Reconstitution of Adiposome and Artificial Lipid Droplets
The Lipid droplet (LD) is a cellular organelle that consists of a neutral lipid core with a phospholipid monolayer membrane associated with proteins. The presence of this organelle in organisms ranging from bacteria to humans demonstrates that it is highly conserved and may be the first membrane-bound organelle in living organisms. Recent progress in LD research demonstrates its important roles in energy homeostasis and metabolic syndromes. However, the mechanisms governing its formation, dynamics, interaction with other cellular organelles, and association with proteins have remained elusive. Therefore, we developed an in vitro system to facilitate the elucidation of these mechanisms, based on the reconstitution of artificial LDs. First, we generated sphere-shaped structures with a neutral lipid core and phospholipid monolayer membrane by mechanically mixing neutral lipids and phospholipids followed by two-step purification. Since the artificial lipid vesicle, a double layer phospholipid membrane structure, is termed as “liposome”, we named this monolayer phospholipid membrane-bound structure “adiposome”. We then recruited LD structure-like/resident proteins to the adiposome, including the bacterial LD protein MLDS, C. elegans LD protein MDT-28, or mammalian LD protein ADRP/PLIN2. We term the functional protein-coated adiposomes, “artificial lipid droplets”. Using this experimental system, different proteins can be recruited to build artificial LDs for myriad biological and medical goals.