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)

In the present study, we investigated the effect of hypoxia on the chronotropic response to norepinephrine (NE) of cultured neonatal rat ventricular myocytes. We measured beating of myocytes with the Fotonic sensor, using a newly developed method for a noncontact displacement measurement. The beating rate counted with the sensor had a high correlation coefficient with that counted visually under a microscope (r = 0.997, P < 0.01). NE concentrations of 10(-8) - 10(-4) M caused negative chronotropy dose dependently in the presence of 5 x 10(-7) M propranolol. NE-induced chronotropy was completely antagonized by 10(-6) M prazosin. Three hours hypoxia decreased the spontaneous beating rate 40% (P < 0.01). Negative chronotropy induced by 10(-4) M NE in normoxia was inverted to positive and was antagonized by prazosin. Hypoxia increased the basal level of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) to 190% (P < 0.01), while NE-stimulated Ins(1,4,5)P3 production was significantly suppressed. Immunoblotting analysis of G protein subunits demonstrated no quantitative changes in Gi alpha, Gq alpha, Go alpha and G beta common subunits in hypoxia. In a saturation binding assay with [3H]prazosin, Kd values were increased to 152% by hypoxia (P < 0.05) without significant change in Bmax. Basal activity of low Km-GTPase was increased to 122% by hypoxia (P < 0.05). These results suggest that the hypoxia-induced increase in low-Km GTPase activity, which could stimulate phospholipase C by an activated alpha GTP subunit of G protein and consequently induce receptor-independent increase in Ins(1,4,5)P3, may be responsible for the inversion of the NE-induced negative chronotropic response in normoxia.
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PMID:Hypoxia inverts the negative chronotropic response to norepinephrine in normoxia in cultured neonatal rat cardiac myocytes: role of the alpha 1 adrenergic signal transduction system. 774 96

To understand the mechanisms by which G protein-coupled signaling systems regulate NHE-1 in epithelial cells, we expressed G alpha q and G alpha 13 in a renal epithelial cell line. We studied two signaling systems that have been implicated in NHE-1 regulation [intracellular Ca (Cai) and phospholipase C activity] and measured NHE-1 activity, mRNA, and antigen. Expression of alpha qWT and alpha qQ209L (a GTPase-deficient mutant) increased basal Cai and altered the kinetics of the bradykinin-induced Cai signal. The initial bradykinin-induced spike in Cai was prolonged and the plateau was higher in cells expressing alpha qWT and alpha qQ209L than in control cells. Cells expressing alpha 13WT also had a higher basal Cai and plateau after stimulation by bradykinin, but Ca release from intracellular stores was similar to that in control cells. Expression of all three alpha-chains increased NHE-1 activity, antigen, and mRNA. The alpha qQ209L had the greatest effect increasing activity by approximately twofold. The alpha 13WT increased NHE-1 activity by approximately 1.5-fold, and alpha qWT increased activity 1.2-fold. These studies demonstrate that alpha q and alpha 13 alter regulation of Cai but by different mechanisms. The Ca signal or another signal generated by alpha q and alpha 13 regulate(s) NHE-1 at the levels of activity, antigen, and mRNA.
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PMID:G alpha q and G alpha 13 regulate NHE-1 and intracellular calcium in epithelial cells. 784 Jan 38

1. The amphiphilic peptide mastoparan is known to affect phosphoinositide breakdown, calcium influx, and exocytosis of hormones and neurotransmitters and to stimulate the GTPase activity of guanine nucleotide-binding regulatory proteins. Another amphiphilic peptide, adenoregulin was recently identified based on stimulation of agonist binding to A1-adenosine receptors. 2. A comparison of the effects of mastoparan and adenoregulin reveals that these peptides share many properties. Both stimulate binding of agonists to receptors and binding of GTP gamma S to G proteins in brain membranes. The enhanced guanyl nucleotide exchange may be responsible for the complete conversion of receptors to a high-affinity state, complexed with guanyl nucleotide-free G proteins. 3. Both peptides increase phosphoinositide breakdown in NIH 3T3 fibroblasts. Pertussis toxin partially inhibits the phosphoinositide breakdown elicited by mastoparan but has no effect on the response to adenoregulin. N-Ethylmaleimide inhibits the response to both peptides. 4. In permeabilized 3T3 cells, both adenoregulin and mastoparan inhibit GTP gamma S-stimulated phosphoinositide breakdown. Mastoparan slightly increases basal cyclic AMP levels in cultured cells, followed at higher concentrations by an inhibition, while adenoregulin has minimal effects. 5. Both peptides increase calcium influx in cultured cells and release of norepinephrine in pheochromocytoma PC12 cells. The calcium influx elicited by the peptides in 3T3 cells is not markedly altered by N-ethylmaleimide. 6. Multiple sites of action appear likely to underlie the effects of mastoparan/adenoregulin on receptors, G proteins, phospholipase C, and calcium.
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PMID:Effects of the amphiphilic peptides mastoparan and adenoregulin on receptor binding, G proteins, phosphoinositide breakdown, cyclic AMP generation, and calcium influx. 784 73

