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)

We report that sphingosine and short-chain ceramides activate adenylate cyclase and stimulate intracellular cyclic AMP formation in airway-smooth-muscle (ASM) cells. In each case, there is a conditional requirement for GTP-Gs alpha. Sphingosine utilizes a protein kinase C-dependent pathway to elicit activation of adenylate cyclase, whereas for short-chain ceramides the mechanism remains unidentified. In contrast, sphingosine phosphate inhibits Gs-stimulated cyclic AMP formation via a Gi-dependent mechanism. Therefore, the potential interconversion of sphingosine and sphingosine phosphate is a switch that can elicit reciprocal changes in cyclic AMP levels. This may have a significant impact upon the regulation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal specific kinase (JNK) by sphingolipids and may help to explain how growth factors that utilize these second messengers evoke pleiotropic responses such as proliferation and cell survival. In this context, short-chain ceramides are poor stimulators of ERKs in ASM cells, and sphingosine is inactive, whereas both sphingolipids are powerful activators of the JNK module. Activated JNK catalyses N-terminal phosphorylation of c-Jun, a kinase cascade that programmes growth arrest. Therefore, in blocking ceramide-stimulated ERK-2 activity, cyclic AMP may allow the ceramide-dependent activation of JNK to programme cells to opt out of the cell cycle. In contrast, sphingosine phosphate activates ERK-2, potentiates growth-factor-stimulated DNA synthesis and fails to activate JNK, indicating that its sequential formation from ceramide and sphingosine may commit cells to DNA synthesis. ERK-2 can be activated by both cyclic AMP-sensitive c-Raf-1 kinase-dependent and cyclic AMP-insensitive c-Raf-1 kinase-independent pathways in ASM cells. In this context, sphingosine phosphate activates ERK-2 exclusively via c-Raf-1 kinase. Sphingosine phosphate-stimulated ERK-2 activity is also abolished by pertussis toxin, indicating that c-Raf-1 kinase is activated via a Gi-dependent mechanism.
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PMID:The differential regulation of cyclic AMP by sphingomyelin-derived lipids and the modulation of sphingolipid-stimulated extracellular signal regulated kinase-2 in airway smooth muscle. 864 77

The chemotactic peptide f-Met-Leu-Phe (fMLP) stimulates leukocyte functions through binding and activation of a specific G-protein-coupled formyl peptide receptor (FPR). Recent studies have shown that stimulation of neutrophils with fMLP induces the activation of two members of the mitogen-activated protein kinase (MAP kinase) family, ERK1 and ERK2, through mechanisms that are not completely understood but may involve the phosphorylation of the adapter protein SHC by the Src-related kinase Lyn. In this study, transfected fibroblasts expressing the rabbit FPR were used to investigate further the role of Lyn and SHC phosphorylation in fMLP-stimulated MAP kinase activation. Stimulation of transfected cells with fMLP resulted in the time- and dose-dependent increase in tyrosine phosphorylation and activation of ERK1 and ERK2 and the activation of MEK, the MAP kinase/ERK kinase. The activation of both ERKs and MEK was inhibited by preincubation of the cells with pertussis toxin, indicating that activation was dependent upon a Gi/Go-like protein that couples to the receptor. Our data also show that, unlike neutrophils, FPR-transfected fibroblasts do not express the Src-related kinase Lyn. In the absence of Lyn, fMLP stimulation did not result in an increased tyrosine phosphorylation of the adapter protein SHC, whereas it was still able to induce MAP kinase activation. These data suggest that Lyn and SHC are not the only upstream signals for activation of the MAP kinase/ERK pathway by fMLP and demonstrate the potential application of the FPR-transfected cells for the delineation of additional signaling mechanisms stimulated by fMLP.
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PMID:Activation of the mitogen-activated protein kinase pathway by fMet-leu-Phe in the absence of Lyn and tyrosine phosphorylation of SHC in transfected cells. 866 60

It has been known for some time that chronic treatment of neuronal cells and tissues with opioids, contrary to their acute effect, leads to an increase in cAMP accumulation. This phenomenon, defined as adenylyl cyclase superactivation, has been implicated in opiate addiction, yet the mechanism by which it is induced remains unclear. Here, we show that this phenomenon can be reproduced and studied in COS-7 cells cotransfected with adenylyl cyclase type V and mu-opioid receptor cDNAs. These cells display acute opioid inhibition of adenylyl cyclase activity, whereas prolonged exposure to the mu-agonist morphine or [-Ala2, N-methyl-Phe4, Gly-ol5]enkephalin leads to a time-dependent superactivation of adenylyl cyclase. This superactivated state is reversible, because it is gradually lost following agonist withdrawal. Adenylyl cyclase superactivation can be prevented by pertussis toxin pretreatment, indicating the involvement of Gi/o proteins, or by cotransfection with the carboxyl terminus of beta-adrenergic receptor kinase or with alpha-transducin (scavengers of Gbetagamma dimers), indicating a role for the G protein betagamma dimers in adenylyl cyclase superactivation. However, contrary to several other Gbetagamma-dependent signal transduction mechanisms (e.g. the extracellular signal-regulated kinase 2/MAP kinase pathway), adenylyl cyclase superactivation is not affected by the Ras dominant negative mutant N17-Ras.
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PMID:Chronic opioid treatment induces adenylyl cyclase V superactivation. Involvement of Gbetagamma. 870 9

