title: A role for 5,6-epoxyeicosatrienoic acid in calcium entry by de novo conformational coupling in human platelets.
abstract: A major pathway for Ca(2+) entry in non-excitable cells is activated following depletion of intracellular Ca(2+) stores. A de novo conformational coupling between elements in the plasma membrane (PM) and Ca(2+) stores has been proposed as the most likely mechanism to activate this capacitative Ca(2+) entry (CCE) in several cell types, including platelets. Here we report that a cytochrome P450 metabolite, 5,6-EET, might be a component of the de novo conformational coupling in human platelets. In these cells, 5,6-EET induces divalent cation entry without having any detectable effect on Ca(2+) store depletion. 5,6-EET-induced Ca(2+) entry was sensitive to the CCE blockers 2-APB, lanthanum, SKF-96365 and nickel and impaired by incubation with anti-hTRPC1 antibody. Ca(2+) entry stimulated by low concentrations of thapsigargin, which selectively depletes the dense tubular system and induces EET production, was impaired by the cytochrome P450 inhibitor 17-ODYA, which has no effect on CCE mediated by depletion of the acidic stores using 2,5-di-(tert-butyl)-1,4-hydroquinone. We have found that 5,6-EET-induced Ca(2+) entry requires basal levels of H(2)O(2), which might maintain a redox state favourable for this event. Finally, our results indicate that 5,6-EET induces the activation of tyrosine kinase proteins and the reorganization of the actin cytoskeleton, which might provide a support for the transport of portions of the Ca(2+) store towards the PM to facilitate de novo coupling between IP(3)R type II and hTRPC1 detected by coimmunoprecipitation. We propose that the involvement of 5,6-EET in TG-induced coupling between IP(3)R type II and hTRPC1 and subsequently CCE is compatible with the de novo conformational coupling in human platelets.
authors.affiliation: Unité de Recherche de Biochimie, Institute Superieur de Biotechnologie, Monastir, Tunisia.
authors.forename: Nidhal
authors.initials: N
authors.lastname: Ben-Amor
authors.forename: Pedro C
authors.initials: PC
authors.lastname: Redondo
authors.forename: Aghleb
authors.initials: A
authors.lastname: Bartegi
authors.forename: José A
authors.initials: JA
authors.lastname: Pariente
authors.forename: Ginés M
authors.initials: GM
authors.lastname: Salido
authors.forename: Juan A
authors.initials: JA
authors.lastname: Rosado
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000199:Actins / Q000032:analysis / Q000502:physiology; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D015638:Cytochalasin D / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology; D003599:Cytoskeleton / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007811:Lanthanum / Q000494:pharmacology; D008345:Manganese / Q000378:metabolism; D009532:Nickel / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology; D050052:TRPC Cation Channels / Q000276:immunology / Q000502:physiology; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D000199:Actins; D000906:Antibodies; D001896:Boron Compounds; D015220:Calcium Channels; C506926:ITPR1 protein, human; D007093:Imidazoles; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D050052:TRPC Cation Channels; C096351:transient receptor potential cation channel, subfamily C, member 1; D015638:Cytochalasin D; D008345:Manganese; D019284:Thapsigargin; D007811:Lanthanum; D009532:Nickel; C040776:5,6-epoxy-8,11,14-eicosatrienoic acid; D003577:Cytochrome P-450 Enzyme System; D006861:Hydrogen Peroxide; C109986:2-aminoethoxydiphenyl borate; D011505:Protein-Tyrosine Kinases; D015126:8,11,14-Eicosatrienoic Acid; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium