title: Golgi localization of ERManI defines spatial separation of the mammalian glycoprotein quality control system.
abstract: The Golgi complex has been implicated as a possible component of endoplasmic reticulum (ER) glycoprotein quality control, although the elucidation of its exact role is lacking. ERManI, a putative ER resident mannosidase, plays a rate-limiting role in generating a signal that targets misfolded N-linked glycoproteins for ER-associated degradation (ERAD). Herein we demonstrate that the endogenous human homologue predominantly resides in the Golgi complex, where it is subjected to O-glycosylation. To distinguish the intracellular site where the glycoprotein ERAD signal is generated, a COPI-binding motif was appended to the N terminus of the recombinant protein to facilitate its retrograde translocation back to the ER. Partial redistribution of the modified ERManI was observed along with an accelerated rate at which N-linked glycans of misfolded α1-antitrypsin variant NHK were trimmed. Despite these observations, the rate of NHK degradation was not accelerated, implicating the Golgi complex as the site for glycoprotein ERAD substrate tagging. Taken together, these data provide a potential mechanistic explanation for the spatial separation by which glycoprotein quality control components operate in mammalian cells.
authors.affiliation: Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Shujuan
authors.initials: S
authors.lastname: Pan
authors.forename: Shufang
authors.initials: S
authors.lastname: Wang
authors.forename: Budi
authors.initials: B
authors.lastname: Utama
authors.forename: Lu
authors.initials: L
authors.lastname: Huang
authors.forename: Neil
authors.initials: N
authors.lastname: Blok
authors.forename: Mary K
authors.initials: MK
authors.lastname: Estes
authors.forename: Kelley W
authors.initials: KW
authors.lastname: Moremen
authors.forename: Richard N
authors.initials: RN
authors.lastname: Sifers
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D058846:Antibodies, Monoclonal, Murine-Derived / Q000737:chemistry; D001665:Binding Sites; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D008361:Mannosidases / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D059748:Proteolysis; D012995:Solubility
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D006023:Glycoproteins; D010446:Peptide Fragments; C568343:MAN1B1 protein, human; D008361:Mannosidases