The alpha subunits of Gq family G proteins, GL1 alpha (G14 alpha), GL2 alpha(G11 alpha), and Gq alpha were expressed with G protein beta 1 and gamma 2 subunits in insect cells using a baculovirus system. The trimeric forms of G proteins, GL1 (GL1 alpha beta gamma), GL2 (GL2 alpha beta gamma), and Gq (Gq alpha beta gamma), were solubilized by 1% sodium cholate and purified by sequential chromatography on three kinds of columns. GL1, GL2, and Gq activated phospholipase C-beta purified from bovine brain in the presence of aluminum fluoride to the same extent. Muscarinic acetylcholine receptor m1 subtype stimulated the guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) binding to GL1, GL2, and Gq in the presence of similar concentrations of carbamylcholine. When m1 receptor, G protein, and phospholipase C-beta were reconstituted in lipid vesicles, each subtype of Gq family G proteins mediated the activation of phospholipase C-beta by carbamylcholine in the presence of either 1 microM GTP gamma S or 1 mM GTP. Phospholipase C-beta stimulated the GTPase activity of GL1, GL2, and Gq in the presence of m1 receptor and carbamylcholine but did not stimulate the GTPase activity of GO. Protein kinase C phosphorylated m1 receptor and phospholipase C-beta, but the phosphorylation did not significantly affect the ability of the m1 receptor to stimulate phospholipase C-beta in the reconstitution system of purified proteins.
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PMID:Characterization of Gq family G proteins GL1 alpha (G14 alpha), GL2 alpha (G11 alpha), and Gq alpha expressed in the baculovirus-insect cell system. 789 Jul 62

We have recently found the calcium dependent glycogenolytic effect of a pancreastatin on rat hepatocytes and the mobilization of intracellular calcium. To further investigate the mechanism of action of pancreastatin on liver we have studied its effect on guanylate cyclase, adenylate cyclase, and phospholipase C, and we have explored the possible involvement of GTP binding proteins by measuring GTPase activity as well as the effect of pertussis toxin treatment of plasma liver membranes on the pancreastatin stimulated GTPase activity and the production of cyclic GMP and myo-inositol 1,4,5-triphosphate. Pancreastatin stimulated GTPase activity of rat liver membranes about 25% over basal. The concentration dependency curve showed that maximal stimulation was achieved at 10(-7)M pancreastatin (EC50 = 3 nM). This stimulation was partially inhibited by treatment of the membranes with pertussis toxin. The effect of pancreastatin on guanylate cyclase and phospholipase C were examined by measuring the production of cyclic GMP and myo-inositol 1,4,5-triphosphate respectively. Pancreastatin increased the basal activity of guanylate cyclase to a maximum of 2.5-fold the unstimulated activity at 30 degrees C, in a time- and dose-dependent manner, reaching the maximal stimulation above control with 10(-7) M pancreastatin at 10 min (EC50 = 0.6 nM). This effect was completely abolished when rat liver membranes had been ADP-ribosylated with pertussis toxin. On the other hand, adenylate cyclase activity was not affected by pancreastatin. Phospholipase C activity of rat liver membranes was rapidly stimulated (within 2-5 min) at 30 degrees C by 10(-7) M pancreastatin, reaching a maximum at 15 min.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pancreastatin activates pertussis toxin-sensitive guanylate cyclase and pertussis toxin-insensitive phospholipase C in rat liver membranes. 791 48

We examined the roles of the Drosophila Gq alpha proteins (DGq) in the phototransduction pathway. The DGq proteins immunolocalized to the ocelli and all eight retinular photoreceptor cell rhabdomeres. An affinity-purified anti-DGq alpha immunoglobulin blocked the light-dependent GTP hydrolysis activity associated with Drosophila head membranes in vitro, suggesting that rhodopsin stimulated DGq. Dominantly active DGq1 mutants exhibited a light-independent GTPase activity and abnormal electrophysiological light responses, such as reduced retinal sensitivity and slow response kinetics compared with wild-type flies. Dominant DGq2 mutants exhibited a light-independent GTPase activity with normal electrophysiological light responses. Retinas of double mutants of DGq1, but not DGq2, with the light-dependent retinal degeneration mutant rdgB degenerated even in the dark. DGq1 stimulation of rdgB retinal degeneration in the dark was norpA-dependent. These results indicate that DGq1 mediates the stimulation by light-activated rhodopsin of the norpA-encoded phospholipase C in the visual transduction cascade.
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PMID:The Drosophila dgq gene encodes a G alpha protein that mediates phototransduction. 794 51

