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)

Adenosine exerts a mitogenic effect on human endothelial cells via stimulation of the A2A-adenosine receptor. This effect can also be elicited by the beta2-adrenergic receptor but is not mimicked by elevation of intracellular cAMP levels. In the present work, we report that stimulation of the A2A-adenosine receptor and of the beta2-adrenergic receptor activates mitogen-activated protein kinase (MAP kinase) in human endothelial cells based on the following criteria: adenosine analogues and beta-adrenergic agonists cause an (i) increase in tyrosine phosphorylation of the p42 isoform and to a lesser extent of the p44 isoform of MAP kinase and (ii) stimulate the phosphorylation of myelin basic protein by MAP kinase; (iii) this is accompanied by a redistribution of the enzyme to the perinuclear region. Pretreatment of the cells with cholera toxin (to down-regulate Gsalpha) abolishes activation of MAP kinase by isoproterenol but not that induced by adenosine analogues. In addition, MAP kinase stimulation via the A2A-adenosine receptor is neither impaired following pretreatment of the cells with pertussis toxin (to block Gi-dependent pathways) nor affected by GF109203X (1 microM; to inhibit typical protein kinase C isoforms) nor by a monoclonal antibody, which blocks epidermal growth factor-dependent signaling. In contrast, MAP kinase activation is blocked by PD 098059, an inhibitor of MAP kinase kinase 1 (MEK1) activation, which also blunts the A2A-adenosine receptor-mediated increase in [3H]thymidine incorporation. Activation of the A2A-adenosine receptor is associated with increased levels of GTP-bound p21(ras). Thus, our experiments define stimulation of MAP kinase as the candidate cellular target mediating the mitogenic action of the A2A-adenosine receptor on primary human endothelial cells; the signaling pathway operates via p21(ras) and MEK1 but is independent of Gi, Gs, and the typical protein kinase C isoforms. This implies an additional G protein which links this prototypical Gs-coupled receptor to the MAP kinase cascade.
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PMID:Stimulation of the mitogen-activated protein kinase via the A2A-adenosine receptor in primary human endothelial cells. 903 93

The three alpha2-adrenergic receptor subtypes (alpha2a, alpha2b, and alpha2c) are highly homologous G protein-coupled receptors. These receptors all couple to pertussis toxin-sensitive G proteins and have relatively similar pharmacological properties. To further explore functional differences between these receptors, we used immunocytochemical techniques to compare the ability of the three alpha2-receptor subtypes to undergo agonist-mediated internalization. The alpha2a-receptor does not internalize after agonist treatment. In contrast, we observed that the alpha2b-receptor is able to undergo agonist-induced internalization and seems to follow the same endosomal pathway used by the beta2-adrenergic receptor. Attempts to examine internalization of the alpha2c-receptor were complicated by the fact that the majority of the alpha2c receptor resides in the endoplasmic reticulum and cis/media Golgi and there is relatively little cell surface localization. Nevertheless, we were able to detect some internalization of the alpha2c-receptor after prolonged agonist treatment. However, we observed no significant movement of alpha2c-receptor from the intracellular pool to the plasma membrane during a 4-hr treatment of cells with cycloheximide, suggesting that these cells are unable to process alpha2c-receptors in the same way they process the alpha2a or alpha2b subtypes.
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PMID:Subtype-specific intracellular trafficking of alpha2-adrenergic receptors. 914 9

The role of beta1- and beta2-adrenergic receptor stimulation in modulating adenosine 3',5'-cyclic monophosphate (cAMP)-regulated Cl- and Ca2+ currents was investigated with use of guinea pig ventricular myocytes. Activation of the Cl- current by the nonselective beta-receptor agonist isoproterenol (Iso) was not affected by the beta2-receptor antagonist ICI-118,551 (ICI), but it was blocked by the beta1-receptor antagonist atenolol. The inability of beta2-receptor stimulation to activate the Cl- current was confirmed by the lack of response to the selective beta2-receptor agonists salbutamol and zinterol. Responses to beta2-adrenergic receptor stimulation were also looked for in pertussis toxin (PTX)-treated myocytes because PTX increases the sensitivity of responses to Iso, and PTX has been reported to increase the responsiveness to beta2- but not beta1-receptor stimulation. PTX treatment increased the sensitivity of the Cl- current to activation by Iso in the presence of ICI, indicating that PTX increases beta1-receptor responsiveness. PTX treatment also resulted in the ability of salbutamol to activate the Cl- current. However, the response to salbutamol was blocked by atenolol but not by appropriate concentrations of ICI, suggesting that salbutamol was activating beta1-receptors. These results indicate that PTX treatment increases the sensitivity to beta1-receptor stimulation, without affecting beta2-responsiveness. To verify that the lack of response to beta2-receptor stimulation was not unique to the Cl- current, the effects of beta2-receptor agonists on the L-type Ca2+ current were also examined. The Ca2+ current was only affected by high concentrations of zinterol or salbutamol, and such responses were blocked by atenolol, but not by ICI, suggesting that activation of beta1-receptors was involved. These results indicate that beta1- but not beta2-adrenergic receptor stimulation plays an important role in modulating the cAMP-regulated Cl- and Ca2+ currents in guinea pig ventricular myocytes.
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PMID:Role of beta1- and beta2-adrenergic receptors in regulation of Cl- and Ca2+ channels in guinea pig ventricular myocytes. 936 29

