The p11 subunit of the annexin II tetramer plays a key role in the stimulation of t-PA-dependent plasminogen activation.
Annexin II tetramer (AIIt) is an important endothelial cell surface protein receptor for plasminogen and t-PA. AIIt, a heterotetramer, is composed of two p36 subunits (called annexin II) and two p11 subunits. In this report, we have compared the ability of the isolated p36 and p11 subunits to stimulate t-PA-dependent [Glu]plasminogen activation. The fluid-phase recombinant p11 subunit stimulated the rate of t-PA-dependent activation of [Glu]plasminogen about 46-fold compared to an approximate stimulation of 2-fold by the recombinant p36 subunit and 77-fold by recombinant AIIt. The stimulation of t-PA-dependent activation of [Glu]plasminogen by the p11 subunit was Ca2+-independent and inhibited by epsilon-aminocaproic acid. [Glu]Plasminogen bound to a p11 subunit affinity column and could be eluted with epsilon-aminocaproic acid. Both AIIt and the p11 subunit protected t-PA and plasmin from inactivation by PAI-1 and alpha2-antiplasmin, respectively. A peptide to the C terminus of the p11 subunit (85-Y-F-V-V-H-M-K-Q-K-G-K-K-96) inhibited the p11-dependent stimulation of t-PA-dependent plasminogen activation. In addition, a deletion mutant of the p11 subunit, missing the last two C-terminal lysine residues, retained only about 15% of the activity of the wild-type p11 subunit. Similarly, a mutant AIIt composed of the wild-type p36 subunit and the p11 subunit deletion mutant possessed about 12% of the wild-type activity. These results, therefore, suggest that the C-terminal lysine residues of the p11 subunit bind plasminogen and participate in the stimulation of t-PA-dependent activation of plasminogen by AIIt.
Kassam
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G
Cancer Biology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
Le
B H
BH
Choi
K S
KS
Kang
H M
HM
Fitzpatrick
S L
SL
Louie
P
P
Waisman
D M
DM
D015119:Aminocaproic Acid; D017306:Annexin A2 / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D005341:Fibrinolysin; D006801:Humans; D008239:Lysine; D016296:Mutagenesis; D010958:Plasminogen / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion; D010959:Tissue Plasminogen Activator / Q000378:metabolism*; D000979:alpha-2-Antiplasmin
D017306:Annexin A2; D017395:Plasminogen Activator Inhibitor 1; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D000979:alpha-2-Antiplasmin; D010958:Plasminogen; C067262:PLAT protein, human; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin; D008239:Lysine; D015119:Aminocaproic Acid