor of PLC phosphatidylinositol-bisphosphate (PIP2) specific; ethanol, an inhibitor of phosphatidic acid (PA) formation by the promotion of a transphosphatidyl reaction of phosphatidylcholine phospholipase D (PC-PLD); and DL propranolol, an inhibitor of phosphatidate phosphohydrolase (PAP), were used in this study. Insulin (0.1 microM) shielded an increase in PA synthesis by [32P] incorporation using [gamma-32P]ATP as substrate and endogenous diacylglycerol (DAG) as co-substrate. This activated synthesis was strongly inhibited either by ethanol or DL propranolol. Pulse chase experiments also showed a PIP2-PLC activation within 1 min exposure to insulin. When exogenous unsaturated 18:0-20:4 DAG was present, insulin increased PA synthesis significantly. However, this stimulatory effect was not observed in the presence of exogenous saturated (di-16:0). In the presence of R59022, a selective DAGK inhibitor, insulin exerted no stimulatory effect on [32P]PA formation, suggesting a strong relationship between increased PA formation by insulin and DAGK activity. These data indicate that the increased synthesis of PA by insulin could be mediated by the activation of both a PC-PLD pathway to provide DAG and a direct DAGK activation that is associated to the use of 18:0-20:4 DAG species. PIP2-PLC activation may contribute at least partly to the insulin effect on DAGK activity.
authors.affiliation: Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur and Consejo Nacional de Investigaciones Cientificas y Técnicas, Bahía Blanca, Argentina.
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Zulian
authors.forename: Mónica G
authors.initials: MG
authors.lastname: Ilincheta de Boschero
authors.forename: Norma M
authors.initials: NM
authors.lastname: Giusto
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology*; D019852:Diacylglycerol Kinase / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D009355:Neomycin / Q000494:pharmacology; D010711:Phosphatidate Phosphatase / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010739:Phospholipase D / Q000502:physiology; D010759:Phosphorus Isotopes / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000187:drug effects*; D010738:Type C Phospholipases / Q000502:physiology
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D010713:Phosphatidylcholines; D010759:Phosphorus Isotopes; D011500:Protein Synthesis Inhibitors; D000255:Adenosine Triphosphate; D019852:Diacylglycerol Kinase; D010711:Phosphatidate Phosphatase; D010738:Type C Phospholipases; D010739:Phospholipase D; D009355:Neomycin