Universität zu Köln

Syx, Delfien, Ishikawa, Yoshihiro ORCID: 0000-0003-2013-0518, Gebauer, Jan ORCID: 0000-0002-3989-4748, Boudko, Sergei P., Guillemyn, Brecht ORCID: 0000-0001-7194-6651, Van Damme, Tim ORCID: 0000-0002-6424-4421, D'hondt, Sanne, Symoens, Sofie, Nampoothiri, Sheela ORCID: 0000-0002-9575-0722, Gould, Douglas B., Baumann, Ulrich, Bachinger, Hans Peter and Malfait, Fransiska (2021). Aberrant binding of mutant HSP47 affects posttranslational modification of type I collagen and leads to osteogenesis imperfecta. PLoS Genet., 17 (2). SAN FRANCISCO: PUBLIC LIBRARY SCIENCE. ISSN 1553-7404

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Abstract

Heat shock protein 47 (HSP47), encoded by the SERPINH1 gene, is a molecular chaperone essential for correct folding of collagens. We report a homozygous p.(R222S) substitution in HSP47 in a child with severe osteogenesis imperfecta leading to early demise. p.R222 is a highly conserved residue located within the collagen interacting surface of HSP47. Binding assays show a significantly reduced affinity of HSP47-R222S for type I collagen. This altered interaction leads to posttranslational overmodification of type I collagen produced by dermal fibroblasts, with increased glycosylation and/or hydroxylation of lysine and proline residues as shown by mass spectrometry. Since we also observed a normal intracellular folding and secretion rate of type I collagen, this overmodification cannot be explained by prolonged exposure of the collagen molecules to the modifying hydroxyl- and glycosyltransferases, as is commonly observed in other types of OI. We found significant upregulation of several molecular chaperones and enzymes involved in procollagen modification and folding on Western blot and RT-qPCR. In addition, we showed that an imbalance in binding of HSP47-R222S to unfolded type I collagen chains in a gelatin sepharose pulldown assay results in increased binding of other chaperones and modifying enzymes. The elevated expression and binding of this molecular ensemble to type I collagen suggests a compensatory mechanism for the aberrant binding of HSP47-R222S, eventually leading to overmodification of type I collagen chains. Together, these results illustrate the importance of HSP47 for proper posttranslational modification and provide insights into the molecular pathomechanisms of the p.(R222S) alteration in HSP47, which leads to a severe OI phenotype. Author summary Heat shock protein 47 (HSP47) is essential for correct collagen folding. We report a homozygous p.(R222S) substitution in HSP47 in a child with severe osteogenesis imperfecta. The highly conserved p.R222 residue is located within the collagen interacting surface and HSP47-R222S shows a significantly reduced affinity for type I collagen. This altered interaction leads to posttranslational overmodification of type I collagen. In contrast to other types of OI, this overmodification is not caused by prolonged exposure of collagen to modifying enzymes, since the intracellular folding rate of type I collagen appears to be normal. We show significant upregulation of several molecular chaperones and collagen-modifying enzymes and increased binding of several of these molecules to unfolded type I collagen chains upon abnormal HSP47-R222S binding. This suggests a compensatory mechanism for aberrant HSP47-R222S binding, eventually leading to overmodification of type I collagen chains, and underscores the importance of HSP47 for proper posttranslational modification.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Syx, Delfien UNSPECIFIED UNSPECIFIED UNSPECIFIED Ishikawa, Yoshihiro UNSPECIFIED orcid.org/0000-0003-2013-0518 UNSPECIFIED Gebauer, Jan UNSPECIFIED orcid.org/0000-0002-3989-4748 UNSPECIFIED Boudko, Sergei P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Guillemyn, Brecht UNSPECIFIED orcid.org/0000-0001-7194-6651 UNSPECIFIED Van Damme, Tim UNSPECIFIED orcid.org/0000-0002-6424-4421 UNSPECIFIED D'hondt, Sanne UNSPECIFIED UNSPECIFIED UNSPECIFIED Symoens, Sofie UNSPECIFIED UNSPECIFIED UNSPECIFIED Nampoothiri, Sheela UNSPECIFIED orcid.org/0000-0002-9575-0722 UNSPECIFIED Gould, Douglas B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Baumann, Ulrich UNSPECIFIED UNSPECIFIED UNSPECIFIED Bachinger, Hans Peter UNSPECIFIED UNSPECIFIED UNSPECIFIED Malfait, Fransiska UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-595692
DOI:	10.1371/journal.pgen.1009339
Journal or Publication Title:	PLoS Genet.
Volume:	17
Number:	2
Date:	2021
Publisher:	PUBLIC LIBRARY SCIENCE
Place of Publication:	SAN FRANCISCO
ISSN:	1553-7404
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SHOCK-PROTEIN 47; CHAPERONE HSP47; MOLECULAR CHAPERONE; TRIPLE-HELIX; ENDOPLASMIC-RETICULUM; RECOGNITION; DEFICIENCY; PROPEPTIDE; VARIANT; FKBP65 Multiple languages Genetics & Heredity Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/59569