Conformational lability of vitronectin: induction of an antigenic change by alpha-thrombin-serpin complexes and by proteolytically modified thrombin.
We previously showed that the alpha-thrombin-antithrombin III complex causes antigenic change in vitronectin as monitored by the monoclonal anti-vitronectin antibody 8E6 (Tomasini & Mosher, 1988). We have extended these studies to other protease-serpin complexes and to gamma-thrombin, a proteolytic derivative of alpha-thrombin. In the presence of heparin, recognition of vitronectin by 8E6 was increased 64- or 52-fold by interaction with the complex of alpha-thrombin and heparin cofactor II or the Pittsburgh mutant (Met358----Arg) of alpha 1-protease inhibitor, respectively. This was comparable to the value obtained with the alpha-thrombin-antithrombin III complex. Factor Xa-serpin complexes were approximately 4-fold less effective than the corresponding thrombin complexes. alpha-Thrombin-serpin complexes but not Xa-serpin complexes formed disulfide-bonded complexes with vitronectin. Antigenic changes and disulfide-bonded complexes were not detected when trypsin- or chymotrypsin-serpin complexes were incubated with vitronectin. gamma-Thrombin caused 7- and 34-fold increases in recognition of vitronectin by MaVN 8E6 in the absence and presence of heparin, respectively. In contrast, alpha-thrombin by itself had no effect. The antigenic change induced by gamma-thrombin was maximal when gamma-thrombin and vitronectin were equimolar, was not dependent on cleavage of vitronectin, and was abolished by inhibition of gamma-thrombin with Phe-Pro-Arg-chloromethyl ketone but not with diisopropyl fluorophosphate. These data indicate that alpha-thrombin is the component in alpha-thrombin-serpin complexes that induces the antigenic change in vitronectin, probably via a region that is preferentially exposed in gamma-thrombin.
Tomasini
B R
BR
Department of Medicine, University of Wisconsin, Madison 53706.
Owen
M C
MC
Fenton
J W
JW
Mosher
D F
DF
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000941:Antigens / Q000276:immunology; D001798:Blood Proteins / Q000302:isolation & purification / Q000378:metabolism*; D004220:Disulfides / Q000493:pharmacokinetics; D004797:Enzyme-Linked Immunosorbent Assay; D006023:Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D006041:Goats; D006493:Heparin / Q000493:pharmacokinetics; D015151:Immunoblotting; D051379:Mice; D011480:Protease Inhibitors / Q000493:pharmacokinetics*; D011487:Protein Conformation / Q000187:drug effects; D011817:Rabbits; D015843:Serpins / Q000493:pharmacokinetics*; D012995:Solubility; D013379:Substrate Specificity / Q000187:drug effects; D013917:Thrombin / Q000037:antagonists & inhibitors / Q000276:immunology; D019096:Vitronectin
D000911:Antibodies, Monoclonal; D000941:Antigens; D001798:Blood Proteins; D004220:Disulfides; D006023:Glycoproteins; D011480:Protease Inhibitors; D015843:Serpins; D019096:Vitronectin; D006493:Heparin; D013917:Thrombin