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)

1. Chinese hamster ovary cells (CHO-K1) express an endogenous 5-hydroxytryptamine (5-HT)1B-like receptor that is negatively coupled to adenylyl cyclase through a pertussis toxin (PTX)-sensitive mechanism. Furthermore, the human adenosine A1 receptor when expressed in CHO-K1 cells (CHO-A1) has been shown to mobilize intracellular Ca2+ through a PTX-sensitive mechanism. Therefore the aim of this investigation was to determine whether the endogenous 5-HT1B-like receptor was able to stimulate increases in intracellular free [Ca2+] ([Ca2+]i) in CHO-A1 cells. 2. In agreement with previous studies using CHO cells, 5-hydroxytryptamine (5-HT) elicited a concentration-dependent inhibition of forskolin-stimulated [3H]-cyclic AMP production in CHO-A1 cells (p[EC50] = 7.73 +/- 0.13). 5-HT (1 microM) inhibited 47 +/- 5% of the [3H]-cyclic AMP accumulation induced by 3 microM forskolin. Forskolin stimulated [3H]-cyclic AMP accumulation was also inhibited by the 5-HT1 receptor agonists (p[EC50] values) 5-carboxyamidotryptamine (5-CT; 8.07 +/- 0.08), RU 24969 (8.12 +/- 0.33) and sumatriptan (5.80 +/- 0.31). 3. 5-HT elicited a concentration-dependent increase in [Ca2+]i in CHO-A1 cells (p[EC50] = 8.07 +/- 0.05). In the presence of 2 mM extracellular Ca2+, 5-HT (1 microM) increased [Ca2+]i from 174 +/- 17 nM to 376 +/- 22 nM. The 5-HT1 receptor agonists (p[EC50] values), 5-carboxyamidotryptamine (5-CT; 7.9 +/- 0.02), RU 24969 (8.1 +/- 0.07) and sumatriptan (5.9 +/- 0.11) all elicited concentration-dependent increases in [Ca2+]i. Similar maximal increases in [Ca2+]i were obtained with each agonist. The selective 5-HT1A receptor agonist, 8-OH-DPAT (10 microM) did not stimulate increases in [Ca2+]i. 5-HT (100 microM) and 5-CT (10 microM) did not stimulate a measurable increase in [3H]-inositol phosphate accumulation in CHO-A1 cells. 4. 5-HT (1 microM)-mediated increases in [Ca2+]i were insensitive to the 5-HT receptor antagonist, ritanserin (5-HT2; 100 nM), ketanserin (5-HT2; 100 nM), LY-278,584 (5-HT3; 1 microM) and WAY 100635 (5-HT1A; 1 microM). The response to 5-HT (100 nM) was antagonized by the non-selective 5-HT1 antagonist, methiothepin (pKb = 8.90 +/- 0.09) and the 5-HT1D antagonist GR 127935 (pKb = 10.44 +/- 0.06). 5. Pretreatment with PTX (200 ng ml-1 for 4 h) completely attenuated the Ca2+ response to 100 microM 5-HT. 6. In untransfected CHO-K1 cells, 5-HT (1 microM), RU 24969 (1 microM), and 5-CT (1 microM) elicited increases in [Ca2+]i similar to those observed in CHO-A1 cells. 7. These data demonstrate that in CHO-K1 cells the endogenously expressed 5-HT1B-like receptor couples to the phospholipase C/Ca2+ signalling pathway through a PTX-sensitive pathway, suggesting the involvement of Gi/Go protein(s).
...
PMID:Coupling of an endogenous 5-HT1B-like receptor to increases in intracellular calcium through a pertussis toxin-sensitive mechanism in CHO-K1 cells. 868 Jul 21

