Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vivo microdialysis of cyclic AMP from prefrontal cortex complemented by ex vivo measures was used to investigate the possibility that lithium produces functional changes in G proteins that could account for its effects on adenylate cyclase activity. Four weeks of lithium administration (serum lithium concentration of 0.85 +/- 0.05 mM; n = 11) significantly increased the basal cyclic AMP content in dialysate from prefrontal cortex of anesthetized rats. Forskolin infused through the probe increased dialysate cyclic AMP, but the magnitude of this increase was unaffected by chronic lithium administration. Inactivation of the inhibitory guanine nucleotide binding protein Gi with pertussis toxin increased dialysate cyclic AMP in control rats, as did stimulation with cholera toxin (which activates the stimulatory guanine nucleotide binding protein Gs). The effect of pertussis toxin was abolished following chronic lithium, whereas the increase in cyclic AMP after cholera toxin was enhanced. In vitro pertussis toxin-catalyzed ADP ribosylation of alpha i (and alpha o) was increased by 20% in prefrontal cortex from lithium-treated rats, but the alpha i and alpha s contents (as determined by immunoblot) as well as the cholera toxin-catalyzed ADP ribosylation of alpha s were unchanged. Taken together, these results suggest that chronic lithium administration may interfere with the dissociation of Gi into its active components and thereby remove a tonic inhibitory influence on adenylate cyclase, with resultant enhanced basal and cholera toxin-stimulated adenylate cyclase activity.
 ...
PMID:In vivo evidence that lithium inactivates Gi modulation of adenylate cyclase in brain. 131 65

The human erythroleukemia cell line (HEL) has been used as a model system for studying signal transduction processes as they might relate to platelet/megakaryocyte function. We were interested in examining the role of thrombin in the regulation of adenylyl cyclase in this cell line. As opposed to its predominantly inhibitory effects on cyclic AMP production in platelets or in membranes from HEL cells, our initial experiments in intact HEL cells revealed that thrombin markedly potentiated the cyclic AMP response to prostaglandin E1 (2.9 +/- 0.2-fold), prostacyclin (1.9 +/- 0.2-fold) and carbacyclin (2.5 +/- 0.5-fold), measured either by radioimmunoassay or by the [3H]adenine preloading procedure. Thrombin, although ineffective alone, also potentiated cyclic AMP production stimulated by vasoactive intestinal peptide (1.6 +/- 0.2-fold), cholera toxin (3.0 +/- 0.6-fold) and AIF4- (2.3 +/- 0.6-fold), but not by forskolin (0.9 +/- 0.1-fold). The thrombin effect 1) produced an increase in the efficacy of the prostaglandins with no change in potency; 2) was long-lived; 3) required the proteolytic activity of thrombin; 4) was insensitive to pertussis toxin; and 5) was at least partially mimicked by trypsin, extracellular ATP and UTP, platelet activating factor and activators of protein kinase C. Down-regulation of protein kinase C or pre-exposure to the protein kinase inhibitor staurosporine blocked the potentiating effect. Together, these results suggest that in HEL cells, the mechanism of thrombin potentiation of cyclic AMP production may involve alterations in the interaction between stimulatory guanine nucleotide binding protein and the catalytic subunit of adenylyl cyclase, possibly involving protein kinase C-mediated phosphorylation.
 ...
PMID:Potentiation of cyclic adenosine monophosphate production by thrombin in the human erythroleukemia cell line, HEL. 133 12

Cultured endothelium derived from three microvascular fractions of human brain was used to characterize adrenergic receptors coupled to adenylate cyclase activity. Catecholamines (norepinephrine, epinephrine) and their analogs (isoproterenol, phenylephrine, 6-fluoronorepinephrine) dose-dependently stimulated endothelial production of cAMP. Antagonists for beta 1 and beta 2 receptors (propranolol, atenolol, and butoxamine) and for alpha 1-receptors (prazosin) dose-dependently blocked cAMP formation induced by the tested adrenergic agonists. Clonidine, an alpha 2 > alpha 1-agonist, also inhibited isoproterenol-stimulated production of cAMP while yohimbine (alpha 2 > alpha 1 antagonist) augmented the norepinephrine or epinephrine-induced accumulation of cAMP. Cholera toxin-induced ADP ribosylation of the stimulatory guanine nucleotide binding protein (Gs) abolished the stimulatory effect of norepinephrine, epinephrine, phenylephrine or 6-fluoronorepinephrine on cAMP formation. ADP ribosylation of the inhibitory guanine nucleotide binding protein (Gi) by pertussis toxin had no effect on either phenylephrine- or 6-fluoronorepinephrine-induced production of cAMP while it increased the norepinephrine and epinephrine-induced accumulation of cAMP. These findings represent the first documentation of beta 1-, beta 2-, alpha 1 and alpha 2-adrenergic receptors linked to adenylate cyclase in endothelium derived from human brain microvasculature. These data also indicate that activation of endothelial alpha 1 -adrenergic receptors is mediated by a signal transduction mechanism associated with Gs protein. The results strongly support the presence of various receptor-controlled adrenergic regulatory mechanisms on human cerebromicrovascular endothelium.
 ...
PMID:Adrenergic receptors coupled to adenylate cyclase in human cerebromicrovascular endothelium. 133 35

