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)

The heat shock response in mammals consists of a complex array of intracellular reactions initiated by stress, although its regulation is poorly understood. We have investigated the role of transmembrane signal transduction in the response, examining mechanisms involved in the activation of phospholipase C (PLC) by heat shock. In rodent fibroblasts permeabilized with digitonin, heat shock and receptor-mediated PLC activity exhibited a strict GTP analog dependency. This indicates that heat shock-mediated phospholipase activation, in common with receptor mediated stimulation, does not involve direct effects on the phospholipases and suggests the participation of GTP binding (G) proteins in the activation process. When cells were treated with the inhibitor pertussis toxin (PTX), the phospholipases retained their inducibility by heat shock, but became refractory to thrombin treatment, indicating that heat shock may influence PLC activity through a distinct population of G proteins compared to thrombin. The data seem to exclude a role for PTX sensitive G proteins in the production of IP3 after heating and suggest a pathway involving the direct thermal activation of the Gq class of G proteins, which are coupled to the PLC beta 1 isoform.
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PMID:Activation of phospholipase C by heat shock requires GTP analogs and is resistant to pertussis toxin. 831 54

C. difficile toxin B is a potent cytotoxin known to disrupt the microfilaments of cultured cells. We have recently shown also increased phospholipase A2 activity in cells treated with toxin B. The activity was detected as a toxin-induced, dose-dependent release of 14C-arachidonic acid from prelabeled fibroblasts. Here is shown that the toxin elicited a 14C-arachidonic acid release in a cell mutant resistant to the toxin B effect on the microfilaments. The toxin-induced release was further characterized using fibroblasts. Within 20 min high doses of toxin B (6 micrograms/ml) elicited a release which increased exponentially with time. Of the major membrane phospholipids the lipase activity affected mainly phosphatidyl ethanolamine. Neither cycloheximide nor pertussis toxin treatment or target cells inhibited the toxin-induced release, while it could be increased with 12-O-tetradecanoylphorbol-13-acetate. Our results also suggest a toxin-mediated increase in phospholipase C activity occurring at a later stage than the phospholipase A2 activation. We conclude that the ability of toxin B to induce phospholipase activation represents a hitherto unrecognized toxin B effect which is neither a cause nor a consequence of toxin-induced microfilament disorganization.
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PMID:Activation of cellular phospholipase A2 by Clostridium difficile toxin B. 832 Feb 70

Bombesin-like peptides including neuromedin B have been proposed as autocrine or paracrine growth factors for carcinomas. To examine signal transduction and regulation of cell growth by NMB, transfectants were created with the rat NMB receptor (NMB-R) gene in BALB/3T3 cells which do not express an endogenous bombesin peptide receptor. The resultant cell line, NMB-8, expresses 800,000 NMB binding sites/cell. Addition of NMB has a biphasic effect on [3H]thymidine ([3H]dT) incorporation in confluent and quiescent cells: up to 10 nM of NMB causes a 1.5-3-fold stimulation of [3H]dT incorporation, but at greater than 10 nM there is inhibition of [3H]dT incorporation, and at 100 nM of NMB there is inhibition of cell growth. NMB causes protracted increases in intracellular Ca2+, and pertussis toxin (PT)-insensitive phosphatidylinositol (PI) turnover. NMB-mediated increase in membrane phospholipase-C activity is stimulated by guanosine 5'-O-(3-thiotriphosphate). Arachidonate release is also activated by NMB in a PT-insensitive manner. Brief exposure to 12-tetradecanoylphorbol 13-acetate inhibits NMB-mediated PI turnover but not arachidonate release. Thus, in NMB-8 cells, distinct mechanisms govern NMB-mediated phospholipase-C activation and arachidonate release. Also, neuromedin-B is potentially a bifunctional regulator of cell growth.
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PMID:Neuromedin-B receptor transfected BALB/3T3 cells: signal transduction and effects of ectopic receptor expression on cell growth. 839 94

The pertussis toxin-insensitive G proteins that stimulate phosphoinositide phospholipase C consist of 42- and 43-kDa alpha-subunits, 35-kDa beta-subunits and 8-kDa gamma-subunits. The alpha-subunits have been identified as alpha q and alpha 11, and both specifically stimulate the beta 1 isozyme of the phospholipase. Activation of Ca(2+)-mobilizing receptors in liver plasma membranes selectively induces the labelling of alpha q and alpha 11 by [alpha-32P]GTP-azidoanilide. Reconstitution of Gq and G11 with M1 muscarinic receptor and the beta 1 isozyme allows GTP gamma S-dependent stimulation of PtdInsP2 hydrolysis by carbachol. These data establish unequivocally that Gq and G11 function as the transducing G proteins for Ca(2+)-mobilizing receptors.
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PMID:Role of G proteins in activation of phosphoinositide phospholipase C. 839 19

Nerve fibers immunoreactive for cholecystokinin (CCK) have been observed in the rat ovary, but the function of this gut peptide in the ovary is not known. These studies were designed to investigate the effects of the CCK C-terminal octapeptide (CCK-8) on the intracellular calcium ion concentration ([Ca2+]i), protein kinase-C (PKC) activity, and progesterone secretion in granulosa cells obtained from the two largest preovulatory follicles (F1 and F2) of hens. [Ca2+]i was measured in cells loaded with the Ca(2+)-responsive fluorescent dye fura-2. The resting [Ca2+]i in these cells was 96 +/- 5 nM. There was a rapid (i.e. within 5-10 sec) 2- to 4-fold increase in [Ca2+]i in 70% of the cells examined after the addition of 10(-7) M CCK-8. The CCK-8-triggered [Ca2+]i transient was not affected by incubating the cells in Ca(2+)-free medium containing 2 mM EGTA or by pretreating the cells with a Ca2+ channel blocker, such as La3+ (1 mM) or D600 (100 microM). The CCK-8-triggered [Ca2+]i surge was abolished by pretreating the cells with the inhibitor of inositol phospholipid hydrolysis, neomycin (1.5 mM), the CCK antagonists proglumide (1 mM) and benzotript (1 mM), or pertussis toxin (50 ng/ml for 12 h). Incubating granulosa cells with CCK-8 (2 x 10(-7) M) for 10 min stimulated a 1.60 +/- 0.04-fold increase in membrane-associated PKC activity over control levels. In 3-h incubations, CCK-8 (10(-6)-10(-8) M) did not affect basal or LH (20 or 100 ng/ml-stimulated progesterone production. These studies demonstrate that CCK-8 causes a transient increase in chicken granulosa cell [Ca2+]i through the release of Ca2+ from intracellular stores and activates membrane-associated PKC activity, but does not affect progesterone production. These results suggest the presence of G-protein-coupled phospholipase-C-activating CCK receptors on the surface of these cells.
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PMID:The effect of cholecystokinin on intracellular Ca2+, membrane-associated protein kinase-C activity, and progesterone production in chicken granulosa cells. 840 42

IK(Ca) activated by intracellular ionophoresis of inositol trisphosphate (IP3) or pressure-applied acetylcholine was inhibited by bradykinin and acetylcholine in NG108-15 cells transfected with m1 receptors. The inhibition of the IP3-evoked current was complete at 10 microM acetylcholine. This inhibition was not seen if the current was evoked by intracellular ionophoresis of calcium ions. Only receptors the activate the phosphoinositide system in these cells produced this inhibition, i.e. transfected muscarinic m1 and m3 and bradykinin receptors, but not muscarinic m2, m4 or adrenergic alpha 2 receptors. This inhibition was not sensitive to pertussis toxin or staurosporine. The concentrations of acetylcholine needed to inhibit the evoked current were identical to those needed to raise intracellular calcium but tenfold less than those needed for the agonist to activate IK(Ca). In a normal calcium-containing superfusate, recovery from inhibition required around 8 min (half-time 4 min) after removal of acetylcholine. When the experiment was performed in calcium-free medium no recovery was seen after 8 min washing in drug-free solution, but complete recovery was seen within 3 min (half-time 1.5 min) after adding calcium. Responses to repeated pressure applications of acetylcholine could be reversibly inhibited by acetylcholine and bradykinin. It seems, then, that there is no direct action of acetylcholine or bradykinin on the IK(Ca) channels themselves but that concentrations below those needed to activate IK(Ca) can empty and inhibit the IP3-sensitive calcium store. This may provide a mechanism for heterologous desensitization for phospholipase-C-linked receptor-mediated responses.
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PMID:Agonist-induced inhibition of inositol-trisphosphate-activated IK(Ca) in NG108-15 neuroblastoma hybrid cells. 843 87

