Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bradykinin receptors have been identified in human gingival fibroblasts; the primary signal transduction pathways and their dependence on calcium have been characterized. Binding data revealed a calcium-independent binding of bradykinin to the cell membrane with a receptor density of 25,000 receptors per cell and a Kd of 1.6 nM. The bradykinin receptor-mediated activation of phospholipase C (PLC) resulted in an extensive and rapid stimulation of phosphoinositide metabolism. Using radioreceptor assay techniques, in the absence of LiCl, the inositol 1,4,5-trisphosphate (Ins 1,4,5P3) generation was found to be transient, with maximal levels attained within 15 s. An EC50 of 12 nM was observed for the accumulation of total inositol polyphosphates. The activation of phospholipase A2 (PLA2), and the subsequent release of arachidonic acid and the primary metabolite prostaglandin E2, also was found to be time- and concentration-dependent. Stimulation of tyrosine kinase activity by bradykinin was concentration-dependent and resulted in the phosphorylation of three substrates of unknown identity. Bradykinin stimulation did not activate adenylate cyclase as there occurred no increase in the generation of cyclic AMP. The mobilization of intracellular calcium stores followed closely the Ins 1,4,5 P3 kinetics and had an EC50 of 11 nM. Chelation of extracellular calcium reduced significantly the duration of the calcium response, while only minimally lowering the rapid, maximal increase in intracellular free calcium concentration ([Ca2+]i). A sustained elevation of [Ca2+]i was found to be essential in PLC and PLA2 signaling, as well as in tyrosine kinase activation, suggesting a major role for membrane calcium channels in bradykinin stimulation of cellular responses in these cells. Bradykinin was found to inhibit dramatically epidermal growth factor-induced DNA synthesis in confluent cells, although to a much lesser degree in subconfluent cells. This pattern was similar to the observed maximal specific increase in bradykinin binding with confluency. Together these results demonstrate the presence of bradykinin receptors in human gingival fibroblasts; these receptors are coupled to signal transduction mechanisms involving the PLC, PLA2, and tyrosine kinase effector systems, all of which require extracellular calcium to achieve maximal activation.
 ...
PMID:Bradykinin receptors and signal transduction pathways in human fibroblasts: integral role for extracellular calcium. 768 36

Bovine pulmonary artery endothelial (CPAE) cells respond to bradykinin, and it has been suggested that the receptors on these cells do not fall into the normal B1/B2 classification of bradykinin receptors [J. Pharmacol. Exp. Ther. 244:646-649 (1988)]. The present study describes a detailed characterization of the subtypes of bradykinin receptors on CPAE cells. The B1-selective agonist des-Arg9-bradykinin and the B2-selective agonist bradykinin both activated polyphosphoinositide phospholipase C (PLC), caused an elevation in cytosolic Ca2+ concentration ([Ca2+]i), and increased the rate of 45Ca2+ efflux in CPAE cells. The pharmacology of these responses was consistent with interactions with B1 and B2 receptors. The effects of maximal concentrations of bradykinin and des-Arg9-bradykinin on the activity of PLC in populations of cells were not additive, suggesting that the two subtypes were expressed on the same cells. Indeed, des-Arg9-bradykinin and bradykinin both evoked increases in [Ca2+]i in 85% of single cells tested. The Ca2+ entry blocker NiCl2 inhibited bradykinin-induced increases in [Ca2+]i and 45Ca2+ efflux. In contrast, NiCl2 did not inhibit the increase in 45Ca2+ efflux evoked by des-Arg9-bradykinin and induced oscillatory increases in [Ca2+]i in response to the B1 agonist. NiCl2 had no effect on [3H]inositol trisphosphate generation by either agonist, indicating that its inhibitory effects on bradykinin-mediated Ca2+ responses were distal to B2 receptor-induced activation of PLC. LaCl3 did not differentiate between the 45Ca2+ efflux responses evoked by bradykinin and des-Arg9-bradykinin, attenuating both to a similar degree. Bradykinin-induced [3H]inositol trisphosphate formation was desensitized after pretreatment with bradykinin, but the response to des-Arg9-bradykinin was unchanged. Pretreatment with the B1 agonist did not inhibit responses evoked by subsequent challenges with either des-Arg9-bradykinin or bradykinin. These results provide pharmacological evidence for the existence of two distinct bradykinin receptor subtypes (B1 and B2) on CPAE cells, with no evidence for heterologous desensitization. Although both subtypes operated similar signal transduction pathways, the Ca2+ responses evoked by the two receptors could be differentiated by NiCl2.
 ...
PMID:Signal transduction pathways for B1 and B2 bradykinin receptors in bovine pulmonary artery endothelial cells. 770 Feb 50

