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At least 361 records · Page 20Linked to original sources
PubMed1999

Ceramide and cyclic adenosine monophosphate (cAMP) induce cAMP response element binding protein phosphorylation via distinct signaling pathways while having opposite effects on myeloid cell survival.

The role of ceramide as a second messenger is a subject of great interest, particularly since it is implicated in signaling in response to inflammatory cytokines. Ceramide induces apoptosis in both cytokine-dependent MC/9 cells and factor-independent U937 cells. Elevation of cyclic adenosine monophosphate (cAMP) levels inhibits apoptosis induced by ceramide and several other treatments. One target of cAMP-mediated signaling is the transcription factor CREB (cAMP response element binding protein), and recently CREB phosphorylation at an activating site has been shown to also be mediated by a cascade involving p38 mitogen-activated protein kinase (MAPK), one of the stress-activated MAP kinases. Because no role for p38 MAPK in apoptosis has been firmly established, we examined the relationship between p38 MAPK and CREB phosphorylation under various conditions. Ceramide, or sphingomyelinase, like tumor necrosis factor- (TNF-) or the hematopoietic growth factor, interleukin-3 (IL-3), was shown to activate p38 MAPK, which in turn activated MAPKAP kinase-2. Each of these treatments led to phosphorylation of CREB (and the related factor ATF-1). A selective p38 MAPK inhibitor, SB203580, blocked TNF-- or ceramide-induced CREB phosphorylation, but had no effect on the induction of apoptosis mediated by these agents. The protective agents cAMP and IL-3 also led to CREB phosphorylation, but this effect was independent of p38 MAPK, even though IL-3 was shown to activate both p38 MAPK and MAPKAP kinase-2. Therefore, the opposing effects on apoptosis observed with cAMP and IL-3, compared with ceramide and TNF-, could not be explained on the basis of phosphorylation of CREB. In addition, because SB203580 had no effect of TNF- or ceramide-induced apoptosis, our results strongly argue against a role for p38 MAPK in the induction of TNF-- or ceramide-induced apoptosis.

Animals↗
PubMed2000

Health appraisal guidelines for day camps and resident camps. American Academy of Pediatrics. Committee on School Health.

The American Academy of Pediatrics recommends that specific guidelines be established for pre-camp health appraisals of young people in day and resident camps. Camp guidelines also should include reference to health maintenance, storage and administration of medication, and emergency medical services. Although camps have diverse environments, there are general guidelines that apply to all situations, and specific recommendations are appropriate under special conditions.

Academies and Institutes↗
PubMed2005

Health appraisal guidelines for day camps and resident camps. American Academy of Pediatrics Committee on School Health .

The American Academy of Pediatrics recommends that specific guidelines be established for health appraisals of young people before participation in day and resident camps. Camp guidelines should include reference to health maintenance, storage and administration of medication, and emergency medical services. Although camps have diverse environments, there are general guidelines that apply to all situations and specific recommendations that are appropriate under special conditions. This policy statement has been reviewed and is supported by the American Camp Association.

Adolescent↗
PubMed1996

Retinoylation of the type II cAMP-binding regulatory subunit of cAMP-dependent protein kinase is increased in psoriatic human fibroblasts.

Previously, we have reported a defect in the cAMP-dependent protein kinases (cAMP-PK) in psoriatic cells (i.e., a decrease in 8-azido-[32P]cAMP binding to the regulatory subunits and a decrease in phosphotransferase activity) which is rapidly reversed with retinoic acid (RA) treatment of these cells. This led us to examine a possible direct interaction between retinoids and the RI and RII regulatory subunits through retinoylation. Retinoylation of RI and RII present in normal and psoriatic human fibroblasts was analysed by [3H]RA treatment of these cells, followed either by chromatographic separation of the regulatory subunits or by their specific immunoprecipitation. These studies indicated that RI and RII can be retinoylated. [3H]RA labeling of the RII subunit was significantly (P < 0.005) greater in psoriatic fibroblasts (nine subjects; mean 7.47 relative units +/- 1.37 SEM) compared to normal fibroblasts (eight subjects; mean 2.46 relative +/- 0.49 SEM). [3H]RA labeling of and the increase in 8-azido-[32P]-binding to the RI and RII subunit in psoriatic fibroblasts showed a similar time course. This suggests that the rapid effect of retinoic acid treatment to enhance 8-azido-[32P]-cAMP binding to the RI and RII in psoriatic fibroblasts may be due, in part, to covalent modification of the regulatory subunits by retinoylation.

