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)

Signaling between embryonic myoblasts involves prostaglandin metabolism, the activation of a membrane receptor and changes in polyphosphatidyl inositol metabolism. Many of these membrane-localized events occur between 33 to 35 h of differentiation, concomitant with a dramatic change in membrane organization, in myoblast aggregates in culture. Since many receptors affect inositol phosphate metabolism by activating a GTP-binding protein (G protein), we asked if there was evidence for such a protein in myogenic signaling. We show that during the period of differentiation in culture when prostaglandin is needed to bind to a transient receptor, a pertussis toxin-sensitive but cholera toxin-insensitive G protein must act. If this activation is blocked, the characteristic change in myoblast cell adhesion and subsequent membrane fusion do not occur. We suggest that a G protein couples the activated prostaglandin receptor and the change in polyphosphatidyl inositol metabolism and that this membrane transduction step is necessary for subsequent membrane differentiation events during myogenesis.
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PMID:Requirement for G protein activity at a specific time during embryonic chick myogenesis. 210 25

The regulation of cAMP generation in rat myometrium during gestation was investigated comparatively to the stimulations evoked in the estrogen-dominated myometrium. At the onset of gestation, there was a progressive attenuation in both tissue cAMP accumulation and adenylate cyclase activation in response to isoproterenol and prostaglandins (PGs) (PGE2 and prostacyclin, PGI2), as well as to cholera toxin and to forskolin. Minimal responses were observed at midgestation (day 12). The decline in isoproterenol-mediated cAMP accumulation could not be ascribed to alterations in either beta-adrenergic receptor density or coupling properties. Treatment of day 12 myometrium with islet-activating protein (IAP), pertussis toxin, caused a reversal of the attenuated beta-adrenergic--as well as cholera toxin--responses, suggesting that the inhibitory regulatory protein, Gi, was involved. However IAP treatment did not improve the PGE2-mediated stimulatory effect. In membranes from day 12 myometrium, the amount of [32P]NAD incorporated by IAP into the Mr = 41,000 peptides (alpha i, subunit of Gi was markedly increased compared to membranes from day 0 tissue. There was also a consistent decrease (25%) of the label incorporated by cholera toxin into the Mr = 52,000 (major) and 45,000/53,000 (minor) peptides (alpha s, subunit of Gs). The advanced stages of gestation were associated with a progressive restoration of cAMP responses to isoproterenol, cholera toxin, and forskolin with a full responsiveness before parturition (day 22). By contrast, the inability of PGE2 to generate any active Gs (stimulatory regulatory protein)-C complex persisted and coincided with the development of PGE2-induced inhibition of cAMP generation due to isoproterenol. The inhibitory effect, which was similarly evoked by PGE2 as well as by PGI2 and PGF2 alpha, was prevented by IAP. The data suggest that alterations of the stimulatory Gs-mediated pathway, which culminated at midgestation, is due at least in part to an increase in the abundance of Gi relative to Gs. Additional alterations operate at the level of the prostaglandin receptor(s) with a conversion from a stimulatory (Gs-mediated) cAMP response in the estrogen-dominated myometrium to an inhibitory (Gi-mediated) effect, fully expressed in the final stage of gestation.
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PMID:Heterologous regulations of cAMP responses in pregnant rat myometrium. Evolution from a stimulatory to an inhibitory prostaglandin E2 and prostacyclin effect. 303 39

We recently identified four isoforms of bovine prostaglandin E receptor EP3 subtype, which are coupled to different signaling pathways; EP3A is coupled to inhibition of adenylate cyclase, while EP3B and EP3C are coupled to its stimulation and EP3D is coupled to phosphatidylinositol turnover, in addition to the adenylate cyclase system (Namba, T., Sugimoto, Y., Negishi, M., Irie, A., Ushikubi, F., Kakizuka, Ito, S., A., Ichikawa, A., and Narumiya, S. (1993) Nature 365, 166-170). We examined here the identity of coupled G proteins and their regulation by one of the isoforms, EP3C, in the membranes of EP3C cDNA-transfected Chinese hamster ovary cells. M&B 28767, an EP3 agonist, stimulated the GTPase activity in the pertussis toxin (PT)-treated cell membrane, but inhibited it in the cholera toxin (CT)-treated cell membrane, while the agonist neither stimulated nor inhibited it in the both PT- and CT-treated cell membrane. In the PT- and CT-treated cell membrane reconstituted with various G proteins, M&B 28767 inhibited the GTPase activity of G(o), but stimulated that of Gs. On the other hand, M&B 28767 did not affect the GTPase activity of Gi1, Gi2, or Gi3. M&B 28767 increased the apparent affinity of G(o) for GDP without any change in that for GTP, as assessed by displacement of [35S]GTP gamma S (guanosine 5'-O-(3-thiotriphosphate)) binding to G(o). In contrast, M&B 28767 increased the apparent affinity of Gs for GTP but decreased that for GDP. These results demonstrated that the EP3 receptor isoform is coupled to two different G proteins, and oppositely regulates their activities, inhibition of G(o), and stimulation of Gs.
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PMID:Opposite coupling of prostaglandin E receptor EP3C with Gs and G(o). Stimulation of Gs and inhibition of G(o). 825 19