Bacterial lipopolysaccharide (LPS)-induced exocytosis is one of the primary immune responses of the Limulus granulocyte (GR). Exocytosis can be mediated by guanine nucleotide-binding protein (G-protein)-linked surface receptors that activate phospholipase C (PLC) to produce inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG). IP3 mobilizes intracellular Ca2+ ([Ca2+]i), which can lead to exocytosis. We used activators and inhibitors of known signal transduction pathways to investigate the signaling pathway responsible for LPS-induced exocytosis in the GR. These compounds have been shown to similarly effect pathways in vertebrate and invertebrate systems and this assumption is made here. Pretreatment of GRs with cholera and pertussis toxins, which modulate G-proteins, and U73122, which inhibits PLC, inhibited LPS-induced exocytosis, but pretreatment with the tyrosine kinase inhibitor herbimycin did not. In contrast, exocytosis was induced with fluoride (a G-protein activator) and thapsigargin with Mg2+ (an inhibitor of endomembranous Ca(2+)-ATPase). Exocytosis was not induced by phorbol ester, which mimics DAG to activate protein kinase C (PKC) and it was not effected by ethanol or chelerythrine, which inhibit phospholipase D and PKC, respectively. Microinjection of GRs with different concentrations of IP3, an IP3 analog (DL-2,3,6,trideoxy-myo-inositol 1,4,5-triphosphate), Mg2+, or Ca2+ induced different percentages of exocytosis in individual cells, while HEPES buffer did not. Microfluorometric analysis of intracellular Mg2+ ([Mg2+]i) and [Ca2+]i, using the dyes Mag Fura-2AM and Calcium Green 5N, respectively, revealed [Mg2+]i and [Ca2+]i fluxes during LPS-induced exocytosis. This study suggests that LPS induces exocytosis in the Limulus GR through activation of G-protein-coupled receptors, which stimulate the IP3 signaling pathway to induce both [Ca2+]i and [Mg2+]i fluxes to facilitate vesicular and plasma membrane fusion. This is the first demonstration of the signal transduction pathway responsible for the primary immune response of the GR.
...
PMID:Signal transduction during exocytosis in Limulus polyphemus granulocytes. 901 85

Metabotropic glutamate receptors (mGluRs) control intracellular signaling cascades through activation of G proteins. The inwardly rectifying K+ channel, GIRK, is activated by the beta gamma subunits of G proteins and is widely expressed in the brain. We investigated whether an interaction between mGluRs and GIRK is possible, using Xenopus oocytes expressing mGluRs and a cardiac/brain subunit of GIRK, GIRK1, with or without another brain subunit, GIRK2. mGluRs known to inhibit adenylyl cyclase (types 2, 3, 4, 6, and 7) activated the GIRK channel. The strongest response was observed with mGluR2; it was inhibited by pertussis toxin (PTX). This is consistent with the activation of GIRK by Gi/Go-coupled receptors. In contrast, mGluR1a and mGluR5 receptors known to activate phospholipase C, presumably via G proteins of the Gq class, inhibited the channel's activity. The inhibition was preceded by an initial weak activation, which was more prominent at higher levels of mGluR1a expression. The inhibition of GIRK activity by mGluR1a was suppressed by a broad-specificity protein kinase inhibitor, staurosporine, and by a specific protein kinase C (PKC) inhibitor, bis-indolylmaleimide, but not by PTX, Ca(2-)chelation, or calphostin C. Thus, mGluR1a inhibits the GIRK channel primarily via a pathway involving activation of a PTX-insensitive G protein and, eventually, of a subtype of PKC, possibly PKC-mu. In contrast, the initial activation of GIRK1 caused by mGluR1a was suppressed by PTX but not by the protein kinase inhibitors. Thus, this activation probably results from a promiscuous coupling of mGluR1a to a Gi/Go protein. The observed modulations may be involved in the mGluRs effects on neuronal excitability in the brain. Inhibition of GIRK by phospholipase C-activating mGluRs bears upon the problem of specificity of G protein (GIRK interaction) helping to explain why receptors coupled to Gq are inefficient in activating GIRK.
...
PMID:Positive and negative coupling of the metabotropic glutamate receptors to a G protein-activated K+ channel, GIRK, in Xenopus oocytes. 910 6

