title: Role of phosphatidylinositol 4,5-bisphosphate in the activation of cytosolic phospholipase A2-alpha.
abstract: Cytosolic phospholipase A(2)-alpha (cPLA(2)) plays an important role in the release of arachidonic acid and in cell injury. Activation of cPLA(2) is dependent on a rise in cytosolic Ca(2+) concentration, membrane association via the Ca(2+)-dependent lipid binding (CaLB) domain, and phosphorylation. This study addresses the activation of cPLA(2) via potential association with membrane phosphatidylinositol 4,5-bisphosphate (PIP(2)), including the role of a "pleckstrin homology (PH)-like" region of cPLA(2) (amino acids 263-354). In cells incubated with complement, phorbol myristate acetate+the Ca(2+) ionophore, A23187, or epidermal growth factor+A23187, expression of the PH domain of phospholipase C-delta1 (which sequesters membrane PIP(2)) attenuated cPLA(2) activity. Stimulated cPLA(2) activity was also attenuated by the expression of cPLA(2) 135-366, or cPLA(2) 2-366, and expression of a PIP(2)-specific 5'-phosphatase. However, in a yeast-based assay that tests the ability of proteins to bind to membrane lipids, including PIP(2), with high affinity, only cPLA(2) 1-200 (CaLB domain) was able to interact with membrane lipids, whereas cPLA(2)s 135-366, 2-366, 201-648, and 1-648 were unable to do so. Therefore, cPLA(2) activity can be modulated by sequestration or depletion of cellular PIP(2), although the interaction of cPLA(2) with membrane PIP(2) appears to be indirect, or of weak affinity.
authors.affiliation: Department of Medicine, McGill University Health Centre, McGill University, Montreal, Quebec, Canada H3A 1A1.
authors.forename: Ludmilla
authors.initials: L
authors.lastname: Le Berre
authors.forename: Tomoko
authors.initials: T
authors.lastname: Takano
authors.forename: Joan
authors.initials: J
authors.lastname: Papillon
authors.forename: Serge
authors.initials: S
authors.lastname: Lemay
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Cybulsky
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D019556:COS Cells; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003600:Cytosol / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects* / Q000502:physiology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D054513:Group IV Phospholipases A2; D007476:Ionophores / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology*; D054803:Phospholipase C delta; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D010766:Phosphorylation; D011453:Prostaglandins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D001095:Arachidonic Acids; D007476:Ionophores; D007527:Isoenzymes; D008563:Membrane Lipids; D019269:Phosphatidylinositol 4,5-Diphosphate; D011453:Prostaglandins; D000001:Calcimycin; D004815:Epidermal Growth Factor; D010741:Phospholipases A; D054513:Group IV Phospholipases A2; D054467:Phospholipases A2; D010738:Type C Phospholipases; D054803:Phospholipase C delta; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium