title: Different effects of calnexin deletion in Saccharomyces cerevisiae on the secretion of two glycosylated amyloidogenic lysozymes.
abstract: Both glycosylated amyloidogenic lysozymes I55T/G49N and D66H/G49N were expressed in wild-type and calnexin-disrupted Saccharomyces cerevisiae. The secretion amounts of mutant I55T/G49N were almost similar in both wild-type and calnexin-disrupted S. cerevisiae. In contrast, the secretion of mutant D66H/G49N greatly increased in calnexin-disrupted S. cerevisiae, while the secretion was very low in the wild-type strain. In parallel, the induction level of the molecular chaperones BiP and PDI located in the endoplasmic reticulum (ER) was investigated when these glycosylated amyloidogenic lysozymes were expressed in wild-type and calnexin-disrupted S. cerevisiae. The mRNA concentrations of BiP and PDI were evidently increased when mutant lysozyme D66H/G49N was expressed in calnexin-disrupted S. cerevisiae, while they were not so increased when I55T/G49N mutant was expressed. This observation indicates that the conformation of mutant lysozyme D66H/G49N was less stable in the ER, thus leading to the higher-level expression of ER molecular chaperones via the unfolded protein response pathway. This suggests that glycosylated amyloidogenic lysozyme I55T/G49N may have a relatively stable conformation in the ER, thus releasing it from the quality control of calnexin compared with mutant lysozyme D66H/G49N.
authors.affiliation: Department of Biological Chemistry, Yamaguchi University, 753-8515, Yamaguchi, Japan.
authors.forename: Youtao
authors.initials: Y
authors.lastname: Song
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Azakami
authors.forename: Begum
authors.initials: B
authors.lastname: Shamima
authors.forename: Jianwei
authors.initials: J
authors.lastname: He
authors.forename: Akio
authors.initials: A
authors.lastname: Kato
mesh_terms: D000682:Amyloid / Q000096:biosynthesis; D002135:Calcium-Binding Proteins / Q000172:deficiency* / Q000235:genetics; D037281:Calnexin; D004721:Endoplasmic Reticulum / Q000378:metabolism; D017353:Gene Deletion; D006031:Glycosylation; D018832:Molecular Chaperones / Q000378:metabolism; D009113:Muramidase / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D000682:Amyloid; D002135:Calcium-Binding Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; D037281:Calnexin; D009113:Muramidase