Although it is well established that activated LH/human (h) CG receptor stimulates adenylyl cyclase activity (via the heterotrimeric stimulatory guanine nucleotide-binding protein, Gs) and in some cells stimulates phospholipase C activity, there is no evidence for a direct physical interaction between the LH/CG receptor and Gs or any other G protein(s). We conducted studies using cholera toxin (CTX) and pertussis toxin (PTX) to determine which G alpha proteins were associated with the LH/CG receptor in ovarian follicular membranes. Since hormone-dependent, CTX-catalyzed ADP ribosylation (AR) constitutes evidence that a G alpha protein is specifically associated with a receptor, CTX-catalyzed AR of membrane proteins was examined both in the presence and absence of guanine nucleotides to determine which G proteins exhibit hCG-dependent labeling by [32P]NAD. Results demonstrated the time- and hCG-dependent AR of both a 45-kDa protein and a 48/50-kDa doublet as well as a 40-kDa protein that was also sensitive to AR by PTX in a time- and hCG-dependent manner. Using anti-G protein antisera to specifically immunoprecipitate photoaffinity-labeled G proteins, we were able to identify the 45- and 48/50 kDa proteins as the short and long forms of Gs alpha and the 40-kDa protein as Gi alpha. A monoclonal anti-hCG antibody immunoprecipitated the activated LH/CG receptor along with the long and short forms of Gs alpha and Gi. These results suggest that a portion of Gi along with the long and short forms of Gs alpha are associated physically with the LH/CG receptor in ovarian follicular membranes.
...
PMID:Luteinizing hormone/choriogonadotropin-dependent, cholera toxin-catalyzed adenosine 5'-diphosphate (ADP)-ribosylation of the long and short forms of Gs alpha and pertussis toxin-catalyzed ADP-ribosylation of Gi alpha*. 913 98

To assess cellular mechanisms mediating afferent (AA) and efferent arteriolar (EA) constriction by angiotensin II (AngII), experiments were performed using isolated perfused hydronephrotic kidneys. In the first series of studies, AngII (0.3 nM) constricted AAs and EAs by 29+/-3 (n = 8, P < 0.01) and 27+/-3% (n = 8, P < 0.01), respectively. Subsequent addition of nifedipine restored AA but not EA diameter. Manganese (8 mM) reversed EA constriction by 65+/-9% (P < 0.01). In the second group, the addition of N-ethylmaleimide (10 microM), a Gi/Go protein antagonist, abolished AngII- induced EA (n = 6) but not AA constriction (n = 6). In the third series of experiments, treatment with 2-nitro-4-carboxyphenyl-N, N-diphenyl-carbamate (200 microM), a phospholipase C inhibitor, blocked both AA and EA constriction by AngII (n = 6 for each). In the fourth group, thapsigargin (1 microM) prevented AngII-induced AA constriction (n = 8) and attenuated EA constriction (8+/-2% decrease in EA diameter at 0.3 nM AngII, n = 8, P < 0.05). Subsequent addition of manganese (8 mM) reversed EA constriction. Our data provide evidence that in AAs, AngII stimulates phospholipase C with subsequent calcium mobilization that is required to activate voltage-dependent calcium channels. Our results suggest that AngII constricts EAs by activating phospholipase C via the Gi protein family, thereby eliciting both calcium mobilization and calcium entry.
...
PMID:Cellular mechanisms mediating rat renal microvascular constriction by angiotensin II. 932 77

The CCK and gastrin families of peptides act as hormones and neuropeptides on central and peripheral receptors to mediate secretion and motility in the gastrointestinal tract in the physiological response to a normal meal. Thus far, two CCK receptors have been molecularly identified to mediate the actions of CCK and gastrin, CCK-A and CCK-B receptors (CCK-AR and CCK-BR, respectively). The regulation of CCK-AR and CCK-BR affinity by guanine nucleotides and the receptor activation of G protein-dependent stimulation of phospholipase C and adenylyl cyclase suggested that they were guanine nucleotide-binding protein-coupled receptors [G protein-coupled receptors (GPCRs)]; however, the eventual cloning of their cDNAs revealed their heptahelical structure and confirmed their membership in the GPCR superfamily. The gastrointestinal system is a rich source of neuroendocrine hormones that interact with a large number of GPCRs to regulate the complex tasks of digestion, absorption, and excretion of a meal. This article focuses on the CCK family of GPCRs, and its activities in the gastrointestinal system.
...
PMID:G protein-coupled receptors in gastrointestinal physiology. I. CCK receptors: an exemplary family. 957 40

