Rapid Production of Platelet-activating Factor Is Induced by Protein Kinase Cα-mediated Phosphorylation of Lysophosphatidylcholine Acyltransferase 2 Protein

Platelet-activating factor (PAF), a potent proinflammatory lipid mediator, is synthesized rapidly in response to extracellular stimuli by the activation of acetyl-CoA:lyso-PAF acetyltransferase (lyso-PAFAT). We have reported previously that lyso-PAFAT activity is enhanced in three distinct ways in mouse macrophages: rapid activation (30 s) after PAF stimulation and minutes to hours after LPS stimulation. Lysophosphatidylcholine acyltransferase 2 (LPCAT2) was later identified as a Ca2+-dependent lyso-PAFAT. However, the mechanism of rapid lyso-PAFAT activation within 30 s has not been elucidated. Here we show a new signaling pathway for rapid biosynthesis of PAF that is mediated by phosphorylation of LPCAT2 at Ser-34. Stimulation by either PAF or ATP resulted in PKCα-mediated phosphorylation of LPCAT2 to enhance lyso-PAFAT activity and rapid PAF production. Biochemical analyses showed that the phosphorylation of Ser-34 resulted in augmentation of Vmax with minimal Km change. Our results offer an answer for the previously unknown mechanism of rapid PAF production. The mechanism for rapid biosynthesis of platelet-activating factor (PAF), a potent proinflammatory lipid mediator, is unclear. Phosphorylation of lysophosphatidylcholine acyltransferase 2 (LPCAT2) at Ser-34 via PKCα enhanced rapid PAF biosynthesis following PAF or ATP stimulation. The molecular basis for rapid PAF biosynthesis in response to inflammatory stimuli is elucidated. These data suggest a better understanding of PAF production in early-phase inflammation.