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At least 469 records · Page 26Linked to original sources
PubMed1993

The helix-loop-helix proteins (salivary-specific cAMP response element-binding proteins) can modulate cAMP-inducible RP4 gene expression in salivary cells.

Salivary-specific and cAMP-inducible expression of the rat proline-rich protein gene RP4 is dependent on a 28-base pair sequence of a salivary-specific cAMP response element (SCRE) (Lin, H. H., and Ann, D. K. (1992) Gene Expression 2, 365-377). To unravel its trans-acting factor(s), we used double-stranded oligoprobes corresponding to the SCRE to screen a randomly primed lambda gt11 cDNA expression library made from RNA of rat salivary cells. In this report, we describe the cDNA cloning of these helix-loop-helix SCRE-binding proteins (SCBPs) and demonstrate that there are at least three isoforms in salivary cells, namely SCBP alpha, SCBP beta, and SCBP gamma. RNA polymerase chain reaction and sequence analyses further confirmed the existence of these three different SCBP isoforms, which code for putative proteins of 707, 706, and 682 amino acids, respectively. Expression of the cloned SCBP cDNAs in salivary cells stimulates the expression of a cotransfected reporter construct containing multicopies of the SCRE cloned upstream of the thymidine kinase promoter and the chloramphenicol acetyltransferase structural gene. This stimulation is much more pronounced in transfections in which SCBP alpha and SCBP beta are cotransfected than when they are transfected individually. Furthermore, when low concentrations of SCBP alpha and SCBP beta are cotransfected with the SCRE reporter gene, coexpression of the catalytic subunit of protein kinase A is required to efficiently activate the expression of the reporter gene. These results strongly suggest that the observed stimulation of the SCRE is achieved through the coordinated expression of the SCBP alpha, SCBP beta, and protein kinase A activities, perhaps via a direct association of the two SCBPs and their phosphorylation by protein kinase A. We conclude that the isolated SCBP alpha and SCBP beta cDNAs encode transcription activators that participate in the control of the inducible RP4 gene expression in salivary cells.

Amino Acid Sequence↗
PubMed1993

Distinct activation domains within cAMP response element-binding protein (CREB) mediate basal and cAMP-stimulated transcription.

Activation of protein kinase A (PKA) by cAMP results in phosphorylation of cAMP response element-binding protein (CREB) and induction of specific gene expression. However, whether CREB participates directly in basal (PKA-independent) transcription is still an open question, and existing studies conflict over the identification of putative basal activation domains. In the present study, the activation domain of CREB, whether fused to the GAL4 DNA binding domain (CRG) or in native CREB, stimulated basal activity of the minimal tk promoter, but not the minimal SV40 early promoter. Cotransfection with PKI, a specific inhibitor of PKA, blocked PKA-induced expression of both promoters, but did not block CRG-mediated basal expression of the tk promoter. In addition, both CRG and a PKA phosphorylation site mutant provided comparable stimulation of basal tk promoter activity. Examination of a series of CREB deletion mutants mapped basal activity to interacting domains, located on either side of the previously identified PKA activation domain (amino acids 98-142). This PKA-independent activity mapped primarily to a bipartite COOH-terminal basal activation domain (amino acids 165-252). Its major component bears no obvious homology to previously identified activation domains, whereas a minor component is glutamine-rich. This COOH-terminal domain acts independently and provides the majority of basal activation but requires an NH2-terminal domain (amino acids 41-86) to provide full basal activity. A repressor domain (amino acids 142-165), deletion of which enhanced both basal and PKA-activated transcription, was also identified. This work establishes that CREB contains distinct basal and PKA-activated domains, that they operate independently for both loss of function and gain of function, and that they work on different promoters in different cell types.

Animals↗
PubMed1996

[CFTR as cAMP-dependent chloride channels and as cAMP-dependent regulator of sodium channels].

Cystic fibrosis transmembrane conductance regulator (CFTR) is mutated in cystic fibrosis (CF) patients. It has been established that CFTR functions as a cAMP-dependent chloride channel. Therefore mutation of CFTR causes the abnormality of the chloride ion secretion. Furthermore, it has been shown recently that CFTR functions as cAMP-dependent negative regulator of sodium channels. The evidence accounts an abnormally high rate of sodium ion in the airway epithelia of the CF patients.

Chloride Channels↗
PubMedDate not supplied

Human DNA Polymerase-beta Promoter: Phorbol Ester Activation Is Mediated through the cAMP Response Element and cAMP-Response-Element-Binding Protein.

