Cargo capture and anterograde transport

In the ER, secretory cargo is loaded into COPII transport vesicles at ER exit sites (ERES). This requires export signals in fully folded client proteins and cargo receptor proteins in the vesicle membrane. COPII vesicles fuse to form the ER-Golgi intermediate compartment (ERGIC). When COPII vesicles are close to the cis-Golgi membrane, they shed their coats - COPII components are recycled for use in other vesicles. The receptors usually return to the ER by retrieval pathways.