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: UMLS:C0043167 (pertussis)
19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

E. coli lipopolysaccharide (LPS) stimulated a dose- and time-dependent release of prostaglandin E2 (PGE2) in cultured rat glomerular mesangial cells. Pertussis toxin, an inhibitor of several GTP-binding proteins (G proteins), blocked nearly 80% of the LPS-stimulated PGE2 formation, while having virtually no effect on calcium ionophore-stimulated PGE2 production. We tested the possibility that a G protein-coupled activation of phospholipase A2 mediated the LPS-stimulated PGE2 production. Evidence for LPS activation of phospholipase A2 included a time-dependent LPS-induced generation of [32P]lysophosphatidylcholine and the inhibitory effects of a phospholipase A2 inhibitor, mepacrine, on LPS-induced PGE2 formation. Possible roles for phospholipase C-dependent activation of PGE2 synthesis by LPS seemed unlikely, as LPS did not elevate the cytosolic free calcium concentration or augment the appearance of water-soluble inositol phosphates. We conclude that LPS-induced PGE2 synthesis in rat glomerular mesangial cells is mediated through a G-protein-coupled phospholipase A2 activation. The activation of phospholipase A2 releases arachidonic acid and stimulates PGE2 synthesis preferentially, thereby improving glomerular hemodynamic events in endotoxemia.
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PMID:Involvement of a pertussis toxin-sensitive G-protein-coupled phospholipase A2 in lipopolysaccharide-stimulated prostaglandin E2 synthesis in cultured rat mesangial cells. 314 15

The mechanisms of activation of cytoplasmic phospholipase A2 (cPLA2) are complex and incompletely defined. In Chinese hamster ovary (CHO) cells, receptor stimulation of cPLA2 is due to the interaction of pathways involving the alpha subunits of at least two guanine-nucleotide-binding (G) proteins, G alpha i2 and G alpha q. Activation of cPLA2 is inhibited by pertussis toxin and G alpha i2 mutants. In addition, activation of phospholipase C via G alpha q results in increased intracellular calcium ([Ca2+]i) and activation of protein kinase C, both of which interact with and activate cPLA2. The present study was undertaken to analyze the mechanism of interaction of G alpha i2 with the phospholipase-C-stimulated pathway in the activation of cPLA2. We addressed this question using a dominant negative G alpha i2 mutant, [G203T]G alpha i2, in which Gly203 is mutated to Thr. [G203T]G alpha i2 inhibits ATP receptor activation of cPLA2. The effect of [G203T]G alpha i2 was specific to G alpha i2-activated pathways, as shown by its lack of effect on other purinergic receptor stimulated pathways: ATP stimulation of [Ca2+]i or mitogen-activated protein kinase phosphorylation is unaltered by [G203T]G alpha i2. We addressed the possibility that the activation of cPLA2 by Ca2+ and/or protein kinase C is dependent on G alpha i2. Activation of cPLA2 by the Ca2+ ionophore, ionomycin, was inhibited by 61 +/- 9% (n = 5) in [G203T]G alpha i2-expressing cells; however the ionomycin-induced [Ca2+]i rise was unaffected by [G203T]G alpha i2. Thus, [G203T]G alpha i2. specifically inhibits Ca2+ activation of cPLA2. In contrast, activation of cPLA2 via protein kinase C by phorbol 12-myristate 13-acetate was unaffected by [G203T]G alpha i2. Our results demonstrate that Ca2+ but not phorbol ester activation of cPLA2 in CHO cells is G alpha i2-dependent. The possibility is discussed that G alpha i2 is downstream of Ca2+ but upstream of protein kinase C activation of cPLA2.
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PMID:The guanine-nucleotide-binding protein subunit G alpha i2 is involved in calcium activation of phospholipase A2. Effects of the dominant negative G alpha i2 mutant, [G203T]G alpha i2, on activation of phospholipase A2 in Chinese hamster ovary cells. 760 Oct 96

