title: Unstable mutant lysozymes are degraded through the interaction with calnexin homolog Cne1p in Saccharomyces cerevisiae.
abstract: Cne1p is a yeast homolog of calnexin, which is a constituent of endoplasmic reticulum (ER)-associated protein quality control system in mammals. Cne1p may be involved in the degradation of misfolded lysozymes in Saccharomyces cerevisiae. To test this, c-Myc-tagged lysozymes were expressed in CNE1-deficient S. cerevisiae. The expression and secretion of an unstable lysozyme mutant G49N/D66H were enhanced and its intracellular localization was changed in the CNE1-deficient strain. Furthermore, when Cne1p was co-expressed with unstable lysozyme mutants (G49N/D66H, G49N/C76A, and K13D/G49N), its affinity to the misfolded mutant proteins was revealed by co-immunoprecipitation. The interaction with Cne1p was abrogated by the addition of tunicamycin, an inhibitor of N-glycosylation, indicating that N-linked carbohydrates might be necessary for protein binding to Cne1p. These results suggest that in yeasts, Cne1p interacts with misfolded lysozyme proteins possibly causing their retention in the ER and subsequent elimination via ER-associated degradation.
authors.affiliation: a Department of Biological Chemistry, Faculty of Agriculture , Yamaguchi University , Yamaguchi , Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Azakami
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Uehara
authors.forename: Ryohei
authors.initials: R
authors.lastname: Matsuo
authors.forename: Yuta
authors.initials: Y
authors.lastname: Tsurunaga
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Usui
authors.forename: Akio
authors.initials: A
authors.lastname: Kato
mesh_terms: D037281:Calnexin / Q000172:deficiency / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D004795:Enzyme Stability; D006031:Glycosylation; D042541:Intracellular Space / Q000378:metabolism; D009113:Muramidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding; D017510:Protein Folding; D021381:Protein Transport; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: C080582:CNE1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D037281:Calnexin; D009113:Muramidase
keywords: Saccharomyces cerevisiae; calnexin; lysozyme; protein quality control