Cytosolic phospholipase A2ε drives recycling through the clathrin-independent endocytic route.

Previous studies have demonstrated that membrane tubule-mediated transport events in biosynthetic and endocytic routes require phospholipase A2 (PLA2) activity. Here, we show that cytosolic phospholipase A2ε (cPLA2ε, also known as PLA2G4E) is targeted to the membrane compartments of the clathrin-independent endocytic route through a C-terminal stretch of positively charged amino acids, which allows the enzyme to interact with phosphoinositide lipids [especially PI(4,5)P2] that are enriched in clathrin-independent endosomes. Ablation of cPLA2ε suppressed the formation of tubular elements that carry internalized clathrin-independent cargoes, such as MHC-I, CD147 and CD55, back to the cell surface and, therefore, caused their intracellular retention. The ability of cPLA2ε to support recycling through tubule formation relies on the catalytic activity of the enzyme, because the inactive cPLA2ε(S420A) mutant was not able to recover either tubule growth or transport from clathrin-independent endosomes. Taken together, our findings indicate that cPLA2ε is a new important regulator of trafficking processes within the clathrin-independent endocytic and recycling route. The affinity of cPLA2ε for this pathway supports a new hypothesis that different PLA2 enzymes use selective targeting mechanisms to regulate tubule formation locally during specific trafficking steps in the secretory and/or endocytic systems.