Open AccessSpecific interaction of vitronectin with the cell‐secreted protease inhibitor glia‐derived nexin and its thrombin complex
Author(s) -
ROVELLI Giorgio,
STONE Stuart R.,
PREISSNER Klaus T.,
MONARD Denis
Publication year - 1990
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1990.tb19293.x
Subject(s) - vitronectin , thrombin , serine protease , chemistry , antithrombin , serpin , biochemistry , biophysics , protease , biology , heparin , integrin , receptor , enzyme , platelet , gene , immunology
Interaction of vitronectin with glia‐derived nexin (GDN), thrombin, and the complex GDN‐thrombin was demonstrated in direct binding assays that indicated the formation of binary and ternary complexes. The concentration of vitronectin necessary to obtain 50% saturation of the immobilized GDN‐thrombin complex binding sites (EC 50 ) was about 1 nM. Under similar experimental conditions, the EC 50 of vitronectin for the immobilized antithrombin‐III–thrombin complex was about fivefold higher. A tight complex was also formed between vitronectin and immobilized GDN (EC 50 ∼ 1.5 nM) but when vitronectin was immobilized, GDN displayed a reduced affinity for vitronectin (EC 50 ∼ 10 nM). These results suggest differences between the immobilized and free conformations of GDN and/or vitronectin. In contrast, vitronectin displayed negligible affinity for antithrombin III. Biotinylated GDN was used to characterize further the binding of GDN or the GDN‐thrombin complex to vitronectin. The interaction of the biotinylated GDN‐thrombin complex with immobilized vitronectin (EC 50 ∼ 2 nM) was completely blocked by nonbiotinylated complexes of thrombin with either GDN or antithrombin III, whereas free GDN, free thrombin and the GDN‐trypsin complex were only weak competitors. Activesite‐blocked urokinase and the complex GDN‐urokinase also strongly competed for binding of the biotinylated GDN‐thrombin complex to vitronectin. Binding of biotinylated GDN to immobilized vitronectin was specific, saturable and was competed with decreasing efficiency by the GDN‐thrombin complex, free GDN and free antithrombin III. These interactions between the adhesive component vitronectin and the serine protease inhibitor GDN may relate to localized control of thrombin and/or urokinase action at certain extravascular sites. These results are discussed in terms of binding sites for vitronectin on GDN, thrombin, and the GDN‐thrombin complex.