A variety of receptors coupled to GTP-binding regulatory proteins (G proteins) initiate signals that culminate in activation of the mitogen-activated protein kinases ERK1 and ERK2. We demonstrate here that the human 5-HT1A receptor expressed in Chinese hamster ovary cells similarly promotes activation of ERK1 and ERK2, but that the pathway used does not conform entirely to those proposed previously for G protein-coupled receptors. Activation of ERK2 by the 5-HT1A receptor-selective agonist 8-hydroxy-N,N-dipropyl-2-aminotetralin hydrobromide (8-OH-DPAT) was inhibited completely by pertussis toxin and substantially by prolonged treatment of cells with phorbol 12-myristate 13-acetate. The implied requirement for protein kinase C, however, was negated in studies with bisindolylmaleimide and Ro-31-8220, which, although completely inhibiting activation of ERK2 by phorbol ester, had no impact on activation by 8-OH-DPAT. The anticipated inhibition by the tyrosine kinase inhibitors genistein and herbimycin A, moreover, was marginal at best. As expected for a Gi-coupled receptor, the inhibitors of phosphatidylinositol 3-kinase wortmannin and LY294002 inhibited activation of ERK2, albeit only partly (70%). Of significance, an inhibitor of a phosphatidylcholine-specific phospholipase C, tricyclodecan-9-yl-xanthogenate (D609), caused a similar degree of inhibition. When the two types of inhibitors were combined, an almost complete inhibition was achieved. Our data suggest that phosphatidylinositol 3-kinase and phosphatidylcholine-specific phospholipase C represent components of different, but partly overlapping pathways that can account almost entirely for the activation of ERK2 by the 5-HT1A receptor.
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PMID:Activation of a mitogen-activated protein kinase (ERK2) by the 5-hydroxytryptamine1A receptor is sensitive not only to inhibitors of phosphatidylinositol 3-kinase, but to an inhibitor of phosphatidylcholine hydrolysis. 879 86

We reported previously that somatostatin inhibits the expression of the immediate early gene c-fos. Accordingly, we characterized the molecular mechanisms by which somatostatin inhibits c-fos gene expression. Because growth factors activate c-fos through a region of its promoter known as the serum response element [SRE; base pairs (bp) -357 to -276] we transfected rat pituitary adenoma cells (GH3) with plasmids containing the SRE or the SRE core fragment (bp -320 to -298) upstream of the luciferase reporter gene. Epidermal growth factor (EGF) stimulated SRE-luciferase activity, and this effect was inhibited by somatostatin and by the analog MK-678. Identical results were obtained with the SRE core plasmid, demonstrating that the sequence between bp -320 and -298 of the c-fos promoter is a somatostatin response element. Because the extracellular signal-regulated protein kinases (ERKs) induce the SRE via phosphorylation of transcription factors such as Elk-1, we examined the effect of somatostatin on ERK phosphorylation and activation. EGF stimulated tyrosine phosphorylation of ERK2, and MK-678 attenuated this effect. In experiments using in-gel kinase assays, MK-678 also inhibited EGF-stimulated ERK activity via a pertussis toxin sensitive pathway, and this effect resulted in inhibition of Elk-1 transcriptional activity. Our data suggest that one mechanism of somatostatin action involves inhibition of ERK activity, Elk-1 phosphorylation and transcriptional activation, and ultimately c-fos gene transcription.
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PMID:Molecular mechanisms for somatostatin inhibition of c-fos gene expression. 914 1

Identification of a new family of proteins (RGS proteins) that function as negative regulators of G protein signaling has sparked new understanding of desensitization of this signaling process. Recent studies with several mammalian RGS proteins has delineated their ability to interact with and function as GTPase-activating proteins specifically for G proteins in the Gi family. Here, we investigated the functional activity of RGS3 and a truncated form of RGS3 on G protein-coupled receptor-mediated activation of adenylyl cyclase, phosphoinositide phospholipase C, and mitogen-activated protein kinase in intact cells. Polymerase chain reaction and 5'-rapid amplification of cDNA ends analyses revealed the tissue-specific expression of a short form of the RGS3 transcript that encodes the approximate carboxyl-terminal half of RGS3. This truncated form of RGS3 (RGS3T) was shown recently to function as a negative regulator of pheromone signaling in yeast (Druey, K. M., Blumer, K. J., Kang, V. R., and Kehrl, J. H. (1996) Nature 379, 742-746). Baby hamster kidney cells transiently transfected with RGS3T cDNA exhibited a pronounced impairment in platelet-activating factor receptor-stimulated inositol phosphate production, a pertussis toxin-insensitive response. Similarly, calcitonin gene-related peptide receptor-stimulated increases in intracellular cAMP and pituitary adenylate-cyclase activating polypeptide receptor-stimulated increases in both cAMP and inositol phosphates were reduced significantly in RGS3T transfectants compared with vector-transfected control cells. In contrast, baby hamster kidney cells transfected with the full-length RGS3 cDNA showed no impairment in cAMP and inositol phosphate production mediated by these G protein-coupled receptors. However, lysophosphatidic acid receptor-stimulated phosphorylation of endogenous ERK1 and ERK2 was impaired markedly in both RGS3 and RGS3T transfectants, demonstrating the functional ability of both RGS forms to modulate Gi-mediated signaling. These results provide the first evidence for regulatory effects of an RGS protein on Gs- and Gq-mediated signaling in intact cells and document that the carboxyl-terminal region of RGS3 comprises the structural domain for this activity.
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PMID:A truncated form of RGS3 negatively regulates G protein-coupled receptor stimulation of adenylyl cyclase and phosphoinositide phospholipase C. 918 81

Angiotensin II type 2 (AT2) receptors are involved in the inhibition of cell proliferation as well as in apoptosis and neuronal differentiation, through intracellular signalling pathways that remain poorly defined. The present study examines the effect of AT2-receptor stimulation on growth-factor-induced pathways leading to the activation of mitogen-activated protein (MAP) kinases. In N1E-115 neuroblastoma cells, AT2 receptors inhibit the activity of MAP kinases induced by serum as well as by epidermal growth factor. The inhibitory effect of angiotensin II (Ang II) is rapid and transient, and affects both ERK1 and ERK2 (extracellular signal-related protein kinase) isoforms of the enzyme. AT2-mediated MAP kinase inactivation is not sensitive to pertussis toxin or okadaic acid, but involves a vanadate-sensitive protein tyrosine phosphatase (PTP). Expression of MAP kinase phosphatase-1 (MKP-1) is not significantly modified upon AT2-receptor activation, and insensitivity to actinomycin D also rules out transcriptional induction of other MKPs as a possible mechanism for AT2-mediated inactivation of MAP kinases. In addition, we report here that both in N1E-115 cells and in Chinese hamster ovary cells expressing recombinant human AT2 receptors, Ang II rapidly stimulates the catalytic activity of SHP-1, a soluble PTP that has been implicated in termination of signalling by cytokine and growth-factor receptors. These findings thus demonstrate functional negative cross-talk between heptahelical AT2 receptors and receptor tyrosine kinases, and suggest that SHP-1 tyrosine phosphatase is an early transducer of the AT2 receptor signalling pathway.
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PMID:Angiotensin II type 2 receptors mediate inhibition of mitogen-activated protein kinase cascade and functional activation of SHP-1 tyrosine phosphatase. 923 Jan 27

We have previously observed that gastrin has a cholecystokinin B (CCK-B) receptor-mediated growth-promoting effect on the AR42J rat pancreatic acinar cell line and that this effect is paralleled by induction of expression of the early response gene c-fos. We undertook these experiments to elucidate the mechanism for induction of c-fos and the linkage of this action to the trophic effects of gastrin. Gastrin (0.1-10 nM) dose dependently induced luciferase activity in AR42J cells transfected with a construct consisting of a luciferase reporter gene coupled to the serum response element (SRE) of the c-fos promoter. This effect was blocked by the specific CCK-B receptor antagonist D2 but not by the specific CCK-A receptor antagonist L-364,718 or by pertussis toxin, indicating that gastrin targets the SRE via specific CCK-B receptors through a mechanism independent of Gi. Inhibition of protein kinase C (PKC) either by prolonged (24 h) exposure of the cells to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (100 nM) or by incubation with the selective inhibitor GF-109203X (3.5 microM) resulted in an 80% reduction in luciferase activity. Similar results were observed in the presence of the specific extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor PD-98059 (50 microM). We measured ERK2 activity in AR42J cells via in-gel kinase assays and observed that gastrin (1 pM-100 nM) induced ERK2 enzyme activity in a dose-dependent manner. Addition of GF-109203X and PD-98059, either alone or in combination, produced, respectively, partial and total inhibition of gastrin-induced ERK2 activity. Gastrin induction of ERK2 activity also resulted in a threefold increase in the transcriptional activity of Elk-1, a factor known to bind to the c-fos SRE and to be phosphorylated and activated by ERK2. PD-98059 blocked the growth-promoting effect of gastrin on the AR42J cells, demonstrating that this effect depends on activation of MEK. Our data lead us to conclude that the trophic actions of gastrin are mediated by ERK2-induced c-fos gene expression via PKC-dependent and -independent pathways.
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PMID:Molecular mechanisms for the growth factor action of gastrin. 935 32