Functional cDNA clones for two isoforms of the mouse prostaglandin E receptor EP3 subtype derived from alternative RNA splicing were obtained. The two isoforms are only different in the sequence of the putative cytoplasmic carboxyl-terminal tail and their hydrophobicity; one isoform, named EP3 alpha, has a hydrophilic tail, and the other, named EP3 beta, has a hydrophobic tail. When expressed, the two receptors displayed identical ligand binding properties but different responses to guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S). Without a change in the Bmax value, GTP gamma S increased Kd for prostaglandin E2 of EP3 beta and decreased that of EP3 alpha. These effects were abolished by the treatment of membranes with pertussis toxin and restored by the addition of Gi2. Although both isoforms exerted inhibition of forskolin-induced cAMP accumulation, three orders lower concentrations of agonists were required for EP3 alpha than EP3 beta for 50% inhibition of cAMP formation. A similar difference in agonist potency was observed also for agonist-induced stimulation of GTPase activity in membranes. Thus, the two receptors with different carboxyl-terminal tails show different coupling to the Gi protein, leading to the opposite responses to GTP in the ligand binding affinity and to different affinities of the agonist-occupied receptors to the G proteins.
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PMID:Two isoforms of the EP3 receptor with different carboxyl-terminal domains. Identical ligand binding properties and different coupling properties with Gi proteins. 838 13

1. The human EP3 prostaglandin receptor is a seven transmembrane, G protein-coupled receptor that couples to inhibition of adenylyl cyclase. The receptor occurs as at least six isoforms which result from alternative splicing. The isoforms are identical over the first 359 amino acids, comprising the seven transmembrane helices, but differ in the carboxyl terminal tail which ranges in length from 6 to 65 amino acids beyond the common region. 2. We have stably expressed in CHO-K1 cells four of the isoforms (EP3I-EP3IV) and a form of the EP3 receptor (T-359) truncated at the carboxyl-terminal region defined by the alternative splicing site at amino acid number 359. 3. Isoforms EP3I and EP3II showed concentration-dependent inhibition of forskolin-stimulated adenylyl cyclase in CHO-K1 cells by the EP3 receptor agonist, sulprostone. The IC50 calculated for sulprostone inhibition was 0.2 nM for EP3I and 0.15 nM for EP3II. The maximum extent of inhibition was 80% for both isoforms. 4. Isoforms EP3III and EP3IV showed marked constitutive activity, inhibiting forskolin-stimulated adenylyl cyclase in the absence of agonist. EP3IV also displayed some agonist-dependent inhibition whereas EP3III was fully constitutively active. 5. The truncated receptor T-359 was fully constitutively active, inhibiting forskolin-stimulated adenylyl cyclase by about 70% in the absence of agonist, and showed no agonist-dependent inhibition, in agreement with a similar truncation of the mouse EP3 receptor. 6. To confirm that differences in cyclic AMP level between isoforms represent constitutive activity, we treated cells with pertussis toxin for 6 h to abolish Gi function. Pertussis toxin reversed sulprostone-mediated inhibition of cyclic AMP formation in EP3I and EP3II and abolished constitutive activity of EP3III, EP3IV and T-359 so that the level of forskolin-stimulated cyclic AMP produced was the same in all cells and similar to that obtained in mock-transfected cells. In mock-transfected cells, sulprostone had no effect on forskolin-stimulated cyclic AMP formation. 7. For these experiments we chose clones that showed similar expression levels of each isoform, as determined by binding of [3H]-prostaglandin E2 (PGE2) (EP3I, 0.71; EP3II, 1.47; EP3IV, 1.59 pmol mg-1 protein). Mock-transfected cells showed no detectable binding of [3H]-PGE2. In addition, we performed a detailed study of the effects of expression level on constitutive activity. Over a six fold range of expression there was no change in the properties of each isoform with regard to whether it was constitutively active or not. 8. The degree of constitutive activity correlated with the inverse of the length of the C-terminal tail of the isoforms. However, no correlation was found between isoforms from human and mouse: whereas EP3II shows no constitutive activity, its mouse homologue, EP3 gamma, shows almost complete constitutive activity, even though the C-terminal domains of the receptors following the splice site differ in only 7 of 29 amino acids.
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PMID:Constitutive activity of human prostaglandin E receptor EP3 isoforms. 915 43

We have cloned two isoforms of the mouse prostaglandin E receptor EP3 subtype, EP3alpha and EP3beta, with different carboxyl-terminal tails, produced through alternative splicing. To determine the functional differences between the two isoforms, we examined the role of the isoforms in regulation of the actin cytoskeleton using Mardin-Darby canine kidney cells expressing these isoforms. The EP3alpha isoform constitutively induced stress fiber formation, independent of an agonist, while the EP3beta isoform agonist-dependently induced stress fiber formation. Pertussis toxin did not prevent stress fiber formation. This signaling pathway is mediated by Rho, because C3 transferase microinjection inhibited stress fiber formation. Therefore, the physiological significance of these isoforms of the EP3 receptor may lie in their different agonist dependency in Rho-mediated stress fiber formation via a pertussis toxin-insensitive G protein.
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PMID:Two isoforms of prostaglandin EP3 receptor exhibiting constitutive activity and agonist-dependent activity in Rho-mediated stress fiber formation. 917 65

The binding of insulin in physiological amounts to human blood platelets, which increases adenylate cyclase-linked prostacyclin receptor numbers on the cell surface, was found to be directly related to the ADP-ribosylation of the Gi alpha. Conversely, resuspension of the insulin-treated platelets in the hormone-free medium decreased both the prostaglandin receptor numbers and ADP-ribosylation of Gi alpha. Furthermore, incubation of platelets with pertussis toxin or its A-protomer, which ADP-ribosylates Gi alpha, also stimulated the binding of the prostanoid. These results suggest that the increase of prostacyclin receptor numbers in platelets is mediated through the ADP-ribosylation of Gi alpha.
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PMID:Insulin-induced expression of prostacyclin receptors on platelets is mediated through ADP-ribosylation of Gi alpha protein. 983 47