Protein and lipid sorting between the endoplasmic reticulum and the Golgi complex

Vesicular traffic within the early secretory pathway is mediated by COPI- and COPII-coated vesicles. While COPII-coated vesicles appear to be involved exclusively in the export of secretory proteins and lipids from the endoplasmic reticulum (ER), COPI-coated vesicles seem to function in both anterograde and retrograde transport between the ER-Golgi intermediate compartment (IC) and the Golgi as well as in intra-Golgi transport. Here, we focus on (i) the mechanisms how these transport carriers are formed from a given donor membrane; and (ii) the possible mechanisms involved in sorting of proteins and lipids into such transport vesicles.