Many of the G-protein-coupled receptors for hormones that bind to the cell surface can signal to the interior of the cell through several different classes of G protein. For example, although most of the actions of the prototype beta2-adrenergic receptor are mediated through Gs proteins and the cyclic-AMP-dependent protein kinase (PKA) system, beta-adrenergic receptors can also couple to Gi proteins. Here we investigate the mechanism that controls the specificity of this coupling. We show that in HEK293 cells, stimulation of mitogen-activated protein (MAP) kinase by the beta2-adrenergic receptor is mediated by the betagamma subunits of pertussis-toxin-sensitive G proteins through a pathway involving the non-receptor tyrosine kinase c-Src and the G protein Ras. Activation of this pathway by the beta2-adrenergic receptor requires that the receptor be phosphorylated by PKA because it is blocked by H-89, an inhibitor of PKA. Additionally, a mutant of the receptor, which lacks the sites normally phosphorylated by PKA, can activate adenylyl cyclase, the enzyme that generates cAMP, but not MAP kinase. Our results demonstrate that a mechanism previously shown to mediate uncoupling of the beta2-adrenergic receptor from Gs and thus heterologous desensitization (PKA-mediated receptor phosphorylation), also serves to 'switch' coupling of this receptor from Gs to Gi and initiate a new set of signalling events.
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PMID:Switching of the coupling of the beta2-adrenergic receptor to different G proteins by protein kinase A. 936 96

The expression of a cloned Drosophila octopamine/tyramine receptor (OctyR99AB) is described in Xenopus oocytes. Agonist stimulation of OctyR99AB receptors increased intracellular Ca2+ levels monitored as changes in the endogenous inward Ca2+-dependent chloride current. The receptor is preferentially sensitive to biogenic amines with a single hydroxyl on the aromatic ring. The G-protein, Galphai, appears to be involved in the coupling of the receptor to the production of intracellular calcium signals, since the effect is pertussis-toxin sensitive and is blocked or substantially reduced in antisense knockout experiments using oligonucleotides directed against Galphai but not by those directed against Galphao, Galphaq and Galpha11. The increase in intracellular calcium levels induced by activation of the OctyR99AB receptor can potentiate the ability of activation of a co-expressed beta2-adrenergic receptor to increase oocyte cyclic AMP levels. A comparison of the pharmacological coupling of OctyR99AB to different second messenger systems when expressed in Xenopus oocytes with previous studies on the expression of the receptor in a Chinese hamster ovary cell line suggests that the property of agonist-specific coupling of the receptor to different second messenger systems may be cell-specific, depending upon the G-protein environment of any particular cell type.
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PMID:The expression of a cloned Drosophila octopamine/tyramine receptor in Xenopus oocytes. 937

