title: Independent and cooperative roles of N-glycans and molecular chaperones in the folding and disulfide bond formation of the low-density lipoprotein (LDL) receptor-related protein.
abstract: The low-density lipoprotein receptor-related protein (LRP) is a large receptor that contains extensive glycosylation sites and disulfide bonds. Here we analyzed how N-linked glycosylation and molecular chaperones function during LRP folding. Treatment of cells with a glycosylation inhibitor tunicamycin significantly impaired LRP folding, although binding to receptor-associated protein (RAP), a specialized chaperone for LRP, was not affected. The effects of tunicamycin on LRP folding were not due to an inhibition of RAP glycosylation since a mutant RAP that harbors a mutation at its sole glycosylation site was still capable of promoting LRP folding. The roles of N-linked glycosylation and the lectin chaperone, calnexin, in LRP folding were further dissected using LRP minireceptors that carry mutations at individual glycosylation sites. Interestingly, we found that RAP interacts with oxidoreductase ERp57 and mediates its interaction with LRP. Since previous studies have shown that N-glycan-bound calnexin/calreticulin are also capable of recruiting ERp57, our results suggest that N-linked glycosylation and RAP can independently and cooperatively recruit oxidoreductases to facilitate protein folding and proper disulfide bond formation.
authors.affiliation: Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: McCormick
authors.forename: Reiko
authors.initials: R
authors.lastname: Urade
authors.forename: Yukino
authors.initials: Y
authors.lastname: Arakaki
authors.forename: Alan L
authors.initials: AL
authors.lastname: Schwartz
authors.forename: Guojun
authors.initials: G
authors.lastname: Bu
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004220:Disulfides / Q000737:chemistry; D006031:Glycosylation; D006801:Humans; D066298:In Vitro Techniques; D026563:LDL-Receptor Related Protein-Associated Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020349:Surface Plasmon Resonance; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D004220:Disulfides; D026563:LDL-Receptor Related Protein-Associated Protein; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D018832:Molecular Chaperones; D011134:Polysaccharides; D011994:Recombinant Proteins; D014415:Tunicamycin