Degradation of a Mutant Secretory Protein, α1-Antitrypsin Z, in the Endoplasmic Reticulum Requires Proteasome Activity

Degradation of proteins that are retained in the quality control apparatus of the endoplasmic reticulum (ER) has been attributed to a third proteolytic system, distinct from the lysosomal and the cytoplasmic ubiquitin-dependent proteosomal proteolytic pathways. However, several recent studies have shown that ER degradation of a mutant membrane protein, CFTRΔF508, is at least in part mediated from the cytoplasmic side by the 26 S proteasome. In...