In UMR-106 osteosarcoma cells we found that PTH activated both the cAMP/protein kinase A and the Ca(2+)-dependent phosphoinositide/protein kinase C (PKC) pathways, but prostaglandin E2 (PGE2) activated only the cAMP pathway. Activation of PKC by the phorbol ester PMA had no effect on cAMP production but enhanced PTH-stimulated cAMP production by 50% or more; the effect on PGE2-induced cAMP was negligible. Inhibition of the alpha-subunit of the inhibitory guanine nucleotide binding protein (Gi) by pertussis toxin pretreatment also enhanced PTH-mediated cAMP production but had no effect on PGE2-induced cAMP production. These results suggest that although PTH-mediated adenylate cyclase activity is regulated via both the stimulatory (Gs) and inhibitory (Gi) guanine nucleotide binding proteins, only Gs regulates PGE2-mediated adenylate cyclase activity in UMR-106 cells. Costimulation with pertussis toxin and PMA did not increase PTH-stimulated cAMP production above that obtained with PMA alone. This implies a similar target of action for pertussis toxin and PMA, that is, the alpha-subunit of Gi. The alpha-subunit of Gi was found to be a substrate for in vitro PKC phosphorylation of membrane fractions from UMR-106 cells, seen as a +/- 40 kD band on SDS-PAGE. Stimulation of in situ 32P-labeled cells with either PMA or PTH also enhanced incorporation of 32P into the 40 kD band. Using the peptide antisera AS/7 and EC/2, we showed that pertussis toxin-labeled subunits of both Gi1 alpha/Gi2 alpha and Gi3 alpha could be immunoprecipitated, respectively, but immunoprecipitation of membrane proteins after in situ phosphorylation and stimulation with PMA precipitated only Gi2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Protein kinase C modulates parathyroid hormone- but not prostaglandin E2-mediated stimulation of cyclic AMP production via the inhibitory guanine nucleotide binding protein in UMR-106 osteosarcoma cells. 133

Biologic responses mediated by adrenoceptors are transduced by a receptor-effector mechanism that involves a guanine nucleotide binding protein (G protein). Recently, we determined that the transduction mechanism for the hypnotic response to dexmedetomidine, a highly selective alpha 2-agonist, is located in the locus coeruleus (LC) of the rat. In this study, we examined the role of pertussis toxin-sensitive (PTX) G proteins in the LC for the hypnotic response to dexmedetomidine. The LC of rats were stereotactically cannulated and treated with PTX, 0.34 micrograms, or vehicle. Five days later, the hypnotic response to dexmedetomidine, 7 micrograms into the LC or 50 micrograms.kg-1 IP, was tested. On the following day, the LC was harvested and assayed to determine whether the G proteins had been ribosylated by pretreatment with PTX in vivo. Quantitative immunoblotting of G0 alpha, Gi alpha 1,2, and Gi alpha 3, the alpha-subunit of three PTX-sensitive proteins, was also performed. In vivo treatment with PTX into the LC blocked the hypnotic response to LC-administered dexmedetomidine and, to a lesser extent, IP-administered dexmedetomidine. The in vivo PTX treatment effectively ribosylated the G proteins. No alteration in the amount of the different species of PTX-sensitive alpha-subunit was produced by in vivo PTX treatment. These data suggest a pivotal role for PTX-sensitive G proteins in the LC in the hypnotic response to alpha 2-agonists in the rat.
 ...
PMID:Pertussis toxin-mediated ribosylation of G proteins blocks the hypnotic response to an alpha 2-agonist in the locus coeruleus of the rat. 136 Jan 60

