The fibrinolytic receptor for urokinase activates the G protein-coupled chemotactic receptor FPRL1/LXA4R

Abstract

The function of urokinase and its receptor is essential for cell migration in pathological conditions, as shown by the analysis of knockout mice phenotypes. How a protease of a fibrinolytic pathway can induce migration is not understood and no link between this protease and migration-promoting G protein-coupled receptors has been described. We now show that FPRL1͞LXA4R, a G protein-coupled receptor for a number of polypeptides and for the endogenous lipoxin A4 (LXA4), is the link between urokinase-type plasminogen activator (uPA) and migration as it directly interacts with an activated, soluble, cleaved form of uPA receptor (uPAR) (D2D3 88 -274) to induce chemotaxis. In this article we show that (i) both uPAR and FPRL1͞LXA4R are necessary for the chemotactic activity of uPA whereas FPRL1͞LXA4R is sufficient to mediate D2D388-274-induced cell migration. (ii) Inhibition or desensitization of FPRL1͞LXA4R by antibodies or specific ligands specifically prevents chemotaxis induced by D2D388-274 in THP-1 cells and human peripheral blood monocytes. (iii) Desensitization of FPRL1͞ LXA4R prevents the activation of tyrosine kinase Hck induced by D2D3 88 -274. (iv) D2D388-274 directly binds to FPRL1͞LXA4R and is competed by two specific FPRL1͞LXA4R agonists, the synthetic MMK-1 peptide and a stable analog of LXA4. Thus, a naturally produced cleaved form of uPAR is a unique endogenous chemotactic agonist for FPRL1͞LXA4R receptor and its activity can be antagonized by specific ligands. These results provide the first direct link, to our knowledge, between the fibrinolytic machinery and the inflammatory response, demonstrating that uPA-derived peptide fragments can activate a specific chemotactic receptor. U rokinase plasminogen activator (uPA) is a serine protease that activates plasminogen (Plg) to plasmin and binds to a specific high affinity cell surface receptor, uPAR (CD87) (1). The phenotype of uPA Ϫ/Ϫ and uPAR Ϫ/Ϫ mice is not caused only by the lack of Plg activation. Indeed, Plg Ϫ/Ϫ mice die early with multiple thrombosis and extensive fibrin deposits, whereas the uPA Ϫ/Ϫ and uPAR Ϫ/Ϫ mice live normally, showing rare thrombotic events and occasional fibrin deposits (2). Lack of uPA, however, causes impaired migration of lymphocytes and macrophages to tissue lesions, with impairment of the host defenses, bacterial spreading, and death (3), or resistance to the development of aneurysms in a mouse model (2). Deficient recruitment of peritoneal or lung neutrophils at inflammatory sites in Pseudomonas aeruginosa infection and deficient Mac-1 function in macrophages and neutrophils is also observed in uPARdeficient mice (4, 5).uPA binding to uPAR induces intracellular signaling affecting cell adhesion, migration, and proliferation. uPA binding to uPAR induces chemotaxis in a variety of cells, with activation of tyrosine kinases (Hck, Src), MEK, c-Raf, Tyk-3, PI-3-K, and Rac (1, 5-7).uPAR is a high affinity cell surface receptor for uPA (1), formed by three extracellular domains (D1, D2, and D3), and anchored to the plasma m...

IL-10 stimulatory effects on human NK cells explored by gene profile analysis

“…By contrast, microarray results showed that IL-10 increased mRNA levels of adhesion/migration-related genes such as L-selectin, VEGF receptor-1, t-PA, HM74, formyl peptide receptor-1 and lipoxin A4 receptor (Figure 3). The last three genes are involved in the synthesis of peptide receptors [38][39][40] that mediates leukocyte chemotaxis by binding peptides derived from protein degrada- tion occurring in damaged/diseased areas. 41 The overexpression of these receptors might play an important role in NK cell migration in response to the liberation of danger signals (eg peptides) freed in the tumor microenvironment.…”

UPARANT: A Urokinase Receptor–Derived Peptide Inhibitor of VEGF-Driven Angiogenesis with Enhanced Stability and In Vitro and In Vivo Potency

“…We found that soluble forms of uPAR, containing the 88 Ser-Arg-Ser-Arg-Tyr 92 sequence (uPAR [88][89][90][91][92] ), as well as the synthetic peptide Ser-Arg-Ser-Arg-Tyr (SRSRY), stimulates in vitro and in vivo angiogenesis in a protease-independent manner (13). The uPAR 88-92 sequence interacts with the formyl peptide receptors (FPR) type 1 and 2, henceforth inducing cell migration in an integrin-dependent manner (9,14,15). Upon binding to FPR, the synthetic peptide SRSRY causes FPR internalization and triggers vitronectin receptor activation with an inside-outside type of mechanism (16).…”

Urokinase Induces Basophil Chemotaxis through a Urokinase Receptor Epitope That Is an Endogenous Ligand for Formyl Peptide Receptor-Like 1 and -Like 2

“…Therefore, uPAR can exist on the cell surface in either a three-domain form (D1D2D3), which is capable of binding uPA, or a two-domain form (D2D3), which does not bind uPA (5). Despite the lack of a transducing cytoplasmic tail, the uPA receptor is able to activate cell signaling pathways, probably by interacting with other cell surface proteins, such as integrins (7,8) and FMLP receptors (9,10), that interact with the cell interior (11).…”