title: A single enzyme catalyzes both platelet-activating factor production and membrane biogenesis of inflammatory cells. Cloning and characterization of acetyl-CoA:LYSO-PAF acetyltransferase.
abstract: Platelet-activating factor (PAF) is a potent proinflammatory lipid mediator eliciting a variety of cellular functions. Lipid mediators, including PAF are produced from membrane phospholipids by enzymatic cascades. Although a G protein-coupled PAF receptor and degradation enzymes have been cloned and characterized, the PAF biosynthetic enzyme, aceyl-CoA:lyso-PAF acetyltransferase, has not been identified. Here, we cloned lyso-PAF acetyltransferase, which is critical in stimulus-dependent formation of PAF. The enzyme is a 60-kDa microsomal protein with three putative membrane-spanning domains. The enzyme was induced by bacterial endotoxin (lipopolysaccharide), which was suppressed by dexamethasone treatment. Surprisingly, the enzyme catalyzed not only biosynthesis of PAF from lyso-PAF but also incorporation of arachidonoyl-CoA to produce PAF precursor membrane glycerophospholipids (lysophosphatidylcholine acyltransferase activity). Under resting conditions, the enzyme prefers arachidonoyl-CoA and contributes to membrane biogenesis. Upon acute inflammatory stimulation with lipopolysaccharide, the activated enzyme utilizes acetyl-CoA more efficiently and produces PAF. Thus, our findings provide a novel concept that a single enzyme catalyzes membrane biogenesis of inflammatory cells while producing a prophlogistic mediator in response to external stimuli.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Tokyo, Hongo, Tokyo, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Shindou
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hishikawa
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nakanishi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Harayama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ishii
authors.forename: Ryo
authors.initials: R
authors.lastname: Taguchi
authors.forename: Takao
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D000123:Acetyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000473:pathology*; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D020404:Glycerophospholipids / Q000096:biosynthesis; D006801:Humans; D007249:Inflammation / Q000473:pathology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D017737:Macrophages, Peritoneal; D008563:Membrane Lipids / Q000096:biosynthesis*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010972:Platelet Activating Factor / Q000031:analogs & derivatives / Q000096:biosynthesis*
chemical_list: D020404:Glycerophospholipids; D008070:Lipopolysaccharides; D008563:Membrane Lipids; C029271:O-deacetyl platelet activating factor; D010972:Platelet Activating Factor; D000123:Acetyltransferases; C046035:1-alkylglycerophosphocholine acetyltransferase