Characterization of common neoantigenic epitopes generated in plasminogen activator inhibitor-1 after cleavage of the reactive center loop or after complex formation with various serine proteinases.
Plasminogen activator inhibitor-1 (PAI-1), an important risk factor for thrombotic diseases, is a member of the superfamily of serine proteinase inhibitors. To define structural rearrangements occurring during interaction between PAI-1 and its target proteinases we have raised monoclonal antibodies against the PAI-1/t-PA complex. Thirteen out of 401 monoclonal antibodies reacted preferentially with the PAI-1/t-PA complex as compared to free PAI-1 or free t-PA. Detailed characterization revealed the presence of two non-overlapping neoantigenic epitopes in the PAI-1/t-PA complex. Both neoantigenic epitopes were also exposed after complex formation between PAI-1 and either urokinase-type plasminogen activator, plasmin or thrombin as well as after cleavage of the reactive site loop of non-inhibitory substrate type PAI-1 variants. Thus, we have identified two neoantigenic epitopes, localized entirely in PAI-1, and commonly exposed after complex formation of active PAI-1 with various proteinases or after cleavage of substrate PAI-1. These monoclonal antibodies should facilitate further studies on the mechanism of interaction between various PAI-1 forms and its target proteinases.
D000911:Antibodies, Monoclonal / Q000276:immunology; D000939:Epitopes; D046911:Macromolecular Substances; D017395:Plasminogen Activator Inhibitor 1 / Q000737:chemistry / Q000276:immunology*; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D010959:Tissue Plasminogen Activator / Q000737:chemistry / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D046911:Macromolecular Substances; D017395:Plasminogen Activator Inhibitor 1; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator