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)

Effects of intracellular Mg2+ in the activation of a muscarinic K+ channel were examined in single atrial cells, using patch-recording techniques. In "cell-attached" patch recordings, acetylcholine (ACh) or adenosine (Ado), present in the pipette, activated a specific population of K+ channels. In "inside-out" patches, openings of the K+ channel by ACh or Ado diminished and did not resume until Mg2+ was added to the perfusate which contained GTP or GTP-gamma S, a non-hydrolyzable GTP analogue. Channel openings caused by GTP faded by removing Mg2+, while GTP-gamma S-induced openings persisted steadily even when both Mg2+ and GTP-gamma S were removed. In contrast to the case of GTP-induced channel openings, the GTP-gamma S-induced openings were not inhibited by the A promoter of pertussis toxin with NAD. From these observations, we concluded: Intracellular Mg2+ is essential for GTP to activate the GTP-binding protein. Deactivation of the N protein may be caused by hydrolysis of GTP to GDP. This process may not require Mg2+. During the activation by GTP analogues, the N protein may be dissociated into its subunits.
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PMID:Role of intracellular Mg2+ in the activation of muscarinic K+ channel in cardiac atrial cell membrane. 243 89

The effect of pertussis toxin on somatostatin-induced K+ current was examined in dissociated human pituitary tumor cells obtained from two acromegalic patients. Somatostatin-induced hyperpolarization or K+ current was observed in 20 of 23 cells in adenoma 1 and 10 of 11 cells in adenoma 2. After treatment with pertussis toxin for 24 h, these responses were completely suppressed (0/14 in adenoma 1, 0/10 in adenoma 2). Spontaneous action potentials, K+, Na+, and Ca2+ currents were well preserved after pertussis toxin treatment. When crude membrane fraction was incubated with [32P]NAD, a 41K protein was ADP-ribosylated by pertussis toxin. Hormone release was inhibited by somatostatin and this inhibition was blocked by pertussis toxin treatment.
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PMID:Pertussis toxin inhibits somatostatin-induced K+ conductance in human pituitary tumor cells. 244 Mar 14

Somatostatin (SS) inhibits secretion from many cells, including clonal GH3 pituitary cells, by a complex mechanism that involves a pertussis toxin (PTX)-sensitive step and is not limited to its cAMP lowering effect, since secretion induced by cAMP analogs and K+ depolarization are also inhibited. SS also causes membrane hyperpolarization which may lead to decreases in intracellular Ca2+ need for secretion. Using patch clamp techniques we now demonstrate: 1) that both (SS) and acetylcholine applied through the patch pipette to the extracellular face of a patch activate a 55-picosiemens K+ channel without using a soluble second messenger; 2) that, after patch excision, the active state of the ligand-stimulated channel is dependent on GTP in the bath, is abolished by treatment of the cytoplasmic face of the patch with activated PTX and NAD+, and after inactivation by PTX, is restored in a GTP-dependent manner by addition of a nonactivated human erythrocyte PTX-sensitive G protein, and 3) that the 55-picosiemens K+ channel can also be activated in a ligand-independent manner with guanosine [gamma-thio] triphosphate (GTP gamma S) or with Mg2+/GTP gamma S-activated erythrocyte G protein. We call this protein GK. It is an alpha-beta-gamma trimer of which we have previously shown that the alpha-subunit is the substrate for PTX and that it dissociates on activation with Mg2+/GTP gamma S into alpha-GTP gamma S plus beta-gamma. A similarly activated and dissociated preparation of GS, the stimulatory regulatory component of adenylyl cyclase, having a different alpha-subunit but the same beta-gamma-dimer, was unable to cause K+ opening.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reconstitution of somatostatin and muscarinic receptor mediated stimulation of K+ channels by isolated GK protein in clonal rat anterior pituitary cell membranes. 245 51

