Ceramide 1-Phosphate Is Required for the Translocation of Group IVA Cytosolic Phospholipase A2 and Prostaglandin Synthesis*

Little is known about the regulation of eicosanoid synthesis proximal to the activation of cytosolic phospholipase A2α (cPLA2α), the initial rate-limiting step. The current view is that cPLA2α associates with intracellular/phosphatidylcholine-rich membranes strictly via hydrophobic interactions in response to an increase of intracellular calcium. In opposition to this accepted mechanism of two decades, ceramide 1-phosphate (C1P) has been shown to increase the membrane association of cPLA2α in vitro via a novel site in the cationic β-groove of the C2 domain (Stahelin, R. V., Subramanian, P., Vora, M., Cho, W., and Chalfant, C. E. (2007) J. Biol. Chem. 282, 20467–204741). In this study we demonstrate that C1P is a proximal and required bioactive lipid for the translocation of cPLA2α to intracellular membranes in response to inflammatory agonists (e.g. calcium ionophore and ATP). Last, the absolute requirement of the C1P/cPLA2α interaction was demonstrated for the production of eicosanoids using murine embryonic fibroblasts (cPLA2α−/−) coupled to “rescue” studies. Therefore, this study provides a paradigm shift in how cPLA2α is activated during inflammation.