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

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

Phosphoinositide phospholipase C (PLC) activity extracted from bovine liver plasma membranes with sodium cholate was stimulated by GTP gamma S-activated G alpha q/G alpha 11, whereas the enzyme from liver cytosol was not. The membrane-associated PLC was subjected to chromatography on heparin-Sepharose, Q Sepharose, and S300HR, enabling the isolation of the G-protein stimulated activity and its resolution from PLC-gamma and PLC-delta. Following gel filtration, two proteins of 150 and 140 kDa were found to correspond to the activatable enzyme. These proteins were identified immunologically as members of the PLC-beta family and were completely resolved by chromatography on TSK Phenyl 5PW. The 150-kDa enzyme was markedly responsive to GTP gamma S-activated alpha-subunits of G alpha q/G alpha 11 or to purified Gq/G11 in the presence of GTP gamma S. The response of this PLC was of much greater magnitude than that of the 140-kDa enzyme. The partially purified 150-kDa enzyme showed specificity for PtdIns(4,5)P2 and PtdIns4P as compared to PtdIns and had an absolute dependence upon Ca2+. These characteristics were similar to those of the brain PLC-beta 1. The immunological and biochemical properties of the 150-kDa membrane-associated enzyme are consistent with its being the PLC-beta isozyme that is involved in receptor-G-protein-mediated generation of inositol 1,4,5-triphosphate in liver.
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PMID:Identification in bovine liver plasma membranes of a Gq-activatable phosphoinositide phospholipase C. 132 Sep 35

A new class of G-proteins, the Gq family, has been recently identified and found to be involved in phospholipase C activation. The alpha subunits of the Gq and G11 members of this family are separate polypeptides but appear to have the same function. In this study, the cellular distribution in the adult rat brain of these G-proteins, Gq alpha/G11 alpha, was determined by immunohistochemistry using an antipeptide antiserum directed against the predicted C-terminal decapeptide which is conserved between these polypeptides. The specificity of the antiserum was verified by Western blot analysis using rat brain homogenates. Immunoreactivity was detected in neurons, where it was localized in the dendrites and at the periphery of the cell bodies. The staining was abundant in the dendrites of cerebellar Purkinje cells and hippocampal CA1 pyramidal cells. Staining was also found in neurons in the olfactory bulb, minor and major islets of Calleja, anterior olfactory nuclei and piriform cortex; the different cortical areas especially in their superficial layers; caudate-putamen, accumbens and olfactory tubercle; lateral septum and amygdala; hippocampal CA2-4 sectors of Ammon's horn, dentate gyrus and hilus; hypothalamic supraoptic nucleus; cerebellar granular layer; colliculi and superficial layers of the dorsal horn of the spinal cord. In conclusion, the brain neuronal localizations of Gq alpha/G11 alpha match that of phospholipase C, 1,4,5-triphosphate receptor and, to a lesser extent 1,4,5-triphosphate-3-kinase.
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PMID:Immunohistochemical distribution of neurons containing the G-proteins Gq alpha/G11 alpha in the adult rat brain. 146 95

Xenopus oocytes that express mouse thyrotropin-releasing hormone receptors (TRH-Rs) after injection if RNA transcribed from TRH-R cDNA respond to THR by a depolarizing current. This response is transduced by activation of phosphoinositide-specific phospholipase C and utilizes an as yet unidentified endogenous guanine nucleotide-binding regulatory (G) protein(s). The alpha subunit of G11 and Gq have recently been shown to couple receptors to activation of phospholipase C. To determine whether there are functional differences between these proteins, we have co-expressed the TRH-R with either alpha 11 or alpha q. alpha 11 potentiated the response to TRH (by 61 +/- 16%), while alpha q inhibited the response (by 37 +/- 9%). The changes in amplitudes were accompanied by inverse changes in response latencies. These data show that alpha 11 and alpha q differentially modulate signal transduction in Xenopus oocytes.
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PMID:G alpha 11 and G alpha q guanine nucleotide regulatory proteins differentially modulate the response to thyrotropin-releasing hormone in Xenopus oocytes. 164 77

A 150-kDa phospholipase C has previously been purified from turkey erythrocytes and has been shown by reconstitution with turkey erythrocyte membranes to be a receptor- and G-protein-regulated enzyme (Morris, A. J., Waldo, G. L., Downes, C.P., and Harden, T. K. (1990) J. Biol. Chem. 265, 13501-13507; Morris, A.J., Waldo, G.L., Downes, C.P., and Harden, T.K. (1990) J. Biol. Chem. 265, 13508-13514). Combination of this 150-kDa protein with phosphoinositide substrate-containing phospholipid vesicles prepared with a cholate extract from purified turkey erythrocyte plasma membranes resulted in conferrence of AlF4- sensitivity to the purified phospholipase C. Guanosine 5'-3-O-(thio)triphosphate also activated the reconstituted phospholipase C in a manner that was inhibited by guanosine 5'-2-O-(thio)-diphosphate. The magnitude of the AlF4- stimulation was increased with increasing amounts of plasma membrane extract, and was also dependent on the concentration of purified phospholipase C. Using reconstitution of AlF4- sensitivity as an assay, the putative G-protein conferring regulation to the 150-kDa phospholipase C was purified to near homogeneity by sequential chromatography over Q-Sepharose, Sephacryl S-300, octyl-Sepharose, hydroxylapatite, and Mono-Q. Reconstituting activity co-purified with an approximately 43-kDa protein identified by silver staining; lesser amounts of a 35-kDa protein was present in the final purified fractions, as was a minor 40-kDa protein. The 43-kDa protein strongly reacted with antiserum against a 12-amino acid sequence found at the carboxyl terminus of Gq and G11, the 35-kDa protein strongly reacted with G-protein beta-subunit antiserum, and the 40-kDa protein reacted with antiserum that recognizes Gi3. Immunoprecipitation of the 43-kDa protein resulted in loss of phospholipase C-stimulating activity of the purified fraction. The idea that this is a phospholipase C-regulating G-protein is further supported by the observation that co-reconstitution of G-protein beta gamma-subunit with the purified phospholipase C-activating fraction resulted in a beta gamma-subunit-dependent inhibition of AlF(4-)-stimulated phospholipase C activity in the reconstituted preparation.
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PMID:Purification of an AlF4- and G-protein beta gamma-subunit-regulated phospholipase C-activating protein. 165 Mar 51

Platelet activation begins with the binding of an agonist to the cell surface and culminates in the events of platelet aggregation, secretion and clot formation. Recent studies have identified two large families of GTP-binding proteins in platelets that are thought to participate in the events of platelet activation. The first of these are the G proteins, heterotrimeric proteins which are best known for their ability to mediate the interaction between agonist receptors and intracellular enzymes such as adenylyl cyclase, phospholipase C and phospholipase A2. To date, at least six G proteins have been identified in platelets: Gs, Gz, three variants of Gi and either Gq or G11 (or both). An additional, pertussis toxin-resistant G protein, Gq, may also be present. The second group of GTP-binding proteins present in platelets is substantially smaller than the heterotrimeric G proteins, ranging in size from 21 to 28 kDa. At least 15 such low molecular weight GTP-binding proteins have been identified in platelets, many of which are homologous to the products of the ras proto-oncogenes. In cells other than platelets, low molecular weight GTP-binding proteins have been implicated in protein transport, cell activation events and malignant transformation. Their role in platelets is unknown.
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PMID:The role of GTP-binding proteins in platelet activation. 166 93