We have shown previously that guinea pig alveolar macrophages (AM) synthesize a secretory phospholipase A2 (PLA2) during in vitro incubation. Here, we report the molecular cloning of this enzyme and show that it has structural features closely related to all known mammalian type-II PLA2. The mRNA and PLA2 activity were undetectable in freshly collected AM, but their levels increased dramatically to reach maximal values after 16 h of culture. Thereafter, the PLA2 activity remained constant with a parallel secretion in the medium, in contrast to mRNA level which returned to near basal values after 32 h. Incubation of AM for 16 h with the inflammatory secretagogue peptide f-Met-Leu-Phe (fMLP) markedly reduced the PLA2 activity and mRNA levels. This inhibition was prevented by preexposure of AM to pertussis toxin, an inhibitor of G-protein. In contrast, when AM were first cultured for 16 h and then incubated with fMLP, no significant change was observed in their PLA2 activity. In conditions where the type-II PLA2 was completely abrogated by fMLP, the latter did not alter the lipopolysaccharide-induced accumulation of tumor necrosis factor alpha mRNA or the release of arachidonic acid induced by the subsequent addition of the calcium ionophore A23187. These studies show that the inflammatory peptide fMLP down-regulates the expression of the type-II PLA2 by AM through a process mediated by G-protein. A possible negative control of the type-II PLA2 expression during AM activation is suggested.
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PMID:Expression of the type-II phospholipase A2 in alveolar macrophages. Down-regulation by an inflammatory signal. 761 34

Recent studies have shown that Ca2+ mobilization in longitudinal muscle is initiated by inositol 1,4,5-trisphosphate (IP3)-independent Ca2+ influx that acts as a trigger for Ca(2+)-induced Ca2R release. The present study examined whether arachidonic acid (AA) acts as mediator of the initial Ca2+ influx. Cholecystokinin octapeptide caused transient concentration-dependent increase in AA release in dispersed intestinal longitudinal but not circular muscle cells followed by sustained increase in both muscle cell types. The initial increase in AA release coincided with the initial Ca2+ transient and muscle contraction: all three events were abolished by guanosine 5'-O-(2-thiodiphosphate), pertussis toxin (PTX), and the phospholipase A2 (PLA2) inhibitor, dimethyleicosadienoic acid, but were not affected by calphostin C or neomycin. Exogenous AA caused concentration-dependent contraction and increase in cytosolic free Ca2+ ([Ca2+]i) in longitudinal but not circular muscle cells; both events were abolished by Ca2+ channel blockers. Depletion of Ca2+ stores with thapsigargin attenuated with thapsigargin attenuated agonist- and AA-mediated increase in [Ca2+]i and contraction in longitudinal muscle cells: the residual [Ca2+]i increase (35%) and contraction (25%) reflected the component of Ca2+ influx. We conclude that AA released by agonist-mediated G protein-dependent PTX-sensitive activation of PLA2 mediates Ca2+ influx, which then triggers Ca(2+)-induced Ca2+ release. The process is independent of phosphatidylinositol hydrolysis and occurs exclusively in longitudinal smooth muscle, in which Ca2+ release channels are highly sensitive to Ca2+, ryanodine, and cyclic ADP-ribose and insensitive to IP3.
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PMID:Agonist-mediated activation of PLA2 initiates Ca2+ mobilization in intestinal longitudinal smooth muscle. 763 4

The steroid hormone 1,25(OH)2-vitamin D-3 [1,25(OH)2D3] stimulated phospholipase A2 (PLA2) activity in embryonic chick myoblasts releasing [3H]arachidonic acid from the sn-2 position of phospholipids. GTP-binding protein mediation of 1,25(OH)2D3-dependent PLA2 activity was investigated in cells prelabeled with [3H]arachidonic acid. AIF4-, a G-protein activator, mimicked 1,25(OH)2D3-stimulated arachidonic acid release from myoblasts in a dose-dependent manner. Consistent with the involvement of a G-protein in the activation of PLA2 by the hormone, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), a stable GTP analogue which activates G-protein mediated signals, strongly enhanced arachidonic acid release in myoblasts. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), which competitively inhibits G-protein activation by GTP and its analogues, abolished 1,25(OH)2D3-dependent arachidonic acid release. Bordetella pertussis toxin pretreatment significantly suppressed the hormone action whereas cholera toxin had minor effects on 1,25(OH)2D3 action. Hormone-induced activation of PLA2 was mimicked by the Ca2+ ionophore A23187 and blocked by nifedipine, but was unaffected by neomycin, a phospholipase C inhibitor, ruling out the contribution of phosphoinositide metabolism to arachidonic acid release. These results suggest that 1,25(OH)2D3-stimulation of PLA2 activity in embryonic chick myoblasts is mediated by a pertussis toxin-sensitive GTP-binding protein coupled to influx of extracellular calcium.
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PMID:1,25(OH)2-vitamin D-3 stimulates phospholipase A2 activity via a guanine nucleotide-binding protein in chick myoblasts. 764 3

