title: Activation of phospholipase C-gamma by the concerted action of tau proteins and arachidonic acid.
abstract: Phospholipase C-gamma (PLC-gamma) isozymes are thought to be activated by receptor-induced tyrosine phosphorylation. Proteins that activate PLC-gamma1 have now been purified from bovine brain and identified as members of the tau family of microtubule-associated proteins. Activation of PLC-gamma by tau was enhanced in the presence of unsaturated fatty acids such as arachidonic acid, saturated fatty acids being ineffective. Maximal (15-20-fold) activation was apparent in the presence of 0.15 microM tau and 25 microM arachidonic acid (AA). The effect of tau and AA was specific to PLC-gamma isozymes in the presence of submicromolar concentrations of Ca2+ and was markedly inhibited by phosphatidylcholine. These results suggest that in cells that express tau, receptors coupled to cytosolic phospholipase A2 may activate PLC-gamma isozymes indirectly in the absence of tyrosine phosphorylation through the hydrolysis of phosphatidylcholine to generate AA.
authors.affiliation: Laboratory of Cell Signaling, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Hwang
authors.forename: D Y
authors.initials: DY
authors.lastname: Jhon
authors.forename: Y S
authors.initials: YS
authors.lastname: Bae
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.forename: S G
authors.initials: SG
authors.lastname: Rhee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism / Q000494:pharmacology*; D001921:Brain / Q000378:metabolism; D002417:Cattle; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D051966:Phospholipase C gamma; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010766:Phosphorylation; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D016875:tau Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D007527:Isoenzymes; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D016875:tau Proteins; D016718:Arachidonic Acid; D014443:Tyrosine; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D051966:Phospholipase C gamma