title: Phosphorylation of lysophosphatidylcholine acyltransferase 2 at Ser34 enhances platelet-activating factor production in endotoxin-stimulated macrophages.
abstract: Platelet-activating factor (PAF) is a potent proinflammatory phospholipid mediator that elicits various cellular functions under physiological and pathological conditions. We have recently identified two enzymes involved in PAF production: lysophosphatidylcholine acyltransferase-1 (LPCAT1) and LPCAT2. We found that LPCAT2 is highly expressed in inflammatory cells and is activated by lipopolysaccharide (LPS) treatment through Toll-like receptor 4. However, the molecular mechanism for the activation remains elusive. In this study, Phos-tag SDS-PAGE revealed the LPS-induced phosphorylation of LPCAT2. Furthermore, mass spectrometry and mutagenesis analyses identified Ser(34) of LPCAT2 as the phosphorylation site to enhance the catalytic activities. The experiments using inhibitors and siRNA against MAPK cascades demonstrated that LPCAT2 phosphorylation through LPS-TLR4 signaling may directly depend on MAPK-activated protein kinase 2 (MAPKAP kinase 2 or MK2). These findings develop a further understanding of both PAF production and phospholipid remodeling triggered by inflammatory stimuli. Specific inhibition of the PAF biosynthetic activity by phosphorylated LPCAT2 will provide a novel target for the regulation of inflammatory disorders.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Tokyo, Hongo 7-3-1, Tokyo 113-0033, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Morimoto
authors.forename: Hideo
authors.initials: H
authors.lastname: Shindou
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Oda
authors.forename: Takao
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D008243:1-Acylglycerophosphocholine O-Acyltransferase / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D017737:Macrophages, Peritoneal / Q000378:metabolism*; D051379:Mice; D016296:Mutagenesis; D010766:Phosphorylation / Q000187:drug effects; D010972:Platelet Activating Factor / Q000096:biosynthesis* / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D008243:1-Acylglycerophosphocholine O-Acyltransferase; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D010972:Platelet Activating Factor; D017346:Protein Serine-Threonine Kinases; D051197:Toll-Like Receptor 4; D000099190:MAP-Kinase-Activated Kinase 2; C493487:Tlr4 protein, mouse