title: Substrate-specific binding of the amino terminus of fibronectin to an integrin complex in focal adhesions.
abstract: The assembly of fibronectin fibrils involves the amino-terminal and cell adhesion domains of fibronectin as well as alpha 5 beta 1 integrins. Efficient binding of biotinylated or radioiodinated 70-kDa amino-terminal fragments occurred only if fibroblasts were plated on fibronectin or on 180- or 85-kDa cell adhesion fragments of fibronectin. On an 11.5-kDa fragment of fibronectin that included the Arg-Gly-Asp (RGD) sequence, but not the synergy site, binding was reduced 50-fold. Conformation of the 180-kDa fragment was important for direct binding interactions with the amino terminus of fibronectin. No binding was seen if cells were plated on type I collagen, vitronectin, RGD peptides or antibodies to alpha 5 beta 1 integrins. High affinity interactions between invasin and alpha 5 beta 1 integrin promoted low levels of binding. Monoclonal antibodies that blocked the function of either the RGD or the synergy site inhibited binding of 125I-labeled 70-kDa fragments to cells by approximately 60%. By fluorescence and interference reflection microscopy, biotinylated 70-kDa fragments were shown to co-localize with alpha 5 beta 1 integrins in focal adhesions. We propose that cell-mediated binding of the amino terminus of fibronectin involves interactions with both fibronectin and its alpha 5 beta 1 integrin receptor in an activated complex.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison 53706.
authors.forename: B J
authors.initials: BJ
authors.lastname: Dzamba
authors.forename: H
authors.initials: H
authors.lastname: Bultmann
authors.forename: S K
authors.initials: SK
authors.lastname: Akiyama
authors.forename: D M
authors.initials: DM
authors.lastname: Peters
mesh_terms: D018829:Adhesins, Bacterial; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D008954:Models, Biological; D009842:Oligopeptides; D010446:Peptide Fragments / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017469:Receptors, Fibronectin; D012867:Skin / Q000378:metabolism
chemical_list: D018829:Adhesins, Bacterial; D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D005353:Fibronectins; D016023:Integrins; D009842:Oligopeptides; D010446:Peptide Fragments; D017469:Receptors, Fibronectin; C053476:invasin, Yersinia; C047981:arginyl-glycyl-aspartic acid; D003513:Cycloheximide