We have demonstrated that stimulation of airway smooth muscle by muscarinic agonists results in a coordinated modulation of two membrane ion channel proteins. Both channels are modulated in a similar way, although their effects on open-channel probability are opposite. The voltage-dependence of channel activity is shifted to more positive potentials in the case of KCa, and to more negative potentials in the case of the voltage-dependent calcium channels. Similarly, KCa channel dwell-time kinetics are shifted to short open lifetimes, whereas the long open state is favored for the large-amplitude voltage-dependent calcium channel. Although little is known about the molecular coupling of calcium channels, muscarinic inhibition of KCa channels is mediated through a pertussis toxin-sensitive guanine nucleotide binding protein.
 ...
PMID:Muscarinic regulation of membrane ion channels in airway smooth muscle cells. 137 Aug 98

Previously, we have extensively studied FSH-receptor interactions using bovine calf testis membranes, and demonstrated that the high-affinity FSH binding to receptors and coupling of FSH receptors with guanine nucleotide-binding protein (Gs protein) in a GTP-sensitive state are important initial events in FSH action. In this study, using the same plasma membrane system, we examined the glycoprotein nature of the FSH receptor and determined the contribution of carbohydrate moieties to these functions of the FSH receptor. Our approach involved enzymic deglycosylation of FSH receptors present in calf testis plasma membranes and then removal of incompletely deglycosylated FSH receptors by lectin affinity chromatography. Following treatment of testis membranes with peptide N-glycosidase, the receptor, as identified by ligand-blot analysis, had a higher electrophoretic mobility indicating a decrease in M(r) from 240-200K. Treatment of testis membranes with neuraminidase caused a reduction (to approximately 225K) in the size of the receptor consistent with desialylation. However, digestion with O-glycosidase (endo-alpha-N-acetylgalactosaminidase) did not affect the mobility of the FSH receptor. These results suggest that bovine testis FSH receptor contains predominantly N-linked oligosaccharide chains, a finding which is consistent with recent predictions that N-linked glycosylation, but not O-linked glycosylation sites are present in cloned FSH receptor from rat testis. Moreover, calf testis membranes after treatment with peptide N-glycosidase F, were solubilized with Triton X-100 under optimum conditions that preserve the physical and functional coupling of FSH receptors with guanine nucleotide-binding protein, and then subjected to lectin affinity chromatography. Scatchard analysis indicated that intact and deglycosylated FSH receptors bound 125I-human FSH with similar affinities. In the presence of GTP, the binding of 125I-human FSH to intact and deglycosylated receptors decreased similarly and in a noncompetitive manner. Treatment of testis membranes with NAD plus cholera toxin, but not NAD plus pertussis toxin, eliminated the GTP effect on FSH binding to enzymic deglycosylated as well as intact receptors, suggesting that the guanine nucleotide binding protein mediating GTP regulation of FSH binding in these membranes is probably Gs protein. Our results suggest that the bovine testis FSH receptor contains predominantly N-linked oligosaccharide chains consistent with recently predicted N-linked glycosylation sites of cloned FSH receptor of rat testis. The bovine testis FSH receptor does not require N-linked carbohydrate for high-affinity hormone binding.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Carbohydrate moiety of follitropin receptor is not required for high affinity hormone-binding or for functional coupling between receptor and guanine nucleotide-binding protein in bovine calf testis membranes. 142 41

Parameters of ligand binding, stimulation of low-Km GTPase, and inhibition of adenylate cyclase were determined in intact human neuroblastoma SH-SY5Y cells and in their isolated membranes, both suspended in identical physiological buffer medium. In cells, the mu-selective opioid agonist [3H]Tyr-D-Ala-Gly(Me)Phe-Gly-ol ([3H]DAMGO) bound to two populations of sites with KD values of 3.9 and 160 nM, with less than 10% of the sites in the high-affinity state. Both sites were also detected at 4 degrees C and were displaced by various opioids, including quaternary naltrexone. The opioid antagonist [3H]naltrexone bound to a single population of sites, and in cells treated with pertussis toxin the biphasic displacement of [3H]naltrexone by DAMGO became monophasic with only low-affinity binding present. The toxin specifically reduced high-affinity agonist binding but had no effect on the binding of [3H]naltrexone. In isolated membranes, both agonist and antagonist bound to a single population of receptor sites with affinities similar to that of the high-affinity binding component in cells. Addition of GTP to membranes reduced the Bmax for [3H]DAMGO by 87% and induced a linear ligand binding component; a low-affinity binding site, however, could not be saturated. Compared with results obtained with membranes suspended in Tris buffer, agonist binding, including both receptor density and affinity, in the physiological medium was attenuated. The results suggest that high-affinity opioid agonist binding represents the ligand-receptor-guanine nucleotide binding protein (G protein) complex present in cells at low density due to modulation by endogenous GTP.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Opioid signal transduction in intact and fragmented SH-SY5Y neural cells. 156 Feb 22

