2021 Volume 33 Issue 193 Pages E55-E62
N-glycan plays a pivotal role in the protein quality control system in the endoplasmic reticulum (ER). Lectin chaperones recognize monoglucosylated glycoproteins to promote their folding. If glycoproteins cannot attain their tertiary structure, mannoses of their N-glycans are trimmed to be recognized by lectin components for degradation. Then, such misfolded glycoproteins are retrotranslocated to the cytosol, where they are degraded by proteasomes. This fundamental machinery is conserved from yeast to mammals, but it becomes more sophisticated through evolution because of multiplied and diverged genes in mammals. In this minireview, I would like to summarize the history and latest research of the N-glycan-dependent quality control system in the ER, especially focusing on the molecular mechanism of mannose trimming and lectin components for destruction in yeast and mammals.