That mammalian DNA polymerase-beta (beta-pol) gene transcription is upregulated by activated ras and also by phorbol ester (TPA) treatment suggests the involvement of protein kinase C in the gene expression control for this DNA repair enzyme. Yet, the core promoters of the human, bovine and rodent beta-pol genes do not have a TPA response element or other binding site for the transcriptional activator AP-1. Instead, these beta-pol promoters appear to be regulated mainly by proteins binding to the cAMP response element (CRE) centered within 50 bp 5' of the transcriptional start site. In this study, the CRE in the human beta-pol promoter was found to mediate TPA upregulation of the cloned promoter in HeLa cell transient expression experiments. To further examine the role of this CRE in TPA stimulation, we used several mutated promoters that were either deficient in protein binding to the CRE or contained extra CRE sites arranged as tandem repeats. All constructs with at least one functional CRE were upregulated by TPA, whereas mutants lacking CRE protein-binding function were not TPA upregulated. Analyses of HeLa nuclear extract DNA-binding proteins indicated that the beta-pol CRE was bound by CRE-binding protein (CREB) family members CREB-1 and activating transcription factor-1, but not by AP-1 or complexes containg AP-1 subunits. These results suggest that CREB, rather than AP-1 proteins, are required for the CRE-mediated TPA activation of the beta-pol promoter.

Journal Article↗
PubMed1995

Phosphorylation and inactivation of rat heart glycogen synthase by cAMP-dependent and cAMP-independent protein kinases.

The regulation of cardiac muscle glycogen metabolism is not well understood. Previous studies have indicated that heart glycogen synthase is heavily phosphorylated in vivo on multiple sites. Using purified enzymes, we have investigated the effect of phosphorylation of different sites on the activity of rat heart glycogen synthase. A convenient procedure was developed for the purification of rat heart glycogen synthase. The enzyme was phosphorylated by selected kinases, and glycogen synthase activity, extent of phosphorylation, and phosphopeptide maps were analyzed. Rat heart glycogen synthase, purified to apparent homogeneity (M(r) 87,000 on SDS-PAGE), had a specific activity of 18 U/mg protein and had an activity ratio of 0.74 (activity in the absence divided by the activity in the presence of glucose 6-P). cAMP-dependent protein kinase, glycogen synthase kinase 3, Ca2+/calmodulin-dependent protein kinase II, protein kinase C, and phosphorylase kinase phosphorylated the enzyme with a concomitant decrease in the activity ratio to values ranging from 0.1 to 0.4. Casein kinase II phosphorylated but did not inactivate glycogen synthase. Six tryptic phosphopeptides, obtained from heart glycogen synthase phosphorylated by the various kinases, were separated by reverse-phase chromatography. The phosphopeptide(s) obtained with each kinase eluted at the same position(s) as corresponding phosphopeptides obtained from rat skeletal muscle glycogen synthase. The study shows that the pattern of phosphorylation and effects on activity are very similar for cardiac and skeletal muscle glycogen synthase. It is suggested that the well known differences in heart and glycogen metabolism may be due to the interplay of kinases and phosphatases which could lead to different phosphorylation and activity states of glycogen synthase.

Animals↗
PubMed2003

Interaction of cAMP receptor protein from Escherichia coli with cAMP and DNA studied by differential scanning calorimetry.

The cyclic AMP receptor protein (CRP) regulates the expression of many genes in Escherichia coli. The protein is a homodimer, and each monomer is folded into two distinct structural domains. In this study, we have used differential scanning calorimetry (DSC) and circular dichroism (CD) to measure the enthalpy change and melting temperature of the apo-CRP and CRP complexes with cAMP or DNA sequences lac, gal, and palindromic ICAP. DSC and CD measurements showed irreversible thermal denaturation process of CRP. Enthalpy of dissociation of the protein-DNA complex, as measured by DSC, depends on the DNA sequence. The thermal transition of the protein in CRP-DNA complexes, measured by CD, indicates that the protein stability in the complex is also DNA sequence-dependent.

Calorimetry, Differential Scanning↗
PubMed2004

Deacetylase inhibitors and the viral transactivator TaxBLV synergistically activate bovine leukemia virus gene expression via a cAMP-responsive element- and cAMP-responsive element-binding protein-dependent mechanism.

Efficient bovine leukemia virus (BLV) transcription requires the virus-encoded transactivator Tax(BLV), which acts through three Tax(BLV)-responsive elements located in the 5' long terminal repeat. It has been proposed that the binding of the CRE-binding protein (CREB) and the activating transcription factor (ATF) to the three imperfect cAMP-responsive elements (CREs) located in each Tax(BLV)-responsive element mediates Tax(BLV) transactivation. Here we demonstrated that deacetylase inhibitors (HDACis) synergistically enhanced the transcriptional activation of the BLV promoter by Tax(BLV) in a CRE-dependent manner. Tax(BLV) was acetylated in vivo at its N(alpha) terminus but not at internal lysine residues. Rather, HDACi potentiation of Tax(BLV) transactivation was mediated by an HDACi indirect action that requires new protein synthesis. Mechanistically, using a dominant-negative form of CREB, we showed that Tax(BLV) and HDACi synergistically activated BLV gene expression via a CREB-dependent mechanism. Moreover, electrophoretic mobility shift assay and Western blot experiments revealed that HDACi increased the in vitro DNA binding activity of CREB/ATF but did not alter CREB/ATF intranuclear presence. Remarkably, chromatin immunoprecipitation assays demonstrated that HDACi treatment increased the level of CREB bound to the BLV promoter in vivo. Our results together suggest that an increase in CREB/ATF occupancy of the viral CREs in response to HDACi potentiates Tax(BLV) transactivation of the BLV promoter.

