The role of an enolase-related molecule in plasminogen binding to cells.
The alpha isoform of enolase is a candidate plasminogen receptor on U937 monocytoid cells [Miles, L. A., Dahlberg, C. L., Plescia, J., Felez, J., Kato, K. & Plow, E. F. (1991) Biochemistry 30, 1682-1691]. In the present study, an enolase-related molecule was detected on the surfaces of peripheral blood monocytes and neutrophils by fluorescence-activated cell sorting. A mRNA transcript encoding a unique membrane form of an enolase-related molecule was not detected by Northern-blotting and primer-extension analyses, consistent with the cell-surface protein being authentic alpha-enolase. Both the alpha and beta isoforms of purified enolase, bound plasminogen with an affinity similar to that of the cell surface. Moreover, immunopurified alpha-enolase enhanced plasminogen activation by tissue plasminogen activator and blocked the binding of plasminogen to alpha 2-antiplasmin, mimicking functions arising from the association of plasminogen with cells. The interaction of the enolase isoforms with plasminogen was dependent upon recognition of the C-terminal lysyl residue of the enolases by the lysine-binding sites of plasminogen, as the interaction was blocked by (a) peptides with C-terminal lysine residues and (b) an antibody to the C-terminal aspect of enolase. A monoclonal antibody was developed, characterized and utilized to quantify the enolase molecules present on the surface of U937 cells. A substantial number of molecules, 1.8 x 10(6)/cell, was present, accounting for approximately 10% of the plasminogen-binding capacity of these cells. These studies clearly establish the role of enolase as a cell-surface plasminogen-binding site with profibrinolytic functions.
Center for Thrombosis and Vascular Biology/FF20, Cleveland Clinic Foundation, Ohio 44195.
A
A
Redlitz
B J
BJ
Fowler
E F
EF
Plow
L A
LA
Miles
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D017931:DNA Primers; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008239:Lysine / Q000378:metabolism; D008969:Molecular Sequence Data; D010751:Phosphopyruvate Hydratase / Q000378:metabolism*; D010958:Plasminogen / Q000378:metabolism*; D011485:Protein Binding
D017931:DNA Primers; D007074:Immunoglobulin G; D010958:Plasminogen; D010751:Phosphopyruvate Hydratase; D008239:Lysine