The hydrolysis of membrane phosphatidylcholine by the enzyme phospholipase D is a key initial step in the intracellular release of the signalling molecules phosphatidic acid, diacylglycerol and arachidonic acid. Guanine nucleotide-dependent pathway leading to PLD activation were investigated in enzymatically dispersed rat submandibular acinar cells. Guanosine 5'-O-[gamma-thio]triphosphate (GTP gamma S) caused the time- and concentration-dependent stimulation of PLD in permeabilized cells. This effect was lost in prepermeabilized cells, from which cytosolic components had been allowed to leak, but was restored when endogenous cytosol, or cytosol from platelets, was added back to such cells. PLD was also activated in cytosol-depleted cells by GTP gamma S in combination with purified ARF (ADP-ribosylation factor), a low M(r) guanine nucleotide-binding protein of the ras superfamily. Additional evidence for the involvement of ARF in PLD activation was the inhibition of carbachol- or GTP gamma S-induced stimulation of the enzyme by brefeldin A, a blocker of ARF activation; and the observed translocation of ARF from cytosol to membrane on GTP gamma S treatment in permeabilized cells. The heterotrimeric G-protein stimulator, AlFn, also activated PLD, and this response, too, was inhibited by brefeldin A, suggesting the downstream involvement of ARF in coupling AlFn action to phospholipase D elevation. PLD activation caused by both GTP gamma S and AlFn was only partially reduced after treatment of cells with U73122, a demonstrated inhibitor of phospholipase C in the Gq-coupled phosphoinositide signal-transduction pathway. It is therefore proposed that in rat submandibular mucous acinar cells, a guanine nucleotide-regulated PLD activation pathway exists that involves the sequential actions of a G heterotrimeric protein and ARF. It is further suggested that this pathway is independent of the Gq/PLC/phosphatidylinositol signal transduction system.
...
PMID:Activation of phospholipase D by ADP-ribosylation factor in rat submandibular acinar cells. 963 Nov 74

Binding of a Y1-subtype-selective agonist of neuropeptide Y (NPY) receptor, (Leu31,Pro34)human peptide YY (LP-PYY), to particulates from four rat brain areas (parietal cortex area 1, piriform cortex, anterior hypothalamus and hippocampus) showed a distinct response to LP-PYY and PYY, a uniformly low sensitivity to ligands selective for the Y2, Y4 and Y5 NPY receptor subtypes and high sensitivity to a Y1 site-selective antagonist, BIBP-3226. The Y1 binding was sensitive to guanine nucleotide-binding protein (G protein) agonist and antagonist nucleotides, with the rank order of guanosine 5'-O-(thiotriphosphate) (GTP gamma S) > GTP > GDP > guanosine 5'-O-(thiodiphosphate). However, guanine nucleotides did not affect about one third of the specific Y1 binding. Most of Y1 binding could be inhibited by a G protein nucleotide site/docking site receptor mimic, mastoparan analog MAS-7. In all areas examined, the Y1 binding of LP-PYY was little affected by up to 100 microM of the antagonists of K+, Na+ and Ca++ channels, protein kinase C, phospholipase A2, phospholipase D and phosphatidylinositol 3-kinase, phospholipase substrate phospholipids, steroids or detergents. However, the binding was potently inhibited by phospholipase C inhibitors (especially the aminosteroid U-73122), which also dissociated the bound Y1 ligand in steady-state conditions. U-73122 also displaced the Y1 binding insensitive to GTP gamma S. Ligand association with the brain Y1 NPY receptor thus strongly depends on activity of both G proteins and phospholipase C, implying specific interactions of these transducers/effectors with the receptor molecule in ligand binding. A portion of brain Y1 sites could be directly coupled to phospholipase(s) C.
...
PMID:Characterization of G protein and phospholipase C-coupled agonist binding to the Y1 neuropeptide Y receptor in rat brain: sensitivity to G protein activators and inhibitors and to inhibitors of phospholipase C. 965 83