Affinity Labels↗
PubMed1983

Dibutyryl cAMP treatment of neuroblastoma-glioma hybrid cells results in selective increase in cAMP-receptor protein (R-I) as measured by monospecific antibodies.

The absolute levels of cAMP-dependent protein kinase (cAMP-dPK) subunits (R-I, R-II and C) and cGMP-dependent protein kinase (cGMP-dPK) holoenzyme were studied in neuroblastoma-glioma hybrid cells before and after dibutyryl-cAMP (Bt2cAMP) treatment which results in differentiation of these cells. The levels were determined by two different techniques utilizing antibodies which had been raised against each individual purified protein kinase subunit (or the holoenzyme in the case of the cGMP-dPK). Electrophoretic transfer of samples from SDS-polyacrylamide gels to nitrocellulose paper, followed by immunolabeling of protein kinase subunits with their respective antibodies and [125I]Protein A, demonstrated the monospecific nature of the antibodies, and a selective, several-fold increase in the R-I subunit in Bt2cAMP-treated cells, with no change in the level of R-II or C subunits. A simple enzyme-linked immunosorbent assay (ELISA) capable of measuring nanogram amounts of the various subunits confirmed the selective increase in the R-I subunit. ELISA assay results also indicated that the R-I subunits present before and after Bt2cAMP treatment are antigenically homologous. In conclusion, the specific, sensitive immunological methods described here demonstrate the capacity of neuroblastoma-glioma hybrid cells to regulate separately the levels of the two distinct subunits (R-I and C) of the Type I cAMP-dPK.

Animals↗
PubMed1991

Analysis of the dominance of mutations in cAMP-binding sites of murine type I cAMP-dependent protein kinase in activation of kinase from heterozygous mutant lymphoma cells.

Structural lesions in cAMP-binding sites of regulatory (R) subunit of cAMP-dependent protein kinase caused identical increases in apparent constants for cyclic nucleotide-dependent kinase activation in preparations from cells that were hemizygous or heterozygous for mutant R1 subunit expression. No wild-type kinase activation was observed in extracts from heterozygous mutant cells. This "dominance" was investigated by characterizing expression of wild-type and mutant R1 subunits and properties of protein kinase from S49 mouse lymphoma cell mutants heterozygous for expression of wild-type R1 subunits and R1 subunits with a lesion (Glu200) that inactivates cAMP-binding site A. By both studies of cAMP dissociation and two-dimensional gel analysis, wild-type R subunits comprised about 35% of total R1 subunits in heterozygous mutants. Synthesis of wild-type and mutant R1 subunits was equivalent, but wild-type subunits were degraded preferentially. Hydroxylapatite chromatography revealed a novel R1 subunit-containing species from heterozygous mutant preparations whose elution behavior suggested a trimeric kinase consisting of an R1 subunit dimer and one catalytic (C) subunit. Wild-type R1 subunit was found only in dimer and "trimer" peaks; the tetrameric kinase peak contained only mutant R1 subunit. It is concluded that C subunit binds preferentially to mutant R1 subunit in heterozygous cells forming either tetrameric kinase with mutant R1 subunit homodimers or trimeric kinase with R1 subunit heterodimers. This preferential binding results both in suppression of wild-type kinase activation and differential stabilization of mutant R1 subunits.

Animals↗
PubMed2000

Mechanism of activation of cAMP-dependent protein kinase: in Mucor rouxii the apparent specific activity of the cAMP-activated holoenzyme is different than that of its free catalytic subunit.

Kinetic constants for peptide phosphorylation by the catalytic subunit of the dimorphic fungus Mucor rouxii protein kinase A were determined using 13 peptides derived from the peptide containing the basic consensus sequence RRASVA, plus kemptide, S6 peptide, and protamine. As a whole, although with a greater Km, the order of preference of the peptides by the M. rouxii catalytic subunit was similar to the one displayed by mammalian protein kinase A. Particularly significant is the replacement of serine by threonine in the basic peptide RRATVA, which impaired its role as a substrate of M. rouxii catalytic subunit. Mucor rouxii protein kinase A is a good model in which to study the mechanism of activation since cAMP alone is not enough to promote activation and dissociation. Four peptides were selected for the study of holoenzyme activation under conditions in which the enzymatic activity was not proportional to the holoenzyme concentration: RRASVA, RRRRASVA, KRRRLSSRA (S6 peptide), and LRRASLG (kemptide); protamine was used as reference. Differential activation degree was observed depending on the peptide used and on cAMP concentration. Ratios of activity between different substrates displayed by the holoenzyme under the above conditions did not reflect the one expected for the free catalytic subunit. The degree of inhibition of the holoenzyme activity by an active peptide derived from the thermostable protein kinase inhibitor was dependent on the substrate used and on the holoenzyme concentration, while it was found to be independent of these two parameters for free catalytic subunit. Polycation modulation of holoenzyme activation by cAMP was also dependent on the polycation itself and on the peptide used as substrate. The observed kinetic differences between holoenzyme and free catalytic subunit were decreased or almost abolished when working at low enzyme or at high cAMP concentrations. Two hypotheses compatible with the results are discussed: substrate participation in the dissociation process and/or holoenzyme activation without dissociation.