In whole-cell patches of inferior colliculus neurons, ADP evoked outwardly rectifying potassium currents with a latency of < 1 sec via P2Y purinoceptor. These currents were blocked by GDP beta S, while not by pertussis toxin (PTX). Additionally, a selective protein kinase C inhibitor, GF109203X, or a selective phospholipase A2 inhibitor, BPB, had no effect on the currents. In outside-out patches, ADP elicited single channel currents with same slope conductances as those obtained in cell-attached patches and the currents were again blocked by GDP beta S. The results presented here indicate that the P2Y purinoceptor-operated potassium channel in inferior colliculus neurons is activated only by a plasma membrane component, most likely by a direct coupling to the beta gamma subunits of a PTX-insensitive G-protein.
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PMID:The P2Y purinoceptor-operated potassium channel is possibly regulated by the beta gamma subunits of a pertussis toxin-insensitive G-protein in cultured rat inferior colliculus neurons. 767 69

Previously, we have shown that alpha-2C and alpha-1A adrenergic receptors (AR) stimulate prostacyclin (PGI2) synthesis through a pertussis toxin-sensitive guanine nucleotide-binding protein (G protein) in vascular smooth muscle cells (VSMC). The purpose of this study was to assess the role of Ca++ in PGI2 production elicited by alpha-AR activation and to investigate the modulation of the Ca++ channel by G proteins coupled to these alpha-AR in VSMC. PGI2 was measured as immunoreactive 6-keto-PGF1 alpha by radioimmunoassay and cytosolic calcium ([Ca++]i) by spectrofluorometry using fura-2. Norepinephrine, methoxamine and UK-14304 enhanced 6-keto-PGF1 alpha production and [Ca++]i, which was inhibited by depletion of extracellular Ca++ and by Ca++ channel antagonists (verapamil, nifedipine and PN 200-110). Moreover, the Ca++ channel activator Bay K 8644 increased 6-keto-PGF1 alpha production in a nifedipine-sensitive manner, indicating the involvement of dihydropyridine-sensitive Ca++ channels in VSMC. Pertussis toxin inhibited AR agonist-induced 6-keto-PGF1 alpha production and the increase in [Ca++]i. Alpha AR agonists increase Ca++ influx in the presence of guanosine 5'-0-(2- thiodiphosphate) (GTP-gamma-S), and this effect was blocked in the presence of guanine 5'-O-(2-thiodiphosphate) (GDP-beta-S) and antiserum against Gi alpha 1-2 protein in reversibly permeabilized cells with beta-escin. VSMC of rabbit aortae contain a G protein(s) that was recognized by Gi alpha 1-2 but not Gi alpha 3 or G0 antibodies at 1:200 dilution. The calmodulin inhibitor W-7 blocked AR agonist and Bay K 8644-stimulated 6-keto-PGF1 alpha production. The phospholipase A2 inhibitors 7,7-dimethyleicosadienoic acid and oleoyloxyethyl phosphocholine but not phospholipase C inhibitor U-73122 reduced 6-keto-PGF1 alpha production in VSMC. These data suggest that a pertussis toxin-sensitive G protein, probably Gi alpha 1-2, coupled to alpha AR regulates Ca++ influx, which, in turn, by interacting with calmodulin, increases phospholipase A2 activity to release arachidonic acid for PGI2 synthesis in VSMC of rabbit aortae.
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PMID:Alpha adrenergic receptor subtypes involved in prostaglandin synthesis are coupled to Ca++ channels through a pertussis toxin-sensitive guanine nucleotide-binding protein. 768 1

