title: Mutants of collagen-specific molecular chaperone Hsp47 causing osteogenesis imperfecta are structurally unstable with weak binding affinity to collagen.
abstract: Osteogenesis imperfecta (OI) is a genetic disorder characterized by fragile bones. Most OI cases are caused by defects in type I collagen structure or synthesis. Mutations in collagen specific molecular chaperone Hsp47, specifically L78P and L326P, lead to OI, yet these mutants are not fully characterized. Here, we found that both Hsp47 mutants were structurally unstable and formed high molecular weight complexes. They were degraded by the ubiquitin-proteasome system, and the collagen-binding ability of the mutants was significantly lower than that of the wild type. Although the chemical chaperone 4-PBA partially restores the solubility of the Hsp47 OI mutants, collagen-binding activity of Hsp47 was not improved.
authors.affiliation: Department of Molecular and Cellular Biology, Institute for Frontier Medical Sciences, Kyoto University, 53 Kawahara-cho, Sakyo-ku, Kyoto City, Kyoto 606-8397, Japan; Department of Molecular Biosciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Ito
authors.affiliation: Department of Molecular Biosciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan; CREST, Japan Science and Technology Agency, Kyoto Sangyo University, Kyoto 603-8555, Japan. Electronic address: nagata@cc.kyoto-su.ac.jp.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Nagata
mesh_terms: D000818:Animals; D001665:Binding Sites; D024042:Collagen Type I / Q000235:genetics* / Q000378:metabolism*; D050958:HSP47 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009154:Mutation / Q000235:genetics; D010013:Osteogenesis Imperfecta / Q000503:physiopathology*; D011485:Protein Binding
chemical_list: D024042:Collagen Type I; D050958:HSP47 Heat-Shock Proteins; C494660:SERPINH1 protein, human
keywords: Chemical chaperone; Collagen; ER stress; Molecular chaperone Hsp47; Osteogenesis imperfecta