Amino Acid Sequence↗
PubMed1984

Cardiac contractility, cAMP concentration, cAMP-dependent protein kinase, and phosphorylase activation during acute pressure overload.

The relationship between increases in myocardial contractility and cAMP and protein kinase activity were studied for hearts of normal rats and those with altered sympathectic capacity produced by the combined treatments of adrenalectomy, and 6-hydroxydopamine and propranolol injections. Increases in myocardial contractility, evaluated from intra-ventricular pressure changes, were produced by occlusion of the ascending aorta for 15, 20, or 25 s. Resting peak left ventricular pressure and the rate of rise of left ventricular pressure were lower (P less than 0.05) in sympathectomized animals, however, aortic occlusion abolished these differences. Time to peak tension and the relationship between end-diastolic pressure and developed pressure were unchanged by sympathectomy. ATP and CP concentrations in freeze clamped samples of the myocardium were lower (P less than 0.05) in both groups after aortic occlusion whereas lactate was elevated (P less than 0.05). Sympathectomy delayed and reduced the magnitude of the increase in the phosphorylase a/a + b ratio produced by aortic occlusion. Myocardial cAMP concentration was increased in the normal rats but decreased in sympathectomized animals after aortic occlusion. cAMP-dependent protein kinase activity followed the pattern of cAMP. The results demonstrate that heart possesses the capacity to increase its contractility to an acute, short-term overload even when devoid of sympathetic control.

Adrenal Medulla↗
PubMed1992

Central effects of the preservative, methylparaben. In vivo activation of cAMP-specific phosphodiesterase and reduction of cortical cAMP.

The phenolic preservative, methylparaben (MPB), has in the past been demonstrated to harbour definite pharmacological effects. In an attempt to examine the possible central effects of MPB, notably on cyclic nucleotides and cyclic nucleotide phosphodiesterase (PDE; EC 3.1.4.17), rats were orally treated with the drug (0.4% in rat food) for 3 weeks with cortex extracts being used for the various determinations. Three isozymes were identified by DEAE-cellulose anion exchange chromatography, namely the calmodulin/calcium-stimulated form or PDE I (peak I), the cGMP-stimulated form or PDE II (peak II), and an independent form not affected by either calmodulin or cGMP also known as PDE IV (peak III). The presence of MPB induced a significant decrease in cortical cAMP, as well as strongly stimulating the activity of PDE IV (peak III). In addition, a small, yet significant, increase in cGMP levels was observed. Since no increase in cGMP hydrolysis was observed, we conclude that chronic ingestion of MPB induces a preference for cAMP hydrolysis, which was confirmed by the increase in PDE IV (peak III) activity. PDE IV is a membrane-bound, low Km PDE exhibiting high selectivity for cAMP hydrolysis. While there was an increase in cGMP, we failed to observe an increase in the activity of the cGMP-stimulated PDE (PDE II). These data are discussed with reference to the possible membrane effects of MPB allowing it to alter both the kinetic properties of PDE IV with the resultant effects on cAMP, as well as a means whereby it may activate guanyl cyclase and increase cGMP.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1991

Regulation of glpD and glpE gene expression by a cyclic AMP-cAMP receptor protein (cAMP-CRP) complex in Escherichia coli.

The glpE gene of E. coli was found to be transcribed divergently with respect to glpD, which is adjacent to glpE head-to-head on the E. coli chromosome. We constructed glpD- and/or glpE-lacZ fusion plasmids, which provided glpD and lacZ as reporter genes. The expression of glpD and glpE, under the control of the cAMP-CRP complex, was examined by measuring the activities in E. coli cells of beta-galactosidase encoded by lacZ and glycerol-3-phosphate dehydrogenase encoded by glpD. In the double-reporter-gene system, the expression of glpD and glpE was found to be positively regulated by cAMP-CRP. We also confirmed that intracellular levels of the translation products and the transcripts from glpD and glpE were positively regulated by cAMP-CRP. The cAMP-mediated induction of gene expression of glpD and glpE was significantly affected by structural alterations of the single CRP-binding site between glpD and glpE. These results indicate that the single CRP-binding site is a cis-acting element involved in the positive regulation of the expression of both glpD and glpE at the transcriptional level.

