Autophagy-independent LC3 function in vesicular traffic.

de Haan, Cornelis A M; Molinari, Maurizio; Reggiori, Fulvio

As protein folding is an imperfect process, the endoplasmic reticulum (ER) contains folding as well as ER-associated degradation (ERAD) machineries. In order to prevent premature interruption of folding, ERAD regulators and effectors such as EDEM1 and OS-9 are selectively cleared from the ER in so-called EDEMosomes to downregulate the degradative activity. The mechanism by which EDEM1 and OS-9 are subjected to rapid turnover, also known as ERAD tuning, shows similarities with, but is clearly distinct from, macroautophagy. Positive strand RNA coronaviruses (CoVs) such as the severe acute respiratory syndrome (SARS)-CoV and mouse hepatitis virus (MHV), induce in infected cells the formation of autophagosome-like, double-membrane vesicles (DMVs) to which their replication and transcription complexes are anchored. While it seems clear that CoVs hijack ER-derived host cell membranes for replication, the mechanism by which these DMVs are assembled has remained completely mysterious.