A new strategy has been successfully applied to reconstitute the brain specific serotonin 5-HT1A receptor-G protein-adenylate cyclase complex. A mild method of tissue preparation gave a stable, membrane-bound form of the receptor (SBP) which retained its natural lipid content. Treatment of SBP with serotonin (1 microM) and 3-[(3-cholamidopropyl) dimethyl ammonio]-1-propanesulphonate (CHAPS) (2%) solubilized the ligand-receptor-G protein-ligand complex along with the associated phospholipids and cholesterol. Dialysis of this extract (SBDS) against buffer containing 25% ethylene glycol produced a stable, reconstituted and active preparation (SBDSE) of vesicles which upon centrifugal separation followed by gentle resuspension retained 95-100% [3H] 8-OH-DPAT binding activity as well as 60% [3H] GppNHp binding and adenylate cyclase activities of SBDSE. The reconstituted receptor preparation compared well with the membrane-bound form in displaying a similar value for KD (2.1 nM) and a single affinity state for [3H] 8-OH-DPAT binding (Bmax = 118 fmol/mg). However, in sharp contrast to the membrane-bound receptor which was negatively coupled to adenylate cyclase, agonist treatment of the solubilized and reconstituted receptor resulted in an increase in adenylate cyclase. This change in receptor-adenylate cyclase coupling following reshuffling of membrane lipids during solubilization and reconstitution suggested that membrane lipids could have a profound effect on receptor-effector coupling. To study the effect of membrane lipid composition on receptor-mediated signal transduction in a stabler and more natural system, neural cells derived from different parts of the brain (hippocampus, HN2; CNS, NCB-20; dorsal root ganglion, F-11) and a non-neural cell line (CHO), all with differing membrane lipid compositions, were selected. Since no known cell line contains the serotonin 5-HT1A receptor (5-HT1A-R), stable transfection of the selected cell lines with a DNA construct encoding the human 5-HT1A-R was carried out and this resulted in a late increase of [3H] 8-OH-DPAT binding in the stationary phase only in the cell lines of neural origin. In the non-neural cell line (CHO), which also displayed marked difference in membrane lipids, the receptor was positively coupled to the phospholipase C-IP3-[Ca2+]i cascade. Even though GPLC was present in the NCB-20 and F-11 cells as evidenced by a bradykinin receptor-mediated increase in inositol phosphates in these cells 8-OH-DPAT treatment resulted in no change in phospholipase C in any of the cell lines of neural origin.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Role of lipids in receptor mediated signal transduction. 800 19

The release of arachidonic acid in A549 cells was stimulated in a time- and dose-dependent manner by the Ca2+ ionophore ionomycin (t1/2 = 4 min), thapsigargin (t1/2 = 8 min), bradykinin (t1/2 = 12 min, EC50 = 3 nM), and interleukin 1 alpha (t1/2 = 28 min, EC50 = 0.3 ng/ml). Bradykinin (10 nM) and interleukin 1 alpha (1 ng/ml) stimulation was blocked by the bradykinin B2 receptor antagonist, D-Arg,[Hyp3,Thi5,8, D-Phe7]bradykinin and interleukin 1 receptor antagonist (IC50 = 30 mM and 20 ng/ml, respectively), suggesting receptor mediation. Diacylglycerol release was < 10% of total arachidonic acid release in all cases, suggesting activation of phospholipase A2 activity was greater than phospholipase C activation by these agents. The effects of ionomycin (3 microM) and thapsigargin (0.3 microM) were abolished in Ca(2+)-free buffer with and without 0.5 mM EGTA. Bradykinin (10 nM) stimulation was reduced by 50% in Ca(2+)-free buffer whereas interleukin 1 alpha (1 ng/ml) stimulation remained unaffected. However, the presence of EGTA completely abolished bradykinin stimulation and partially blocked the effect of interleukin 1 alpha (43% inhibition). In the presence of extracellular Ca2+, ionomycin (3 mM), thapsigargin (0.3 mM), bradykinin (10 nM), and interleukin 1 alpha (1 ng/ml) stimulation of arachidonic acid release was blocked by the Ca2+ influx blocker LaCl3 (29, 44, 35, and 41% inhibition, respectively). Nifedipine also blocked ionomycin and thapsigargin stimulation but only partially blocked bradykinin and interleukin 1 alpha stimulation. These results suggest that following B2 receptor activation, cytosolic phospholipase A2 is stimulated by a rise in intracellular Ca2+ levels which are sensitive to the action of EGTA, whereas interleukin 1 alpha stimulation of cytosolic phospholipase A2 is mediated by a rise in intracellular Ca2+ from both EGTA-sensitive and resistant pools. Furthermore the results of ionomycin and thapsigargin indicate that extracellular Ca2+ is important for activation of cytosolic phospholipase A2 in A549 cells.
 ...
PMID:Differential role of extra- and intracellular calcium in bradykinin and interleukin 1 alpha stimulation of arachidonic acid release from A549 cells. 813 Feb 63

1. Guinea-pig tracheal smooth muscle cells were isolated and maintained in culture for 14-21 days prior to the study of the effect of a selective bradykinin B1 agonist and B2 antagonists upon bradykinin-stimulated phospholipase C and D activities. 2. Bradykinin-stimulated phospholipase C activity was determined by mass measurement of inositol (1,4,5)trisphosphate (Ins(1,4,5)P3) in unlabelled cells, whereas phospholipase D activity was assayed by the accumulation of [3H]-phosphatidylbutanol ([3H]-PtdBut) in [3H]-palmitate-labelled cells, which were stimulated in the presence of butan-1-o1 (0.3%, v/v). 3. Bradykinin elicited the rapid and transient formation of Ins(1,4,5)P3, in a concentration-dependent manner (log EC50 = -7.55 +/- 0.1 M, N = 3). Bradykinin also rapidly activated the concentration-dependent (log EC50 = -8.3 +/- 0.4 M, n = 3) phospholipase D-catalysed accumulation of [3H]-PtdBut; the accumulation of [3H]-PtdBut was sustained. These effects were not inhibited by pretreatment of the cells with indomethacin (1 microM). 4. The bradykinin B1 agonist, desArg9-bradykinin (1 microM) was without effect upon phospholipase C or phospholipase D activity. Bradykinin-stimulated (10 nM, EC40) Ins(1,4,5)P3 formation was inhibited by B2 receptor antagonists, D-Arg-[Hyp3,D-Phe7]-bradykinin (NPC 567) and D-Arg-[Hyp3,Thi5,8,D-Phe7]-bradykinin (NPC 349), with log IC50 values of -6.3 +/- 0.5 M and -6.3 +/- 0.4 M, respectively. However, bradykinin-stimulated (10 nM, EC100) [3H]-PtdBut accumulation was poorly inhibited and with low potency by each B2 receptor antagonist and bradykinin-stimulated phospholipase D activity persisted at concentrations of antagonist that completely blocked bradykinin-stimulated Ins(1,4,5)P3 formation (30 microM). 5. These observations suggest that the activation of phospholipase C by bradykinin may be mediated through a bradykinin B2 receptor population, whereas bradykinin-stimulated phospholipase D may be activated via a distinct population of bradykinin receptors that do not appear to be either B1 or B2 receptor types, based upon pharmacological specificity. The mechanism of the activation of phospholipase D by bradykinin and the role of the putative B3 bradykinin receptor are discussed.
 ...
PMID:Differential effects of B2 receptor antagonists upon bradykinin-stimulated phospholipase C and D in guinea-pig cultured tracheal smooth muscle. 822 Sep 10

Cd2+ provokes inositol trisphosphate production and releases stored Ca2+, apparently by binding to a zinc site in the external domain of an orphan receptor. One microM Cd2+ evokes an immediate spike in cytosolic free Ca2+, which is similar to that evoked by bradykinin. Platelet-derived growth factor (PDGF) also increases free Ca2+ in human dermal fibroblasts, but there is a distinct lag before free Ca2+ rises in response to PDGF. Genistein, which selectively inhibits tyrosine kinases, markedly inhibited Ca2+ mobilization evoked by PDGF. Calcium mobilization triggered by cadmium or bradykinin was relatively insensitive to genistein. The PDGF receptor is known to be a tyrosine kinase, which phosphorylates and thereby activates phospholipase C gamma, whereas a G protein couples the bradykinin receptor to another phospholipase C isoform. These findings support the hypothesis that the orphan receptor triggered by cadmium is coupled to phospholipase C via a G protein.
 ...
PMID:Genistein inhibits calcium release by platelet-derived growth factor but not bradykinin or cadmium in human fibroblasts. 824 30

The presence of a bradykinin receptor on guinea pig peritoneal macrophages was evidenced by binding studies and by the effect of bradykinin on activation of the phospholipase C and the increase in intracellular calcium concentration ([Ca2+]i). Binding studies demonstrated a specific, saturable binding for [3H]bradykinin inhibited by the bradykinin B2 (HOe 140) but not bradykinin B1 (des-Arg9[Leu8]bradykinin) receptor antagonist. Scatchard analysis revealed a single class B2 bradykinin binding site with a binding affinity (kd) of 0.8 nM and a receptor concentration (Bmax) of 35 fmol/5 x 10(6) cells, representing approximately 4000 bradykinin receptors per cells. Kinetic studies confirmed the presence of this single binding site by the determination of similar binding affinity. Activation of peritoneal macrophages by bradykinin resulted in a time- and dose-dependent release of inositol phosphates determined by anion exchange chromatography and intracellular calcium analyzed using fura-2/AM. The increase in [Ca2+]i induced by bradykinin was blocked by the specific bradykinin B2 receptor antagonist HOE 140 but not the bradykinin B1 receptor antagonist des-Arg9[leu8]-BK. These studies provide novel information regarding the nature of kinin receptors on guinea pig peritoneal macrophages and their signal transduction pathways.
 ...
PMID:Bradykinin receptors in signal transduction pathways in peritoneal guinea pigs macrophages. 856 66

Bradykinin and platelet-derived growth factor (PDGF) are inflammatory mediators important in the response to vascular injury. Based upon the known effect of oncogenic Ras to increase bradykinin receptor expression and the ability of PDGF to stimulate Ras, we examined whether PDGF regulates bradykinin B2 receptor expression in cultured arterial smooth muscle cells. Treatment with PDGF (AB and BB, but not AA) produced a dose- and time-dependent increase in both mRNA (6-7-fold increase at 2-4 h) and cell surface receptors (2-4-fold at 6-12 h) for the B2 receptor. There was a 60-min delay between exposure to PDGF and the initial increase in B2 receptor mRNA. Transcriptional inhibitors, actinomycin D or 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole, completely blocked the increase in B2 receptor mRNA when added up to 60 min after stimulation with PDGF. However, protein synthesis was not required, as treatment with cycloheximide did not block but rather superinduced the PDGF-induced increase in B2 receptor mRNA. Comparison with the immediate early response gene c-fos demonstrated that the increase in B2 receptor mRNA was similarly inhibited by the tyrosine kinase inhibitor, tyrphostin, as well as staurosporine. However, stimulation of c-fos was slightly more sensitive to genistein, while the B2 receptor mRNA was more sensitive to inhibition by the protein kinase C inhibitor, calphostin C. The increase in cell surface B2 receptors were functionally coupled to an increase in phosphoinositide-specific phospholipase C, and the effects of PDGF were selective as there was no increase in either angiotensin II- or arginine vasopressin-induced inositol phosphate formation or intracellular calcium release. Taken together, these results demonstrate that the B2 receptor is a delayed early response gene for PDGF in vascular smooth muscle cells.
 ...
PMID:The bradykinin B2 receptor is a delayed early response gene for platelet-derived growth factor in arterial smooth muscle cells. 866 83