Dynamin, a 100 kDa GTPase, is critical for endocytosis, synaptic transmission and neurogenesis. Endocytosis accompanies receptor processing and plays an essential role in attenuating receptor tyrosine kinase signal transduction. Dynamin has been demonstrated to be involved in the endocytic processing at the cell surface and may play a general role in coupling receptor activation to endocytosis. Src homology (SH) domain dependent protein-protein interactions are important to tyrosine kinase receptor signal transduction. The C-terminus of dynamin contains two clusters of SH3 domain binding proline motifs; these motifs may interact with known SH3 domain proteins during tyrosine kinase receptor activation. We demonstrate here that SH3 domain-containing signal transduction proteins, such as phospholipase C gamma-1 (PLC gamma-1), do indeed bind to dynamin in a growth factor inducible manner. The induction of PLC gamma-1 binding to dynamin occurs within minutes of the addition of platelet derived growth factor (PDGF) to cells. Binding of these signal transduction proteins to dynamin involves specific sorting to individual proline motif clusters and appears to be responsible for co-immunoprecipitation of tyrosine phosphorylated PDGF receptors with dynamin following PDGF stimulation of mammalian cells. The binding of dynamin to SH3 domain-containing proteins may therefore be important for formation of the protein complex required for the endocytic processing of activated tyrosine kinase receptors.
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PMID:Growth factor-induced binding of dynamin to signal transduction proteins involves sorting to distinct and separate proline-rich dynamin sequences. 801 57

Expression of the GTPase-deficient G alpha 16 polypeptide G alpha 16Q212L, a member of the Gq family of heterotrimeric G proteins, constitutively activated phospholipase C beta activity in Swiss 3T3 cells. Expression of G alpha 16Q212L appears to persistently stimulte a low level of protein kinase C activity which also increases protein kinase A activity in Swiss 3T3 cells. Growth of G alpha 16Q212L expressing cells was significantly inhibited relative to wild-type Swiss 3T3 cells. Bombesin-stimulated DNA synthesis was completely inhibited in G alpha 16Q212L expressing clones, whereas the growth responses to platelet-derived growth factor (PDGF) and serum were inhibited 50-80% relative to wild-type cells. In addition to the inhibition of cell growth, G alpha 16Q212L expression significantly inhibited the stimulation of protein kinase C, Raf-1, MEK, mitogen-activated protein kinase, phospholipase A2 activity, and Ca2+ mobilization in response to PDGF. In contrast, PDGF receptor activation of phospholipase C gamma, phosphatidylinositol 3-kinase, and Ras GTP loading was similar in wild-type and G alpha 16Q212L expressing clones. PDGF regulation of membrane ruffling and actin fiber assembly, responses mediated in part by phosphatidylinositol 3-kinase, were unaffected in G alpha 16Q212L expressing clones. The growth inhibitory action of G alpha 16Q212L expression in Swiss 3T3 cells is downstream of the initial SH2 domain-encoded signal transduction proteins regulated in response to PDGF receptor autophosphorylation. The findings demonstrate that constitutively activated G alpha 16Q212L persistently activates phospholipase C activity and effectively inhibits a subset of cytoplasmic signal transduction pathways involved in growth factor tyrosine kinase receptor stimulation of cell growth. G16/Gq-regulated signal transduction can acutely stimulate specific response pathways involved in mitogenesis; but persistent activation of G16/Gq-regulated effectors, including phospholipase C beta, inhibit tyrosine kinase-initiated mitogenesis. One role for G16/Gq response systems may be to modulate growth factor receptor signaling.
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PMID:Expression of GTPase-deficient G alpha 16 inhibits Swiss 3T3 cell growth. 802 Dec 43

Staurosporine in the micromolar range raised inositol trisphosphate in intact human platelets to levels comparable to that mediated by thrombin. This response was inhibited by neomycin, a phospholipase C antagonist. Staurosporine alone induced a weak, transient rise in cytosolic free calcium levels ([Ca2+]i) from release of internal Ca2+ stores but potentiated the effect induced by thrombin. Therefore, it is unlikely that this alkaloid suppressed inositol trisphosphate mobilization of Ca2+. Additional studies show that staurosporine, 0.5-5 microM, stimulated GTPase activity in platelet membranes while 2 microM K252a and 20 microM H7 were inactive. Present results suggest that staurosporine may activate platelet phospholipase C at the level of G proteins or receptors.
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PMID:Staurosporine induces hydrolysis of phosphatidyl inositol 4,5-bisphosphate in human platelets. 816 13

Src homology 3 (SH3) domains are found in a variety of proteins that are involved in signal transduction or represent components of the cytoskeleton. These domains are thought to serve as modules that mediate specific protein-protein interactions that include proline-rich sequences on the target protein. We have identified proteins of 110, 80, 65, and 43 kDa in human embryonic fibroblasts that bind specifically to the SH3 domain of phospholipase C gamma, a primary substrate of receptor tyrosine kinases, and characterized the 110-kDa band as the microtubule-activated GTPase dynamin. In addition, dynamin binds the son of sevenless adaptor protein GRB-2 with even higher affinity. This interaction does not require the dynamin GTPase function and involves a proline-rich target sequence between residues 812 and 820 of dynamin.
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PMID:Dynamin binds to SH3 domains of phospholipase C gamma and GRB-2. 820 97


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