Intermediate Compartment: A Sorting Station between the Endoplasmic Reticulum and the Golgi Apparatus

The intermediate compartment (IC) is a pleiomorphic membrane system that mediates two-way trafficing in the early biosynthetic-secretory pathway of mammalian cells. The IC associates with the cytoskeleton, binds COPI (coat protein I) coats and generates vesicular, tubular and saccular transport carriers. It recieves newly made proteins and lipids from the endoplasmic reticulum (ER) and sorts them for transport to the Golgi apparatus or recycling back to the ER. Although the IC appears to be functionally complex and resides at the crossroads of multiple transport routes, it is still disputed whether it represents a transient or stable structure.