An endothelial cell receptor for plasminogen/tissue plasminogen activator (t-PA). II. Annexin II-mediated enhancement of t-PA-dependent plasminogen activation.
In the preceding paper (Hajjar, K. A., Jacovina, A. T., and Chacko, J. (1994) J. Biol. Chem. 269, 21191-21197), we identified a M(r) = 40,000 endothelial cell receptor for tissue plasminogen activator (t-PA) and plasminogen (PLG) as the calcium- and phospholipid-binding protein, annexin II (Ann-II). Here, we examined the effect of Ann-II on t-PA-dependent plasminogen activation in a purified system. Purified native Ann-II bound t-PA, plasminogen, and plasmin with high affinity (Kd = 25 nM, 161 nM, and 75 nM, respectively). At fixed plasminogen concentrations, preincubation with purified native Ann-II was associated with an approximately 21-fold increase in the rate of Glu-PLG activation and an approximately 14-fold increase in activation of Lys-PLG. Three irrelevant proteins had no effect on plasmin formation, while fibrinogen increased the rate of Glu-PLG activation by approximately 4-fold. Annexin-II-mediated enhancement of t-PA-dependent plasminogen activation was 90-95% inhibited by epsilon-aminocaproic acid or by pretreatment of Ann-II with carboxypeptidase B, indicating a carboxyl-terminal lysine-dependent interaction. Kinetic analyses revealed that Ann-II conferred an approximately 60-fold increase in catalytic efficiency upon t-PA-dependent activation of either Glu-PLG or Lys-PLG. Thus, Ann-II-mediated assembly of plasminogen and t-PA may promote and localize constitutive plasmin generation on the surface of the blood vessel wall.
Cesarman
G M
GM
Department of Pediatrics, Cornell University Medical College, New York, New York 10021.
Guevara
C A
CA
Hajjar
K A
KA
D000595:Amino Acid Sequence; D017306:Annexin A2 / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005341:Fibrinolysin / Q000096:biosynthesis; D006801:Humans; D008969:Molecular Sequence Data; D010958:Plasminogen / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000378:metabolism*
D017306:Annexin A2; D011956:Receptors, Cell Surface; D010958:Plasminogen; C067262:PLAT protein, human; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin