title: STT3B-dependent posttranslational N-glycosylation as a surveillance system for secretory protein.
abstract: Nascent secretory proteins are extensively scrutinized at the endoplasmic reticulum (ER). Various signatures of client proteins, including exposure of hydrophobic patches or unpaired sulfhydryls, are coordinately utilized to reduce nonnative proteins in the ER. We report here the cryptic N-glycosylation site as a recognition signal for unfolding of a natively nonglycosylated protein, transthyretin (TTR), involved in familial amyloidosis. Folding and ER-associated degradation (ERAD) perturbation analyses revealed that prolonged TTR unfolding induces externalization of cryptic N-glycosylation site and triggers STT3B-dependent posttranslational N-glycosylation. Inhibition of posttranslational N-glycosylation increases detergent-insoluble TTR aggregates and decreases cell proliferation of mutant TTR-expressing cells. Moreover, this modification provides an alternative pathway for degradation, which is EDEM3-mediated N-glycan-dependent ERAD, distinct from the major pathway of Herp-mediated N-glycan-independent ERAD. Hence we postulate that STT3B-dependent posttranslational N-glycosylation is part of a triage-salvage system recognizing cryptic N-glycosylation sites of secretory proteins to preserve protein homeostasis.
authors.affiliation: Department of Molecular Medicine, Global COE Cell Fate Regulation Research and Education Unit, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-Honmachi, Kumamoto 862-0973, Japan. tsato@kumamoto-u.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Sako
authors.forename: Misato
authors.initials: M
authors.lastname: Sho
authors.forename: Mamiko
authors.initials: M
authors.lastname: Momohara
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Suico
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Shuto
authors.forename: Hideki
authors.initials: H
authors.lastname: Nishitoh
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Okiyoneda
authors.forename: Koichi
authors.initials: K
authors.lastname: Kokame
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kaneko
authors.forename: Manabu
authors.initials: M
authors.lastname: Taura
authors.forename: Masanori
authors.initials: M
authors.lastname: Miyata
authors.forename: Keisuke
authors.initials: K
authors.lastname: Chosa
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Koga
authors.forename: Saori
authors.initials: S
authors.lastname: Morino-Koga
authors.forename: Ikuo
authors.initials: I
authors.lastname: Wada
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Kai
mesh_terms: D000595:Amino Acid Sequence; D001383:Azetidinecarboxylic Acid / Q000494:pharmacology; D002135:Calcium-Binding Proteins; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006031:Glycosylation / Q000187:drug effects; D057809:HEK293 Cells; D006602:Hexosyltransferases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D008361:Mannosidases; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011134:Polysaccharides / Q000378:metabolism; D011228:Prealbumin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D034622:RNA Interference; D055571:Secretory Pathway / Q000187:drug effects; D017386:Sequence Homology, Amino Acid; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D043323:alpha-Mannosidase
chemical_list: D002135:Calcium-Binding Proteins; D008565:Membrane Proteins; D011134:Polysaccharides; D011228:Prealbumin; D001383:Azetidinecarboxylic Acid; C471617:UBE2G2 protein, human; C489967:UBE2J1 protein, human; D044763:Ubiquitin-Conjugating Enzymes; C482345:SYVN1 protein, human; D044767:Ubiquitin-Protein Ligases; D006602:Hexosyltransferases; C551978:STT3B protein, human; D008361:Mannosidases; C573113:EDEM3 protein, human; D043323:alpha-Mannosidase