Abstract 2353 Lipid flux: Tracking lipids through physical & chemical space

Eukaryotic cells produce over 1000 different lipid species which tune organelle membrane properties, control signalling and store energy. Organelle-specific lipid distributions are maintained by local metabolism and transport of lipids via vesicular and non-vesicular routes. How lipids are sorted in these routes is largely unknown due to the difficulty to image lipid species in cells. Here, we developed a method for high resolution imaging of minimally modified lipid probes which enabled us to quantify the transport of individual phospholipid species from the plasma membrane through the endomembrane system. Our data reveals that non-vesicular lipid transport provides both higher molecular specificity and faster kinetics compared to vesicular lipid trafficking and is at least one order of magnitude faster than lipid metabolism. Organelle membrane compositions and intracellular lipid homeostasis are thus likely maintained by non-vesicular lipid transport. By combining lipid imaging with ultra-high resolution lipidomics, we demonstrate that lipid metabolizing enzymes use dedicated lipid metabolite pools within the same organelle. This suggests that the cellular lipid handling machinery is much less redundant than previously assumed. Taken together, we anticipate that our lipid imaging pipeline will facilitate a comprehensive structure-function analysis of the mammalian lipidome, which is required for understanding the molecular underpinnings of common lipid-related diseases such as fatty liver disease and obesity.