title: Transient calnexin interaction confers long-term stability on folded K+ channel protein in the ER.
abstract: We recently showed that an unglycosylated form of the Shaker potassium channel protein is retained in the endoplasmic reticulum (ER) and degraded by proteasomes in mammalian cells despite apparently normal folding and assembly. These results suggest that channel proteins with a native structure can be substrates for ER-associated degradation. We have now tested this hypothesis using the wild-type Shaker protein. Wild-type Shaker is degraded by cytoplasmic proteasomes when it is trapped in the ER and prevented from interacting with calnexin. Neither condition alone is sufficient to destabilize the protein. Proteasomal degradation of the wild-type protein is abolished when ER mannosidase I trimming of the core glycan is inhibited. Our results indicate that transient interaction with calnexin provides long-term protection from ER-associated degradation.
authors.affiliation: Department of Physiology and Molecular Biology Institute, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095-1751, USA.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Khanna
authors.forename: Eun Jeon
authors.initials: EJ
authors.lastname: Lee
authors.forename: Diane M
authors.initials: DM
authors.lastname: Papazian
mesh_terms: D037281:Calnexin / Q000378:metabolism*; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008361:Mannosidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D021381:Protein Transport
chemical_list: D037281:Calnexin; D008361:Mannosidases; C046090:mannosyl-oligosaccharide 1,2-alpha-mannosidase; D046988:Proteasome Endopeptidase Complex