The transport mechanism of transport vesicle on membrane traffic from endoplasmic reticulum to the Golgi apparatus

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Membrane and secretion proteins synthesized on ER are transported first to the Golgi apparatus. After the maturation of the sugar chain modification etc. there, proteins are sorted and transported into each localization compartment. Recently, the mechanism of the transport from ER to Golgi has been becoming clear a little. The mechanism of the transport from ER to Golgi has become clear to some degree. Recently, it is thought that the COPII vesicles budding from ER exit sites that lie scattered in the cell periphery fuse each other to form bigger membrane structure VTCs (tubulo vesicular compartments), and then VTCs are carried to the Golgi apparatus around nuclear.I have analyzed the function of vesicle tethering factor p115 using p115 knock down (KD) cells. By the process of the analysis, p115 has been found playing important role to transport the membrane structure that budding as COPII vesicles to the Golgi apparatus. Depletion of p115 caused fragmentation of the Golgi apparatus. The fragmented Golgi was distinct from VTCs and ER exit sites, maintained mini-stack structures with cis-to trans-organization. While no alternation of microtubule networks was found in p115 KD cells, the fragmented Golgi resembled those in cells treated with anti-microtubule drug. Furthermore, p115 was co-precipitated with anti Bicaudal-D antibody. Bicaudal-D is known to interact with microtubule motor, dynein-dynactin complex. These results suggested that the scattered Golgi in p115 KD cells was derived from VTCs, which were not able to interact with the motor complex on microtubules, resulting in the formation of the mini-stacked Golgi distributed near the ER exit sites. It is likely t hat p115 plays a role in promoting the interaction of COPII-derived VTCs with the motor complex on microtubules.