Receptors for a growing family of secreted phospholipases A2

Phospholipases A2 (PLA2s) are enzymes that catalyse the hydrolysis of the sn-2 acyl bond of glycerophospholipids to produce free fatty acids and lysophospholipids. Numerous intracellular and secreted PLA2s (sPLA2s) have now been characterized. Because PLA2 products are important for cell signalling and the biosynthesis of biologically active lipids, including eicosanoids and platelet-activating factor, PLA2s are generally considered as key enzymes that control the release of lipid mediator precursors. However, the increasing number of mammalian sPLA2s and the recent identification of different membrane proteins that bind sPLA2s makes it likely that these enzymes also behave as ligands for receptors, and that their physiological function is not limited to their catalytic activity. Here, the current state of awareness regarding the different types of sPLA2-binding proteins is described. To date, five distinct mammalian sPLA2s and two main types (M and N) of sPLA2 receptors have been identified. Because most is known about the M-type receptor, particular attention will be paid to it, including a description of it molecular properties and of its possible biological roles with regard to sPLA2 function.