We used pertussis toxin to study the mechanism(s) by which divalent cations lower cellular cAMP content in bovine parathyroid cells. In cultured parathyroid cells, high extracellular Ca2+ (5 mM) or Mg2+ (5-10 mM) lowers dopamine-stimulated cAMP content by 70-90%. Pertussis toxin (0.5 microgram/ml) totally blocks the inhibitory effects of Ca2+ and Mg2+ on cAMP content. Ba2+ and Sr2+ (5 mM) also lower cAMP content by 80-90%, and this effect is, likewise, blocked by pertussis toxin. Pretreatment with pertussis toxin had no effect on the release of cAMP into the extracellular fluid. The toxin also did not modify phosphodiesterase activity in sonicates of parathyroid cells (42.68 +/- 3.26 vs. 47.00 +/- 2.82 pmol cAMP hydrolyzed/10(6) cells.20 min in control and toxin-treated cells, respectively). Moreover, addition of the phosphodiesterase inhibitor isobutyl-methylxanthine did not modify the inhibition of dopamine-stimulated cAMP accumulation by 5 mM Ca2+ in control cells (85% vs. 86% inhibition, respectively, with and without isobutylmethylxanthine). Pertussis toxin-catalyzed ADP ribosylation in homogenates of control cells demonstrated the presence of two substrates with mol wt of 40K and 41K. Preexposure of cells to pertussis toxin overnight resulted in the complete loss of both substrates on subsequent ADP ribosylation with [32P]NAD. Pertussis toxin pretreatment did not enhance adenylate cyclase activity indirectly via reducing the extracellular Ca2+-induced rise in cytosolic Ca2+, since the cytosolic Ca2+ level at 5 mM Ca2+ was about 60% higher in pertussis toxin-treated than in control cells (531 +/- 85 vs. 326 +/- 35 nM; P less than 0.05). In addition, ionomycin had no significant effect on cellular cAMP levels in control cells despite increasing the cytosolic Ca2+ concentration to levels as high as 1700 nM at 10(-5) M. Thus, changes in cytosolic Ca2+ phosphodiesterase activity, or efflux of cAMP from the cell cannot explain the inhibition of cAMP accumulation by divalent cations or the reversal of this effect by pertussis toxin. Instead, the present data suggest that extracellular divalent cations modulate the formation of cellular cAMP in parathyroid cells by a process involving a pertussis toxin-sensitive guanine nucleotide regulatory protein, presumably inhibition of adenylate cyclase by Gi via a receptor-like mechanism.
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PMID:Divalent cations suppress 3',5'-adenosine monophosphate accumulation by stimulating a pertussis toxin-sensitive guanine nucleotide-binding protein in cultured bovine parathyroid cells. 246 88

In rat osteosarcoma (ROS 17/2.8) cells, which express osteoblastic features in culture, basic fibroblast growth factor (bFGF) reduces the level of alkaline phosphatase, type I collagen, and osteocalcin mRNA and increases osteopontin mRNA, independent of growth stimulation. The fibroblast growth factor (FGF) effects are dose dependent (EC50 about 6 pM) and are detected 24 h after addition of the growth factor. bFGF also reduces parathyroid hormone-stimulatable adenylate cyclase and alkaline phosphatase activity in these cells. Concomitant treatment with pertussis toxin (20 ng/ml) opposes the FGF effects. Although cyclic AMP elevating agents mimic pertussis toxin action on some parameters, they produce opposite effects on others, indicating that antagonism between pertussis toxin and bFGF is not mediated by cyclic AMP. bFGF caused a small reduction in steady state NAD-dependent ADP-ribosylation and had no detectable effects on the steady-state levels of the Gi alpha (alpha subunit of the inhibitory G protein) 1, 2, and 3, visualized with specific antibodies in these cells. Although the site of interaction of pertussis toxin and FGF remains to be determined, the findings presented here suggest separate control of growth and differentiation by bFGF and show that pertussis toxin treatment can modulate differentiation in these cells, presumably via Gi proteins.
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PMID:Opposing effects of fibroblast growth factor and pertussis toxin on alkaline phosphatase, osteopontin, osteocalcin, and type I collagen mRNA levels in ROS 17/2.8 cells. 247 40