Muscarinic acetylcholine receptor subtypes (m1-m5) differentially regulate phosphoinositide-specific phospholipase (PLC) through the activation of distinct guanine nucleotide-binding (G) proteins which can be distinguished on the basis of their sensitivity to inhibition by pertussis toxin (PTX). In transfected Chinese hamster ovary cells, the m2 receptor subtype regulates the stimulation of PLC and inhibition of adenylyl cyclase (AC) through PTX-sensitive G proteins. In this study, we utilized the ability of cholera toxin (CTX) to ADP-ribosylate PTX-sensitive alpha subunits as part of the ternary complex formed by heterotrimeric G proteins and agonist-bound receptors to detect and characterize the interactions between transfected m2 receptors and endogenous G proteins in Chinese hamster ovary cells. In membranes derived from cells expressing the m2, but not the m3 receptor, the cholinergic agonist carbachol stimulated CTX modification of a 40-kDa species (G alpha 40). Importantly, similar carbachol dose dependence values and PTX dose sensitivities were observed for m2 receptor-mediated PLC signaling and G alpha 40-CTX modification. High resolution urea-SDS-polyacrylamide gel electrophoresis analysis revealed that G alpha i2 (40 kDa) and G alpha i3 (41 kDa) were components of the G alpha 40 identified by m2 receptor-dependent CTX modification. Furthermore, the sensitivities of G alpha i2 and G alpha i3 to PTX modification were determined to be the same as those for PTX inhibition of G alpha 40 labeling by CTX and m2 receptor-mediated PLC signaling. Similarly, agonist-induced desensitization of m2 receptor-G protein signaling required doses of agonist associated with stimulation of PLC. Desensitization involved receptor sequestration and down-regulation of G alpha i3; however, only the reduction of G alpha i3 required prior activation PLC signaling. Finally, desensitization of m2-G protein coupling could be partially mimicked by treatment with thapsigargin, an inducer of intracellular Ca2+ release, without altering the number of cell surface receptors or G protein levels. These results demonstrate that m2 receptors couple to both G alpha i2 and G alpha i3 in vivo and that this interaction is integral to both positive and negative regulatory pathways leading to activation of PLC and desensitization of receptor signaling.
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PMID:Transfected m2 muscarinic acetylcholine receptors couple to G alpha i2 and G alpha i3 in Chinese hamster ovary cells. Activation and desensitization of the phospholipase C signaling pathway. 844 30

Of the various arachidonate cyclooxygenation eicosanoids synthesized in the normal and injured renal glomerular capillary, prostaglandin F2alpha (PGF2alpha) is the most abundant and potent in eliciting signaling events and biologic responses including contraction and proliferation of glomerular capillary pericytes known as mesangial cells. The regulation of PGF2alpha-induced signaling in these cells is unknown. The present studies assessed two key signaling events in response to PGF2alpha in mesangial cells; activation of phospholipase C (PLC) and protein kinase C (PKC). Mechanisms regulating PLC activation were also explored. Incubation of cultured growth arrested rat mesangial cells with PGF2alpha (1 microM) resulted in activation of a phosphatidyl inositol-specific phospholipase C (PI-PLC) assessed as increased generation of polyphosphates in myo-[3H]-inositol-labeled cells and as increased diacylglycerol (DAG) mass levels measured by a radioenzymatic assay. Generation of both inositol 1,4,5-trisphosphate and inositol 1,3,4-trisphosphate occurred, the former constituting 70% of total inositol trisphosphates. Enhanced generation of inositol 1,4-bisphosphate (IP2) also occurred and was greater than that of inositol 1,4,5-trisphosphate (IP3), indicating that PI-PLC utilized the phosphatidyl inositol monophosphate (PIP) to a greater extent than the phosphatidyl inositol bisphosphate (PIP2) substrate. Generation of DAG in response to PGF2alpha occurred in a biphasic pattern characterized by an early transient rise that peaked concomitantly with IP3 at 15 sec, and a late sustained increase at 2, 5, and 15 min that was not associated with an increase in IP3. PGF2alpha also activated PKC assessed as translocation of enzyme activity from cytosolic to membrane fractions. Inhibition of PKC using H-7 enhanced PGF2alpha-induced generation of IP3 at 15 sec but attenuated generation of DAG at 15 min. A more selective PKC inhibitor, Calphostin C, dose-dependently increased basal IP3 generation and also attenuated generation of DAG in response to PGF2alpha. This indicates that PKC negatively modulates PGF2alpha-induced PI-PLC activation, and that the late sustained DAG generation in response to PGF2alpha is regulated by a PKC-dependent phospholipase other than PLC. The mechanisms of PI-PLC stimulation in response to PGF2alpha were further explored using inhibitors of protein tyrosine phosphorylation and of guanine nucleotide-binding (G) protein activation. Inhibition of protein tyrosine phosphorylation using genistein had no effect on IP3 or DAG generation. ADP ribosylation of Gi using pertussis toxin (PTx) had no effect on IP3 generation in response to PGF2alpha. The inhibitor of receptor-coupled PI-PLC activation aminosteroid compound U-73122 that blocks G(PLC) was also ineffective. The observations indicate that PGF2alpha stimulates a PI-PLC which is under negative feedback regulatory control by PKC, and a phospholipase other than PLC which is under positive regulatory control by PKC. PGF2alpha-induced PI-PLC activation is independent of protein tyrosine phosphorylation and of PTx-sensitive G proteins.
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PMID:PGF2alpha-induced signaling events in glomerular mesangial cells. 865 Feb 55

