Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

P. aeruginosa is selectively internalized by human endothelial cells but is not efficiently killed in the intracellular (IC) compartment. To investigate whether IC survival is associated with failure in bacteria-containing endosome-lysosome (E-L) fusion, endothelial cells were exposed to albumin-colloidal gold complex and to bacterial suspension and submitted to transmission electron microscopy (TEM). Gold granules were detected in P. aeruginosa-containing vacuoles, indicating that E-L fusion had occurred. Bacteria were also seen apparently free in the cell cytoplasm, suggesting disruption of endosome membranes. To ascertain whether phospholipase C (PLC) could account for vacuolar lysis, PLC producing PAO1 and PAK strains were compared with a PLC deficient mutant (PLCN) in their IC survival. All three strains were equally uptaken by the endothelial cells, as determined by the gentamicin exclusion assay. After 3 h of infection, the IC concentration of PAK and PAO1 increased significantly while the concentration of the mutant decreased to 56.8 +/- 18.2% of the viable counts at 1 h of infection. After 5 h, the IC concentration of P. aeruginosa corresponded to 83.1 +/- 34.6%, 109 +/- 22.6% and 26.2 +/- 14.7% of the viable counts detected at 1 h, for PAK, PAO1 and the mutant, respectively. By TEM, while most PAO1-containing vacuoles presented partially lysed membranes, in cells infected with the PLCN mutant bacteria were most often observed in vacuoles with intact membranes. These observations suggest that the IC survival of P. aeruginosa results from a competition between the microbicidal activity of endothelial cells following E-L fusion and the capacity of bacteria to escape from endosomes.
...
PMID:Concomitant endosome-phagosome fusion and lysis of endosomal membranes account for Pseudomonas aeruginosa survival in human endothelial cells. 916 17

Recombinant human group II phospholipase A2 (sPLA2) added to human platelets in the low microg/ml range induced platelet activation, as demonstrated by measurement of platelet aggregation, thromboxane A2 generation and influx of intracellular free Ca2+ concentration and by detection of time-dependent tyrosine phosphorylation of platelet proteins. The presence of Ca2+ at low millimolar concentrations is a prerequisite for the activation of platelets by sPLA2. Mg2+ cannot replace Ca2+. Mg2+, given in addition to the necessary Ca2+, inhibits sPLA2-induced platelet activation. Pre-exposure to sPLA2 completely blocked the aggregating effect of a second dose of sPLA2. Albumin or indomethacin inhibited sPLA2-induced aggregation, similarly to the inhibition of arachidonic acid-induced aggregation. Platelets pre-treated with heparitinase or phosphatidylinositol-specific phospholipase C lost their ability to aggregate in response to sPLA2, although they still responded to other agonists. This suggests that a glycophosphatidylinositol-anchored platelet-membrane heparan sulphate proteoglycan is the binding site for sPLA2 on platelets. Previous reports have stated that sPLA2 is unable to activate platelets. The inhibitory effect of albumin and Mg2+, frequently used in aggregation studies, and the fact that isolated platelets lose their responsiveness to sPLA2 relatively quickly, may explain why the platelet-activating effects of sPLA2 have not been reported earlier.
...
PMID:Human group II 14 kDa phospholipase A2 activates human platelets. 935 61

We determined whether activation of phosphatidylinositol-specific phospholipase C (PI-PLC) and a subsequent increase in cytosolic calcium concentration ([Ca2+]i) was an obligatory signaling event mediating the increase in transendothelial permeability induced by bradykinin (BK) and alpha-thrombin (alpha-T). Both BK and alpha-T (each at a concentration range of 0.01-1 microM) caused dose-dependent increases in transendothelial 125I-albumin permeability in cultured bovine pulmonary artery endothelial cell monolayers. Both agonists also produced a rise in inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] by 10 sec that was followed by a prolonged increase in [Ca2+]i. Pretreatment of endothelial cells with the PLC inhibitor, 1-(6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1 H-pyrrole-2,5-dion [(U73122) at 10 microM for 15 min], prevented the increases in Ins(1,4,5)P3 and [Ca2+]i induced by both BK and alpha-T. However, inhibition of PLC with U73122 or another PLC inhibitor, neomycin, did not prevent the increase in endothelial permeability induced by either agonist. In contrast, depletion of cellular protein kinase C (PKC) with phorbol-12-myristate 13-acetate (0.01 microM for 20 hr) increased both BK- and alpha-T-induced phosphoinositide turnover but inhibited the agonist-induced increase in permeability. A PKC inhibitor, staurosporine (5 microM) likewise inhibited the BK-induced increase in endothelial cell permeability to albumin. We conclude that increases in endothelial permeability induced by the inflammatory mediators, BK and thrombin, can occur independently of PLC activation and increased [Ca2+]i but that a PKC-dependent pathway is required for the permeability response.
...
PMID:Bradykinin- and thrombin-induced increases in endothelial permeability occur independently of phospholipase C but require protein kinase C activation. 936 52

