Ammonia promotes accumulation of intracellular cAMP in differentiating amoebae of Dictyostelium discoideum

Development ◽  
1990 ◽  
Vol 109 (3) ◽  
pp. 715-722
Author(s):  
B.B. Riley ◽  
S.L. Barclay
Keyword(s):  
Dictyostelium Discoideum ◽  
Active Species ◽  
Spore Formation ◽  
Intracellular Camp ◽  
Simultaneous Exposure ◽  
High Ph ◽  
Camp Hydrolysis ◽  
Extracellular Camp ◽  
Camp Levels

We used sporogenous mutants of Dictyostelium discoideum to investigate the mechanism(s) by which exogenous NH4Cl and high ambient pH promote spore formation during in vitro differentiation. The level of NH4Cl required to optimize spore formation is correlated inversely with pH, indicating that NH3 rather than NH4+ is the active species. The spore-promoting activity of high ambient pH (without exogenous NH4Cl) was eliminated by the addition of an NH3-scavenging cocktail, suggesting that high pH promotes spore differentiation by increasing the ratio of NH3:NH4+ secreted into the medium by developing cells. High ammonia levels and high pH stimulated precocious accumulation of intracellular cAMP in both sporogenous and wild-type cells. In both treatments, peak cAMP levels equaled or exceeded control levels and were maintained for longer periods than in control cells. In contrast, ammonia strongly inhibited accumulation of extracellular cAMP without increasing the rate of extracellular cAMP hydrolysis, indicating that ammonia promotes accumulation of intracellular cAMP by inhibiting cAMP secretion. These results are consistent with previous observations that factors that raise intracellular cAMP levels increase spore formation. Lowering intracellular cAMP levels with caffeine or progesterone inhibited spore formation, but simultaneous exposure to these drugs and optimal concentrations of NH4Cl restored both cAMP accumulation and spore formation to normal levels. These data suggest that ammonia, which is a natural Dictyostelium morphogen, favors spore formation by promoting accumulation or maintenance of high intracellular cAMP levels.

Chloroquine stimulates absorption and inhibits secretion of ileal water and electrolytes

1982 ◽  
Vol 243 (2) ◽  
pp. G117-G126
Author(s):  
R. Fogel ◽  
G. W. Sharp ◽  
M. Donowitz
Keyword(s):  
Cholera Toxin ◽  
Calcium Content ◽  
Intracellular Camp ◽  
Rabbit Ileum ◽  
Camp Content ◽  
Serosal Surface ◽  
Ileal Absorption ◽  
Camp Levels

The effects of chloroquine diphosphate, a drug with "'membrane-stabilizing" properties, were studied on basal ileal absorption and on ileal secretion induced by increased intracellular cAMP levels and calcium (serotonin). The studies were performed on rat (in vivo) and rabbit ileum (in vitro). Intraluminal chloroquine (10(-4) M) reversed cholera toxin- and theophylline-induced secretion in rat ileum but did not alter the cholera toxin- and theophylline-induced increases in cAMP content. Addition of chloroquine (10(-4) M) to the mucosal surface of rabbit ileum did not alter basal active electrolyte transport or the serotonin-induced decreased Na and Cl absorption but inhibited the theophylline-induced C1 secretion. Addition of chloroquine (10(-4)) M) to the serosal surface stimulated net Na and Cl absorption. This effect may involve intracellular calcium. Chloroquine increased the rabbit ileal calcium content and decreased 45Ca2+ influx from the serosal surface. Both the mucosal and serosal effects of chloroquine described led to a net increase in absorptive function of the intestine and should prove useful in developing treatment of diarrheal diseases.

scholarly journals A pharmacologically distinct cyclic AMP receptor is responsible for the regulation of gp80 expression in Dictyostelium discoideum.

