Figures & data
Figure 1. Biogenesis of lipid droplet through COPI vesicles. In I, ER and Golgi trafficking through COPI and COPII vesicles. COPII vesicles bud from the ER and transport proteins and lipids from the ER to the Golgi. COPI vesicles mediate recycling of resident proteins from the Golgi back to the ER and from distal to proximal cisternae within the stack. In the proposed model, lipid droplets form in close association with ER membrane seeded from a COPI vesicle. As SNARE proteins and other trafficking machinery proteins will be present in the droplet, COPI and COPII can fuse with the growing droplet. Association with the ER persists throughout the life of the lipid droplet facilitating exchange of lipids and proteins. In II, COPI-derived lipid droplets form from Golgi membrane using the COPI coat machinery, and subsequently translocate to the ER. The ER holds the newly emerged lipid droplet in a cup-like incubator and feeding the droplet. In III, two lipid droplets fuse via the respective regions that provide opposing bilayers incorporating required transmembrane SNARE proteins such as Syntaxin 5.
