cPLA2α and EHD1 interact and regulate the vesiculation of cholesterol-rich, GPI-anchored, protein-containing endosomes

The lipid modifier phospholipase A2 catalyzes the hydrolysis of phospholipids to inverted-cone-shaped lysophospholipids that contribute to membrane curvature and/or tubulation. Conflicting findings exist regarding the function of cytosolic phospholipase A2 (cPLA2) and its role in membrane regulation at the Golgi and early endosomes. However, no studies addressed the role of cPLA2 in the regulation of cholesterol-rich membranes that contain glycosylphosphatidylinositol-anchored proteins (GPI-APs). Our studies support a role for cPLA2 alpha in the vesiculation of GPI-AP-containing membranes, using endogenous CD59 as a model for GPI-APs. On cPLA2 alpha depletion, CD59-containing endosomes became hypertubular. Moreover, accumulation of lysophospholipids induced by a lysophospholipid acyltransferase inhibitor extensively vesiculated CD59-containing endosomes. However, overexpression of cPLA2 alpha did not increase the endosomal vesiculation, implying a requirement for additional factors. Indeed, depletion of the "pinchase" EHD1, a C-terminal Eps15 homology domain (EHD) ATPase, also induced hypertubulation of CD59-containing endosomes. Furthermore, EHD1 and cPLA2 alpha demonstrated in situ proximity (<40 nm) and interacted in vivo. The results presented here provide evidence that the lipid modifier cPLA2 alpha and EHD1 are involved in the vesiculation of CD59-containing endosomes. We speculate that cPLA2 alpha induces membrane curvature and allows EHD1, possibly in the context of a complex, to sever the curved membranes into vesicles.