1990 ◽  
Vol 10 (7) ◽  
pp. 3297-3306 ◽  
Author(s):  
P C Ma ◽  
C H Siu
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Dictyostelium Discoideum ◽  
Surface Glycoprotein ◽  
Intracellular Camp ◽  
Cell Surface Glycoprotein ◽  
Cyclase Activation ◽  
Adenylate Cyclase Activation ◽  
Camp Receptor

The EDTA-resistant cell-cell adhesion expressed at the aggregation stage of Dictyostelium discoideum is mediated by a cell surface glycoprotein of Mr 80,000 (gp80). The expression of gp80 is developmentally regulated by cyclic AMP (cAMP). In vitro nuclear run-on experiments show that transcription of the gp80 gene is initiated soon after the onset of development. The basal level of gp80 transcription is significantly augmented by exogenous cAMP pulses. Interestingly, in analog studies, 2'-deoxy-cAMP, 8-bromo-cAMP, and N6-monobutyryl-cAMP are all capable of inducing a rapid accumulation of gp80 mRNA, suggesting the presence of a unique cAMP receptor that responds equally well to these analogs. To determine whether intracellular cAMP plays a role in the regulation of gp80 expression, caffeine was used to block cAMP-induced receptor-mediated adenylate cyclase activation. Expression of gp80 mRNA was blocked in caffeine-treated cells but could be substantially restored by treatment with exogenous cAMP pulses, suggesting that adenylate cyclase activation is not required. gp80 expression was also examined in the signal transduction mutants synag 7 and frigid A. In both mutants, gp80 was expressed at the basal level. Pulses of cAMP as well as 2'-deoxy-cAMP and N6-monobutyryl-cAMP were capable of restoring the normal level of gp80 expression in synag 7 cells. These results, taken together, indicate bimodal regulation of gp80 expression during development and the involvement of a novel cAMP receptor in the transmembrane signalling pathway that regulates gp80 gene expression.

Modulation of human neutrophil function in vitro by gastrin

1997 ◽  
Vol 153 (3) ◽  
pp. 475-483 ◽  
Author(s):  
M De la Fuente ◽  
M Carrasco ◽  
A Hernanz
Keyword(s):  
Superoxide Anion ◽  
Latex Bead ◽  
Human Neutrophils ◽  
Intracellular Camp ◽  
Maximal Effect ◽  
Superoxide Anion Production ◽  
Phagocytic Process ◽  
Anion Production ◽  
Camp Levels

Abstract We have studied the effects in vitro of gastrin-17 and gastrin-34, at concentrations from 10−14 m to 10−6 m, on several of the functions of peripheral blood human neutrophils, i.e. adherence to substrate, mobility (spontaneous and directed by a chemical gradient or chemotaxis), ingestion of inert particles (latex beads) and cells (Candida albicans) and superoxide anion production. Both gastrins inhibited several steps of the phagocytic process of human neutrophils, such as mobility and ingestion. By contrast, these peptides increased adherence and had no effect on superoxide anion production. In general, these effects were significant at peptide concentrations between 10−12 m and 10−8 m with a maximal effect at 10−10 m. In addition, gastrin peptides induced a significant increase in intracellular cAMP levels at 30, 60 and 120 s. Moreover, the inhibitory effect of gastrin-17 on the ingestion capacity of neutrophils (latex bead phagocytosis) was similar to that obtained with EGTA, a well-known extracellular calcium chelating compound. Gastrin-17 was found to inhibit completely the stimulation of latex bead phagocytosis in neutrophils caused by the calcium ionophore A23187. These results suggest that gastrin is a negative modulator of the phagocytic process of human neutrophils, and that this effect might involve an increase in intracellular cAMP levels and a decrease in calcium entry into the cells. Journal of Endocrinology (1997) 153, 475–483

Aminophylline and progesterone prevent inflammation-induced preterm parturition in the mouse†

