title: Functional association of type IIA secretory phospholipase A(2) with the glycosylphosphatidylinositol-anchored heparan sulfate proteoglycan in the cyclooxygenase-2-mediated delayed prostanoid-biosynthetic pathway.
abstract: An emerging body of evidence suggests that type IIA secretory phospholipase A(2) (sPLA(2)-IIA) participates in the amplification of the stimulus-induced cyclooxygenase (COX)-2-dependent delayed prostaglandin (PG)-biosynthetic response in several cell types. However, the biological importance of the ability of sPLA(2)-IIA to bind to heparan sulfate proteoglycan (HSPG) on cell surfaces has remained controversial. Here we show that glypican, a glycosylphosphatidylinositol (GPI)-anchored HSPG, acts as a physical and functional adaptor for sPLA(2)-IIA. sPLA(2)-IIA-dependent PGE(2) generation by interleukin-1-stimulated cells was markedly attenuated by treatment of the cells with heparin, heparinase or GPI-specific phospholipase C, which solubilized the cell surface-associated sPLA(2)-IIA. Overexpression of glypican-1 increased the association of sPLA(2)-IIA with the cell membrane, and glypican-1 was coimmunoprecipitated by the antibody against sPLA(2)-IIA. Glypican-1 overexpression led to marked augmentation of sPLA(2)-IIA-mediated arachidonic acid release, PGE(2) generation, and COX-2 induction in interleukin-1-stimulated cells, particularly when the sPLA(2)-IIA expression level was suboptimal. Immunofluorescent microscopic analyses of cytokine-stimulated cells revealed that sPLA(2)-IIA was present in the caveolae, a microdomain in which GPI-anchored proteins reside, and also appeared in the perinuclear area in proximity to COX-2. We therefore propose that a GPI-anchored HSPG glypican facilitates the trafficking of sPLA(2)-IIA into particular subcellular compartments, and arachidonic acid thus released from the compartments may link efficiently to the downstream COX-2-mediated PG biosynthesis.
authors.affiliation: Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Murakami
authors.forename: T
authors.initials: T
authors.lastname: Kambe
authors.forename: S
authors.initials: S
authors.lastname: Shimbara
authors.forename: S
authors.initials: S
authors.lastname: Yamamoto
authors.forename: H
authors.initials: H
authors.lastname: Kuwata
authors.forename: I
authors.initials: I
authors.lastname: Kudo
mesh_terms: D002460:Cell Line; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D054501:Group II Phospholipases A2; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism*; D008565:Membrane Proteins; D010741:Phospholipases A / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D011485:Protein Binding; D013347:Subcellular Fractions / Q000201:enzymology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D017261:Glycosylphosphatidylinositols; D019812:Heparan Sulfate Proteoglycans; D007375:Interleukin-1; D007527:Isoenzymes; D008565:Membrane Proteins; D014409:Tumor Necrosis Factor-alpha; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D015232:Dinoprostone