title: Participation of the urokinase-type plasminogen activator receptor (uPAR) in neutrophil transendothelial migration.
abstract: The mechanisms underlying migration of neutrophils across endothelium are not completely understood. The urokinase-type plasminogen activator receptor (uPAR) plays a key role in neutrophil adhesion and migration. In the present study, we addressed whether uPAR regulates neutrophil transendothelial migration. We first showed that siRNA-mediated knockdown of uPAR in human umbilical vein endothelial cells (HUVECs) did not affect neutrophil migration across HUVEC monolayers indicating that endothelial uPAR does not regulate neutrophil transmigration. In contrast, the transmigration was significantly inhibited by Fab' fragment of anti-uPAR monoclonal antibody and proteolytically inactive urokinase (uPA), whereas inhibition of proteolytical activity of endogenous uPA (with amiloride or plasminogen activator inhibitor-1) did not affect the transmigration. Both the anti-uPAR Fab' fragment and proteolytically inactive uPA did not exert significant effects upon the transmigration conducted in the presence of F(ab')(2) fragment of blocking antibody to integrin Mac-1 indicating that uPAR regulates Mac-1-dependent transmigration. Mac-1-dependent, but not Mac-1-independent, transmigration was significantly reduced in the presence of N-acetyl-d-glucosamine and d-mannose, the saccharides that disrupt uPAR/Mac-1 association, but was unaffected in the presence of control saccharides (d-sorbitol and sucrose). We conclude that physical association of uPAR with Mac-1 mediates the regulatory effect of uPAR over the transmigration. Finally, we provide evidence that the functional cooperation between uPAR and Mac-1 is essential at both adhesion and diapedesis steps of neutrophil migration across endothelium. Thus, uPAR expressed on neutrophil plasma membrane regulates transendothelial migration independently of uPA proteolytical activity and acting as a cofactor for integrin Mac-1.
authors.affiliation: Department of Biological and Medical Chemistry, Faculty of Fundamental Medicine, Moscow State University, Lomonosovsky Pr., 31-5, Moscow 119192, Russia.
authors.forename: Boris K
authors.initials: BK
authors.lastname: Pliyev
authors.forename: Olga A
authors.initials: OA
authors.lastname: Antonova
authors.forename: Mikhail
authors.initials: M
authors.lastname: Menshikov
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D004727:Endothelium / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D016177:Macrophage-1 Antigen / Q000378:metabolism; D009005:Monosaccharides / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D034741:RNA, Small Interfering / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator / Q000378:metabolism*; D057705:Transendothelial and Transepithelial Migration / Q000187:drug effects; D014471:Umbilical Veins / Q000166:cytology; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D016177:Macrophage-1 Antigen; D009005:Monosaccharides; D034741:RNA, Small Interfering; D055293:Receptors, Urokinase Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator