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)

The agonist profiles for Ca++ elevations mediated by the human alpha-2 adrenoceptor subtypes alpha-2A, alpha-2B and alpha-2C were compared in the clones of Chinese hamster ovary cells expressing comparable numbers of receptors. No difference was seen between the different clones with respect to the maximum Ca++ mobilizations or the concentrations producing half-maximal stimulation in response to noradrenaline. Ca++ elevations were sensitive to phospholipase C inhibitor U-73122 (1-[6-([17beta]-3-methoxyestra-1,3, 5[10]-trien-17-yl)aminohexyl]-1H-pyrrole-2,5-dione) and pertussis toxin-pretreatment. Although noradrenaline was equally potent and active in all the clones, marked differences in the response to the other agonists were seen. UK14,304 (5-bromo-N-[4, 5-dihydro-1H-imidazol-2-yl]-6-quinoxalinamine) was a full agonist (when compared to noradrenaline) for alpha-2A and alpha-2C, D-medetomidine ([+]-[S]-[4-(1-[2, 3-dimethylphenyl]ethyl)-1H-imidazole]HCl) was a full agonist for alpha-2B and alpha-2C and oxymetazoline (3-[(4, 5-dihydro-1H-imidazol-2-yl-)methyl]-6-[1,1-dimethylethyl]-2, 4-dimethylphenol HCl) was a full agonist only for alpha-2B receptors. Clonidine (2-[2,6-dichloroaniline]-2-imidazoline HCl) was a partial agonist in all the cases; almost no response to this ligand was obtained in the alpha-2B-expressing cells. When the Ca++ responses are compared to the previously published results on cAMP inhibition in Chinese hamster ovary cells, clonidine seems to be significantly less efficacious in elevating Ca++ than in decreasing cAMP.
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PMID:Ligand- and subtype-selective coupling of human alpha-2 adrenoceptors to Ca++ elevation in Chinese hamster ovary cells. 980 94

The ability of cloned human alpha2B-adrenoceptors heterologously expressed in Sf9 cells and endogenous alpha2B-adrenoceptors in NG 108-15 neuroblastoma x glioma cells to couple to increase of intracellular Ca2+ was studied. Ca2+ increases in NG 108-15 cells were detectable but slight, whereas those in alpha2B-adrenoceptor-expressing Sf9 cells were greater. In the latter, the maximum Ca2+ increase correlated positively, and the EC50-value of noradrenaline negatively, with the receptor expression density. The order of potency of the agonists was D-medetomidine ([D]-4-[5]-[1-(2,3-dimethylphenyl)ethyl]-1H-imidazole) > noradrenaline approximately = clonidine > oxymetazoline, with clonidine and UK14,304 (5-bromo-N-[4,5-dihydro-1H-imidazole-2-yl]-6-quinoxalinamine) being weak partial agonists. In Sf9 cells Ca2+ increases consisted of concomitant mobilization from an intracellular store and influx of extracellular Ca2+. In these cells alpha2B-adrenoceptor stimulation also increased the inositol 1,4,5-trisphosphate mass. We conclude that alpha2B-adrenoceptors can couple to intracellular Ca2+ increases which may involve prior activation of phospholipase C.
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PMID:Alpha2B-adrenoceptors couple to Ca2+ increase in both endogenous and recombinant expression systems. 987 83

The endogenous nucleoside adenosine is thought to play a role in the pathophysiology of asthma by stimulating mast cells. We previously showed that the human mast cell line HMC-1 expresses A2A and A2B receptors, and that both receptors activate adenylate cyclase via Gs-protein but that only A2B receptors are also coupled to phospholipase C via Gq proteins. Stimulation of A2B but not A2A receptors induced production of interleukin-8 (IL-8) from HMC-1 cells. The mechanism by which adenosine promotes IL-8 synthesis has not been defined. In this study, we tested the hypothesis that mitogen-activated protein kinase (MAPK) signaling pathways are involved in this process. Stimulation of HMC-1 with the stable adenosine analog NECA (5'-N-ethylcarboxamidoadenosine) activated p21(ras) and both p42 and p44 isoforms of extracellular signal-regulated kinase (ERK). NECA (10 microM) induced a 1.9 +/- 0. 06-fold increase in ERK activity, whereas 10 microM of the selective A2A agonist CGS 21680 (4-((N-ethyl-5'-carbamoyladenos-2-yl)-aminoethyl)-phenylpropionic acid) had no effect. NECA, in parallel with the activation of ERK, also stimulated the p46 isoform of c-Jun N-terminal kinase (MEK) and p38 MAPK. Furthermore, the selective MAPK/ERK kinase 1 inhibitor PD 98059 (2'-amino-3'-methoxyflavone), and p38 MAPK inhibitors SB 202190 (4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole) and SB 203580 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H- imidaz ole) blocked A2B receptor-mediated production of IL-8. These results indicate that extracellular adenosine can regulate ERK, c-Jun N-terminal kinase, and p38 MAPK signaling cascades and that activation of ERK and p38 MAPK pathways are essential steps in adenosine A2B receptor-dependent stimulation of IL-8 production in HMC-1.
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PMID:Role of p38 mitogen-activated protein kinase and extracellular signal-regulated protein kinase kinase in adenosine A2B receptor-mediated interleukin-8 production in human mast cells. 1010 Oct 31

The effect of the ether lipid 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphorylcholine (ET-18-OCH3) on the intracellular free Ca2+ concentration ([Ca2+]i) in Madin Darby canine kidney (MDCK) cells was studied using fura-2 as the Ca2+ probe. In Ca2+ medium, ET-18-OCH3 induced a significant rise in [Ca2+]i at concentrations between 10-100 microM with a concentration-dependent delay of 45-175 s. The [Ca2+]i signal was composed of a gradual rise and a sustained plateau. In Ca2+-free medium, ET-18-OCH3 (10-100 microM) induced a Ca2+ release from internal Ca2+ stores with a concentration-dependent delay of 45-175 s. This discharge of internal Ca2+ triggered capacitative Ca2+ entry in a concentration-dependent manner. This capacitative Ca2+ entry was not inhibited by econazole (25 microM), 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride (SKF96365; 50 microM), nifedipine (10 microM), verapamil (10 microM), diltiazem (10 microM) and cadmium (0.5 microM). Methyl 2-(phenylthio)ethyl-1,4-dihydro-2,4,6-trimethylpyridine-3,5-dicarboxylat e (PCA-4248), a platelet-activating factor (PAF) receptor antagonist, inhibited 25 microM ET-18-OCH3-induced [Ca2+]i rise in a concentration-dependent manner between 1-20 microM, with 20 microM exerting a complete block. The [Ca2+]i rise induced by ET-18-OCH3 (25 microM) was not altered when the production of inositol 1,4,5-trisphosphate (IP3) was suppressed by the phospholipase C inhibitor U73122 (2 microM), but was partly inhibited by the phospholipase D inhibitor propranolol (0.1 mM) or the phospholipase A2 inhibitor aristolochic acid (20-40 microM). In Ca2+-free medium, pretreatment with 25 microM ET-18-OCH3 completely depleted the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin-sensitive Ca2+ store. In contrast, pretreatment with thapsigargin abolished 0.1 mM ATP-induced [Ca2+]i rise without altering the ET-18-OCH3-induced [Ca2+]i rise. This suggests that ET-18-OCH3 depleted thapsigargin-sensitive Ca2+ stores and also released Ca2+ from thapsigargin-insensitive stores. The thapsigargin-insensitive stores involve mitochondria because the mitochondria uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP; 2 microM) induced a release of mitochondrial Ca2+ which was abolished by pretreatment with 25 microM ET-18-OCH3. ET-18-OCH3 (25 microM) induced a significant Mn2+ quench of fura-2 fluorescence at 360 nm excitation wavelength confirming that ET-18-OCH3 induced capacitative Ca2+ entry. La3+ (0.1 mM) or Gd3+ (50 microM) abolished the ET-18-OCH3-induced Mn2+ quench and [Ca2+]i rise. Our data imply that ET-18-OCH3 induced a [Ca2+]i rise in MDCK cells by activating PAF receptors leading to an internal Ca2+ release followed by capacitative Ca2+ entry. Phospholipase D and phospholipase A2, but not phospholipase C, might be involved in mediating the capacitative Ca2+ entry. La3+ abolished the ET-18-OCH3-induced [Ca2+]i rise presumably by inhibiting PAF receptors.
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PMID:The ether lipid ET-18-OCH3 increases cytosolic Ca2+ concentrations in Madin Darby canine kidney cells. 1045 2

1. The effect of chlorpromazine on the store-operated Ca2+ entry activated via the phospholipase C signalling pathway was investigated in PC12 cells. 2. Chlorpromazine inhibited the sustained increase after the initial peak in the intracellular Ca2+ concentration produced by bradykinin while having no effect on the initial transient response. The inhibition was lowered by the removal of extracellular free Ca2+. However, chlorpromazine did not inhibit bradykinin-induced inositol 1,4,5-trisphosphate production. 3. Chlorpromazine inhibited the bradykinin-induced noradrenaline secretion in a concentration-dependent manner (IC(50): 24+/-5 microM, n=3). 4. To test for a direct effect of chlorpromazine on store-operated Ca2+ entry, thapsigargin, an inhibitor of microsomal Ca(2+)-ATPase, was used to induce store-operated Ca2+ entry in PC12 cells. Chlorpromazine reduced the thapsigargin-induced sustained Ca2+ level (IC(50): 24+/-2 microM, n=3), and the inhibition also occluded the inhibitory action of 1-[-[3-(4-methoxyphenyl) propoxy]-4-methoxyphenyl]-1H-imidazole hydrochloride (SK&F96365). 5. The results suggest that chlorpromazine negatively modulates the store-operated Ca2+ entry activated subsequent to PLC activation.
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PMID:Chlorpromazine inhibits store-operated calcium entry and subsequent noradrenaline secretion in PC12 cells. 1115 89

Experiments were designed to differentiate the mechanisms of bradykinin receptors mediating the changes in intracellular Ca(2+) concentration ([Ca(2+)](i)) in canine cultured corneal epithelial cells (CECs). Bradykinin and Lys-bradykinin caused an initial transient peak of [Ca(2+)](i) in a concentration-dependent manner, with half-maximal stimulation (pEC(50)) obtained at 6.9 and 7.1, respectively. Pretreatment of CECs with pertussis toxin (PTX) or cholera toxin (CTX) for 24 h did not affect the bradykinin-induced [Ca(2+)](i) changes. Application of Ca(2+) channel blockers, diltiazem and Ni(2+), inhibited the bradykinin-induced Ca(2+) mobilization, indicating that Ca(2+) influx was required for the bradykinin-induced responses. Addition of thapsigargin (TG), which is known to deplete intracellular Ca(2+) stores, transiently increased [Ca(2+)](i) in Ca(2+)-free buffer, and subsequently induced Ca(2+) influx when Ca(2+) was readded to this buffer. Pretreatment of CECs with TG completely abolished bradykinin-induced initial transient [Ca(2+)](i), but had slight effect on bradykinin-induced Ca(2+) influx. Pretreatment of CECs with 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole (SKF96365) and 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122) inhibited the bradykinin-induced Ca(2+) release and Ca(2+) influx, consistent with the inhibition of receptor-gated Ca(2+) channels and phospholipase C (PLC) in CECs, respectively. These results demonstrate that bradykinin directly stimulates B(2) receptors and subsequently Ca(2+) mobilization via a PTX-insensitive G protein in canine CECs. These results suggest that bradykinin-induced Ca(2+) influx into the cells is not due to depletion of these Ca(2+) stores, as prior depletion of these pools by TG has no effect on the bradykinin-induced Ca(2+) influx that is dependent on extracellular Ca(2+) in CECs.
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PMID:Mechanisms of bradykinin-mediated Ca(2+) signalling in canine cultured corneal epithelial cells. 1148 9

Ehrlichia chaffeensis, a bacterium that cannot survive outside the eukaryotic cell, proliferates exclusively in human monocytes and macrophages. In this study, signaling events required for ehrlichial infection of human monocytic cell line THP-1 were characterized. Entry and proliferation of E. chaffeensis in THP-1 cells were significantly blocked by various inhibitors that can regulate calcium signaling, including 8-(diethylamino)octyl-3,4,5-trimethoxybenzoate and 2-aminoethoxydiphenyl borate (intracellular calcium mobilization inhibitors), verapamil and 1-[beta-[3-(4-methoxyphenyl)propyl]-4-methoxyphenethyl]-1H-imidazole (SKF-96365) (calcium channel inhibitors), neomycin and 1-(6-[[17beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl)-1H-pyrrole-2,5-dione (U-73122) (phospholipase C [PLC] inhibitors), monodansylcadaverine (a transglutaminase [TGase] inhibitor), and genistein (a protein tyrosine kinase [PTK] inhibitor). Addition of E. chaffeensis resulted in rapid increases in the level of inositol 1,4,5-trisphosphate (IP(3)) and the level of cytosolic free calcium ([Ca(2+)](i)) in THP-1 cells, which were prevented by pretreatment of THP-1 cells with inhibitors of TGase, PTK, and PLC. E. chaffeensis induced rapid tyrosine phosphorylation of PLC-gamma2, and the presence of a PLC-gamma2 antisense oligonucleotide in THP-1 cells significantly blocked ehrlichial infection. Furthermore, tyrosine-phosphorylated proteins and PLC-gamma2 were colocalized with ehrlichial inclusions, as determined by double-immunofluorescence labeling. The heat-sensitive component of viable E. chaffeensis cells was essential for these signaling events. E. chaffeensis, therefore, can recruit interacting signal-transducing molecules and induce the following signaling events required for the establishment of infection in host cells: protein cross-linking by TGase, tyrosine phosphorylation, PLC-gamma2 activation, IP(3) production, and an increase in [Ca(2+)](i).
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PMID:Rapid activation of protein tyrosine kinase and phospholipase C-gamma2 and increase in cytosolic free calcium are required by Ehrlichia chaffeensis for internalization and growth in THP-1 cells. 1179 24

We demonstrated recently that in Chinese hamster ovary cells stably expressing human recombinant endothelin(A) receptors (CHO-ET(A)R), endothelin-1 (ET-1) activates two types of Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and a store-operated Ca2+ channel (SOCC), which can be distinguished by Ca(2+) channel blockers such as 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenylethyl]-1H-imidazole hydrochloride (SK&F 96365) and (R,S)-(3,4-dihydro-6,7-dimethoxy-isochinolin-1-yl)-2-phenyl-N,N-di[2-(2,3,4-trimethoxyphenyl)ethyl]acetamid mesylate (LOE 908). We also reported that CHO-ET(A)R couples with G12 in addition to G(q) and G(s). The purpose of the present study was to identify the G proteins involved in the activation of these Ca2+ channels by ET-1, using mutated ET(A)Rs with coupling to either G(q) or G(s)/G12 (designated ET(A)RDelta385 and SerET(A)R, respectively) and a dominant-negative mutant of G12 (G12G228A). ET(A)RDelta385 is truncated immediately downstream of Cys385 in the C terminus as palmitoylation sites, whereas SerET(A)R is unpalmitoylated because of substitution of all the cysteine residues to serine (Cys383Cys385-388 --> Ser383Ser385-388). In CHO-ET(A)RDelta385, stimulation with ET-1 activated only SOCC. In CHO-SerET(A)R or CHO-ET(A)R pretreated with U73122, an inhibitor of phospholipase C (PLC), ET-1 activated only NSCC-1. Dibutyryl cAMP alone did not activate any Ca2+ channels in the resting and ET-1-stimulated CHO-SerET(A)R. Microinjection of G12G228A abolished the activation of NSCC-1 and NSCC-2 in CHO-ET(A)R and that of NSCC-1 in CHO-SerET(A)R. These results indicate that ET(A)R activates three types of Ca2+ channels via different G protein-related pathways. NSCC-1 is activated via a G12-dependent pathway, NSCC-2 via G(q)/PLC- and G12-dependent pathways, and SOCC via a G(q)/PLC-dependent pathway.
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PMID:Molecular mechanisms for the activation of voltage-independent Ca2+ channels by endothelin-1 in chinese hamster ovary cells stably expressing human endothelin(A) receptors. 1206 57

It has been known that endothelin-1 (ET-1) exerts important actions in gastrointestinal smooth muscle motility, but its precise mechanism remains unsolved. We investigated the intracellular mechanism of ET-1-induced circular smooth muscle cell contraction in cat esophagus. ET-1 produced contraction of smooth muscle cells isolated by enzymatic digestion. The contraction in response to ET-1 was concentration-dependent. Pertussis toxin (PTX) blocked contraction induced by ET-1 in intact cells. To identify the specific G protein involved in the contraction, muscle cells were permeabilized with saponin. The G(i3) or G(beta) protein antibody inhibited the contraction. Neomycin phospholipase C (PLC) inhibitor inhibited the contraction, but 7,7-dimethyleicosadienoic acid (phospholipase A(2) inhibitor) and p-chloromercuribenzoic acid (phospholipase D inhibitor) had no effects. Incubation of permeabilized cells with PLC-beta(3) isozyme antibody inhibited the contraction. 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine, chelerythrine [protein kinase C (PKC) inhibitor], or genistein (protein tyrosine kinase inhibitor) inhibited the contraction, but not by diacylglycerol (DAG) kinase inhibitor, R59949. To test whether the contraction may be PKC isozyme-specific, we examined the effect of PKC isozymes antibodies on the contraction. PKC-epsilon antibody inhibited the contraction. To characterize further the specific PKC isozymes that mediate the contraction, we used, as an inhibitor, N-myristoylated peptides (myr-PKC) derived from the pseudosubstrate sequences of PKC-alphabetagamma, -alpha, -delta, or -epsilon. myr-PKC-epsilon inhibited the contraction, confirming that PKC-epsilon isozyme is involved in the contraction. To examine whether mitogen-activated protein kinases (MAPKs) mediate the contraction, specific MAPK inhibitors [MAPK kinase inhibitor, PD98059, (2'-amino-3'-methoxy-flavone), and p38 MAPK inhibitor, SB202190 (4-4-fluorophenyl) 2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole)] were used. PD98059 or SB202190 blocked the contraction. ET-1 increased the intensity of the detection bands identified by immunological methods as MAPK monoclonal p44/p42 peptides. PD98059 decreased the intensity of the detection bands compared with ET-1. In conclusion, ET-1-induced contraction in cat esophageal circular muscle cells depends on PTX-sensitive G(i3) protein and PLC-beta(3) isozyme, resulting in the activation of PKC-epsilon- or protein-tyrosine kinase-dependent pathway, subsequently mediating the activation of p44/p42 MAPK or p38 MAPK pathway.
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PMID:The signal transduction of endothelin-1-induced circular smooth muscle cell contraction in cat esophagus. 1218 48

Characteristics of pituitary adenylate cyclase-activating polypeptide (PACAP)-induced increase of Ca(2+) entry and catecholamine (CA) release were studied in bovine adrenal medullary chromaffin cells. PACAP induced intracellular free Ca(2+) concentration ([Ca(2+)](i)), showing an initial transient [Ca(2+)](i) rise followed by a sustained rise and CA release, which were not blocked by the blocking agents for nicotinic acetylcholine receptor (nAChR) channel, the voltage-dependent Ca(2+) channel (VOC), or the Na(+) channel. The sarcoendoplasmic Ca(2+)-ATPase inhibitors thapsigargin and cyclopiazonic acid did not affect the PACAP-induced sustained rise of [Ca(2+)](i), but did inhibit the initial [Ca(2+)](i) rise. In cells pretreated with cyclopiazonic acid or membrane-permeable, low-affinity Ca(2+) chelator N',N',N',N'-tetrakis(2-pyridylmethyl)ethylenediamine, PACAP further stimulated the entry of Ca(2+) or Mn(2+), whereas these treatments masked [Ca(2+)](i) dynamics induced by bradykinin. PACAP-induced sustained [Ca(2+)](i) rise and Mn(2+) entry were enhanced by acidic extracellular solution and reduced by alkalinization, whereas thapsigargin-induced Mn(2+) entry was regulated by the opposite. PACAP-induced [Ca(2+)](i) rise and Mn(2+) entry were not affected by blockers of cAMP-dependent protein kinase, phospholipase C, or protein kinase C. All store-operated Ca(2+) channel (SOC) blocking agents tested inhibited thapsigargin-induced Mn(2+) entry. 1(beta-[3-(4-Methoxyphenyl)-propoxy]-4-methoxyphenylethyl)-1H-imidazole hydrochloride (SK&F 96365), (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxyphenyl)ethyl]-acetamide, and econazole inhibited PACAP-induced Ca(2+) or Mn(2+) entry, whereas GdCl(3), 7,8-benzoflavone, nor-dihydroguaiaretic acid, 5-nitro-2-(3-phenylpropylamino)benzoic acid, fulfenamic acid, and niflumic acid did not. SK&F 96365 and econazole but not GdCl(3) inhibited PACAP-induced CA release. These results suggest that PACAP activates a novel Ca(2+) entry pathway associated with sustained CA release independent of the nAChR channel, VOC and SOC, activated by acid pH, with different sensitivity to blockers of SOC. This pathway may provide a useful model for the study of receptor-operated Ca(2+) entry.
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PMID:Pituitary adenylate cyclase-activating polypeptide induces a sustained increase in intracellular free Ca(2+) concentration and catechol amine release by activating Ca(2+) influx via receptor-stimulated Ca(2+) entry, independent of store-operated Ca(2+) channels, and voltage-dependent Ca(2+) channels in bovine adrenal medullary chromaffin cells. 1218 54


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