ERGolgi

ERGolgi refers to the cellular pathway that coordinates transport between the endoplasmic reticulum (ER) and the Golgi apparatus, a central flow in the secretory system. It encompasses the formation of cargo-containing vesicles at the ER, their delivery to the Golgi, and the retrieval of resident proteins and trafficking signals.

Cargo exit from the ER begins at ER exit sites with coat protein complex II (COPII). The small GTPase Sar1 initiates coat assembly, followed by inner coat Sec23/24 and outer coat Sec13/31, which bud off to form transport vesicles. Sec24 contributes to cargo selection, incorporating properly folded secretory proteins and membrane proteins into vesicles. Vesicles then fuse with the early ER–Golgi compartment, the ER-Golgi intermediate compartment (ERGIC), directed by Rab1 and tethering factors such as p115 and ZW10–RINT-1, and SNARE proteins that drive membrane fusion.

From the ERGIC, cargo proceeds to the cis-Golgi where processing begins. The Golgi apparatus conducts sequential modifications, including glycosylation and sulfuration, with different enzymes resident in distinct cisternae (cis, medial, trans). The precise mechanism of forward movement remains debated, but both vesicular transport and cisternal maturation models are discussed, with evidence for forward progression of enzymes and cargo through maturation of Golgi compartments.

Retrograde transport via COPI vesicles retrieves escaped ER residents and recycling receptors back to the ER, maintaining compartmental organization. The KDEL receptor retrieves ER residents, ensuring proper sorting and homeostasis.

Disruptions of ER–Golgi trafficking can affect protein maturation and glycosylation and are implicated in certain congenital disorders of glycosylation and other diseases, highlighting the ERolgi pathway’s essential role in cell biology.