The effect of angiotensin II (AII) on adenylate cyclase was studied in the rat and rabbit heart sarcolemma. AII inhibited adenylate cyclase activity in the rat and rabbit sarcolemma in a concentration-dependent manner. Maximal inhibition of about 35-40% was observed in the rat, with an apparent Ki of about 3 nM; about 30% inhibition, with an apparent Ki of about 6 nM, was noted in rabbit sarcolemma. The inhibitory effect of AII was dependent on the presence of guanine nucleotides and was blocked by saralasin. In addition, AII also inhibited the stimulatory effects of isoproterenol and glucagon on adenylate cyclase. Ninhibin, a sperm factor which has been shown to modify the characteristics of inhibitory guanine nucleotide regulatory protein (Gi), attenuated the inhibitory effects of AII on basal and hormone-sensitive adenylate cyclase. Furthermore, pertussis toxin (PT) treatment of the sarcolemma in the presence of [32P]NAD resulted in ADP-ribosylation of a single 41-kD protein. PT also attenuated the AII-mediated inhibition of basal and hormone-sensitive adenylate cyclase and enhanced the magnitude of the stimulatory effects of isoproterenol and glucagon on adenylate cyclase activity. These data suggest that the rat myocardial sarcolemma contains AII receptors that are negatively coupled to adenylate cyclase through Gi protein.
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PMID:Angiotensin II receptors negatively coupled to adenylate cyclase in rat myocardial sarcolemma. Involvement of inhibitory guanine nucleotide regulatory protein. 249 5

The antiserum AS7 can specifically immunoprecipitate alpha-Gi from membrane extracts as well as from a mixture of purified alpha-Gi and alpha-Go as ascertained using [32P]ADP-ribosylated G-proteins. Using this antiserum to immunoprecipitate alpha-Gi from hepatocytes labelled with 32P it was evident that alpha-Gi was phosphorylated under basal (resting) conditions. Challenge of hepatocytes with the tumour promoting phorbol ester TPA, however, elicited a marked enhancement of the phosphorylation state of alpha-Gi. This was accompanied by the loss of inhibitory effect of Gi on adenylate cyclase, as judged by the inability of low concentrations of p[NH]ppG to inhibit forskolin-stimulated adenylate cyclase activity. Such actions were mimicked by treatment of hepatocytes with either glucagon or TH-glucagon, an analogue of glucagon which is incapable of activating adenylate cyclase and elevating intracellular cyclic AMP concentrations. Pre-treatment of hepatocytes with either glucagon, TPA or insulin did not affect the ability of pertussis toxin to cause the NAD+-dependent, [32P]ADP-ribosylation of alpha-Gi in membrane fractions isolated from such pre-treated hepatocytes. We suggest that protein kinase C can elicit the phosphorylation and functional inactivation of alpha-Gi in intact hepatocytes. As pertussis toxin only causes the ADP-ribosylation of the holomeric form of Gi, it may be that phosphorylation leaves alpha-Gi in its holomeric state.
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PMID:Treatment of intact hepatocytes with either the phorbol ester TPA or glucagon elicits the phosphorylation and functional inactivation of the inhibitory guanine nucleotide regulatory protein Gi. 249 92

The presence of GTP-binding proteins (G proteins) has been studied in murine adult choroid plexuses and cultured fetal choroidal or hypothalamic ependymal cells by ADP-ribosylation catalyzed by Bordetella pertussis toxin (PTX) and by immunodetection using affinity-purified polyclonal antibodies against the alpha subunit of the Go protein (Go alpha), the major brain G protein. ADP-ribosylation with 32P-NAD and PTX of choroid plexus revealed an intense labeling at the 40 kDa level in addition to the known PTX-substrates at 41 kDa (Gi alpha) and 39 kDa (Go alpha). This 40 kDa substrate was also predominant in cultured ependymal cells. However, a positive immunoreactivity with the anti-Go alpha antibodies was detected at the level of the 39 kDa faster component, indicating the presence of Go alpha in both choroid plexuses and cultured ependymal cells. In thin frozen sections as well as in cultured cells, Go alpha was mainly immunolocalized at the apical pole of choroidal ependymocytes and in the kinocilia of ciliated ependymal cells. At the ultrastructural level, using gold immunoprobes, the immunoreactivity of a Go alpha-like protein was detected on the cytoplasmic face of the apical plasma membrane, coated pits and vesicles, and in the apical cytoplasmic matrix. In ciliated ependymal cells, the positive immunostaining displayed a dotted pattern at the surface of demembranated axonema of apical kinocilia. These findings strongly suggest that G proteins, especially Go, are involved in transducing chemical signals that modulate traffic and exchanges between cerebrospinal fluid and ependyma through the apical membrane of ependymocytes.
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PMID:Apical localization of the alpha subunit of GTP-binding protein Go in choroidal and ciliated ependymocytes. 249 7

