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 the complex signal transduction networks involving G protein-coupled receptors there are numerous examples where G(i)-linked receptors augment G(q)-dependent signals. The mechanistic basis of such occurrences is thought to entail signal convergence at phospholipase Cbeta (PLCbeta) via the G protein betagamma-dimers. Herein, we explored the possibility that augmentation by betagamma-dimers requires preactivation of PLCbeta. COS-7 cells were transiently cotransfected with cDNAs encoding various combinations of receptors and G protein subunits. The G(i)-coupled delta- and kappa-opioid receptors could not stimulate PLCbeta unless they were coexpressed with Galpha(16). The opioid-induced response was dose-dependent and partially inhibited by pertussis toxin or coexpression with transducin, indicating the involvement of betagamma-subunits released from the G(i) proteins. When PLCbeta was preactivated by constitutively active mutants of Galpha(16), Galpha(q), or Galpha(14), opioids enhanced the activity by 80 to 300% and such responses were mostly pertussis toxin-sensitive. The opioid-induced enhancement was dose-dependent and could not be blocked by staurosporin, a protein kinase C inhibitor. Other G(i)-coupled receptors that were ineffective on their own also acquired the ability to stimulate PLCbeta in the presence of a constitutively active mutant of Galpha(q). Coactivation of endogenous or exogenous G(q)-coupled receptors with the delta-opioid receptor produced strong stimulations of PLCbeta and such responses could be partially blocked by pertussis toxin. These results show that enhancement of G(q)-dependent signals by G(i)-coupled receptors requires activated PLCbeta and is mediated via the betagamma-dimer.
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PMID:Preactivation permits subsequent stimulation of phospholipase C by G(i)-coupled receptors. 1072 15

Many types of cells exhibit increased adenylyl cyclase (AC) activity after chronic agonist treatment of G(i/o)-coupled receptors. This phenomenon, defined as AC superactivation or sensitization, has mostly been studied for the opioid receptors and is implicated in opiate addiction. Here we show that this phenomenon is also observed on chronic activation of the CB(1) cannabinoid receptor. Moreover, using COS-7 cells cotransfected with CB(1) receptor and individual AC isozymes, we could show selective superactivation of AC types I, III, V, VI, and VIII. The level of superactivation was dependent on the concentration of agonist and time of agonist exposure and was not dependent on the AC stimulator used. No superactivation of AC types II, IV, or VII was observed in COS-7 cells cotransfected with CB(1). The superactivation of AC type V was abolished by pretreatment with pertussis toxin and by cotransfection with the carboxy terminus of beta-adrenergic receptor kinase, which serves as a scavenger of G(betagamma) dimers, implying a role for the G(i/o) proteins and especially G(betagamma) dimers in the cannabinoid-induced superactivation of AC.
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PMID:Differential superactivation of adenylyl cyclase isozymes after chronic activation of the CB(1) cannabinoid receptor. 1072 21

Prolonged G(i/o) protein-coupled receptor activation has been shown to lead to receptor internalization and receptor desensitization. In addition, it is well established that although acute activation of these receptors leads to inhibition of adenylyl cyclase (AC), long-term activation results in increased AC activity (especially evident on removal of the inhibitory agonist), a phenomenon defined as AC superactivation or sensitization. Herein, we show that chronic exposure to agonists of G(i)-coupled receptors also leads to a decrease in cholate detergent solubility of G protein subunits, and that antagonist treatment after such chronic agonist exposure leads to a time-dependent reversal of the cholate insolubility. With Chinese hamster ovary and COS cells transfected with several G(i/o)-coupled receptors (i.e., mu- and kappa-opioid, and m(4)-muscarinic), we observed that although no overall change occurred in total content of G(alphai)- and beta(1)-subunits, chronic agonist treatment led to a marked reduction in the ability of 1% cholate to solubilize G(betagamma) as well as G(alphai). This solubility shift is exclusively observed with G(alphai), and was not seen with G(alphas). The disappearance and reappearance of G(alphai) and G(betagamma) subunits from and to the detergent-soluble fractions occur with similar time courses as observed for the onset and disappearance of AC superactivation. Lastly, pertussis toxin, which blocks acute and chronic agonist-induced AC inhibition and superactivation, also blocks the shift in detergent solubility. These results suggest a correlation between the solubility shift of the heterotrimeric G(i) protein and the generation of AC superactivation.
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PMID:Alterations in detergent solubility of heterotrimeric G proteins after chronic activation of G(i/o)-coupled receptors: changes in detergent solubility are in correlation with onset of adenylyl cyclase superactivation. 1072 31