The present study was designed to evaluate the effect of the activation of bradykinin (BK) receptors on intracellular cAMP levels in isolated glomeruli as well as in cultured rat mesangial cells. BK affected basal cAMP content only in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine. Furthermore, BK inhibited forskolin-, prostaglandin E2-, and isoproterenol-stimulated cAMP accumulation, both in the presence and in the absence of isobutylmethylxanthine. The inhibitory effect of BK was independent of stimulation of cAMP degradation by phosphodiesterase. No direct inhibition of the in vitro adenylyl cyclase activity was observed, suggesting a requirement for cytoplasmic constituents. Use of the phospholipase A2 inhibitor mepacrine and treatment with pertussis toxin did not modify the inhibitory effect of BK, indicating that neither the phospholipase A2 pathway nor the inhibitory G protein is involved. The effect of BK was completely prevented by two selective protein kinase C (PKC) inhibitors, staurosporine and bisindolylmaleimide. Furthermore, use of the diacylglycerol analog 1-oleoyl-2-acetyl-rac-glycerol and direct activation of PKC with phorbol-12-myristate-13-acetate mimicked the effect of BK, whereas the biologically inactive phorbol ester 4 alpha-phorbol-12, 13-didecanoate was without effect. Furthermore, down-regulation of PKC by long term pretreatment with phorbol-12-myristate-13-acetate abolished the inhibitory effect of BK on stimulated cAMP levels. These results demonstrate that BK inhibits forskolin-, prostaglandin E2-, and isoproterenol-stimulated cAMP formation through activation of the phospholipase C pathway. The subsequent production of diacylglycerol associated with stimulation of PKC in turn inhibits stimulated cAMP accumulation.
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PMID:Indirect inhibition by bradykinin of cyclic AMP generation in isolated rat glomeruli and mesangial cells. 769 69

Lysophosphatidylinositol has been previously shown to stimulate cell proliferation in differentiated and in K-ras transformed thyroid cells. Increased levels of lysophosphatidylinositol, but not lysophosphatidylcholine or lysophosphatidylethanolamine, are present in thyroid as well as in other ras-transformed cell lines. We have now investigated the mechanism of action of this lysolipid by analysing its effects in a differentiated thyroid cell line. Lysophosphatidylinositol did not increase the levels of cAMP, the main stimulator of cell proliferation in the thyroid, whereas it stimulated phosphoinositide breakdown, mobilization of cytosolic Ca2+ and arachidonic acid release, suggesting that it activates both phospholipases C and A2. None of the effects of lysophosphatidylinositol were prevented by pretreatment of cells with pertussis toxin. Instead, the tyrosine kinase inhibitors, tyrphostins AG18 and AG561, completely blocked its mitogenic action. The effects of lysophosphatidylinositol were distinguishable from those of the well known mitogen lysophosphatidic acid, which affected differently the signalling pathways analysed and was not mitogenic in ras-transformed cells. These results suggest that the mitogenic activity of lysophosphatidylinositol is associated with the activation of phospholipase C and phospholipase A2 and is relatively specific for ras-transformed cells.
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PMID:Signalling pathways involved in the mitogenic action of lysophosphatidylinositol. 778 56

The serotonin 5-HT2C receptor (formerly designated the 5-HT1C receptor) of the choroid plexus triggers phosphoinositide turnover. In the present study, we demonstrate that receptor activation also triggers the formation of cyclic GMP (cGMP). Application of 1 microM 5-HT to porcine choroid plexus tissue slices resulted in stimulation of cGMP formation to a maximum of five-fold basal level, with an EC50 of 11 nM. This response was not inhibited by muscarinic or beta-adrenergic receptor antagonists. Serotonin receptor antagonists inhibited cGMP formation with apparent Ki values of 1.3 (mianserin), 200 (ketanserin), and 5,500 (spiperone) nM, respectively. Neither serotonin-stimulated cGMP formation nor PI turnover was inhibited by pertussis toxin pretreatment. Preliminary biochemical studies suggested that serotonin-stimulated cGMP formation was calcium, phospholipase A2, and lipoxygenase dependent, as incubation in low calcium buffers or inclusion of the phospholipase A2 or lipoxygenase inhibitors p-bromophenacylbromide or BW 755c resulted in significant reduction of cGMP formation. The present results suggest that in addition to triggering phosphoinositide turnover, choroid plexus serotonin 5-HT2C receptors trigger cGMP formation in a calcium-sensitive manner.
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PMID:Serotonin 5-HT2C receptor stimulates cyclic GMP formation in choroid plexus. 779 14


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