Heparin-binding vitronectin up-regulates latent TGF-beta production by bovine aortic endothelial cells.
Vitronectin, a serum and extracellular matrix protein, is present in vivo in two different conformations: a native form, which does not bind heparin, and a heparin-binding conformer, which results from interactions of native vitronectin with either the thrombin-antithrombin III complex or the terminal complement complex, C5b-9. We found that vitronectin stimulates the activity of the growth regulatory peptide, TGF-beta, in the conditioned media of bovine aortic endothelial cells as a result of increased production of latent TGF-beta. This effect is specific for the denatured, heparin-binding, form of vitronectin, since native vitronectin has no effect on the production of latent TGF-beta by those cells. Stimulation is time and concentration-dependent, but is independent of protease activity. Stimulation is dependent on the presence of cells, since there was no increase in TGF-beta activity observed when vitronectin was added to the conditioned media after removal from cells. Furthermore, incubation of recombinant latent TGF-beta with vitronectin in a cell-free system does not result in increased TGF-beta activity. Assays of total TGF-beta levels in heat-treated conditioned media showed that vitronectin treatment elevates the levels of total TGF-beta in the conditioned media. These results were further confirmed by western blot analysis of the conditioned media with antibodies specific for latent TGF-beta. These data suggest that vitronectin regulates expression and/or secretion of TGF-beta by bovine aortic endothelial cells. This cellular response to the heparin-binding form of vitronectin seems to be mediated by alpha v beta 3 integrins.(ABSTRACT TRUNCATED AT 250 WORDS)
Ribeiro
S M
SM
Department of Pathology, University of Alabama at Birmingham 35294-0019, USA.
Schultz-Cherry
S
S
Murphy-Ullrich
J E
JE
D000818:Animals; D000906:Antibodies; D001011:Aorta; D007611:Aprotinin / Q000494:pharmacology; D015153:Blotting, Western; D002417:Cattle; D002460:Cell Line; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000494:pharmacology; D006023:Glycoproteins / Q000378:metabolism / Q000494:pharmacology*; D006493:Heparin / Q000378:metabolism*; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000494:pharmacology; D019699:Thrombospondins; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000096:biosynthesis* / Q000378:metabolism; D019096:Vitronectin
D000906:Antibodies; D017077:Culture Media, Conditioned; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D007976:Leupeptins; D008562:Membrane Glycoproteins; D019699:Thrombospondins; D016212:Transforming Growth Factor beta; D019096:Vitronectin; D006493:Heparin; D007611:Aprotinin; C032854:leupeptin