The agonist-bound gonadotropin-releasing hormone (GnRH) receptor engages several distinct signaling cascades, and it has recently been proposed that coupling of a single type of receptor to multiple G proteins (G(q), G(s), and G(i)) is responsible for this behavior. GnRH-dependent signaling was studied in gonadotropic alphaT3-1 cells endogenously expressing the murine receptor and in CHO-K1 (CHO#3) and COS-7 cells transfected with the human GnRH receptor cDNA. In all cell systems studied, GnRH-induced phospholipase C activation and Ca(2+) mobilization was pertussis toxin-insensitive, as was GnRH-mediated extracellular signal-regulated kinase activation. Whereas the G(i)-coupled m2 muscarinic receptor interacted with a chimeric G(s) protein (G(s)i5) containing the C-terminal five amino acids of Galpha(i2), the human GnRH receptor was unable to activate the G protein chimera. GnRH challenge of alphaT3-1, CHO#3 and of GnRH receptor-expressing COS-7 cells did not result in agonist-dependent cAMP formation. GnRH challenge of CHO#3 cells expressing a cAMP-responsive element-driven firefly luciferase did not result in increased reporter gene expression. However, coexpression of the human GnRH receptor and adenylyl cyclase I in COS-7 cells led to clearly discernible GnRH-dependent cAMP formation subsequent to GnRH-elicited rises in [Ca(2+)](i). In alphaT3-1 and CHO#3 cell membranes, addition of [alpha-(32)P]GTP azidoanilide resulted in GnRH receptor-dependent labeling of Galpha(q/11) but not of Galpha(i), Galpha(s) or Galpha(12/13) proteins. Thus, the murine and human GnRH receptors exclusively couple to G proteins of the G(q/11) family. Multiple GnRH-dependent signaling pathways are therefore initiated downstream of the receptor/G protein interface and are not indicative of a multiple G protein coupling potential of the GnRH receptor.
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PMID:Gonadotropin-releasing hormone receptor initiates multiple signaling pathways by exclusively coupling to G(q/11) proteins. 1073 55

Fusion proteins were constructed between a recombinant human alpha(2A)-adrenoceptor and either a rat wild-type G(alphai1) or putative pertussis toxin-resistant form of the G(alphai1) protein (G(alphai1)Cys(351)Gly). [(3)H]2-[2-(2-Methoxy-1, 4-benzodioxanyl)]imidazoline hydrochloride (RX 821002) saturation binding experiments demonstrated that both fusion proteins were expressed at a similar level as the alpha(2A)-adrenoceptor co-expressed with either a wild-type G(alphai1) or mutant G(alphai1)Cys(351)Gly protein in COS-7 cells, and displayed a ligand binding profile similar to that for the alpha(2A)-adrenoceptor protein. In alpha(2A)-adrenoceptor-transfected COS-7 cells, 5-bromo-6-(2-imidazolin-2-yl-amino) quinoxaline tartrate (brimonidine, 10 microM) induced stimulation (151 +/- 28%) of adenosine 3',5'-cyclic monophosphate (cAMP) formation which was prevented by cholera toxin treatment, demonstrating a direct coupling of the alpha(2A)-adrenoceptor to an endogenous G(alphas) protein in COS-7 cells. Expression of either the wild-type G(alphai1) or mutant G(alphai1)Cys(351)Gly protein in co-expression or fusion with the alpha(2A)-adrenoceptor in COS-7 cells suppressed the brimonidine-induced stimulation of cAMP formation, both in the presence and absence of pertussis toxin pretreatment. Hence, the G(alphai1) protein apparently blocks the G(s)-coupled alpha(2A)-adrenoceptor-mediated pathway in a pertussis toxin-non-sensitive way.
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PMID:alpha(2A)-adrenoceptor: G(alphai1) protein-mediated pertussis toxin-resistant attenuation of G(s) coupling to the cyclic AMP pathway. 1079 49

