Phosphorylation of cPLAα at Ser Is Necessary for Its Translocation to PtdInsP-Enriched Membranes.

Group IVA cytosolic phospholipase Aα (cPLAα) is a key enzyme in physiology and pathophysiology because it constitutes a rate-limiting step in the pathway for the generation of pro- and anti-inflammatory eicosanoid lipid mediators. cPLAα activity is tightly regulated by multiple factors, including the intracellular Ca concentration, phosphorylation reactions, and cellular phosphatidylinositol (4,5) bisphosphate levels (PtdInsP). In the present work, we demonstrate that phosphorylation of the enzyme at Ser is an important step for the translocation of the enzyme to PtdInsP-enriched membranes in human cells. Constructs of eGFP-cPLA mutated in Ser to Ala (S505A) exhibit a delayed translocation in response to elevated intracellular Ca, and also in response to increases in intracellular PtdInsP levels. Conversely, translocation of a phosphorylation mimic mutant (S505E) is fully observed in response to cellular increases in PtdInsP levels. Collectively, these results suggest that phosphorylation of cPLAα at Ser is necessary for the enzyme to translocate to internal membranes and mobilize arachidonic acid for eicosanoid synthesis.