2019 ◽  
Vol 101 (4) ◽  
pp. 813-822 ◽  
Author(s):  
Bronwen R Herbert ◽  
Danijela Markovic ◽  
Ektoras Georgiou ◽  
Pei F Lai ◽  
Natasha Singh ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Phosphodiesterase Inhibitor ◽  
Adenosine Monophosphate ◽  
Cytokine Gene Expression ◽  
Intracellular Camp ◽  
Myometrial Cells ◽  
Anti Inflammatory ◽  
Camp Levels

Abstract Although progesterone (P4) supplementation is the most widely used therapy for the prevention of preterm labor (PTL), reports of its clinical efficacy have been conflicting. We have previously shown that the anti-inflammatory effects of P4 can be enhanced by increasing intracellular cyclic adenosine monophosphate (cAMP) levels in primary human myometrial cells. Here, we have examined whether adding aminophylline (Am), a non-specific phosphodiesterase inhibitor that increases intracellular cAMP levels, to P4 might improve its efficacy using in vivo and in vitro models of PTL. In a mouse model of lipopolysaccharide (LPS)-induced PTL, we found that the combination of P4 and Am delayed the onset of LPS-induced PTL, while the same dose of P4 and Am alone had no effect. Pup survival was not improved by either agent alone or in combination. Myometrial prolabor and inflammatory cytokine gene expression was reduced, but the reduction was similar in P4 and P4/Am treated mice. There was no effect of the combination of P4 and Am on an ex vivo assessment of myometrial contractility. In human myometrial cells and myometrial tissue explants, we found that the combination had marked anti-inflammatory effects, reducing cytokine and COX-2 mRNA and protein levels to a greater extent than either agent alone. These data suggest that the combination of P4 and Am has a more potent anti-inflammatory effect than either agent alone and may be an effective combination in women at high-risk of PTL.

scholarly journals Cyclic AMP Promotes Neuronal Survival by Phosphorylation of Glycogen Synthase Kinase 3β

2000 ◽  
Vol 20 (24) ◽  
pp. 9356-9363 ◽  
Author(s):  
Mingtao Li ◽  
Xiaomin Wang ◽  
Mary Kay Meintzer ◽  
Tracey Laessig ◽  
Morris J. Birnbaum ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Glycogen Synthase ◽  
Neuronal Survival ◽  
Glycogen Synthase Kinase ◽  
Intracellular Camp ◽  
Glycogen Synthase Kinase 3Β ◽  
Gsk 3Β ◽  
Camp Levels

ABSTRACT Agents that elevate intracellular cyclic AMP (cAMP) levels promote neuronal survival in a manner independent of neurotrophic factors. Inhibitors of phosphatidylinositol 3 kinase and dominant-inactive mutants of the protein kinase Akt do not block the survival effects of cAMP, suggesting that another signaling pathway is involved. In this report, we demonstrate that elevation of intracellular cAMP levels in rat cerebellar granule neurons leads to phosphorylation and inhibition of glycogen synthase kinase 3β (GSK-3β). The increased phosphorylation of GSK-3β by protein kinase A (PKA) occurs at serine 9, the same site phosphorylated by Akt. Purified PKA is able to phosphorylate recombinant GSK-3β in vitro. Inhibitors of GSK-3 block apoptosis in these neurons, and transfection of neurons with a GSK-3β mutant that cannot be phosphorylated interferes with the prosurvival effects of cAMP. These data suggest that activated PKA directly phosphorylates GSK-3β and inhibits its apoptotic activity in neurons.

Genetic Polymorphisms of the ß2-Adrenergic Receptor Relate to Guanosine Protein-coupled Stimulator Receptor Dysfunction in Fibromyalgia Syndrome

2011 ◽  
Vol 38 (6) ◽  
pp. 1095-1103 ◽  
Author(s):  
YANGMING XIAO ◽  
WEIJING HE ◽  
I. JON RUSSELL
Keyword(s):  
Adrenergic Receptor ◽  
Fibromyalgia Syndrome ◽  
Mononuclear Cells ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Intracellular Camp ◽  
Peripheral Blood Mononuclear ◽  
Genotype Frequencies ◽  
Camp Levels