Agonist-stimulated high affinity GTPase activity of fusion proteins between the alpha(2A)-adrenoreceptor and the alpha subunits of forms of the G proteins G(i1), G(i2), G(i3), and G(o1), modified to render them insensitive to the action of pertussis toxin, was measured following transient expression in COS-7 cells. Addition of a recombinant regulator of G protein signaling protein, RGS4, did not significantly affect basal GTPase activity nor agonist stimulation of the fusion proteins containing Galpha(i1) and Galpha(i3) but markedly enhanced agonist-stimulation of the proteins containing Galpha(i2) and Galpha(o1.) The effect of RGS4 on the alpha(2A)-adrenoreceptor-Galpha(o1) fusion protein was concentration-dependent with EC(50) of 30 +/- 3 nm and the potency of the receptor agonist UK14304 was reduced 3-fold by 100 nm RGS4. Equivalent reconstitution with Asn(88)-Ser RGS4 failed to enhance agonist function on the alpha(2A)-adrenoreceptor-Galpha(o1) or alpha(2A)-adrenoreceptor-Galpha(i2) fusion proteins. Enzyme kinetic analysis of the GTPase activity of the alpha(2A)-adrenoreceptor-Galpha(o1) and alpha(2A)-adrenoreceptor-Galpha(i2) fusion proteins demonstrated that RGS4 both substantially increased GTPase V(max) and significantly increased K(m) of the fusion proteins for GTP. The increase in K(m) for GTP was dependent upon RGS4 amount and is consistent with previously proposed mechanisms of RGS function. Agonist-stimulated GTPase turnover number in the presence of 100 nm RGS4 was substantially higher for alpha(2A)-adrenoreceptor-Galpha(o1) than for alpha(2A)-adrenoreceptor-Galpha(i2). These studies demonstrate that although RGS4 has been described as a generic stimulator of the GTPase activity of G(i)-family G proteins, selectivity of this interaction and quantitative variation in its function can be monitored in the presence of receptor activation of the G proteins.
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PMID:The regulator of G protein signaling RGS4 selectively enhances alpha 2A-adreoreceptor stimulation of the GTPase activity of Go1alpha and Gi2alpha. 1080 34

Single-transmembrane natriuretic peptide clearance receptor (NPR-C), which is devoid of a cytoplasmic guanylyl cyclase domain, interacts with pertussis toxin (PTx)-sensitive G proteins to activate endothelial nitric oxide synthase (eNOS) expressed in gastrointestinal smooth muscle cells. We examined the ability of NPR-C to activate other effector enzymes in eNOS-deficient tenia coli smooth muscle cells; these cells expressed NPR-C and NPR-B but not NPR-A. Atrial natriuretic peptide (ANP), the selective NPR-C ligand cANP-(4-23), and vasoactive intestinal peptide (VIP) inhibited (125)I-ANP and (125)I-VIP binding to muscle membranes in a pattern indicating high-affinity binding to NPR-C. Interaction of VIP with NPR-C was confirmed by its ability to inhibit (125)I-ANP binding to membranes of NPR-C-transfected COS-1 cells. In tenia muscle cells, all ligands selectively activated G(i-1) and G(i-2); VIP also activated G(s) via VIP(2) receptors. All ligands stimulated phosphoinositide hydrolysis, which was inhibited by ANP-(1-11), PTx, and antibodies to phospholipase C-beta3 (PLC-beta3) and Gbeta. cANP-(4-23) contracted tenia muscle cells; contraction was blocked by U-73122 and PTx and by antibodies to PLC-beta3 and Gbeta in intact and permeabilized muscle cells, respectively. VIP and ANP contracted muscle cells only after inhibition of cAMP- and cGMP-dependent protein kinases. ANP and cANP-(4-23) inhibited forskolin-stimulated cAMP in a PTx-sensitive fashion. We conclude that NPR-C is coupled to activation of PLC-beta3 via betagamma-subunits of G(i-1) and G(i-2) and to inhibition of adenylyl cyclase via alpha-subunits.
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PMID:G(i-1)/G(i-2)-dependent signaling by single-transmembrane natriuretic peptide clearance receptor. 1085 28

