Subsequent signaling by PGE 2 via EP2 receptors activated macrophage adenylyl cyclase and protein kinase A. Lyso-PS, either made endogenously in apoptosing neutrophils or supplied exogenously in liposomes along with lyso-PS neg apoptotic cells, signaled to macrophages in a G2A-dependent manner for their enhanced production of prostaglandin E 2 (PGE 2) via a calcium-dependent cytosolic phospholipase A 2/cyclooxygenase-mediated mechanism. Here, we investigated the signaling pathway downstream of G2A. We have recently demonstrated that lysophosphatidylserine (lyso-PS) generated and retained on neutrophils following short term activation of the NADPH oxidase in vitro and in vivo enhanced their clearance via signaling through the macrophage G-protein-coupled receptor G2A. Phosphatidylserine (PS) and oxidized PS species have been identified as key ligands on apoptotic cells important for their recognition and removal (efferocytosis) by phagocytes, a requisite step for resolution of inflammation.
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