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)

Calcium currents can be modulated by receptor activation of the GTP-binding protein G(o). We have determined whether the two forms of G(o), Go1 and Go2, differentially regulate calcium current magnitude. Using identified neurons of the pond snail Helisoma, we demonstrate that a high-voltage-activated (HVA) calcium current is reduced by addition of the neuropeptide Phe-Met-Arg-Phe-amide (FMRFamide) and that this inhibition is mediated by a pertussis toxin (PTX)-sensitive G protein pathway. Using this calcium current as an assay for G protein activity, we microinjected GTP gamma S-activated alpha-subunits of G proteins into neuronal somata. We demonstrate that the calcium current is differentially regulated by the two forms of alpha o. Microinjection of alpha o2*, but not alpha o1*, reduces calcium current magnitude.
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PMID:Microinjection of the alpha-subunit of the G protein Go2, but not Go1, reduces a voltage-sensitive calcium current. 141 84

1. The modulation of the voltage-activated Ca2+ current by the neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFa) was investigated in dissociated central neurons from Helix aspersa using whole-cell voltage-clamp recording techniques. External Ba2+ was always used as the charge carrier in this study, and the intracellular Ca2+ concentration was buffered to 20 nM with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). 2. Run-down of the Ca2+ currents was not a problem as long as the neurons were dialyzed with a patch electrode filling solution containing ATP (1 or 2 mM). In ATP-dialyzed neurons, the rate of inactivation of the calcium current increased with time without any significant change in the rate of activation. However, when neurons were dialyzed with guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; 100 microM; with ATP), the rate of inactivation decreased with time. There was no effect of GTP gamma S on the rate of activation of the Ca2+ current. This suggests that guanosine 5'-triphosphate (GTP)-binding proteins (G proteins) are able to modulate the rate of inactivation of the Ca2+ current in Helix neurons. 3. FMRFa both decreased and enhanced the amplitude of the Ca2+ current in these neurons. This inhibition was observed in most neurons, while the enhancement was observed in 20% of the neurons. Although the enhancement usually was preceded by the inhibitory response, sometimes the enhancement was observed separately. 4. The FMRFa-induced inhibition of the Ca2+ current usually consisted of a decrease in both the amplitude and the rate of inactivation of this current, effects that were reduced as the membrane potential was stepped to more depolarized potentials. A pertussis toxin (PTX)-sensitive G protein mediated this response, whereas no evidence was found to suggest the involvement of any known intracellular messenger. Therefore this inhibition may have resulted from a direct coupling between the FMRFa receptor and the Ca2+ channels via a PTX-sensitive G protein. 5. Arachidonic acid (100 microM) irreversibly reduced the amplitude of the Ca2+ current, but it did not alter the relative inhibition of this current by FMRFa. 6. The FMRFa-induced enhancement of the Ca2+ current was difficult to study because it was observed infrequently, and was rarely observed independently of the FMRFa-induced inhibitory response. In addition, the ability of FMRFa to enhance this current usually disappeared with time.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The neuropeptide FMRFa both inhibits and enhances the Ca2+ current in dissociated Helix neurons via independent mechanisms. 165