The early signaling mechanism of sphingosine 1-phosphate (S1P) on extracellular signal-regulated kinase (ERK) activation was investigated in C6 glioma cells. S1P activated the enzyme in association with a shift in the mobility on electrophoresis reflecting phosphorylation of both ERK1/ERK2 at as low as 10 nM. The lipid-induced ERK1/2 activation was partially inhibited by treatment of the cells with either phorbol 12-myristate 13-acetate (a long-term treatment to desensitize protein kinase C) or pertussis toxin (PTX) and was completely inhibited by a simultaneous treatment with both agents. Similarly, either calphostin C, an inhibitor of protein kinase C, or U73122, an inhibitor of phospholipase C, partially inhibited the S1Pinduced ERK1/2 activation in the nontreated cells with PTX and completely in the toxin-treated cells. On the other hand, the S1P-induced ERK activation was hardly affected by ethanol, which switched the product of phospholipase D from phosphatidic acid to metabolism-resistant phosphatidylethanol. S1P was able to activate ERK1/2 without a detectable increase in the intracellular content of the lipid, but sphingosine, a substrate of sphingosine kinase, which is an enzyme for S1P generation in the cells, hardly affected the ERK1/2 activation in spite of a marked elevation of intracellular S1P accumulation. This indicates that intracellular increase in S1P is not necessary for the S1P-induced ERK activation, and hence suggests the extracellular action mechanism of S1P. Supporting this idea, mRNAs of recently identified S1P specific receptors, Edg-1 and AGR16/H218, were expressed in C6 cells. Taken together, these results suggested that S1P acts on C6 cells extracellularly possibly through S1P receptors which are linked to at least two signaling pathways, i.e., the PTX-sensitive Gi/Go protein pathway and the toxin-insensitive Gq/G11-phospholipase C-PKC pathway, resulting in the activation of ERK.
...
PMID:Possible involvement of cell surface receptors in sphingosine 1-phosphate-induced activation of extracellular signal-regulated kinase in C6 glioma cells. 988 6

The accumulation of inositol phosphates (IPs) induced by agonist-activated opioid receptors was analysed in mouse spinal cord slices pre-labelled with myo-[3H]inositol. Agonists showing selectivity to mu-opioid receptors, morphine and [D-Ala2,MePhe4, Gly(ol)5]enkephalin (DAMGO), promoted concentration-dependent increases in the formation of IPs. The activation of delta-opioid receptors by the selective agonists [D-Pen2,5]enkephalin (DPDPE) and [D-Ala2]deltorphin II produced similar increases in phosphoinositide (PI) metabolism. Pre-treatment of the slices with pertussis toxin (PTX) blocked the effect of opioid agonists on IP production. The involvement of Gi/Go-protein (guanine nucleotide-binding protein) classes in this opioid effect is therefore suggested. The activity of the opioid agonists was reduced by the opioid antagonists naltrexone and naloxone. The antagonist at delta1-receptors, 7-benzylidenenaltrexone (BNTX), exhibited greater potency than the antagonists at delta2-receptors, naltriben methanesulphonate (NTB) or naltrindrole 5'-isothiocyanate (NT II), in reducing the activating effect of DPDPE on phosphoinositide metabolism. Conversely, NTB and NT II were more potent antagonists of the activity of [D-Ala2]deltorphin II than BNTX. This work demonstrates the coupling of spinal mu- and delta-opioid receptors to phospholipase C and the generation of IPs. It also provides biochemical evidence for pharmacological subtypes of delta-opioid receptors in the activation of this signalling pathway.
...
PMID:Stimulation of mu- and delta-opioid receptors enhances phosphoinositide metabolism in mouse spinal cord: evidence for subtypes of delta-receptors. 1033 74


<< Previous 1 2 3 4 5 6 7 8 9 Next >>

---