Bradykinin is a mediator of the protection of myocardium by angiotensin I-converting enzyme/kininase II inhibitors. We reported that the activation of B2 bradykinin receptors in neonatal rat cardiac myocytes in primary culture was followed by hydrolysis of phosphatidylinositol 4,5-bisphosphate and formation of inositol 1,4,5-trisphosphate (IP3). Here we examine the regulation of IP3 formation stimulated by bradykinin. Activation of myocytes with 1 mu/L bradykinin increased IP3 production from 117 +/- 8.3 to 1011 +/- 48.6 pmol/mg protein. Treatment of the cells with 10 mu/L indomethacin or 1 mu/L dexamethasone partially blocked this bradykinin-induced response. Moreover, either U73122, a phospholipase C inhibitor, or (p-amylcinnamoyl) anthranilic acid, a phospholipase A2 inhibitor, blunted the IP3 response to bradykinin. Because thromboxane A2 stimulates inositol bisphosphate metabolism in guinea pig atria, we also investigated the effect of the thromboxane A2 receptor antagonist BM 13177 (1 mu/L), which strongly attenuated the stimulated IP3 production. Since thromboxane A2 appears to partly mediate the IP3 response to bradykinin, we examined the effect of the stable thromboxane A2 mimetic U46619. Control cultures were stimulated more by U46619 than by bradykinin (1629 +/- 14.5 versus 1011 +/- 48.6 pmol IP3/mg protein). This property of U46619 was selectively antagonized by BM 13177. Inhibition of either phospholipase C or phospholipase A2 blunted the IP3 response to U46619. Short-term (30 minutes) activation of protein kinase C with phorbol 12-myristate 13-acetate (10 pmol/L to 1 mu/L) attenuated the IP3 accumulation in response to bradykinin; the effect of phorbol 12-myristate 13-acetate was reversed with 1 mu/L staurosporine, a protein kinase C inhibitor. Treatment with 1 microgram/mL cholera toxin or pertussis toxin for 4 hours amplified the IP3 response to 10 nmol/L bradykinin from 570 +/- 20.0 to 1150 +/- 51.3 and to 1016.7 +/- 21.9 pmol/mg protein. Bradykinin mobilized 9.4% of intracellular calcium stores in cardiomyocytes as assessed by chlortetracycline-based fluorometry, and this effect of bradykinin was blocked by BM 13177 or the B2 bradykinin receptor blocker Hoe 140 by more than 70%. In functional studies, bradykinin (1 mu/L) increased by 12% the twitch contractile force of neonatal rat ventricular strips paced at threshold intensity, but this was unaffected by BM 13177. In conclusion, in cardiomyocytes, bradykinin enhances IP3 production mostly via phospholipase A2 stimulation and thromboxane A2 formation. This prostanoid in turn stimulates its receptor and activates phospholipase C, which then splits phosphatidylinositol 4,5-bisphosphate into IP3 and diacylglycerol. The effect of bradykinin on phospholipase C, via thromboxane A2, is negatively regulated by protein kinase C activation.
 ...
PMID:Thromboxane A2 mediates the stimulation of inositol 1,4,5-trisphosphate production and intracellular calcium mobilization by bradykinin in neonatal rat ventricular cardiomyocytes. 879 31

We provided evidence that calcium-calmodulin plays a major role in bradykinin-induced arachidonic acid release by bovine aortic endothelial cells. In cells labeled for 16 hr with 3H-arachidonic acid, ionomycin and Ca2(+)-mobilizing hormones such as bradykinin, thrombin and platelet activating factor induced arachidonic acid release. However, arachidonic acid release was not induced by agents known to increase cyclic AMP (forskolin, isoproterenol) or cyclic GMP (sodium nitroprusside). Bradykinin induced the release of arachidonic acid in a dose-dependent manner (EC50 = 1.6 +/- 0.7 nM). This increase was rapid, reaching a maximal value of fourfold above basal level in 15 min. In a Ca2(+)-free medium, bradykinin was still able to release arachidonic acid but with a lower efficiency. Quinacrine (300 microM), a blocker of PLA2, completely inhibited bradykinin-induced arachidonic acid release. The B2 bradykinin receptor antagonist HOE-140 completely inhibited bradykinin-induced arachidonic acid release. The B1-selective agonist DesArg9-bradykinin was inactive and the B1-selective antagonist [Leu8] DesArg9-bradykinin had no significant effect on bradykinin-induced arachidonic acid release. The phospholipase C inhibitor U-73122 (100 microM) decreased bradykinin-induced arachidonic acid release. The calmodulin inhibitor W-7 (50 microM) drastically reduced the bradykinin- and ionomycin-induced arachidonic acid release. Also, forskolin decreased bradykinin-induced arachidonic acid release. These results suggest that the activation of PLA2 by bradykinin in BAEC is a direct consequence of phospholipase C activation. Ca2(+)-calmodulin appears to be the prominent activator of PLA2 in this system.
 ...
PMID:Calcium-calmodulin plays a major role in bradykinin-induced arachidonic acid release by bovine aortic endothelial cells. 891 80


<< Previous 1 2 3 4 5 Next >>