Objective.To determine the genotype frequencies of ß2-adrenergic receptor (ß2AR) gene polymorphisms (Gly16Arg, Glu27Gln) in patients with fibromyalgia syndrome (FM) by comparison with unrelated healthy controls. We sought any clinical association with these polymorphisms and determined whether the polymorphisms would associate with a biologic guanosine protein-coupled stimulator receptor (Gs) dysfunction in FM.Methods.Study subjects included 97 clinically characterized patients with FM and 59 controls. The ß2AR polymorphisms at codons 16 and 27 were determined using polymerase chain reaction-restriction fragment length polymorphism. The Gs functions of peripheral blood mononuclear cells (PBMC) were tested using isoproterenol (ISO) as the adrenergic Gs ligand and measuring intracellular cyclic adenosine monophosphate (cAMP) levels.Results.The frequency of the ß2AR gene polymorphism Gly16Arg in FM (43.5%) was significantly lower than in controls (63.2%), suggesting that this genotype might have some effect on the risk of developing FM. The only clinical association in FM was with sleep dysfunction. Patients with FM who carried the ß2AR polymorphism Arg16Arg also exhibited significantly lower PBMC basal cAMP levels (p < 0.05) and lower ISO-stimulated cAMP levels (p < 0.05) than FM carrying Gly16Gly or Gly16Arg.Conclusion.This confirms a relationship between ß2AR polymorphism and FM. It is the first study to demonstrate ß2AR polymorphism-related differences in intracellular cAMP responses of FM PBMC after ß2AR stimulationin vitro. These findings may explain some of the differences in responsiveness of FM subgroups to the adrenergic agonist medications currently approved for FM treatment.

scholarly journals EppA, a Putative Substrate of DdERK2, Regulates Cyclic AMP Relay and Chemotaxis in Dictyostelium discoideum

2006 ◽  
Vol 5 (7) ◽  
pp. 1136-1146 ◽  
Author(s):  
Songyang Chen ◽  
Jeffrey E. Segall
Keyword(s):  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Mitogen Activated Protein Kinase ◽  
Intracellular Camp ◽  
Mitogen Activated Protein ◽  
Delayed Development ◽  
Induced Signal ◽  
Extracellular Camp ◽  
Intracellular Camp Accumulation ◽  
Dimensional Electrophoresis

ABSTRACT The mitogen-activated protein kinase DdERK2 is critical for cyclic AMP (cAMP) relay and chemotaxis to cAMP and folate, but the details downstream of DdERK2 are unclear. To search for targets of DdERK2 in Dictyostelium discoideum,32PO4 3−-labeled protein samples from wild-type and Dderk2 − cells were resolved by 2-dimensional electrophoresis. Mass spectrometry was used to identify a novel 45-kDa protein, named EppA (ERK2-dependent phosphoprotein A), as a substrate of DdERK2 in Dictyostelium. Mutation of potential DdERK2 phosphorylation sites demonstrated that phosphorylation on serine 250 of EppA is DdERK2 dependent. Changing serine 250 to alanine delayed development of Dictyostelium and reduced Dictyostelium chemotaxis to cAMP. Although overexpression of EppA had no significant effect on the development or chemotaxis of Dictyostelium, disruption of the eppA gene led to delayed development and reduced chemotactic responses to both cAMP and folate. Both eppA gene disruption and overexpression of EppA carrying the serine 250-to-alanine mutation led to inhibition of intracellular cAMP accumulation in response to chemoattractant cAMP, a pivotal process in Dictyostelium chemotaxis and development. Our studies indicate that EppA regulates extracellular cAMP-induced signal relay and chemotaxis of Dictyostelium.

scholarly journals Human CD4+T lymphocytes with increased intracellular cAMP levels exert regulatory functions by releasing extracellular cAMP

