Shape up or ship out

When proteins become misfolded in the ER, a quality control system targets them to the cytoplasm for degradation. On page 355, Vashist et al. have uncovered two separate sorting systems involved in ER quality control, and have identified a novel gene required for one of the two pathways. The findings indicate that ER quality control is more complex than previously believed.

By tracking the fates of several mutant proteins in Saccharomyces cerevisiae, the authors identified a sorting step in the ER in which misfolded proteins are targeted to one of two pathways. Some proteins are packaged into COPII transport vesicles, while others are excluded from vesicles and retained in the ER. Proteins packaged into vesicles are transported to the Golgi apparatus, then returned to the ER by retrograde transport, at which point the two pathways converge...