-Transgenic mouse models have been developed to manipulate beta-adrenergic receptor (betaAR) signal transduction. Although several of these models have altered betaAR subtypes, the specific functional sequelae of betaAR stimulation in murine heart, particularly those of beta2-adrenergic receptor (beta2AR) stimulation, have not been characterized. In the present study, we investigated effects of beta2AR stimulation on contraction, [Ca2+]i transient, and L-type Ca2+ currents (ICa) in single ventricular myocytes isolated from transgenic mice overexpressing human beta2AR (TG4 mice) and wild-type (WT) littermates. Baseline contractility of TG4 heart cells was increased by 3-fold relative to WT controls as a result of the presence of spontaneous beta2AR activation. In contrast, beta2AR stimulation by zinterol or isoproterenol plus a selective beta1-adrenergic receptor (beta1AR) antagonist CGP 20712A failed to enhance the contractility in TG4 myocytes, and more surprisingly, beta2AR stimulation was also ineffective in increasing contractility in WT myocytes. Pertussis toxin (PTX) treatment fully rescued the ICa, [Ca2+]i, and contractile responses to beta2AR agonists in both WT and TG4 cells. The PTX-rescued murine cardiac beta2AR response is mediated by cAMP-dependent mechanisms, because it was totally blocked by the inhibitory cAMP analog Rp-cAMPS. These results suggest that PTX-sensitive G proteins are responsible for the unresponsiveness of mouse heart to agonist-induced beta2AR stimulation. This was further corroborated by an increased incorporation of the photoreactive GTP analog [gamma-32P]GTP azidoanilide into alpha subunits of Gi2 and Gi3 after beta2AR stimulation by zinterol or isoproterenol plus the beta1AR blocker CGP 20712A. This effect to activate Gi proteins was abolished by a selective beta2AR blocker ICI 118,551 or by PTX treatment. Thus, we conclude that (1) beta2ARs in murine cardiac myocytes couple to concurrent Gs and Gi signaling, resulting in null inotropic response, unless the Gi signaling is inhibited; (2) as a special case, the lack of cardiac contractile response to beta2AR agonists in TG4 mice is not due to a saturation of cell contractility or of the cAMP signaling cascade but rather to an activation of beta2AR-coupled Gi proteins; and (3) spontaneous beta2AR activation may differ from agonist-stimulated beta2AR signaling.
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PMID:Coupling of beta2-adrenoceptor to Gi proteins and its physiological relevance in murine cardiac myocytes. 991 73

A novel thiadiazole compound, SCH-202676 (N-(2,3-diphenyl-1,2, 4-thiadiazol-5-(2H)-ylidene)methanamine), has been identified as an inhibitor of both agonist and antagonist binding to G protein-coupled receptors (GPCRs). SCH-202676 inhibited radioligand binding to a number of structurally distinct, heterologously expressed GPCRs, including the human mu-, delta-, and kappa-opioid, alpha- and beta-adrenergic, muscarinic M1 and M2, and dopaminergic D1 and D2 receptors, but not to the tyrosine kinase epidermal growth factor receptor. SCH-202676 had no direct effect on G protein activity as assessed by [35S]guanosine-5'-O-(gamma-thio)triphosphate binding to purified recombinant G(oalpha)- or G(betagamma)-stimulated ADP-ribosylation of G(oalpha) by pertussis toxin. In addition, SCH-202676 inhibited antagonist binding to the beta2-adrenergic receptor expressed in Escherichia coli, a system devoid of classical heterotrimeric G proteins. SCH-202676 inhibited radiolabeled agonist and antagonist binding to the alpha2a-adrenergic receptor with an IC50 value of 0.5 microM, decreased the Bmax value of the binding sites with a slight increase in the KD value, and inhibited agonist-induced activation of the receptor. The effects of SCH-202676 were reversible. Incubation of plasma membranes with 10 microM SCH-202676 did not alter subsequent radioligand binding to the alpha2a-adrenergic receptor and the dopaminergic D1 receptor. Taken together, our data suggest that SCH-202676 has the unique ability to allosterically regulate agonist and antagonist binding to GPCRs in a manner that is both selective and reversible. The scope of the data presented suggests this occurs by direct interaction with a structural motif common to a large number of GPCRs or by activation/inhibition of an unidentified accessory protein that regulates GPCR function.
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PMID:SCH-202676: An allosteric modulator of both agonist and antagonist binding to G protein-coupled receptors. 1112 21

