An ELISA method detecting the active form of suPAR

suPAR in cardiovascular disease

Soluble urokinase plasminogen activator receptor (suPAR), the soluble counterpart of urokinase plasminogen activator receptor, is found in the circulation at various levels. suPAR and its parent molecule, cell surface uPAR, exhibit similar structure and extracellular functional roles facilitating fibrinolysis, cellular adhesion, and migration. Studies have assessed the correlation between suPAR in cardiovascular disease (CVD). It is postulated that suPAR may serve as an indicator of inflammatory activation and burden during CVD progression. Increased suPAR independently predicts poorer outcomes in acute coronary syndromes, in heart failure, as well as in coronary artery disease and atherosclerosis. To guide translation into clinical utization, suPAR has been assessed in numerous CVD settings for improved risk discrimination independently or in association with established traditional risk factors. Whilst the involvement of suPAR has been explored in other diseases such as kidney diseases and cancer, there is only emerging evidence of suPAR's mechanistic involvement in cardiovascular disease. In this review, we provide a background into suPAR and its potential role as a biomarker in CVD.

Structural Dynamics-Driven Discovery of Anticancer and Antimetastatic Effects of Diltiazem and Glibenclamide Targeting Urokinase Receptor

Diltiazem and glibenclamide are commonly used hypotensive and antidiabetic drugs. This study reports the discovery of the potential antitumor and antimetastatic effects of these two drugs using a structural dynamics-driven virtual screening targeting urokinase receptor (uPAR). Owing to uPAR's high flexibility, currently resolved crystal structures of uPAR, all in ligand-bound states, provide limited representations of its physiological conformation. To improve the accuracy of screening, we performed a long-timescale molecular dynamics simulation and obtained the representative conformations of apo-uPAR as the targets for our screening. Experimentally, we demonstrated that diltiazem and glibenclamide bound uPAR with K_D values in the micromolar range. In addition, both compounds effectively suppressed tumor growth and metastasis in a uPAR-dependent manner in vitro and in vivo. This work not only provides two potent uPAR inhibitors but also reports a proof-of-concept study on the potential off-label antitumor and antimetastatic uses of diltiazem and glibenclamide.

Crystal structure and cellular functions of uPAR dimer

Receptor dimerization of urokinase-type plasminogen activator receptor (uPAR) was previously identified at protein level and on cell surface. Recently, a dimeric form of mouse uPAR isoform 2 was proposed to induce kidney disease. Here, we report the crystal structure of human uPAR dimer at 2.96 Å. The structure reveals enormous conformational changes of the dimer compared to the monomeric structure: D1 of uPAR opens up into a large expanded ring that captures a β-hairpin loop of a neighboring uPAR to form an expanded β-sheet, leading to an elongated, highly intertwined dimeric uPAR. Based on the structure, we identify E49P as a mutation promoting dimer formation. The mutation increases receptor binding to the amino terminal fragment of its primary ligand uPA, induces the receptor to distribute to the basal membrane, promotes cell proliferation, and alters cell morphology via β1 integrin signaling. These results reveal the structural basis for uPAR dimerization, its effect on cellular functions, and provide a basis to further study this multifunctional receptor.

Therapeutics targeting the fibrinolytic system

The function of the fibrinolytic system was first identified to dissolve fibrin to maintain vascular patency. Connections between the fibrinolytic system and many other physiological and pathological processes have been well established. Dysregulation of the fibrinolytic system is closely associated with multiple pathological conditions, including thrombosis, inflammation, cancer progression, and neuropathies. Thus, molecules in the fibrinolytic system are potent therapeutic and diagnostic targets. This review summarizes the currently used agents targeting this system and the development of novel therapeutic strategies in experimental studies. Future directions for the development of modulators of the fibrinolytic system are also discussed.

