title: Opposing effects of collagen I and vitronectin on fibronectin fibril structure and function.
abstract: Extracellular matrix fibronectin fibrils serve as passive structural supports for the organization of cells into tissues, yet can also actively stimulate a variety of cell and tissue functions, including cell proliferation. Factors that control and coordinate the functional activities of fibronectin fibrils are not known. Here, we compared effects of cell adhesion to vitronectin versus type I collagen on the assembly of and response to, extracellular matrix fibronectin fibrils. The amount of insoluble fibronectin matrix fibrils assembled by fibronectin-null mouse embryonic fibroblasts adherent to collagen- or vitronectin-coated substrates was not significantly different 20 h after fibronectin addition. However, the fibronectin matrix produced by vitronectin-adherent cells was ~10-fold less effective at enhancing cell proliferation than that of collagen-adherent cells. Increasing insoluble fibronectin levels with the fibronectin fragment, anastellin did not increase cell proliferation. Rather, native fibronectin fibrils polymerized by collagen- and vitronectin-adherent cells exhibited conformational differences in the growth-promoting, III-1 region of fibronectin, with collagen-adherent cells producing fibronectin fibrils in a more extended conformation. Fibronectin matrix assembly on either substrate was mediated by α5β1 integrins. However, on vitronectin-adherent cells, α5β1 integrins functioned in a lower activation state, characterized by reduced 9EG7 binding and decreased talin association. The inhibitory effect of vitronectin on fibronectin-mediated cell proliferation was localized to the cell-binding domain, but was not a general property of αvβ3 integrin-binding substrates. These data suggest that adhesion to vitronectin allows for the uncoupling of fibronectin fibril formation from downstream signaling events by reducing α5β1 integrin activation and fibronectin fibril extension.
authors: Department of Biomedical Engineering, University of Rochester, Rochester, NY 14627, USA.
authors: Candace D
authors: CD
authors: Gildner
authors: Department of Biomedical Engineering, University of Rochester, Rochester, NY 14627, USA.
authors: Daniel C
authors: DC
authors: Roy
authors: Department of Biomedical Engineering, University of Rochester, Rochester, NY 14627, USA.
authors: Christopher S
authors: CS
authors: Farrar
authors: Department of Biomedical Engineering, University of Rochester, Rochester, NY 14627, USA; Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA. Electronic address: denise_hocking@urmc.rochester.edu.
authors: Denise C
authors: DC
authors: Hocking
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000235:genetics; D049109:Cell Proliferation / Q000235:genetics; D024042:Collagen Type I / Q000737:chemistry / Q000378:metabolism*; D005109:Extracellular Matrix / Q000235:genetics* / Q000648:ultrastructure; D005353:Fibronectins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D039081:Integrin alpha5beta1 / Q000378:metabolism; D039302:Integrin alphaVbeta3 / Q000378:metabolism; D051379:Mice; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D019096:Vitronectin / Q000235:genetics* / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D005353:Fibronectins; D039081:Integrin alpha5beta1; D039302:Integrin alphaVbeta3; D010446:Peptide Fragments; D019096:Vitronectin; C423921:anastellin
keywords: Cell proliferation; Collagen; Extracellular matrix; Fibronectin; Integrin; Vitronectin