title: Human fibronectin and MMP-2 collagen binding domains compete for collagen binding sites and modify cellular activation of MMP-2.
abstract: The region of fibronectin (FN) surrounding the two type II modules of FN binds type I collagen. However, little is known about interactions of this collagen binding domain with other collagen types or extracellular matrix molecules. Among several expressed recombinant (r) human FN fragments from the collagen binding region of FN, only rI6-I7, which included the two type II modules and both flanking type I modules, bound any of several tested collagens. The rI6-I7 interacted specifically with both native and denatured forms of types I and III collagen as well as denatured types II, IV, V and X collagen with apparent K(d) values of 0.2-3.7 x 10(-7) M. Reduction with DTT disrupted the binding to gelatin verifying the functional requirement for intact disulfide bonds. The FN fragments showed a weak, but not physiologically important, binding to heparin, and did not bind elastin or laminin. The broad, but selective range of ligand interactions by rI6-I7 mirrored our prior observations for the collagen binding domain (rCBD) from matrix metalloproteinase-2 (MMP-2) [J. Biol. Chem. 270 (1995) 11555]. Subsequent experiments showed competition between rI6-I7 and rCBD for binding to gelatin indicating that their binding sites on this extracellular matrix molecule are identical or closely positioned. Two collagen binding domain fragments supported cell attachment by a beta1-integrin-dependent mechanism although neither protein contains an Arg-Gly-Asp recognition sequence. Furthermore, activation of MMP-2 and MMP-9 was greatly reduced for HT1080 fibrosarcoma cells cultured on either of the fibronectin fragments compared to full-length FN. These observations imply that the biological activities of FN in the extracellular matrix may involve interactions with a broad range of collagen types, and that exposure to pathologically-generated FN fragments may substantially alter cell behavior and regulation.
authors.affiliation: Department of Periodontics MC 7894, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA. steffensenb@uthscsa.edu
authors.forename: Bjorn
authors.initials: B
authors.lastname: Steffensen
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Xu
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Martin
authors.forename: Gustavo
authors.initials: G
authors.lastname: Zardeneta
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002448:Cell Adhesion / Q000502:physiology; D003094:Collagen / Q000378:metabolism*; D024042:Collagen Type I / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D004926:Escherichia coli / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology; D008024:Ligands; D020778:Matrix Metalloproteinase 2 / Q000737:chemistry / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D019012:Integrin beta1; D008024:Ligands; D010446:Peptide Fragments; D011994:Recombinant Proteins; D003094:Collagen; D020778:Matrix Metalloproteinase 2