title: Design and synthesis of oligosaccharides that interfere with glycoprotein quality-control systems.
abstract: Calnexin (CNX) and its soluble homologue calreticulin (CRT) are lectin-like molecular chaperones that help newly synthesized glycoproteins to fold correctly in the rough endoplasmic reticulum (ER). To investigate the mechanism of glycoprotein-quality control, we have synthesized structurally defined high-mannose-type oligosaccharides related to this system. This paper describes the synthesis of the non-natural undecasaccharide 2 and heptasaccharide 16, designed as potential inhibitors of the ER quality-control system. Each possesses the key tetrasaccharide element (Glc1Man3) critical for the CNX/CRT binding, while lacking the pentamannosyl branch required for glucosidase II recognition. These oligosaccharides were evaluated for their ability to bind CRT by isothermal titration calorimetry (ITC). As expected, each of them had a significant affinity towards CRT. In addition, these compounds were shown to be resistant to glucosidase II digestion. Their activities in blocking the chaperone function of CRT were next measured by using malate dehydrogenase (MDH) as a substrate. Their inhibitory effects were shown to correlate well with their CRT-binding affinities, both being critically dependent upon the presence of the terminal glucose (Glc) residue.
authors.affiliation: RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Midori A
authors.initials: MA
authors.lastname: Arai
authors.forename: Ichiro
authors.initials: I
authors.lastname: Matsuo
authors.forename: Shinya
authors.initials: S
authors.lastname: Hagihara
authors.forename: Kiichiro
authors.initials: K
authors.lastname: Totani
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Maruyama
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kitamoto
authors.forename: Yukishige
authors.initials: Y
authors.lastname: Ito
mesh_terms: D037281:Calnexin; D037282:Calreticulin / Q000037:antagonists & inhibitors*; D015195:Drug Design; D004721:Endoplasmic Reticulum / Q000502:physiology; D006023:Glycoproteins / Q000737:chemistry*; D006801:Humans; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors*; D009844:Oligosaccharides / Q000138:chemical synthesis / Q000494:pharmacology*; D017510:Protein Folding
chemical_list: D037282:Calreticulin; D006023:Glycoproteins; D018832:Molecular Chaperones; D009844:Oligosaccharides; D037281:Calnexin