Role of cell-surface lysines in plasminogen binding to cells: identification of alpha-enolase as a candidate plasminogen receptor.
Plasminogen binding to cell surfaces results in enhanced plasminogen activation, localization of the proteolytic activity of plasmin on cell surfaces, and protection of plasmin from alpha 2-antiplasmin. We sought to characterize candidate plasminogen binding sites on nucleated cells, using the U937 monocytoid cell as a model, specifically focusing on the role of cell-surface proteins with appropriately placed lysine residues as candidate plasminogen receptors. Lysine derivatives with free alpha-carboxyl groups and peptides with carboxy-terminal lysyl residues were effective inhibitors of plasminogen binding to the cells. One of the peptides, representing the carboxy-terminal 19 amino acids of alpha 2-antiplasmin, was approximately 5-fold more effective than others with carboxy-terminal lysines. Thus, in addition to a carboxy-terminal lysyl residue, other structural features of the cell-surface proteins may influence their affinity for plasminogen. Affinity chromatography has been used to isolate candidate plasminogen receptors from U937 cells. A major protein of Mr 54,000 was recovered and identified as alpha-enolase by immunochemical and functional criteria. alpha-Enolase was present on the cell surface and was capable of binding plasminogen in ligand blotting analyses. Plasminogen binding activity of a molecular weight similar to alpha-enolase also was present in a variety of other cell types. Carboxypeptidase B treatment of alpha-enolase abolished its ability to bind plasminogen, consistent with the presence of a C-terminal lysyl residue. Thus, cell-surface proteins with carboxy-terminal lysyl residues appear to function as plasminogen binding sites, and alpha-enolase has been identified as a prominent representative of this class of receptors.
Miles
L A
LA
Committee on Vascular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
Dahlberg
C M
CM
Plescia
J
J
Felez
J
J
Kato
K
K
Plow
E F
EF
D000595:Amino Acid Sequence; D001667:Binding, Competitive; D043424:Carboxypeptidase B; D002268:Carboxypeptidases / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008239:Lysine; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010455:Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D010751:Phosphopyruvate Hydratase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010958:Plasminogen / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D012689:Sequence Homology, Nucleic Acid
D008024:Ligands; C524898:PLAUR protein, human; D010455:Peptides; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D010958:Plasminogen; D002268:Carboxypeptidases; D043424:Carboxypeptidase B; D010751:Phosphopyruvate Hydratase; D008239:Lysine