Analysis of Two Major Intracellular Phospholipases A2 (PLA2) in Mast Cells Reveals Crucial Contribution of Cytosolic PLA2α, Not Ca2+-independent PLA2β, to Lipid Mobilization in Proximal Mast Cells and Distal Fibroblasts

• Published in: The Journal of biological chemistry 2011-10, Vol.286 (43), p.37249-37263
• Main Authors: Ueno, Noriko, Taketomi, Yoshitaka, Yamamoto, Kei, Hirabayashi, Tetsuya, Kamei, Daisuke, Kita, Yoshihiro, Shimizu, Takao, Shinzawa, Koei, Tsujimoto, Yoshihide, Ikeda, Kazutaka, Taguchi, Ryo, Murakami, Makoto
• Format: Article
• Language: English
• Subjects: Allergy; Arachidonic Acid; Gene Knock-out; Lipids; Mass Spectrometry (MS); Mast Cell; Phospholipase A; Phospholipid Metabolism; Prostaglandins
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.290312

Mast cells release a variety of mediators, including arachidonic acid (AA) metabolites, to regulate allergy, inflammation, and host defense, and their differentiation and maturation within extravascular microenvironments depend on the stromal cytokine stem cell factor. Mouse mast cells express two major intracellular phospholipases A2 (PLA2s), namely group IVA cytosolic PLA2 (cPLA2α) and group VIA Ca2+-independent PLA2 (iPLA2β), and the role of cPLA2α in eicosanoid synthesis by mast cells has been well documented. Lipidomic analyses of mouse bone marrow-derived mast cells (BMMCs) lacking cPLA2α (Pla2g4a−/−) or iPLA2β (Pla2g6−/−) revealed that phospholipids with AA were selectively hydrolyzed by cPLA2α, not by iPLA2β, during FcϵRI-mediated activation and even during fibroblast-dependent maturation. Neither FcϵRI-dependent effector functions nor maturation-driven phospholipid remodeling was impaired in Pla2g6−/− BMMCs. Although BMMCs did not produce prostaglandin E2 (PGE2), the AA released by cPLA2α from BMMCs during maturation was converted to PGE2 by microsomal PGE synthase-1 (mPGES-1) in cocultured fibroblasts, and accordingly, Pla2g4a−/− BMMCs promoted microenvironmental PGE2 synthesis less efficiently than wild-type BMMCs both in vitro and in vivo. Mice deficient in mPGES-1 (Ptges−/−) had an augmented local anaphylactic response. These results suggest that cPLA2α in mast cells is functionally coupled, through the AA transfer mechanism, with stromal mPGES-1 to provide anti-anaphylactic PGE2. Although iPLA2β is partially responsible for PGE2 production by macrophages and dendritic cells, it is dispensable for mast cell maturation and function. Background: Mast cells express cPLA2α and iPLA2β. Results: Knock-out of cPLA2α, not iPLA2β, hampers arachidonic acid mobilization in mast cells and adjacent fibroblasts. Conclusion: Mast cell cPLA2α is coupled with stromal synthesis of anti-allergic PGE2, whereas iPLA2β is dispensable for mast cell function. Significance: The cPLA2α-dependent transcellular PGE2 synthesis opens new insight into the lipid biochemistry and mast cell biology fields.