A possible role for G proteins in contributing to the chronic actions of opiates was investigated in the rat locus coeruleus (LC). The LC is a relatively homogeneous brain region that appears to play an important role in mediating acute and chronic opiate action in animals, as well as in humans. It was found that chronic, but not acute, treatment of rats with morphine, under conditions known to induce states of opiate tolerance and dependence, produced an increase in the level of pertussis toxin-mediated ADP-ribosylation of G proteins in the LC. The morphine-induced increase in ADP-ribosylation occurred in both Gi and Go, and was observed over a 30-fold range of NAD concentrations used. Concomitant treatment of rats with the opiate receptor antagonist naltrexone blocked the ability of morphine to produce this effect. In contrast, chronic morphine had no effect on pertussis toxin-mediated ADP-ribosylation of Gi and Go in the other brain regions studied, including the neostriatum, frontal cortex, and dorsal raphe. Chronic morphine also had no effect on cholera toxin-mediated ADP-ribosylation of Gs in the LC and these other brain regions. Preliminary immunoblot analysis revealed that increased ADP-ribosylation levels of the alpha subunit of Go in the LC were associated with equivalent increases in the immunoreactivity of this protein in this brain region. It is possible that the observed regulation of G-proteins by morphine in the LC represents part of the changes that underlie opiate addiction in these neurons.
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PMID:Regulation of G proteins by chronic morphine in the rat locus coeruleus. 249 49

The predominant guanine nucleotide-binding protein (G-protein) of bovine lung membranes, termed GL, has been purified and compared biochemically, immunochemically and functionally with Gi and Go purified from rabbit brain. The purified GL appeared to have a similar subunit structure to Gi and Go, being composed of alpha, beta and possibly gamma subunits. On Coomassie Blue-stained SDS/polyacrylamide gels and immunoblots, the alpha subunit of GL (GL alpha) displayed an intermediate mobility (40 kDa) between those of Gi and Go (Gi alpha and Go alpha). GL alpha was [32P]ADP-ribosylated in the presence of pertussis toxin and [32P]NAD+. Analysis of [32P]ADP-ribosylated alpha subunits by SDS/polyacrylamide-gel electrophoresis and isoelectric focusing showed that GL alpha was distinct from Gi alpha and Go alpha, but very similar to the predominant G-protein in neutrophil membranes. Immunochemical characterization also revealed that GL was distinct from Gi and Go, but was indistinguishable from the G-protein of neutrophils, which has been tentatively identified as Gi2 [Goldsmith, Gierschik, Milligan, Unson, Vinitsky, Maleck & Spiegel (1987) J. Biol. Chem. 262, 14683-14688]. In functional studies, higher Mg2+ concentrations were required for guanosine 5'-[gamma-[35S]thio]triphosphate (GTP[35S]) binding to GL than were required for nucleotide binding to Go, whereas Gi showed a Mg2+-dependence similar to that of GL. The kinetics of GTP[35S] binding to GL was quite different from those of Gi and Go; t1/2 values of maximal binding were 30, 15 and 5 min respectively. In contrast, the rate of hydrolysis of [gamma-32P]GTP by GL (t1/2 approximately 1 min) was approx. 4 times faster than that by Gi or Go. These results indicated that the predominant G-protein purified from lung is structurally and functionally distinct from Gi and Go of brain, but structurally indistinguishable from Gi2 of neutrophils.
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PMID:Purification and characterization of predominant G-protein from bovine lung membranes. Biochemical and immunochemical comparison with Gi1 and Go purified from brain. 249 37


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