In normal cells, proteins and lipids are assembled into vesicles during intracellular trafficking. Coat protein (COP) complexes include COPI and COPII and mediate the intracellular cargos to the designation through Golgi to the Endoplasmic reticulum (ER) or ER to Golgi respectively. Each TRAPP subunit provides and regulates several stages of vesicle trafficking by participating COPI and COPII complexes. In addition to this cofunction, one of the TRAPP complexes (TRAPP II) regulates COPII vesicle docking and fusion to the target membrane. Particularly, the TRAPPC9, which is the main subunit of TRAPP II complex, is essential for this interaction and therefore cytosolic lipid homeostasis in general.
TRAPPC9