Base Sequence↗
PubMed1995

Participation of cAMP and cAMP-dependent protein kinase in beta-adrenoceptor-mediated interleukin-1 beta mRNA induction in cultured microglia.

We previously reported evidence of beta-adrenoceptor-mediated induction of IL-1 beta mRNA in the rat hypothalamus. The present in vitro studies using northern blot analysis showed that the beta-adrenoceptor agonist isoproterenol (1 x 10(-8) to 1 x 10(-5) M) caused a marked induction of IL-1 beta mRNA in microglia, but not in astrocytes. This induction was remarkably suppressed by pretreatment of cells with the beta-adrenoceptor antagonist propranolol. These phenomena were confirmed by in situ hybridization with digoxigenin-labelled IL-1 beta RNA probe. Furthermore, dibutyryl cyclicAMP (dbcAMP) (5 x 10(-4) and 5 x 10(-5) M) markedly induced IL-1 beta mRNA in microglia. The intracellular level of cAMP in microglia was elevated in a dose-dependent manner when they were treated with isoproterenol, and this elevation was completely blocked by propranolol. The induction of IL-1 beta mRNA by either isoproterenol or dbcAMP was strongly inhibited by a cAMP-dependent protein kinase inhibitor, H8. These results, taken together, suggest that (1) microglia primarily induce IL-1 beta mRNA by stimulation of beta-adrenoceptors, and (2) cAMP and cAMP-dependent protein kinase presumably participate in a signal transduction mechanism involved in the induction of IL-1 beta mRNA via beta-adrenoceptors.

Adrenergic beta-Agonists↗
PubMed1992

Effect of triiodothyronine on cAMP-dependent and cAMP-independent protein kinase activities in developing chick embryo liver.

1. Changes in liver cytosol cAMP-dependent kinase and cAMP-independent growth-related quercetin-inhibited casein kinase activities during chick embryo development were studied. 2. Both kinase activities were found to increase continuously during the experimental period. 3. Upon treatment of embryos with triiodothyronine, an activation of cAMP-dependent kinase A and cAMP-independent casein kinase was observed which was most pronounced on days 12 and 14.

Animals↗
PubMed1999

cAMP levels in cells attached to AN69 and Cuprophan: cAMP dependence of cell aggregation and the influence of serum.

We have examined the link between the aggregation or spreading of cells adhering to substrata of differing biocompatibility and activation of the cyclic AMP (cAMP) pathway. We compared the rate at which the Mouse Swiss 3T3 fibroblasts attached to Cuprophan (CU), AN69 and a control plastic in the presence and absence of foetal calf serum (FCS). Serum had no effect on the kinetics of cell attachment to CU or AN69. Cells incubated in culture medium containing 10% FCS aggregated on CU, whereas they spread on AN69 and plastic. Aggregated cells contained significantly higher concentrations of cAMP than cells spreading, and aggregation was prevented by treatment with miconazole, an inhibitor of adenylyl cyclase. cAMP-dependent cell aggregation occurred on all three substrata in serum-free medium, suggesting that proteins adsorbed onto AN69 and plastic in the presence of serum helped protect the cells. Far less serum protein was adsorbed onto CU than onto AN69 or plastic, consistent with the similar increases in cAMP in cells attached to CU with or without serum.

3T3 Cells↗
PubMed1989

An amphitropic cAMP-binding protein in yeast mitochondria. 3. Membrane release requires both Ca2(+)-dependent phosphorylation of the cAMP-binding protein and a phospholipid-activated mitochondrial phospholipase.

The amphitropic cAMP-binding protein in mitochondria of the yeast Saccharomyces cerevisiae is released from the inner membrane into the intermembrane space by the degradation of its lipid membrane anchor consisting of or containing phosphatidylinositol. The releasing reaction depends on the presence of an N-ethylmaleimide-sensitive protein (releasing factor) in the intermembrane space and is controlled by Ca2+ and phospholipid (or lipid derivatives). Here we demonstrate that these two effector molecules act on different activation steps within a complex releasing pathway involving both the cAMP receptor and the releasing factor: Ca2(+)-dependent phosphorylation of the receptor protein seems to be prerequisite for its subsequent lipolytic liberation from the inner membrane. In the presence of phospholipid (or lipid derivatives) the previously soluble releasing factor, which may be identical with a soluble diacylglycerol-binding protein in the mitochondrial intermembrane space, associates with the inner membrane. This change in the intramitochondrial location of the releasing factor, which thus exhibits amphitropic behavior itself, may be required for (direct or indirect) activation of the mitochondrial phospholipase which then releases the cAMP receptor from the inner membrane in a form liable to dissociation from the C subunit by cAMP.

