title: Regulation of Mac-2BP secretion is mediated by its N-glycan binding to ERGIC-53.
abstract: The leguminous-type (L-type) lectin ER-Golgi intermediate compartment (ERGIC)-53, a homo-oligomeric endoplasmic reticulum (ER)-Golgi recycling protein, functions as a transport receptor for newly synthesized glycoproteins in the early secretory pathway. Although a limited subset of cargo glycoproteins transported by ERGIC-53, such as the coagulation factors V and VIII, cathepsin C and Z and α1-antitrypsin, has been identified, the exact role of the N-glycan binding of ERGIC-53 in the transport of secretory glycoproteins for ER exit has yet to be clarified. By screening a cDNA library isolated from HepG2 cells via a green fluorescent protein fragment complementation assay, we assessed several candidate luminal ERGIC-53-interacting partners and identified Mac-2 binding protein (Mac-2BP) as a novel ERGIC-53-transported cargo glycoprotein. Using an N-glycan-binding-deficient mutant of ERGIC-53 (N156A) or treatment with N-glycosylation processing inhibitors, as well as the introduction of the ER-mis-targeting mutant (KKAA), we demonstrated that the high-mannose-type N-glycan binding of ERGIC-53 contributes to its interaction with Mac-2BP, which is essential for the ERGIC-53-mediated ER-Golgi transport of nascent proteins during early secretion. Furthermore, we also provide evidence that MCFD2 is involved in the secretion of Mac-2BP. These observations reveal a distinct role for the N-glycan binding of ERGIC-53 in the receptor-mediated ER exit of newly synthesized Mac-2BP in the early secretion pathway.
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, 277-8562 Chiba, Japan.
authors.forename: Yang
authors.initials: Y
authors.lastname: Chen
authors.forename: Sanae
authors.initials: S
authors.lastname: Hojo
authors.forename: Naoki
authors.initials: N
authors.lastname: Matsumoto
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D000951:Antigens, Neoplasm / Q000378:metabolism*; D005936:Glucans / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D037241:Mannose-Binding Lectins / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding; D021381:Protein Transport; D055571:Secretory Pathway; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D005936:Glucans; C084004:LMAN1 protein, human; C475146:MCFD2 protein, human; D037241:Mannose-Binding Lectins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C114782:TAA90K protein, human; D033921:Vesicular Transport Proteins
keywords: ERGIC-53; Mac-2BP; cargo receptor; secretion