The human leukaemic cell line K562 is a pluripotent stem cell with the potential to mature along a megakaryocytic or erythroid line. In these cells, thrombin and U46619 (9,11-dideoxy-9 alpha, 11 alpha-methanoepoxy prostaglandin F2 alpha), a thromboxane A2 analogue, increased intracellular Ca2+ in a rapid and concentration-dependent manner. The peak transient observed with both thrombin and U46619 was preserved upon stimulation in the absence of extracellular calcium and blunted with phorbol myristate acetate, suggestive of activation of phospholipase C. Short-term treatment with leupeptin abolished the calcium response to thrombin, but did not alter that to U46619. Both pertussis toxin (PT) and DMSO pretreatment inhibited thrombin- but not U46619-stimulated intracellular calcium elevation, indicating that these agonists signal through different G-proteins. Western blot analysis of crude membranes from K562 cells revealed the presence of G12 alpha and G13 alpha; the other known PT-substrates, Gi1 alpha and G0 alpha, were not detected. Consistent with this observation, ADP-ribosylation experiments revealed the presence of two PT substrates which co-migrated with human erythrocyte G12 alpha and G13 alpha. An antibody raised against Gq/11 alpha, a subfamily of G-protein alpha subunits unmodified by PT, specifically recognized 42 kDa protein(s) in K562 cells. PCR amplification of reverse-transcribed K562 RNA followed by DNA sequencing showed that these cells express messages for both Gq alpha and G11 alpha. Treatment of K562 cells with DMSO reduced the levels of thrombin receptor mRNA, without simultaneous changes in the expression of G12 alpha and G13 alpha. We have thus identified Ca(2+)-mobilizing agonists and related G-proteins in K562 cells, together with changes induced by DMSO in this signalling pathway.
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PMID:Ca2+ signalling in K562 human erythroleukaemia cells: effect of dimethyl sulphoxide and role of G-proteins in thrombin- and thromboxane A2-activated pathways. 749 5

Smooth muscle cells isolated from the circular muscle layer of cat esophagus and lower esophageal sphincter (LES) exhibit distinct contractile intracellular signal transduction pathways in response to acetylcholine. To determine whether these contractile pathways are muscle type dependent, the authors examined the signal transduction pathways utilized by substance P and bombesin, which in other tissues, use different signal transduction pathways, and by the GTP analog, guanosine 5'-O-3-thiotriphosphate (GTP gamma S), which activates all available G proteins. Western blot analysis of esophageal and LES circular muscle revealed the presence of Gq-G11 (42 kD), Gi1-Gi2 (40 kD) and Go-Gi3 (40 kD) types of G proteins. The responses of esophageal cells to bombesin and substance P were blocked by 1) a Gi3 protein antibody, 2) the inhibitor of specific phosphatidylcholine-phospholipase C (PLC) D609 potassium tricyclo-[5.2.1.0(2.6)]-decyl-(9[8])-xanthogenate, 3) inhibition of phosphatidic acid phosphohydrolase by propranolol, 4) the protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H7) and 5) incubation in Ca(++)-free medium. Conversely, the responses of LES muscle cells to bombesin and substance P were blocked by 1) a Gq-G11 antibody, 2) a phosphatidylinositol-specific PLC antagonist U-73122 (1-[6-[[17 beta-3-methoxyestra-1,3,5(10)-trien-17- yl]amino]hexyl]-1H-pyrrole-2,5-dione), 3) the calmodulin inhibitor CGS9343B (1,3-Dihydro-1-[1-((4-methyl-4H,6H-pyrrolo[1,2-a]-[4,1]benzoxazepin++ +-4 - yl)methyl-4-piperindinyl]-2H-benzimidazol-2-one maleate) and 4) incubation in Sr++. After permeabilization by saponin, inositol 1,4,5-trisphosphate contracted LES but not esophageal cells. The inositol 1,4,5-trisphosphate receptor antagonist heparin and depletion of intracellular Ca++ stores by thapsigargin or A23187 4-Benzoxazolecarboxylic acid, 5-(methylamino)-2-[[3,9,11-trimethyl-8-[1-methyl-2-oxo-2-(1H-pyrrol- 2-yl)ethyl]-1,7-dioxaspiro[5.5]undec-2-yl]methyl]-, [6s-[6.alpha. (2S*,3S*),8.beta. (R*), 9.beta., 11. alpha.]]-(9Cl), blocked bombesin- and substance P-induced contraction of LES but not of esophageal muscle. In addition, contraction in response to GTP gamma S, which activates all G proteins, was blocked in esophageal cells by a Gi3-protein antibody, propranolol, D609 and H7. In LES muscle cells, the response to GTP gamma S was blocked by a Gq protein antibody, U-73122 and CGS934B. These data demonstrate that, in esophageal muscle, different agonists activate the same Gi3 protein, phosphatidylcholine-specific phospholipases and protein kinase C-dependent pathway.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Agonist-independent, muscle-type-specific signal transduction pathways in cat esophageal and lower esophageal sphincter circular smooth muscle. 753 46

A selective polyclonal antibody directed toward the C-terminal decapeptide common to the alpha subunits of Gq and G11 G proteins (G alpha q/G alpha 11) was prepared and used to investigate the subcellular distribution fo these proteins in WRK1 cells, a rat mammary tumor cell line. In immunoblots, the antibody recognized purified G alpha q and G alpha 11 proteins and labeled only two bands corresponding to these alpha subunits. Functional studies indicated that this antibody inhibited vasopressin- and guanosine 5'-[alpha-thio]triphosphate-sensitive phospholipase C activities. Immunofluorescence experiments done with this antibody revealed a filamentous labeling corresponding to intracytoplasmic and perimembranous actin-like filament structures. Colocalization of G alpha q/G alpha 11 and F-actin filaments (F-actin) was demonstrated by double-labeling experiments with anti-G alpha q/G alpha 11 and anti-actin antibodies. Immunoblot analysis of membrane, cytoskeletal, and F-actin-rich fractions confirmed the close association of G alpha q/G alpha 11 with actin. Large amounts of G alpha q/G alpha 11 were recovered in the desmin- and tubulin-free F-actin-rich fraction obtained by a double depolymerization-repolymerization cycle. Disorganization of F-actin filaments with cytochalasin D preserved G alpha q/G alpha 11 and F-actin colocalization but partially inhibited vasopressin- and fluoroaluminate-sensitive phospholipase C activity, suggesting that actin-associated G alpha q/G alpha 11 proteins play a role in signal transduction.
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PMID:Close association of the alpha subunits of Gq and G11 G proteins with actin filaments in WRK1 cells: relation to G protein-mediated phospholipase C activation. 766 4

ISOFORMS OF ANGIOTENSIN II RECEPTORS: So far, three isoforms of angiotensin II receptors have been identified by complementary DNA cloning, all with seven transmembrane domain structures. AT1A and AT1B are the most common isoforms. They are coupled to phospholipase C through Gq/G11 proteins and to a calcium channel, and negatively coupled to adenyl cyclase. AT2 is only remotely related to the AT1 family. KNOWN STRUCTURAL DETAILS OF ANGIOTENSIN II RECEPTORS: Ligand-binding domains are being defined in the space surrounded by transmembrane helices. Coupling to Gq seems to involve the second cytosolic loop. Receptor proteins undergo transition to a low-affinity form, which is desensitized and internalized. CHROMOSOME LOCATION: In the rat, AT1A, AT1B and AT2 are located on chromosomes 17, 2 and X, respectively. SIGNALING PATHWAY: Studies with receptors are revealing several different pathways of angiotensin signaling that modulate protein tyrosine phopsphorylation.
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PMID:Molecular biology of angiotensin II receptors: an overview. 776 96

The C5a chemoattractant factor receptor, when expressed in COS-7 cells, can stimulate phosphoinositide-specific phospholipase C activity through the activation of the G16 isoform of the heterotrimeric G protein, but not through the G11 isoform. To identify the regions of the G alpha 16 subunit protein that are responsible for its activation by the C5a receptor, a series of chimeras between G alpha 16 and G alpha 11 were constructed and tested for their ability to be activated by the C5a receptor. Co-transfection experiments with chimeras in which the carboxyl-terminal regions of G alpha 11 were replaced with the corresponding regions of G alpha 16 demonstrated that changes in the carboxyl terminus, e.g., replacement of 134 amino acids, were not sufficient to confer receptor specificity. An additional segment encompassing residues 220-240 of G alpha 16 was required to confer C5a-induced activation. Testing of a reciprocal series of chimeras composed of G alpha 16 sequences at the amino terminus and G alpha 11 sequences at the carboxyl terminus revealed that certain sequences extending from the amino terminus to amino acid 209 of G alpha 16 were sufficient to endow the chimera with much of the specificity for C5a-induced activation. These results suggest that receptor specificity may involve specific conformations of the G protein stabilized by concerted interactions of multiple amino acid sequences distributed throughout the G alpha protein.
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PMID:Multiple regions of G alpha 16 contribute to the specificity of activation by the C5a receptor. 787 28


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