title: Mechanism of arachidonic acid action on syntaxin-Munc18.
abstract: Syntaxin and Munc18 are, in tandem, essential for exocytosis in all eukaryotes. Recently, it was shown that Munc18 inhibition of neuronal syntaxin 1 can be overcome by arachidonic acid, indicating that this common second messenger acts to disrupt the syntaxin-Munc18 interaction. Here, we show that arachidonic acid can stimulate syntaxin 1 alone, indicating that it is syntaxin 1 that undergoes a structural change in the syntaxin 1-Munc18 complex. Arachidonic acid is incapable of dissociating Munc18 from syntaxin 1 and, crucially, Munc18 remains associated with syntaxin 1 after arachidonic-acid-induced syntaxin 1 binding to synaptosomal-associated protein 25 kDa (SNAP25). We also show that the same principle operates in the case of the ubiquitous syntaxin 3 isoform, highlighting the conserved nature of the mechanism of arachidonic acid action. Neuronal soluble N-ethyl maleimide sensitive factor attachment protein receptors (SNAREs) can be isolated from brain membranes in a complex with endogenous Munc18, consistent with a proposed function of Munc18 in vesicle docking and fusion.
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Emma
authors.initials: E
authors.lastname: Connell
authors.forename: Frédéric
authors.initials: F
authors.lastname: Darios
authors.forename: Kerensa
authors.initials: K
authors.lastname: Broersen
authors.forename: Naomi
authors.initials: N
authors.lastname: Gatsby
authors.forename: Sew-Yeu
authors.initials: SY
authors.lastname: Peak-Chew
authors.forename: Colin
authors.initials: C
authors.lastname: Rickman
authors.forename: Bazbek
authors.initials: B
authors.lastname: Davletov
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D001923:Brain Chemistry; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004213:Dissociative Disorders; D008969:Molecular Sequence Data; D051938:Munc18 Proteins / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D025941:Protein Interaction Mapping; D050765:Qa-SNARE Proteins / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D050600:SNARE Proteins / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25 / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism; D050827:Syntaxin 1 / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D051938:Munc18 Proteins; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D016718:Arachidonic Acid