Since previous studies had indicated a role for tyrosine kinases in alpha 2-adrenoceptor-induced contractile responses in other blood vessels, as well as in the activation of phospholipase D, we examined the sensitivity of these responses in rat aorta to the tyrosine kinase inhibitor genistein. Contractions induced by both noradrenaline and the alpha 2-adrenoceptor-selective agonist UK14304 (5-bromo-6-[2-imidazolin-2-yl-amino]-quinoxaline) were fully inhibited by genistein, with the latter responses being more sensitive. Contractions induced by high K+ buffer were also inhibited, but to a lesser extent. Both agonists caused a stimulation of phospholipase D activity, which could be blocked by pretreatment with pertussis toxin, indicating involvement of either Gi or Go. Genistein completely inhibited the agonist-induced phospholipase D activity and also substantially reduced the basal level of phospholipase D activity. Pretreatment with either the alpha 1-adrenoceptor antagonist prazosin or the alpha 2-adrenoceptor antagonist rauwolscine was also effective in eliminating the agonist-induced increase of phospholipase D. These results indicate that a tyrosine kinase-regulated phospholipase D plays a critical role in alpha-adrenoceptor-induced contractions of the rat aorta and that stimulation of both alpha 1- and alpha 2-adrenoceptors is essential to allow phospholipase activation.
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PMID:A tyrosine kinase regulates alpha-adrenoceptor-stimulated contraction and phospholipase D activation in the rat aorta. 879 Oct 6

1. Prostaglandin E2 (PGE2) is an autacoid that decreases proteoglycan synthesis, increases metalloprotease production by cultured chondrocytes, and can modulate some of the actions of interleukin-1 on cartilage. The objective of the present study was to characterize the subtype of prostaglandin E2 receptor present in bovine chondrocytes in culture. 2. Primary cultures of articular chondrocytes were prepared from slices of bovine carpal cartilage by sequential digestion with type III hyaluronidase, trypsin, type II collagenase, followed by overnight incubation in Dulbecco's Modified Eagle's Medium (DMEM) with type II collagenase, washing, and seeding at a density of 2 x 10(5) cells cm-2 in DMEM with 10% foetal bovine serum. 3. PGE2 and carbaprostacyclin induced dose-dependent increases in intracellular cyclic AMP in bovine chondrocytes in culture. The potencies of these compounds were different, and maximal doses of PGE2 and carbaprostacyclin had an additive effect. PGD2 induced a small increase in intracellular cyclic AMP only at a high concentration (10(-5) M). 4. PGE2 was more potent that the EP2 agonist 11-deoxy-PGE1 at inducing increases in intracellular cyclic AMP. The EP2 agonist butaprost, however, induced only a small increase at a concentration of 10(-5)M. 17-Phenyl-PGE2 (EP1 agonist), sulprostone and MB 28767 (15S-hydroxy-9-oxo-16-phenoxy-omega-tetranorprost-13E-enoic acid) (EP3 agonists) did not induce an increase in intracellular cyclic AMP at concentrations up to 10(-5)M. 5. The EP4 antagonist AH 23848B ([1 alpha(Z),2 beta, 5 alpha]-(+/-) -7-[5-[[(1,1'-biphenyl)-4-yl]methoxyl-2-(4-morpholinyl) -3-oxocyclopentyl]-5-heptenoic acid) antagonized PGE2 but not carbaprostacyclin effects on intracellular cyclic AMP. The Schild plot slope was different from 1 but this could be due to an interaction of PGE2 with IP receptors in high doses. The exact nature of the antagonism by compound AH 23848B could not be definitely established in these experimental conditions. 6. Neither PGE2 nor any of its analogues inhibited the increase in intracellular cyclic AMP induced by forskolin, and pertussis toxin did not alter the response to PGE2, suggesting that no Gi-coupled PGE2 receptors are present in these cells. Stimulation with PGE2 did not induce significant increases in intracellular inositol-trisphosphate levels nor increases in intracellular free calcium as determined by confocal microscopy, suggesting the absence of phospholipase-C-coupled or of calcium channel-coupled PGE2 receptors in bovine chondrocytes in these experimental conditions. 7. These results show for the first time that bovine chondrocytes in culture present a functional PGE2 receptor that has some pharmacological characteristics of an EP4 subtype, as well as an IP receptor.
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PMID:Characterization of the PGE2 receptor subtype in bovine chondrocytes in culture. 884 20


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