Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

These experiments were designed to determine whether hypercholesterolemia and the accumulation of cholesterol or cholesteryl esters in rabbit carrageenan granuloma macrophages might influence selected markers of macrophage activation. Granulomas induced by subcutaneous injection of carrageenan into rabbits were harvested after 4, 14, and 28 days. Macrophages were isolated from granuloma tissues by collagenase digestion and cultured overnight. Secretion of lysosomal beta-glucuronidase, membrane 5'-nucleotidase, cellular plasminogen activator, and superoxide anion generation were measured as markers of activation. beta-Glucuronidase activity secreted into the media by granuloma macrophages from normocholesterolemic (NC) and hypercholesterolemic (HC) rabbits showed a trend toward an increase with time between 4 and 14 days in both groups. This was confirmed in a separate experiment with a significant increase by 14 days, together with a significantly greater secretion by NC macrophages and a significantly elevated level of cellular beta-glucuronidase activity in NC relative to HC macrophages. Activity of the membrane ectoenzyme 5'-nucleotidase was minimal in lysates of NC or HC macrophages, in contrast to freshly isolated human monocytes, indicating that both NC and HC granuloma macrophages were highly activated. Cellular plasminogen activator activity was significantly increased between 4 and 14 days, and was significantly greater in HC than in NC macrophages at 14 days. Stimulation of macrophages with phorbol myristate acetate increased superoxide anion generation by both NC and HC macrophages; however, no difference in superoxide anion generation was observed between macrophages from NC and HC rabbits. On the basis of the 5'-nucleotidase findings, it is concluded that both the NC and HC granuloma macrophages are highly activated, and further that hypercholesterolemia does not enhance macrophage generation of superoxide anion, either spontaneously or as the result of phorbol myristate acetate stimulation. Although hypercholesterolemia results in macrophage activation in terms of an increased cellular plasminogen activator activity, the secretion of the lysosomal enzyme beta-glucuronidase is diminished. Thus, hypercholesterolemia associated with macrophage cholesterol and cholesteryl ester accumulation has no consistent overall influence on activation, a finding of potential importance in the context of atherogenesis.
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PMID:Influence of hypercholesterolemia and cholesterol accumulation on rabbit carrageenan granuloma macrophage activation. 283 4

The subcellular localization of plasminogen activator (PA) in human neutrophils was studied. The cells were disrupted by nitrogen cavitation and fractionated on Percoll density gradients into three major components containing the plasma membranes, the specific granules, and the azurophilic granules. The biochemical markers we used to identify these organelles were alkaline phosphatase, vitamin B12-binding protein, and beta-glucuronidase, respectively. Using the radioactive fibrin plate method, PA activity and plasminogen-independent fibrinolytic activity were measured. In resting neutrophils, PA was associated mainly with the membranes of the specific granules. In five individual experiments the activity of this fraction varied from 79 to 100% of the total; the remaining activity was found to be associated with the plasma membrane, and no activity was present in the azurophilic granules. In neutrophils that were activated by exposure to PMA (20 ng/ml for 15 min at 37 degrees C), the total recoverable PA activity remained unchanged; however, the main peak of activity (85% of total) shifted from the specific granules to the plasma membranes. The magnitude of the reduction of the enzyme in the specific granules paralleled that of vitamin B12-binding protein. PMA-activated, intact neutrophils had approximately 12-fold more surface-bound PA activity than resting cells. Recovery of PA activity from neutrophils was critically dependent on pretreatment of the intact cells with DFP before cavitation; 100-fold more PA activity was detected in DFP-pretreated cells. At the same time, this pretreatment reduced the plasminogen-independent fibrinolytic activity by approximately sevenfold. We determined that PA present in the neutrophils is of the urokinase (UK) type and that the enzyme is produced and stored as a pro-UK, a form insensitive to DFP inhibition. The reduction in the level of proteases (measured as fibrinolytic activity) and the resistance of pro-UK to DFP are most likely the two major reasons for the greatly improved recovery of PA from the DFP-pretreated cells. These findings show that in resting neutrophils PA is stored in the specific granules, and that during activation, it translocates to the outer surface of the plasma membranes, thus equipping the cell with an ecto-proteolytic potential.
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PMID:Human neutrophil plasminogen activator is localized in specific granules and is translocated to the cell surface by exocytosis. 374

Leukocytes use urokinase receptors (uPAR; CD87) in adhesion, migration, and proteolysis of matrix proteins. Typically, uPAR clusters at cell-substratum interfaces, at focal adhesions, and at the leading edges of migrating cells. This study was undertaken to determine whether uPAR clustering mediates activation signaling in human polymorphonuclear neutrophils. Cells were labeled with fluo-3/AM to quantitate intracellular Ca2+ ([Ca2+]i) by spectrofluorometry, and uPAR was aggregated by Ab cross-linking. Aggregating uPAR induced a highly reproducible increase in [Ca2+]i (baseline to peak) of 295 +/- 37 nM (p = 0.0002). Acutely treating cells with high m.w. urokinase (HMW-uPA; 4000 IU/ml) produced a response of similar magnitude but far shorter duration. Selectively aggregating uPA-occupied uPAR produced smaller increases in [Ca2+]i, but saturating uPAR with HMW-uPA increased the response to approximate that of uPAR cross-linking. Cross-linking uPAR induced rapid and significant increases in membrane expression of CD11b and increased degranulation (release of beta-glucuronidase and lactoferrin) to a significantly greater degree than cross-linking control Abs. The magnitude of degranulation correlated closely with the difference between baseline and peak [Ca2+]i, but was not dependent on the state of uPA occupancy. By contrast, selectively cross-linking uPA-occupied uPAR was capable of directly inducing superoxide release as well as enhancing FMLP-stimulated superoxide release. These results could not be duplicated by preferentially cross-linking unoccupied uPAR. We conclude that uPAR aggregation initiates activation signaling in polymorphonuclear neutrophils through at least two distinct uPA-dependent and uPA-independent pathways, increasing their proinflammatory potency (degranulation and oxidant release) and altering expression of CD11b/CD18 to favor a firmly adherent phenotype.
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PMID:Clustering of urokinase receptors (uPAR; CD87) induces proinflammatory signaling in human polymorphonuclear neutrophils. 1097 52