Our previous studies have shown that inflammatory mediators increase microvascular permeability through a phospholipase C-nitric oxide synthase (NOS)-guanylate cyclase cascade. The aim of this study is to delineate in more detail the signaling pathway leading to microvascular hyperpermeability. Endothelial cytosolic calcium and the apparent permeability coefficient of albumin (Pa) were measured in isolated and perfused coronary venules. Histamine stimulated a rapid increase in cytosolic calcium followed by a transient elevation in Pa. The NOS inhibitor NG-monomethyl-L-arginine (L-NMMA) and the guanosine 3',5'-cyclic monophosphate-dependent protein kinase G (PKG) inhibitor KT-5823 abolished the hyperpermeability but did not affect the calcium response to histamine. Similarly, the calcium ionophore ionomycin produced a calcium spike preceding venular hyperpermeability. Blockage of the NOS-PKG cascade inhibited the increase in Pa, whereas the endothelial calcium was still elevated on administration of ionomycin. Furthermore, the relationship between protein kinase C (PKC) and the calcium-NOS-PKG pathway in modulation of venular permeability was investigated. Stimulation of PKC with phorbol 12-myristate 13-acetate (PMA) dramatically increased basal Pa without significantly changing the cytosolic calcium level. The selective PKC inhibitor bisindolylmaleimide abolished the effect of PMA but did not alter the effect of histamines on Pa. In contrast, both L-NMMA and KT-5823 were able to greatly attenuate the increase in Pa caused by PMA. These results suggest that 1) elevation of endothelial cytosolic calcium is an early signaling event preceding nitric oxide (NO) synthesis in the transduction of endothelial hyperpermeability, and 2) activation of PKC may alter the endothelial barrier function partially through the modulation of NO production.
...
PMID:Interaction of PKC and NOS in signal transduction of microvascular hyperpermeability. 937 83

The lysophospholipid (LPL) mediators lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are generated by enzymatic cleavage of stores of glycerophospholipids and sphingomyelin, respectively, in membranes of stimulated cells. LPLs are albumin bound, distributed widely in mammalian tissues, and increased in concentration by physiological activation of platelets and some other cells, tissue injury, inflammation, and neoplasia. The principal effects of LPA and S1P are growth related, including induction of cellular proliferation, alterations in differentiation and survival, and suppression of apoptosis. LPA and S1P also evoke cellular effector functions, which are dependent on cytoskeletal responses such as contraction, secretion, adhesion, and chemotaxis. The extracellular mediator activities of LPLs are transduced by subfamilies of G-protein-coupled receptors (GPCRs), of which the most completely characterized are those encoded by the endothelial differentiation genes (edgs). One homology cluster composed of Edg-1, -3, and -5 recognizes and responds to S1P, and the other cluster of Edg-2 and -4 is dedicated to LPA. Edg proteins are developmentally regulated and differ in tissue distribution, but couple similarly to multiple types of G-proteins to signal through ras and mitogen-activated protein kinase, rho, phospholipase C, and several protein tyrosine kinases. Numerous interactions between glycerophospholipids and sphingolipids are observed in their biosynthetic and signaling pathways. Many of the cellular effects of LPA and S1P are attributable to modifications in the content and/or activity of a major functional protein. Examples are increases in nuclear levels of transcription factors that regulate the serum response element, suppression of death caspase activities in apoptosis, and elevation of membrane content of heparin binding-epidermal growth factor-like growth factor, which serves as an autocrine and juxtacrine stimulus of proliferation. These ubiquitous LPL mediators of cellular growth, differentiation, and activities thus act directly through complex subfamilies of GPCRs and by regulating expression of biologically critical proteins.
...
PMID:Diversity of cellular receptors and functions for the lysophospholipid growth factors lysophosphatidic acid and sphingosine 1-phosphate. 983 49

