Regulated endosomal trafficking of Diacylglycerol lipase alpha (DAGLα) generates distinct cellular pools; implications for endocannabinoid signaling

Diacylglycerol lipase alpha (DAGL alpha) generates the endocannabinoid (eCB) 2-arachidonylglycerol (2-AG) that regulates the proliferation and differentiation of neural stem cells and serves as a retrograde signaling lipid at synapses. Nothing is known about the dynamics of DAGL alpha expression in cells and this is important as it will govern where 2-AG can be made and released. We have developed a new construct to label DAGL alpha at the surface of live cells and follow its trafficking. In hippocampal neurons a cell surface pool of DAGL alpha co-localizes with Homer, a postsynaptic density marker. This surface pool of DAGL alpha is dynamic, undergoing endocytosis and recycling back to the postsynaptic membrane. A similar cycling is seen in COS-7 cells with the intemalized DAGL alpha initially transported to EEA1 and Rab5-positive early endosomes via a clathrin-independent pathway before being transported back to the cell surface. The internalized DAGL alpha is present on reticular structures that co-localize with microtubules. Importantly, DAGL alpha cycling is a regulated process as inhibiting PKC results in a significant reduction in endocytosis. This is the first description of DAGL alpha cycling between the cell surface and an intracellular endosomal compartment in a manner that can regulate the level of the enzyme at the cell surface. (C) 2016 Elsevier Inc. All rights reserved.