Human polymorphonuclear neutrophils (PMN) respond to ATP with an elevation in intracellular calcium and a marked enhancement of O2-production in response to stimulation by the chemotactic peptide N'-formyl-Met-Leu-Phe (FMLP). These pertussis toxin-sensitive pathways appear to be mediated by a nucleotide receptor(s) on the surface of human PMN. In the current study, we have examined the binding to intact human PMN of the ATP analog, adenosine 5'-O-(3-thio[35S] triphosphate) [( 35S]ATP gamma S). On the basis of Scatchard analysis, the binding of [35S]ATP gamma S involves at least two sites, one of high and one of low affinity. In the presence of sodium thiophosphate, a compound which did not affect intracellular increases in calcium induced by ATP or N'-formyl-Met-Leu-Phe, a significant fraction of the [35S]ATP gamma S binding was eliminated. This reduction involved both high and low affinity binding of [35S]ATP gamma S and was related to a reduction in numbers of binding sites. The Kd values for the high affinity binding site were unaffected by the presence of sodium thiophosphate, although the low affinity Kd values were numerically increased by 2-fold. In the presence of thiophosphate, [35S]ATP gamma S binding was specific, saturable, and reversible, and was related to a single class of high affinity (Kd = 36 +/- 19 nM) binding sites (184 +/- 144 sites/cell), together with a second class of low affinity (Kd = 1110 +/- 503 nM) binding sites (13,562 +/- 6,851 sites/cells). Competitive binding experiments, based on the ability of nucleotides and ATP analogs to block [35S]ATP gamma S binding to PMN, revealed a rank order of ATP gamma S greater than ATP greater than 2-MeS-ATP = 8-Bromo ATP greater than ADP = ITP greater than AMP-PCP = GTP much greater than CTP. A comparison between the ability of nucleotides to compete with [35S]ATP gamma S binding and their ability to induce a biologic response (elevation of intracellular calcium) revealed a close correlation (r2 = 0.83). These findings support the possibility of a common nucleotide PMN receptor functionally linked to a cellular response which involves increases in intracellular calcium.
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PMID:Adenosine-5'-O-(3-thiotriphosphate) binding to human neutrophils. Evidence for a common nucleotide receptor. 165 77

The alpha-subunit of Gi-2, in addition to that of Gs (GTP-binding proteins involved in adenylate cyclase inhibition and stimulation, respectively) was ADP-ribosylated by cholera toxin in HL-60 cell membranes when a chemotactic receptor was stimulated by formyl-Met-Leu-Phe (fMLP), and the sites modified by cholera and pertussis toxins on the alpha-subunit of Gi-2 were different (Iiri, T., Tohkin, M., Morishima, N., Ohoka, Y., Ui, M., and Katada, T. (1989) J. Biol. Chem. 264, 21394-21400). In order to investigate how the functions of Gi-2 were modified by cholera toxin, the ADP-ribosylated and unmodified proteins were purified from HL-60 cell membranes that had been incubated in the presence and absence of cholera toxin, respectively. The modified Gi-2 displayed unique properties as follows. 1) The ADP-ribosylated alpha-subunit had a more acidic pI than the unmodified one, leading to a partial resolution of the modified Gir2 trimer from the unmodified protein by an anion column chromatography. 2) When the purified proteins were incubated with [gamma-32P]GTP, the radioactivity was more greatly retained in the modified Gi-2 than in the unmodified protein. 3) The actual catalytic rate (kcat) of GTP hydrolysis was, indeed, markedly inhibited by cholera toxin-induced modification. 4) There was an increase in the apparent affinity of Gi-2 for GDP by cholera toxin-induced modification. 5) The modified Gi-2 exhibited a low substrate activity for pertussis toxin-catalyzed ADP-ribosylation. 6) A high-affinity fMLP binding to HL-60 cell membranes was more effectively reconstituted with the ADP-ribosylated Gi-2 than with the unmodified protein. These results suggested that the agonist-fMLP receptor complex was effectively coupled with the ADP-ribosylated Gi-2, resulting in the GTP-bound form, and that the hydrolysis of GTP on the modified alpha-subunit was selectively attenuated. Thus, cholera toxin ADP-ribosylated Gi-2 appeared to be not only a less sensitive pertussis toxin substrate but also an efficient signal transducer between receptors and effectors.
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PMID:Modification of the function of pertussis toxin substrate GTP-binding protein by cholera toxin-catalyzed ADP-ribosylation. 173 Jun 31