Molecular cloning and expression of canine (ca) serotonin 5-HT(1B) and ca 5-HT(1D) receptor subtypes showed that besides the lower binding affinity of ketanserin for the ca 5-HT(1D) receptor, the ligand binding profiles were similar to their human homologues. Site-directed mutagenesis studies suggest that a Gln(189) residue in the second extracellular loop of the ca 5-HT(1D) receptor may partially account for the lower binding affinity of ketanserin. The coupling of ca 5-HT(1B) and ca 5-HT(1D) receptor subtypes to the phospholipase C pathway was analyzed by measuring stimulation of inositol phosphate formation in COS-7 cells. Zolmitriptan potently stimulated (EC(50) = 4.9 nM) the inositol phosphate formation at ca 5-HT(1D) receptors in a fully pertussis toxin (PTX)-dependent manner, whereas only a weak PTX-resistant inositol phosphate response (26-29% at 10 microM zolmitriptan) could be detected for the ca 5-HT(1B) receptor at a similar expression level. In contrast, both ca 5-HT(1B) and ca 5-HT(1D) receptor subtypes yielded a similar maximal magnitude of inositol phosphate formation (300-340% at 10 microM zolmitriptan) upon co-expression with a mouse (m) G(alpha15) protein. PTX treatment and co-expression with a beta-adrenergic receptor kinase C-terminal polypeptide partially (20-46%) abolished the m G(alpha15) protein-dependent ca 5-HT(1B) and ca 5-HT(1D) receptor-mediated stimulation of inositol phosphate formation. This study suggests both 5-HT receptor subtypes can activate betagamma subunits of endogenous G(i/o) proteins besides their coupling to recombinant m G(alpha15) protein.
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PMID:Coupling of canine serotonin 5-HT(1B) and 5-HT(1D) receptor subtypes to the formation of inositol phosphates by dual interactions with endogenous G(i/o) and recombinant G(alpha15) proteins. 1093 1

Neuropeptides like galanin produced and released by small cell lung cancer (SCLC) cells are considered principal mitogens in these tumors. We identified the galanin receptor type 2 (GALR2) as the only galanin receptor expressed in H69 and H510 cells. Photoaffinity labeling of G proteins in H69 cell membranes revealed that GALR2 activates G proteins of three subfamilies: G(q), G(i), and G(12). In H69 cells, galanin-induced Ca2+ mobilization was pertussis toxin-insensitive. While phorbol ester-induced extracellular signal-regulated kinase (ERK) activation required protein kinase C (PKC) activity, preincubation of H69 cells with the PKC-inhibitor GF109203X had no effect on galanin-dependent ERK activity. A rise of the intracellular calcium concentration was necessary and sufficient to mediate galanin-induced ERK activation. In support of G(i) coupling, stimulation of GALR2 expressed in HEK293 cells inhibited isoproterenol-induced cAMP accumulation and raised cAMP levels in COS-7 cells when coexpressed with a chimeric G alpha(S)-G alpha(i) protein In H69 cells, galanin activated the monomeric GTPase RhoA and induced stress fiber formation in Swiss 3T3 cells expressing GALR2. Thus, we provide the first direct evidence that in SCLC the mitogenic neuropeptide galanin, interacting with GALR2, simultaneously activates multiple classes of G proteins and signals through the G(q) phospholipase C/calcium sequence and a G(12)/Rho pathway. Oncogene (2000) 19, 4199 - 4209
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PMID:The galanin receptor type 2 initiates multiple signaling pathways in small cell lung cancer cells by coupling to G(q), G(i) and G(12) proteins. 1098 May 93

Chronic treatment with micro or kappa opioid agonists (>/=2 h) inhibits EGF-induced ERK activation in opioid receptor overexpressing COS-7 cells. Although acute mu and kappa opioids activate ERK via a pertussis toxin-sensitive G protein, pertussis toxin insensitivity of the chronic mu (but not kappa) action was observed. Here, we tested several pertussis toxin-insensitive G proteins as candidates to transduce acute and/or chronic opioid modulation of ERK. Overexpressed Galpha(z) (but not Galpha(12)) transduced acute mu (but not kappa) ERK activation in pertussis toxin-treated COS-7 cells. Chronic mu (but not kappa) inhibited EGF stimulation of ERK in pertussis toxin-treated cells overexpressing Galpha(z) or Galpha(12). Transfection of Galpha(13) or Galpha(q) blocked inhibition under the same conditions. Overexpressed interfering and non-interfering Galpha(z) mutants differentially affected mu inhibition of ERK consistent with G(z) transduction. In this and prior studies, Galpha(z) and Galpha(12) immunoreactivity were detected in untransfected COS-7 cells, suggesting that these G proteins may be endogenous mediators of chronic mu inhibitory actions on ERK.
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PMID:Evidence for transduction of mu but not kappa opioid modulation of extracellular signal-regulated kinase activity by G(z) and G(12) proteins. 1098 84


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