In this report we show that extracellular signal-regulated kinase-1 and -2 (ERK-1 and -2) respond differently to signals that elicit proliferation and/or differentiation of myoblasts using the C2C12 cell line and nondifferentiating mutant NFB4 cells derived from them. Induction of differentiation by withdrawal of serum rendered ERKs in C2C12 myoblasts relatively insensitive to restimulation by serum. Instead, myogenic differentiation of C2C12 cells was associated with sustained activation of ERK-2 dependent on the insulin-like growth factor II (IGF-II) autocrine loop. By contrast, mutant NFB4 cells cultured under the same conditions remained proliferative and demonstrated robust activation of ERKs in response to serum. Similarly, a Gi-dependent signaling pathway induced activation of ERKs in NFB4 cells, but not in C2C12 cells, after stimulation by lysophosphatidic acid (LPA). In NFB4 cells partially rescued by prolonged IGF-I treatment, ERK activity remained responsive to Gi-dependent LPA stimulation, whereas rescue of NFB4 cells by constitutive expression of myogenin or MyoD, associated with activation of the IGF-II autocrine loop, rendered the Gi-signaling pathway refractory to LPA stimulation. Relatively high levels of G(alpha i2) were detected in NFB4 cells and IGF-I treated NFB4 cells, which correlated with responsive Gi signaling. Activation of the IGF-II autocrine loop in C2C12 and NFB4 myoblasts or treatment with IGF-II was associated with loss of G(alpha i2) and inhibition of Gi-dependent signaling. Thus, IGF-I and IGF-II activate distinct signaling cascades, with IGF-II eliciting a stronger differentiation effect correlated with down-regulation of G(alpha i2) protein. Short-term stimulation of NFB4 cells with IGF-I, a mitogenic signal for myoblasts, also induced ERK-1 and -2 activation. Transient stimulation of NFB4 cells with IGF-I while blocking activation of Gi-proteins is with pertussis toxin resulted in preferential activation of ERK-2 characteristic of differentiated C2C12 cells, suggesting that proliferation induced by IGF-I is Gi-dependent and separable from the IGF-I-signaling pathway that leads to differentiation.
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PMID:Extracellular signal-regulated kinase-1 and -2 respond differently to mitogenic and differentiative signaling pathways in myoblasts. 941 7

Recent results indicate that a fluoroalumino complex (AlFx) is probably the molecule responsible for the mitogenic effect of fluoride in MC3T3-E1 osteoblast-like cells. Initial analysis suggested that a tyrosine phosphorylation (tyr phos) process similar to that induced by thrombin and activation of the p42 MAP kinase (ERK 2) mediate this cellular response. In the present study, the signaling mechanism activated by AlFx was further investigated. The results indicated that AlFx dose-dependently enhanced the tyr phos of the cell adhesion proteins FAK and paxillin, as well as of the adaptor molecules p46shc, p52shc, and p66shc and their association with GRB2. Pretreatment of MC3T3-E1 cells with cytochalasin D completely prevented FAK and paxillin tyr phos without any alteration in the tyr phos of Shc proteins and activation of ERK2 induced by AlFx. This observation suggests that in confluent MC3T3-E1 cells, there is no link between the activation of FAK induced by AlFx and the stimulation of ERK2. Pretreatment of the cells with pertussis toxin inhibited Shc phosphorylation, activation of ERK2, and markedly reduced cell replication induced by AlFx. This toxin also significantly reduced the stimulation of Pi transport activity induced by AlFx in these cells. Alteration in tyr phos induced by AlFx was not associated with any detectable inhibition of tyrosine phosphatase activity in MC3T3-E1 cell homogenates, suggesting that enhanced tyr phos induced by AlFx probably resulted from activation of a tyrosine kinase. In conclusion, the results of this study suggest that the mitogenic effect of fluoride in MC3T3-E1 osteoblast-like cells is mediated by the activation of a pertussis toxin-sensitive Gi/o protein and suggest an important role for these heterotrimeric G proteins in controlling the growth and differentiation of bone-forming cells.
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PMID:Mechanism of the mitogenic effect of fluoride on osteoblast-like cells: evidences for a G protein-dependent tyrosine phosphorylation process. 942 Dec 30


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