title: TNF-alpha binds to the N-terminal domain of fibronectin and augments the beta 1-integrin-mediated adhesion of CD4+ T lymphocytes to the glycoprotein.
abstract: Certain inflammatory cytokines and growth factors have been previously shown to interact with glycosaminoglycan moieties of the extracellular matrix (ECM). We have examined the association of the pleiotropic cytokine TNF-alpha with glycoprotein constituents of ECM. TNF-alpha interacted with fibronectin (FN) and laminin, and to a lesser degree with collagen. The major binding site for TNF-alpha on FN was localized to its 30-kDa N-terminal fragment (FN-N') with a Ki in the sub-nM range. The binding of 125I-labeled TNF-alpha to immobilized FN or FN-N' persisted for at least 24 h, and was specifically inhibited by antibodies to FN, mAb directed against the FN-N' domain, unlabeled TNF-alpha, and by the truncated forms of TNF-alpha receptors. Once bound to immobilized FN or FN-N', the cytokine could not be released by the soluble TNF-alpha-receptors, although it could be released by anti-TNF-alpha Ab. TNF-alpha was also found to interact with soluble FN, although with a lower affinity. Similar to the soluble cytokine, the FN-bound TNF-alpha appears to be functional; it augmented the beta 1-integrin-mediated adhesiveness of activated CD4+ human T cells to the glycoprotein. Hence, binding of TNF-alpha to immobilized FN, which modifies its functional accessibility to soluble TNF-alpha receptors, does not abolish but rather may locally restrict its activity. This study suggests that a major ECM glycoprotein can present, in a restricted manner, a functional adhesion-modulating cytokine to immune cells, and that ECM glycoproteins may regulate their intrinsic cell-adhesive properties by associating with cytokines.
authors.affiliation: Department of Biophysics and Membrane Research, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: R
authors.initials: R
authors.lastname: Alon
authors.forename: L
authors.initials: L
authors.lastname: Cahalon
authors.forename: R
authors.initials: R
authors.lastname: Hershkoviz
authors.forename: D
authors.initials: D
authors.lastname: Elbaz
authors.forename: B
authors.initials: B
authors.lastname: Reizis
authors.forename: D
authors.initials: D
authors.lastname: Wallach
authors.forename: S K
authors.initials: SK
authors.lastname: Akiyama
authors.forename: K M
authors.initials: KM
authors.lastname: Yamada
authors.forename: O
authors.initials: O
authors.lastname: Lider
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology*; D002448:Cell Adhesion; D002478:Cells, Cultured; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D011485:Protein Binding; D012995:Solubility; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D014409:Tumor Necrosis Factor-alpha; D006493:Heparin