The fibrinolytic system was originally identified to dissolve blood clots, and is shown to have important roles in other pathological processes, including cancer progression, inflammation, and thrombosis. Molecules or therapeutics targeting fibrinolytic system have been successfully used in the clinical treatments of cancer and thrombotic diseases. The clinical studies and experimental models targeting fibrinolytic system are reviewed by Haili Lin at Sanming First Hosipital, Mingdong Huang at Fuzhou University in China, and Peng Xu at A*STAR in Singapore to demonstrate fibrinolytic system as novel therapeutic targets. As an example, the inhibition of fibrinolytic system protein can be used to suppress cancer prolifieration and metastasis. This review also discusses the potential therapeutic effects of inhibitiors of fibrinolytic system on inflammatory disorders.

Soluble urokinase plasminogen activator receptor (suPAR) as a biomarker of early pregnancy location and viability compared with hCG, progesterone and estradiol

A circulating biomarker of early pregnancy outcome independent of ultrasonography and gestational age is a coveted goal. This study evaluated soluble urokinase plasminogen activator receptor (suPAR), a well-described marker of inflammation and immunological activation, for this purpose, and compared it with established early pregnancy biomarkers of the luteoplacental phase: progesterone, estradiol and hCG. We merged data from two prospective first trimester cohorts to conduct a case-control study comparing these analytes in women who had either a live birth, a miscarriage or an ectopic pregnancy. The ability to predict pregnancy location and viability was assessed by areas under the receiver operating characteristic curves (AUC). Comparing women irrespective of gestational age with a live birth, miscarriage or ectopic pregnancy showed significantly lower suPAR values in the latter group (2.4 vs. 2.4 vs. 2.0 μg/L, p = 0.032, respectively), as were all other analytes. Before 6 weeks' gestation, suPAR was significantly inferior to progesterone, estradiol and hCG in pregnancy location and viability prediction (in 124 pregnancies, suPAR AUC_location = 0.69 [CI: 0.54-0.83] and AUC_viability = 0.58 [CI: 0.48-0.69], while progesterone AUC_location = 0.95 [CI: 0.87-1.00] and AUC_viability = 0.84 [CI: 0.75-0.92]). After 6 weeks' gestation, suPAR prediction improved but was inferior to hCG, progesterone and estradiol (in 188 pregnanices, suPAR AUC_location = 0.71 [CI: 0.63-0.78] and AUC_viability = 0.70 [CI: 0.63-0.78] compared with hCG AUC_location = 0.96 [CI: 0.93-0.99] and AUC_viability = 0.96 [CI: 0.93-0.98]). Collectively, suPAR is less useful as a predictor of early pregnancy outcome than hCG, progesterone and estradol.

Detection of Salmonella Infection in Chickens by an Indirect Enzyme-Linked Immunosorbent Assay Based on Presence of PagC Antibodies in Sera

The outcomes of infection of humans and animals with Salmonella range from a persistent asymptomatic carrier state to temporal mild gastroenteritis or severe systemic infection. A rapid and accurate diagnostic test would help formulate strategies for effective prevention of their infections in the animal population. Current sequencing data predict that the outer membrane protein, PagC, is present in all common Salmonella serovars with sequence similarities of more than 98%. PagC sequences in other bacterial species are less than 65% similarity at the amino acid level to those of Salmonella PagC. We hypothesized that PagC could be immunogenic and detection of antibodies to this protein could be an accurate indicator of Salmonella infection. The pagC gene from Salmonella enterica serovar Typhimurium CVCC542 was expressed in Escherichia coli. The purified recombinant PagC protein was immobilized in microtiter plate wells. Sera from SPF chickens infected with Salmonella or other non-Salmonella pathogens by injection were added and binding of PagC protein was detected by the horseradish peroxidase (HRP)-labeled goat anti-chicken antibody. Sera from Salmonella-infected chickens showed high specificity in contrast to the sera from chickens infected with other bacteria. When 87 Salmonella antibody-positive sera from Salmonella Pullorum orally infected SPF chicken and 93 negative sera from uninfected SPF chicken were tested, 98.3% agreement was detected. The rPagC enzyme-linked immunosorbent assay (ELISA) and agglutination had 80.6% agreement in detecting 252 clinical chicken sera samples. These results suggest that PagC antibody-based indirect ELISA can serve as a convenient and novel method for the diagnosis of Salmonella infection.