We previously demonstrated that vascular endothelial growth factor (VEGF)-elicited increase in the permeability of coronary venules was blocked by the nitric oxide (NO) synthase inhibitor NG-monomethyl-L-arginine (L-NMMA). The aim of this study was to delineate in more detail the signaling pathways upstream from NO production in VEGF-induced venular hyperpermeability. The apparent permeability coefficient of albumin (Pa) and endothelial cytosolic Ca2+ concentration ([Ca2+]i) were measured in intact perfused porcine coronary venules using fluorescence microscopy. VEGF (10(-10) M) induced a two- to threefold increase in Pa, which was blocked by a monoclonal antibody directed against the VEGF receptor Flk-1/KDR, the phospholipase C (PLC) antagonist U-73122, or the protein kinase C (PKC) antagonist bisindolylmaleimide (BIM). In 12 venules that displayed the [Ca2+]i response to bradykinin (10(-6) M) and ionomycin (10(-6) M), only 4 vessels responded to VEGF with a transient increase in [Ca2+]i. Furthermore, Western blot analysis of cultured human umbilical vein endothelial cells showed that VEGF increased tyrosine phosphorylation of PLC-gamma and serine phosphorylation of endothelial constitutive NO synthase (ecNOS). The hyperphosphorylation of PLC-gamma was greatly attenuated by the KDR receptor antibody and U-73122, but not by BIM or L-NMMA. In contrast, U-73122 and BIM were able to inhibit VEGF-elicited serine phosphorylation of ecNOS. The results suggest that VEGF induces venular hyperpermeability through a KDR receptor-mediated activation of PLC. In turn, ecNOS is activated by PLC-mediated PKC and/or cytosolic Ca2+ elevation stimulation.
...
PMID:Role of phospholipase C, protein kinase C, and calcium in VEGF-induced venular hyperpermeability. 995 Aug 55

Progesterone rapidly increased intracellular free calcium ([Ca2+]i) in human sperm, removal of extracellular Ca2+ prevented the increase in [Ca2+]i. The Ca2+ influx was not blocked by the T-type Ca2+ channel blocker mibefradil. However T-type calcium channels do appear to be present in human sperm because the neoglycoprotein mannose-albumin, an inducer of the acrosome reaction, was able to promote Ca2+ influx, which was blocked by mibefradil and more potently inhibited by Ni2+ than Cd2+. The receptor for progesterone that promotes the Ca2+ influx was located on the plasma membrane using FITC-progesterone-albumin. It is concluded that progesterone stimulates Ca2+ influx in human sperm via a unique Ca2+ channel possibly similar to a store-operated channel (SOC) or a receptor-operated channel (ROC). We have found that progesterone metabolites, such as pregnanolone and pregnanediol, promote a rapid rise in [Ca2+]i and aggregation in human platelets, similar to that observed with thrombin. The increase in [Ca2+]i was prevented when extracellular Ca2+ was removed or by the SOC inhibitor SKF-96365. The phospholipase C inhibitor U-73122 also prevented the increase in [Ca2+]i, suggesting that these metabolites interact with a cell surface receptor on the platelet to activate phospholipase C to produce inositol-P3, which mobilizes intracellular Ca2+, thereby activating the SOC in the plasma membrane. Progesterone and estradiol conjugated to albumin, also produced a rapid increase in [Ca2+]i, which was prevented by Ca2+ removal from the medium or when SKF-96365 or U-73122 were added. It is proposed that human platelets possess cell surface receptors for steroids.
...
PMID:Extragenomic actions of progesterone in human sperm and progesterone metabolites in human platelets. 1032 84

