Want to leave the ER? We offer vesicles, tubules, and tunnels

Abstract

Export from the ER is COPII-dependent. However, there is disagreement on the nature of the cargo-containing carriers that exit the ER. Two new studies from Shomron et al. (2021. J. Cell Biol.https://doi.org/10.1083/jcb.201907224) and Weigel et al. (2021. Cell. https://doi.org/10.1016/j.cell.2021.03.035) present a new model, where COPII helps to select secretory cargo but does not coat the carriers leaving the ER.

Figure 1.

Depiction of different possible modes of ER export. (A) The classical (vesicular) transport model that includes budding of a coated vesicle followed by homotypic fusion of COPII vesicles. (B) ERES can give rise to tubular structures, which either depart as tubules followed by COPI recruitment or may form tunnels with distal compartments.