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Sel1p/Ubx2p Participates in a Distinct Cdc48p‐Dependent Endoplasmic Reticulum‐Associated Degradation Pathway
Author(s) -
Wilson JoshuaD.,
Liu Yiting,
Bentivoglio ChristineM.,
Barlowe Charles
Publication year - 2006
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2006.00460.x
Subject(s) - endoplasmic reticulum associated protein degradation , endoplasmic reticulum , microbiology and biotechnology , biology , unfolded protein response , secretory pathway , secretory protein , ubiquitin , protein degradation , protein folding , biogenesis , biochemistry , secretion , golgi apparatus , gene
The endoplasmic reticulum (ER) serves a critical role in the biogenesis of secretory proteins. Folding of nascent polypeptides occurs in the ER before anterograde transport through the secretory pathway, whereas terminally misfolded secretory proteins are recognized and eliminated by ER‐associated degradation (ERAD). Here, we investigated the role of the ubiquitin regulatory X (UBX) domain‐containing protein Sel1p in ER quality control and transport. Mutant sel1 Δ yeast displayed a constitutively active unfolded protein response and a mildly reduced rate of secretory protein transport from the ER. Immunoisolation of Sel1p from detergent‐solubilized ER microsomes revealed a protein complex containing both Cdc48p and Npl4p and suggested a direct role for Sel1p in ERAD. In cells that lack Sel1p, we observed a reduction in the level of Cdc48p bound to ER membranes and a decrease in the turnover rate of two model ERAD substrates, carboxypeptidase Y* and Ste6*. In addition, we found that Sel1p and a second UBX domain‐containing protein, Shp1p, associated with Cdc48p in a mutually exclusive manner. Interestingly, the association of Sel1p with Cdc48p was regulated by ATP, while the interaction of Shp1p with Cdc48p was not influenced by ATP. Based on these findings, we conclude that Sel1p operates in the ERAD pathway by coupling Cdc48p to ER membranes and that Shp1p acts in a distinct Cdc48p‐dependent protein degradation pathway.