title: Activation of distinct alpha5beta1-mediated signaling pathways by fibronectin's cell adhesion and matrix assembly domains.
abstract: The interaction of cells with fibronectin generates a series of complex signaling events that serve to regulate several aspects of cell behavior, including growth, differentiation, adhesion, and motility. The formation of a fibronectin matrix is a dynamic, cell-mediated process that involves both ligation of the alpha5beta1 integrin with the Arg-Gly-Asp (RGD) sequence in fibronectin and binding of the amino terminus of fibronectin to cell surface receptors, termed "matrix assembly sites," which mediate the assembly of soluble fibronectin into insoluble fibrils. Our data demonstrate that the amino-terminal type I repeats of fibronectin bind to the alpha5beta1 integrin and support cell adhesion. Furthermore, the amino terminus of fibronectin modulates actin assembly, focal contact formation, tyrosine kinase activity, and cell migration. Amino-terminal fibronectin fragments and RGD peptides were able to cross-compete for binding to the alpha5beta1 integrin, suggesting that these two domains of fibronectin cannot bind to the alpha5beta1 integrin simultaneously. Cell adhesion to the amino-terminal domain of fibronectin was enhanced by cytochalasin D, suggesting that the ligand specificity of the alpha5beta1 integrin is regulated by the cytoskeleton. These data suggest a new paradigm for integrin-mediated signaling, where distinct regions within one ligand can modulate outside-in signaling through the same integrin.
authors.affiliation: Department of Physiology and Cell Biology, Albany Medical College, Albany, New York 12208, USA.
authors.forename: D C
authors.initials: DC
authors.lastname: Hocking
authors.forename: J
authors.initials: J
authors.lastname: Sottile
authors.forename: P J
authors.initials: PJ
authors.lastname: McKeown-Longo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002460:Cell Line; D002465:Cell Movement; D003513:Cycloheximide / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D005109:Extracellular Matrix / Q000737:chemistry / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D005353:Fibronectins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D007365:Intercellular Junctions / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D008297:Male; D009842:Oligopeptides; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017469:Receptors, Fibronectin / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D012867:Skin
chemical_list: D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D005353:Fibronectins; D009842:Oligopeptides; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; C496063:Pxn protein, rat; D017469:Receptors, Fibronectin; D011994:Recombinant Proteins; D019000:Phosphotyrosine; D015638:Cytochalasin D; C047981:arginyl-glycyl-aspartic acid; D003513:Cycloheximide; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496052:Ptk2 protein, rat