title: A comparative analysis of the fibulin protein family. Biochemical characterization, binding interactions, and tissue localization.
abstract: Fibulins are a family of five extracellular matrix proteins characterized by tandem arrays of epidermal growth factor-like domains and a C-terminal fibulin-type module. They are widely distributed and often associated with vasculature and elastic tissues. In this study, we expressed the three more recently identified family members, fibulin-3, fibulin-4, and fibulin-5, as recombinant proteins in mammalian cells. The purified proteins showed short rod structures of approximately 20 nm with a globule at one end, after rotary shadowing and electron microscopy. Two forms of mouse fibulin-3 were purified, and the O-glycan profiles of the larger form were characterized. Polyclonal antibodies raised against the purified proteins did not show any cross-reactivity with other family members and were used to assess the levels and localization of the fibulins in mouse tissues. Their binding interactions, cell adhesive properties, and tissue localization were analyzed in parallel with the previously characterized fibulin-1 and -2. Binding to tropoelastin was strong for fibulin-2 and -5, moderate for fibulin-4 and -1, and relatively weak for fibulin-3. Fibulin-4, but not fibulin-3 and -5, exhibited distinct interactions with collagen IV and nidogen-2 and moderate binding to the endostatin domain from collagen XV. Cell adhesive activities were not observed for all fibulins, except mouse fibulin-2, with various cell lines tested. All five fibulins were found in perichondrium and various regions of the lungs. Immunoelectron microscopy localized fibulin-4 and -5 to fibrillin microfibrils at distinct locations. Our studies suggest there are unique and redundant functions shared by these structurally related proteins.
authors.affiliation: Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Günter
authors.initials: G
authors.lastname: Kostka
authors.forename: Jörg H O
authors.initials: JH
authors.lastname: Garbe
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Keene
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Bächinger
authors.forename: Franz-Georg
authors.initials: FG
authors.lastname: Hanisch
authors.forename: Dessislava
authors.initials: D
authors.lastname: Markova
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tsuda
authors.forename: Rupert
authors.initials: R
authors.lastname: Timpl
authors.forename: Mon-Li
authors.initials: ML
authors.lastname: Chu
authors.forename: Takako
authors.initials: T
authors.lastname: Sasaki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D002448:Cell Adhesion; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014018:Tissue Distribution; D014333:Tropoelastin / Q000737:chemistry
chemical_list: D002135:Calcium-Binding Proteins; C492278:Efemp1 protein, mouse; D016326:Extracellular Matrix Proteins; D011134:Polysaccharides; D014333:Tropoelastin; C060820:fibulin; D006026:Glycoside Hydrolases