Calcium↗
PubMed2001

Interaction of cAMP receptor protein from Escherichia coli with cAMP and DNA studied by dynamic light scattering and time-resolved fluorescence anisotropy methods.

Cyclic AMP receptor protein (CRP) regulates the expression of more than 100 genes in Escherichia coli when complexed with cyclic AMP. Dynamic light scattering (DLS) and fluorescence decay anisotropy measurements of CRP were performed in solution, in the absence and presence of cAMP. We have also measured the effect of DNA sequences, including lac and gal promoter sequences, on the shape of CRP-DNA complexes. DLS measurements show that upon cAMP binding at low nucleotide concentration, the Stokes radius decreases from the value of 2.8 nm for apo-CRP to the value of 2.7 nm. At higher cAMP concentration, only a very small further decrease was detected. Fluorescence anisotropy decay measurements, with the use of CRP labeled at Cys-178 with 1,5-I-AENS, indicate that apo-CRP exhibits two rotational correlation times. The longer time, theta1 = 23.3 ns, corresponds to the overall motion of the protein, and the shorter time, theta2 = 1.4 ns, exhibits segmental mobility of the C-terminal domain of CRP. Binding of cAMP into CRP induced substantial increase of theta1 to the value of 30.7 ns, whereas theta2 remained unchanged. The DLS measurements indicate that the binding of CRP into a fragment of DNA possessing a sequence of lac promoter induces a larger increase in the Stokes radius of lac-CRP complex than in case of gal-CRP complex. Similarly, a higher change was detected in rotational correlation time, theta1, in the case of lac-CRP complex than in case of gal-CRP. Because the lac and gal promoters are characteristic for the two different classes of CRP-dependent promoters, one can expect that the observed differences in lac-CRP and gal-CRP complexes are important in activation of transcription in Escherichia coli.

Chymotrypsin↗
PubMed2003

Epac: a new cAMP target and new avenues in cAMP research.

Five years ago, Epac--a guanine nucleotide exchange factor for the Ras-like small GTPases Rap1 and Rap2--was found to be a new target of cyclic AMP, which opened up new avenues for cAMP research. Structural analysis of the cAMP-binding domains of Epac2 has identified a unifying mechanism for how cAMP activates proteins, and the design and synthesis of an Epac-specific cAMP analogue has paved the way for future discoveries.

Animals↗
PubMed2000

Action of rolipram on specific PDE4 cAMP phosphodiesterase isoforms and on the phosphorylation of cAMP-response-element-binding protein (CREB) and p38 mitogen-activated protein (MAP) kinase in U937 monocytic cells.

U937 monocytic cells are shown here to express a range of PDE4, cAMP-specific phosphodiesterase (PDE) isoenzymes: the long isoenzymes, PDE4A4, PDE4D5 and PDE4D3, plus the short isoenzyme, PDE4B2. These isoenzymes provide around 76% of the total cAMP PDE activity of U937 cells. The specific activities of the total PDE4A, PDE4B and PDE4D activities were 0.63+/-0.09, 8.8+/-0.2 and 34.4+/-2.9 pmol/min per mg of protein respectively. The PDE4 selective inhibitor, rolipram, inhibited immunopurified PDE4B and PDE4D activities similarly, with IC(50) values of approx. 130 nM and 240 nM respectively. In contrast, rolipram inhibited immunopurified PDE4A activity with a dramatically lower IC(50) value of around 3 nM. Rolipram increased phosphorylation of cAMP-response-element-binding protein (CREB) in U937 cells in a dose-dependent fashion, which implied the presence of both high affinity (IC(50) value approx. 1 nM) and low affinity (IC(50) value approx. 120 nM) components. Rolipram dose-dependently inhibited the interferon-gamma (IFN-gamma)-stimulated phosphorylation of p38 mitogen-activated protein (MAP) kinase in a simple monotonic fashion with an IC(50) value of approx. 290 nM. On this basis, it is suggested that rolipram inhibition of PDE4A4 is involved in regulating CREB phosphorylation but not IFN-gamma-stimulated p38 MAP kinase phosphorylation. PDE4A4 was also selectively activated by challenge of U937 cells with either bacterial lipopolysaccharide (LPS) or IFN-gamma through a process which was attenuated by both wortmannin and rapamycin. It is proposed that the PDE4A4 isoform is involved in compartmentalized cAMP signalling responses in U937 monocytes.

3',5'-Cyclic-AMP Phosphodiesterases↗