2006 ◽  
Vol 80 (4) ◽  
pp. 880-888 ◽  
Author(s):  
Silvia Vendetti ◽  
Mario Patrizio ◽  
Antonella Riccomi ◽  
Maria Teresa De Magistris
Keyword(s):  
T Lymphocytes ◽  
Intracellular Camp ◽  
Regulatory Functions ◽  
Extracellular Camp ◽  
Camp Levels

The interactive effects of fluoride and N-formyl-L-methionyl-L-leucyl-L-phenylalanine on superoxide production and cAMP levels in human neutrophils

1983 ◽  
Vol 61 (7) ◽  
pp. 569-578 ◽  
Author(s):  
Kenneth Wong
Keyword(s):  
Adenylate Cyclase ◽  
Interactive Effects ◽  
Human Neutrophils ◽  
Intracellular Camp ◽  
Chemotactic Peptide ◽  
Lag Period ◽  
Camp Levels ◽  
Kinetics Of ◽  
Generating System

The kinetics of superoxide (O2−) production and intracellular cAMP levels were monitored in human neutrophils incubated in vitro with sodium fluoride and the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP). F− activation of both the O2−-generating system, NAD(P)H oxidase, and adenylate cyclase was characterized by a prolonged lag period of 8 to 10 min at 37 °C. Adenylate cyclase agonists or cAMP analogues which inhibited FMLP-induced O2− bursts did not affect O2− production of F−-activated cells. Prior treatment of cells with F− suppressed the short rapid burst elicited by FMLP but not the binding of the tripeptide. FMLP reciprocally decreased the lag period of the F−-induced burst by 40 to 50% and, in the case of cells incubated at temperatures below 37 °C, increased the rate of O2− production. A similar potentiating effect of FMLP on F−-induced elevation of intracellular cAMP levels was observed.

scholarly journals Seven Dictyostelium discoideum phosphodiesterases degrade three pools of cAMP and cGMP

2007 ◽  
Vol 402 (1) ◽  
pp. 153-161 ◽  
Author(s):  
Sonya Bader ◽  
Arjan Kortholt ◽  
Peter J. M. Van Haastert
Keyword(s):  
Dictyostelium Discoideum ◽  
Cyclic Nucleotide ◽  
Class Ii ◽  
Class I ◽  
Intracellular Camp ◽  
Specific Class ◽  
High Affinity ◽  
Intracellular Cgmp ◽  
Rare Class ◽  
Extracellular Camp

The Dictyostelium discoideum genome uncovers seven cyclic nucleotide PDEs (phosphodiesterases), of which six have been characterized previously and the seventh is characterized in the present paper. Three enzymes belong to the ubiquitous class I PDEs, common in all eukaryotes, whereas four enzymes belong to the rare class II PDEs that are present in bacteria and lower eukaryotes. Since all D. discoideum PDEs are now characterized we have calculated the contribution of each enzyme in the degradation of the three important pools of cyclic nucleotides: (i) extracellular cAMP that induces chemotaxis during aggregation and differentiation in slugs; (ii) intracellular cAMP that mediates development; and (iii) intracellular cGMP that mediates chemotaxis. It appears that each cyclic nucleotide pool is degraded by a combination of enzymes that have different affinities, allowing a broad range of substrate concentrations to be degraded with first-order kinetics. Extracellular cAMP is degraded predominantly by the class II high-affinity enzyme DdPDE1 and its close homologue DdPDE7, and in the multicellular stage also by the low-affinity transmembrane class I enzyme DdPDE4. Intracellular cAMP is degraded by the DdPDE2, a class I enzyme regulated by histidine kinase/phospho-relay, and by the cAMP-/cGMP-stimulated class II DdPDE6. Finally, basal intracellular cGMP is degraded predominantly by the high-affinity class I DdPDE3, while the elevated cGMP levels that arise after receptor stimulation are degraded predominantly by a cGMP-stimulated cGMP-specific class II DdPDE5. The analysis shows that the combination of enzymes is tuned to keep the concentration and lifetime of the substrate within a functional range.

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