Study on the Mechanism of the Annexin Ⅱ -Mediated Co- Assembly of t-PA and Plasminogen

摘要

In order to further investigate the effect of annexin Ⅱ (Ann- Ⅱ ) on tissue plasminogen activator (t-PA) -dependent plasminogen (PLG) activation and its interactive mechanism, recombinant native Ann- Ⅱ bound t-PA, PLG and plasmin with high affinity was examined. The flow cytometric assay showed that the ann- Ⅱ expression rate was higher in the human umbilical vein endothelial cell (HUVEC) (87.65 %) than in the HL-60 cells as controls (35. 79 %). Two irrelevant proteins, bovine serum albumin (BSA) and equine IgG (EIG) had no effect on the production of plasmin. Ann-Ⅱ -mediated enhancement of t-PA-dependent PLG activation was inhibited by Ⅱ-aminocaproic acid or by pretreatment of Ann-Ⅱ with carboxypeptidase B with the inhibitive rate being 77. 8 % and 77. 0 % , respectively. It was revealed that the effect of Ann- Ⅱ on PLG activation was specific for t-PA. Urokinase didn't bind to Ann- Ⅱ , demonstrating the role of receptor-related lysine residues on activation of PLG, showing that the Ann- Ⅱ -PLG interaction was dependent upon carboxyl- terminal lysine residues. These findings suggest that annexin Ⅱ-mediated co-assembly of t-PA and PLG may promote plasmin generation and play a key role in modulating fibrinolysis on the endothelial surface.