Since human polymorphonuclear neutrophils (PMN) exposed to ATP or its poorly hydrolyzable analogue, adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S), respond with increases in intracellular calcium and enhanced O2- responses to the chemotactic peptide N'-formyl-Met-Leu-Phe (fMLP), we systematically evaluated responses of PMN to various nucleotides. The P2X and P2Y receptor agonists, 2-methylthioadenosine triphosphate and beta, gamma-methyleneadenosine triphosphate, failed to induce increases in intracellular calcium and did not desensitize PMN to increases in intracellular calcium induced by ATP gamma S. Since it has been suggested that P2Z receptor occupancy with the ATP4- species caused nonselective increases in cell permeability, the ability of ATP to induce increases in intracellular calcium was evaluated in the presence and absence of extracellular Ca2+ and Mg2+. In the presence of these cations, 5-fold greater concentrations of ATP were required. The effects of ATP4- were not associated with changes in cell membrane permeability. This suggests that ATP4- is the active species but that its effect on PMN is not linked to a nonselective increase in permeability of the cell membrane. With respect to responses of PMN to purine and pyrimidine nucleotides as defined by increases in intracellular calcium, the rank order of potency for the nucleotides was ATP = UTP greater than ATP gamma S greater than or equal to ITP greater than GTP greater than or equal to CTP. These responses were blocked by pretreatment of PMN with pertussis toxin. Prior exposure of PMN to ATP gamma S blocked cellular responses (calcium increases) to these nucleotides but not to fMLP. Likewise, exposure of PMN to any nucleotides blocked subsequent cellular responses to ATP gamma S but not to fMLP. These data support the concept that nucleotide responses of PMN utilize either a common receptor or a common signal transduction pathway involving a guanine nucleotide binding protein in events leading to elevations in intracellular calcium. Nucleotide interaction with PMN does not follow the established pattern of responses associated with P2X or P2Y purinergic receptor occupancy.
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PMID:Nucleotide responses of human neutrophils. 184 54

Stimulation by N-formyl-Met-Leu-Phe (fMLP) of rabbit peritoneal neutrophils, in which phosphatidylcholine was preferentially labeled with 1-O-[3H]octadecyl lyso platelet-activating factor, activated phospholipase D, resulting in the formation of [3H]PA from [3H]PC. A direct activator of GTP-binding proteins (G-proteins), NaF, also stimulated [3H]PA formation. fMLP-stimulated [3H]PA formation was inhibited by pertussis toxin (IAP) in a time- and dose-dependent manner. IAP also inhibited fMLP-stimulated IP3 formation, but the inhibition of IP3 formation was significantly greater than that of [3H]PA formation. These results indicate that activation of phospholipase D by fMLP in rabbit neutrophils is mediated by an IAP-sensitive G-protein that may be distinct from a phospholipase C-regulating protein.
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PMID:Activation of phospholipase D in rabbit neutrophils by fMet-Leu-Phe is mediated by a pertussis toxin-sensitive GTP-binding protein that may be distinct from a phospholipase C-regulating protein. 184 91

We investigated the requirement for N-formyl peptide receptor-mediated transmembrane signalling in transfected mouse fibroblasts that express the receptor. Stably transfected cells displayed specific binding for N-formyl-Met-Leu-[3H]Phe with a dissociation constant of 3 nM. The cells responded to ligand stimulation with mobilization of calcium from intracellular stores. Calcium mobilization was ligand dose-dependent (EC50 = 3 nM fMet-Leu-Phe) and could be inhibited by pertussis toxin treatment. These results provide the first demonstration that expression of the single-chain N-formyl peptide receptor in mouse fibroblasts is sufficient for mediating ligand-induced early transmembrane signalling events, which do not appear to require other neutrophil-specific cellular components.
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PMID:Transmembrane signalling by the N-formyl peptide receptor in stably transfected fibroblasts. 188 72