We present evidence of a link between low-density lipoprotein (LDL) receptor binding and activation of a platelet G-coupled protein. LDL stimulation induced cytosolic [Ca2+]i mobilization, increase in inositol 1,4,5-triphosphate (IP3) formation and a rapid cytosol-to-membrane translocation of protein kinase C (PKC) enzymatic activity. Pertussis toxin inhibited all the stimulatory effects, whereas cholera toxin had no effect. Using ligand-binding assays, we demonstrated that exposing platelet LDL receptors to high concentrations of LDL (1.5 g/l) caused a rapid down-regulation and desensitization, as shown by the reduction in the Bmax, intracellular [Ca2+]i mobilization and IP3 formation to 65, 73 and 63%, respectively. The inhibitory effects were reversible and dose and time dependent. Furthermore, VLDL (0.2 g/l) and IDL (0.07 g/l) induced similar desensitization effects. However, HDL3 (up to 1.5 g/l), chylomicrons (up to 0.5 g/l) and cyclohexandione-modified LDL (which does not bind to platelets) had no significant effects. Protein kinase C inhibitors (150 nmol/l staurosporine, 100 micromol/l H-7, and 10 nmol/l bisindolylmaleimide) inhibited desensitization to 71%, on average. Sequestration blocking agents (0.30 g/l, concanavalin A) had no significant effect if phosphorylation was operative. However, there was a complete blockade with the concurrent inhibition of both pathways. In contrast, cAMP-dependent protein kinase inhibitors (PKI, 1 micromol/l) or beta2-adrenergic receptor kinase inhibitors (100 nmol/l, heparin), had no effect. Overall results indicate that LDL binds to a pertussis sensitive G-protein coupled receptor and that high levels of lipoproteins down-regulate the number of receptors and desensitize its mediated response by a mechanism that involves PKC-phosphorylation and sequestration of binding sites. This new regulatory mechanism may have implications for the thrombogenicity in hyperlipidemia and for effects of lipid lowering therapy.
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PMID:Low-density lipoprotein (LDL) binds to a G-protein coupled receptor in human platelets. Evidence that the proaggregatory effect induced by LDL is modulated by down-regulation of binding sites and desensitization of its mediated signaling. 1122 31

The frizzled receptors, which mediate development and display seven hydrophobic, membrane-spanning segments, are cell membrane-localized. We constructed a chimeric receptor with the ligand-binding and transmembrane segments from the beta2-adrenergic receptor (beta2AR) and the cytoplasmic domains from rat Frizzled-1 (Rfz1). Stimulation of mouse F9 clones expressing the chimera (beta2AR-Rfz1) with the beta-adrenergic agonist isoproterenol stimulated stabilization of beta-catenin, activation of a beta-catenin-sensitive promoter, and formation of primitive endoderm. The response was blocked by inactivation of pertussis toxin-sensitive, heterotrimeric guanine nucleotide-binding proteins (G proteins) and by depletion of Galphaq and Galphao. Thus, G proteins are elements of Wnt/Frizzled-1 signaling to the beta-catenin-lymphoid-enhancer factor (LEF)-T cell factor (Tcf) pathway.
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PMID:G protein signaling from activated rat frizzled-1 to the beta-catenin-Lef-Tcf pathway. 1138 77

The beta2-adrenergic receptor (beta2-AR)-mediated increase in cardiac L-type Ca2+ current (I(Ca,L)) has been documented in normal subjects. However, the role and mechanism of beta2-AR activation on I(Ca,L) in heart failure (HF) are unclear. Accordingly, we compared the effect of zinterol (ZIN), a highly selective beta2-AR agonist, on I(Ca,L) in isolated left ventricular cardiomyocytes obtained from normal control and age-matched rats with HF induced by left coronary artery ligation (4 months). I(Ca,L) was measured by using the whole-cell voltage-clamp technique. In normal myocytes, superfusion of ZIN (10(-5) M) caused a 21% increase in I(Ca,L) (9.21 +/- 0.24 versus 7.59 +/- 0.20 pA/pF) (p < 0.05). In HF myocytes, the same concentration of ZIN produced a significantly greater increase (30%) in I(Ca,L) (6.20 +/- 0.24 versus 4.75 +/- 0.17 pA/pF) (p < 0.01). This ZIN-induced increase in I(Ca,L) was further augmented in both normal and HF myocytes (normal: 59 versus 21%; HF: 71 versus 30%) after the incubation of myocytes with pertussis toxin (PTX, 2 microg/ml, 36 degrees C, 6 h). These effects were not modified by the incubation of myocytes with CGP-20712A (3 x 10(-7) M), a beta1-AR antagonist, but were abolished by pretreatment of myocytes with ICI-118551 (10(-7) M), a beta2-AR antagonist. In addition, all of the effects induced by ZIN were completely prevented in the presence of an inhibitory cAMP analog, Rp-cAMPS (100 microM, in the patch-pipette solution). In conclusion, beta2-AR activation stimulates L-type Ca2+ channels and increases I(Ca,L) in both normal and HF myocytes. In HF, beta2-AR activation-induced augmentation of I(Ca,L) was increased. These effects are likely to be mediated through a cAMP-dependent mechanism and coupled with both stimulatory G protein and PTX-sensitive G protein.
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PMID:Enhanced cardiac L-type calcium current response to beta2-adrenergic stimulation in heart failure. 1140 41


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