Islets from fed and 24-h-fasted rats were studied immediately after collagenase isolation. (1) After a 24-h fast, the insulin secretory responses to 8 mM glucose measured during perifusion were reduced by more than 90% from islets of fasted donors. (2) Increasing glucose to 11 or 27.5 mM resulted in enhanced insulin secretion from islets of fasted animals. (3) Fasting did not reduce islet insulin content. (4) Responses to 8 or 27.5 mM glucose were not affected if fatty acid-free albumin was used during the perifusion. (5) Inclusion of alpha-ketoisocaproate (5 mM), monomethyl succinate (10 mM) or carbachol (10 microM) significantly amplified insulin release from fasted islets in the simultaneous presence of 8 mM glucose. (6) Phospholipase C activation by glucose, carbachol or their combination was not adversely affected by fasting. (7) The response to the protein kinase C activator, phorbol 12-myristate 13-acetate (500 nM), was reduced by about 60% after fasting. (8) Extending the fast to 48 h resulted in a severe decline in response to 11 mM glucose; however, the further addition of 10 microM carbachol still enhanced release from these islets. The results confirm that caloric restriction impairs islet sensitivity to glucose stimulation and that protein kinase C may be involved in the reduction of glucose-induced insulin release from these islets. The activation of phospholipase C by cholinergic stimulation may contribute to the maintenance of insulin secretion from calorically restricted animals. These results also demonstrate that free fatty acids are not essential for glucose to evoke secretion from isolated islets of fasted donors.
...
PMID:Glucose-induced insulin secretion from islets of fasted rats: modulation by alternate fuel and neurohumoral agonists. 1085 89

Binding of bilirubin to human erythrocyte membranes was studied after various enzymatic treatments as well as calcium loading. Whereas phospholipase D treatment of erythrocyte membranes resulted in 23% increase in bilirubin binding, phospholipase C-treated membranes showed remarkable enhancement in bilirubin binding. Polar head groups in general and negatively charged phosphate moieties, in particular, of phospholipids of the membrane appear to inhibit a large amount of bilirubin from binding to the membranes. Neuraminidase treatment of the membranes also led to a slight increase in bilirubin binding as compared to untreated membranes. Membrane proteins and carbohydrates seem to play significant regulatory role in bilirubin binding. However, no direct correlation was found between the increase in bilirubin binding and the amount of carbohydrate released upon tryptic digestion of membranes. Increase in bilirubin binding to trypsin-treated membranes can be ascribed to the increase in free bilirubin concentration in the incubation mixture as a result of tryptic hydrolysis of albumin by the membrane-bound tryptic activity. Calcium-loaded erythrocyte membranes also showed remarkable increase in bilirubin binding as a result of negative charge shielding and calcium-induced hydrophobic aggregation. Taken together, these results suggest the inhibitory role of polar head groups of phospholipids (phosphate in particular), carbohydrate and sialic acid in the binding of bilirubin to erythrocyte membranes.
...
PMID:Bilirubin binding to normal and modified human erythrocyte membranes: effect of phospholipases, neuraminidase, trypsin and CaCl2. 1185 37

Regulation of endothelial barrier function often occurs through signalling involving phospholipase C activation which produces diacylglycerol (DAG), a lipidic second messenger activator of protein kinase C (PKC). Therefore, modification of lipidic composition of endothelial cell membranes might modify DAG production and, as a result, alter regulation of endothelial permeability. We investigated the in vitro effects of natural 1-O-alkylglycerols on porcine aortic endothelial cell permeability to dye-labelled albumin. [3H]-1-O-alkylglycerols (10 microm) were substantially incorporated into phosphatidylcholine (6.6%) and phosphatidylethanolamine (4.4%). Stimulation of endothelial cell monolayer with phorbol-myristate-acetate or with the calcium ionophore A23187 resulted in a raise in permeability to albumin. Pre-treatment with 1-O-alkylglycerols (10 microm, 24 h) had no effect on basal albumin permeability but totally inhibited the effect of phorbol-myristate-acetate, and brought the permeability of A23187-stimulated endothelial cell monolayers below control. After incubation of cells with [3H]-1-O-alkylglycerols (10 microm, 24 h), we detected the production of the analogue of DAG, and PKC inhibitor, [3H]-1-O-alkyl-2-acyl-glycerol, in resting cells. This production was increased by 58% under A23187 stimulation while phorbol-myristate-acetate had no effect. Our data demonstrate that natural 1-O-alkylglycerols modify endothelial permeability, and suggest that this effect could be mediated through alteration of lipidic signalling.
...
PMID:Modulation of endothelial permeability by 1-O-alkylglycerols. 1244 31


<< Previous 1 2 3 4 5 6 Next >>

---