We have previously described FSH receptor-mediated influx of 45Ca++ in cultured Sertoli cells from immature rats and receptor-enriched proteoliposomes via activation of voltage-sensitive and voltage-independent calcium channels. We have further shown that this effect of FSH does not require cholera toxin- or pertussis toxin-sensitive guanine nucleotide binding protein or activation of adenylate cyclase. In the present study, we have identified regions of human FSH-beta-subunit which appear to be involved in mediating calcium influx. We screened 11 overlapping peptide amides representing the entire primary structure of hFSH-beta-subunit for their effects on 45Ca++ flux in FSH receptor-enriched proteoliposomes. hFSH-beta-(1-15) and hFSH-beta-(51-65) induced uptake of 45Ca++ in a concentration-related manner. This effect of hFSH-beta-(1-15) and hFSH-beta-(51-65) was also observed in liposomes lacking incorporated FSH receptor, suggesting that the peptide amides may act as ionophores or channel-formers. Reducing membrane fluidity by incubating liposomes (containing no receptor) with hFSH-beta-(1-15) or hFSH-beta-(51-65) at temperatures lower than the transition temperatures of their constituent phospholipids resulted in no significant (P greater than 0.05) difference in 45Ca++ uptake. The effectiveness of the calcium ionophore A23187, however, was abolished. Ruthenium red, a voltage-independent calcium channel antagonist, was able to completely block uptake of 45Ca++ induced by hFSH-beta-(1-15) and hFSH-beta-(51-65) whereas nifedipine, a calcium channel blocker specific for L-type voltage-sensitive calcium channels, was without effect. These results suggest that in addition to its effect on voltage-sensitive calcium channel activity, interaction of FSH with its receptor may induce formation of transmembrane aqueous channels which also facilitate influx of extracellular calcium.
 ...
PMID:Synthetic peptides corresponding to human follicle-stimulating hormone (hFSH)-beta-(1-15) and hFSH-beta-(51-65) induce uptake of 45Ca++ by liposomes: evidence for calcium-conducting transmembrane channel formation. 164 50

Exposure of pig epidermis to adenylate cyclase stimulators results in receptor-specific desensitization. We investigated the nature of the agonist-induced desensitization, which was compared with the phorbol ester-induced, receptor-nonspecific desensitization. Both phorbol ester-induced desensitization and the agonist-induced desensitization were accompanied by an increase in forskolin- and cholera toxin-induced cyclic AMP accumulations. The magnitude of the increase in the agonist-induced desensitization was parallel to the degree of the initial cyclic AMP accumulation; histamine and adenosine, which increase more cyclic AMP than epinephrine, resulted in a more marked increase in forskolin- and cholera toxin-induced cyclic AMP accumulations. Similarly, epidermis desensitized to multiple receptors revealed more marked forskolin- and cholera toxin-induced cyclic AMP accumulations than epidermis desensitized to a single receptor. In contrast to the phorbol ester-induced desensitization, agonist-induced desensitization was not affected by the protein kinase C inhibitors H-7 and staurosporin. Further, agonist-induced desensitization was still inducible in phorbol ester-desensitized epidermis and vice versa. In contrast to the agonist-induced desensitization, which is accompanied by the preceding adenylate cyclase stimulation, no evidence for the stimulation of the adenylate cyclase during phorbol ester treatment was obtained. Neither agonist-induced desensitization nor phorbol ester-induced desensitization affected the content of inhibitory guanine nucleotide binding protein of the epidermis, which was monitored by the pertussis toxin (IAP)-catalyzed ADP ribosylation reaction. Our results indicate that agonist-induced desensitization and the phorbol ester-induced desensitization are independent of each other. Although both processes are characterized by increased forskolin- and toxin-induced cyclic AMP accumulations, the former is accompanied by initial cyclic AMP accumulation; the latter is not.
 ...
PMID:Desensitization of the epidermal adenylate cyclase system: agonists and phorbol esters desensitize by independent mechanisms. 164 51


1 2 3 4 5 6 7 8 9 10 Next >>