Human polymorphonuclear leukocytes (PMN) respond via pertussis toxin-sensitive pathways to extracellular nucleotides with an elevation in intracellular calcium ([Ca2+]i) and enhancement of the O2- generation induced by the chemotactic peptide N'-formyl-Met-Leu-Phe (fMLP). Binding studies with adenosine 5'-O-(3-thio[35S]triphosphate) ([35S]ATP gamma S) have recently identified at least two classes of receptors on intact human neutrophils. In this study, we further characterize nucleotide binding to this receptor with respect to its specific structural requirements. Utilizing [35S]ATP gamma S as the primary ligand and various nucleotides and ATP analogues, competitive binding studies demonstrate that: (1) the triphosphate tail is essential for maximal receptor binding; (2) chemical modifications of the phosphate tail have profound effects on binding efficacy; (3) the base ring is recognized by the receptor, with purines being preferentially recognized; and (4) except for a spacing function, the ribose ring of nucleotides does not appear to be important for nucleotide binding. In addition, we demonstrate that the presence of divalent cations inhibits [35S]ATP gamma S binding, suggesting that the tetraanionic form of ATP (ATP4-) is the nucleotide species reactive with the receptor.
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PMID:Structural requirements for binding of adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S) to human neutrophils. 228 71

Vasoactive intestinal polypeptide (VIP) was incubated in an adenylate cyclase assay with a particulate fraction of caudate-putamen (CP) tissue of the rat in order to examine the effect of the peptide on forskolin-activated adenylate cyclase in vitro. Forskolin induced an enhancement of cyclic AMP formation that was mediated by an effect on catalytic subunit and stimulatory guanine nucleotide regulatory protein (Ns). In our preparation, VIP did not influence basal adenylate cyclase activity or the stimulation by dopamine and sodium fluoride but, in the absence of guanylylimidodiphosphate (guanosine 5'-(beta, y-imido)-triphosphate) VIP inhibited the forskolin-stimulation of the enzyme in a noncompetitive manner. Met-encephalin, acting on a D-2 receptor-coupled putative inhibitory guanine nucleotide regulatory protein (Ni), inhibited the adenylate cyclase activity stimulated by forskolin to a slightly greater extent than VIP. When assayed together, these inhibition effects were additive, implying that the peptide receptors are not identical. The Ni-antagonist, MnCl2 completely blocked the inhibition of met-encephalin but had no significant effect on VIP-induced inhibition. In addition, pertussis toxin did not influence the effect of VIP on forskolin-stimulation in contrast to cholera toxin which did antagonize the VIP effect via the stimulatory guanine nucleotide regulatory protein (Ns). Furthermore, specific D-1 and D-2 dopaminergic receptor antagonists alpha(+)-flupentixol and spiperone had no effect on VIP-modulated forskolin-stimulated adenylate cyclase activity. These results suggest that the neuromodulatory effect of VIP is mediated by a Ns distinct from those involved in several adenylate cyclase pools sensitive to stimulation by dopamine and VIP in the rat striatum.
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PMID:The effect of vasoactive intestinal polypeptide (VIP) on forskolin stimulated adenylate cyclase in the caudate-putamen of the rat. 232 84

We have found that basophils (n = 9) treated with pertussis toxin (1.0 microgram/ml) fail to respond to a subsequent challenge with either 1.0 microM f-Met peptide (p less than 0.0005) or 0.24 microgram/ml of C5a (p less than 0.0005) although their responses to anti-IgE (0.1 microgram/ml) and A23187 (1.0 microgram/ml) were unaltered. These results were confirmed in purified (average purity = 89 +/- 3%) basophils (n = 4). Leukotriene C4 release was also reduced to 15 +/- 5% of control (p less than 0.005) when pertussis toxin-treated basophils were exposed to 1.0 microM f-Met peptide, although no inhibition was noted when anti-IgE or A23187 were used as the stimuli. The effect of pertussis toxin on basophils appears to be independent of the presence of contaminating mononuclear cells. We found that pertussis toxin inhibited f-Met peptide-induced histamine release regardless of the magnitude of the stimulus (0.01 microM to 1.0 microM f-Met peptide), although anti-IgE-induced release was unaffected over a dose-response curve. The effect of pertussis toxin was found to be both time- and concentration-dependent. The maximum effects were obtained after a 3-hr incubation with 1 microgram/ml of toxin. Lower (0.01 to 0.05 microgram/ml) concentrations of toxin or shorter (30 to 60 min) incubation periods did not significantly (p greater than 0.05) inhibit mediator release.
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PMID:The effect of pertussis toxin on mediator release from human basophils. 243 48


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