title: A type VII collagen subdomain mutant is thermolabile and shows enhanced proteolytic degradability - Implications for the pathogenesis of recessive dystrophic epidermolysis bullosa?
abstract: Type VII collagen is the major constituent of anchoring fibrils. It has a central collagenous domain that is surrounded by a small C-terminal non-collagenous domain (NC2) and a large N-terminal non-collagenous (NC1) domain. Mutations in type VII collagen can lead to hereditary skin blistering disease dystrophic epidermolysis bullosa (DEB). Most of the pathogenic missense mutations are within the collagenous domain. NC1 domain mediates interactions with other extracellular matrix molecules and only very few missense mutations within NC1 causing DEB have been reported. Interestingly, fibronectin III like (FNIII) domain 8 in the human protein can harbour different mutations at position 886 with one (R886P) leading to recessive DEB, whereas the others do not. We characterized subdomains of murine NC1, the FNIII domains 7-8, and the individual domains FNIII7 and FNIII8 by NMR- and CD-spectroscopy. We analysed the influence on stability for a mutation causing DEB and a non-pathogenic mutation. Whereas the silent mutation behaves as the wild type, the pathogenic mutation leads to a dramatic decrease in thermal stability of the FNIII8 domain. The melting temperature lowered from 77°C to 40°C compared to the wild type protein. This renders the domain susceptible to protease cleavage which could be shown by degradation tests with cathepsin G, cathepsin K, and MMP9. Our data show partial unfolding of type VII collagen due to the mutation causes an increased degradation. This could lead to skin blistering and opens new concomitant treatment options in some types of type VII collagen related skin blistering diseases.
authors.affiliation: Institute of Chemistry, University of Lübeck, Ratzeburger Allee 160, 23562 Lübeck, Germany.
authors.forename: Cordula
authors.initials: C
authors.lastname: Windler
authors.affiliation: Institute of Chemistry, University of Lübeck, Ratzeburger Allee 160, 23562 Lübeck, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Hermsdorf
authors.affiliation: Department of Dermatology, University of Lübeck, Ratzeburger Allee 160, 23562 Lübeck, Germany; Institute of Virology and Cell Biology, University of Lübeck, Ratzeburger Allee 160, 23562 Lübeck, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Brinckmann
authors.affiliation: Institute of Chemistry, University of Lübeck, Ratzeburger Allee 160, 23562 Lübeck, Germany. Electronic address: karsten.seeger@chemie.uni-luebeck.de.
authors.forename: Karsten
authors.initials: K
authors.lastname: Seeger
mesh_terms: D000818:Animals; D024143:Collagen Type VII / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016108:Epidermolysis Bullosa Dystrophica / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D020125:Mutation, Missense; D017354:Point Mutation; D011487:Protein Conformation; D000072417:Protein Domains; D055550:Protein Stability; D058767:Protein Unfolding; D059748:Proteolysis
chemical_list: D024143:Collagen Type VII
keywords: Dystrophic epidermolysis bullosa; Protease cleavage; Type VII collagen