title: Loss of fibulin-4 disrupts collagen synthesis and maturation: implications for pathology resulting from EFEMP2 mutations.
abstract: Homozygous recessive mutations in either EFEMP2 (encoding fibulin-4) or FBLN5 (encoding fibulin-5), critical genes for elastogenesis, lead to autosomal recessive cutis laxa types 1B and 1A, respectively. Previously, fibulin-4 was shown to bind lysyl oxidase (LOX), an elastin/collagen cross-linking enzyme, in vitro. Consistently, reported defects in humans with EFEMP2 mutations are more severe and broad in range than those due to FBLN5 mutations and encompass both elastin-rich and collagen-rich tissues. However, the underlying disease mechanism in EFEMP2 mutations has not been fully addressed. Here, we show that fibulin-4 is important for the integrity of aortic collagen in addition to elastin. Smooth muscle-specific Efemp2 loss in mouse (termed SMKO) resulted in altered fibrillar collagen localization with larger, poorly organized fibrils. LOX activity was decreased in Efemp2-null cells, and collagen cross-linking was diminished in SMKO aortas; however, elastin cross-linking was unaffected and the level of mature LOX was maintained to that of wild-type aortas. Proteomic screening identified multiple proteins involved in procollagen processing and maturation as potential fibulin-4-binding partners. We showed that fibulin-4 binds procollagen C-endopeptidase enhancer 1 (Pcolce), which enhances proteolytic cleavage of the procollagen C-terminal propeptide during procollagen processing. Interestingly, however, procollagen cleavage was not affected by the presence or absence of fibulin-4 in vitro. Thus, our data indicate that fibulin-4 serves as a potential scaffolding protein during collagen maturation in the extracellular space. Analysis of collagen in other tissues affected by fibulin-4 loss should further increase our understanding of underlying pathologic mechanisms in patients with EFEMP2 mutations.
authors.affiliation: Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Christina L
authors.initials: CL
authors.lastname: Papke
authors.affiliation: Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Tsunezumi
authors.affiliation: Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada.
authors.forename: Léa-Jeanne
authors.initials: LJ
authors.lastname: Ringuette
authors.affiliation: NC Oral Health Institute, University of North Carolina, Chapel Hill, NC 27599, USA and.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nagaoka
authors.affiliation: NC Oral Health Institute, University of North Carolina, Chapel Hill, NC 27599, USA and.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Terajima
authors.affiliation: Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA, Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Yamashiro
authors.affiliation: Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Greg
authors.initials: G
authors.lastname: Urquhart
authors.affiliation: NC Oral Health Institute, University of North Carolina, Chapel Hill, NC 27599, USA and.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Yamauchi
authors.affiliation: Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada.
authors.forename: Elaine C
authors.initials: EC
authors.lastname: Davis
authors.affiliation: Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA, Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan hiromi.yanagisawa@utsouthwestern.edu.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yanagisawa
mesh_terms: D000818:Animals; D001011:Aorta / Q000378:metabolism*; D003094:Collagen / Q000096:biosynthesis* / Q000378:metabolism; D004549:Elastin / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D017353:Gene Deletion; D006720:Homozygote; D051379:Mice; D009130:Muscle, Smooth / Q000378:metabolism; D010084:Oxidation-Reduction; D008249:Protein-Lysine 6-Oxidase / Q000378:metabolism; D040901:Proteomics
chemical_list: C403672:EFEMP2 protein, human; C485883:Efemp2 protein, mouse; D016326:Extracellular Matrix Proteins; D003094:Collagen; D004549:Elastin; D008249:Protein-Lysine 6-Oxidase