Animals↗
PubMed1994

Influence of halothane on the effect of cAMP-dependent and cAMP-independent positive inotropic agents in human myocardium.

Volatile anaesthetics have a variety of effects on the myocardium, namely a negative inotropic effect and a catecholamine sensitizing effect. The present study was designed to see if the hydrocarbon anaesthetics interact specifically with subcellular targets of the myocardial cell, by examining the effects of halothane in the presence of positive inotropic agents with different mechanisms of action. Experiments were performed in isolated electrically driven left ventricular preparations (1 Hz, 37 degrees C, Ca2+ 1.8 mmol litre-1) from human hearts obtained at cardiac surgery. The concentration-response curves of noradrenaline, milrinone, BayK 8644 and Ca2+ were investigated in the absence and in the presence of halothane. Halothane enhanced the efficacy of noradrenaline and milrinone but not of Ca2+ or BayK 8644. The potency of milrinone was also increased by halothane, whereas the potency of BayK 8644 was decreased and those of noradrenaline and Ca2+ were unchanged. Halothane differentially influences the effects of agents with different positive inotropic mechanisms. This experimental approach can be taken as a functional method to localize the mechanisms of action of the inhalation anaesthetics in human myocardium, namely sensitization of cAMP formation and interaction with L-type Ca2+ channels.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2003

Dietary assessment of refugees living in camps: a case study of Mae La Camp, Thailand.

This study presents data on consumption patterns, methods of food procurement, and adequacy of dietary intake among Burmese refugee camp households living along Thailand's border with Burma. Households established for one or more years and with children under 15 years of age were sampled. A questionnaire was used to determine economic, food-consumption, and dietary intake patterns; foods consumed were weighed and measured using a 24-hour recall for the household unit; and nutritional status was determined by a Microtoise tape and digital standing scales. In total, 182 households containing 1,159 people were surveyed. The average household energy and protein intakes were 96.6% and 111.4%, respectively, of the recommended daily allowance (RDA) for healthy Thais. Twelve percent of protein was derived from animal sources. Carbohydrate, protein, and fat accounted for 84%, 9%, and 7% of total energy, respectively. The intake of vitamins A, B1, B2, and C and of calcium ranged from 24.2% to 53.1% of the RDA. Iron intake was 85.3% of the RDA, derived mainly from rice, fermented fish, mung beans, green leafy vegetables, and eggs. Ration foods supplied 60.5% to 98.18% of all nutrients consumed in the households, with the exception of vitamins A and C. Among children under five years of age, 33.7% were underweight, 36.4% were studied, and 8.7% were wasted. Although the refugees were able to procure some nonration foods by foraging, planting trees and vegetables, raising animals, and purchasing and exchanging ration foods for other items, the quantity and quality were not sufficient to compensate for the nutrients that were low or lacking in the ration. The overwhelming majority of dietary nutrients were provided by ration foods, and although the ration and the overall diet may be adequate for short-term subsistence, they do not suffice for long-term survival and optimal growth, especially for younger children.

Adolescent↗
PubMed2004

Orthovanadate stimulates cAMP phosphodiesterase 3 activity in isolated rat hepatocytes through mitogen-activated protein kinase activation dependent on cAMP-dependent protein kinase.

Orthovanadate (vanadate) as well as insulin stimulated phosphodiesterase 3 (PDE3) in the particulate fraction of rat hepatocytes. The vanadate-induced activations of PDE3 and mitogen-activated protein kinase (MAPK) were inhibited by H-89 and PD98059, suggesting that the MAPK activation via cAMP-dependent protein kinase (PKA) and MAPK kinase is involved in the vanadate action. On the other hand, the insulin-induced activations of PDE3 and Akt were inhibited by wortmannin, suggesting involvement of the Akt activation via phosphatidylinositol 3-kinase (PI3K) in the insulin action. The vanadate-induced activations of PKA and PDE3 were inhibited in part by propranolol or genistein, suggesting that vanadate may exert its actions via dual signaling pathways of beta-adrenergic receptors and receptor tyrosine kinases of growth factors. Vanadate, in contrast to insulin, did not promote the phosphorylation of insulin receptor substrate-1. The vanadate-induced increase in the phosphorylation of a main isoform of MAPKs, p44 protein, was detected by immunoblotting migration patterns of SDS-PAGE. A partially purified PDE3 activity was increased by addition of MAPK or Akt to the reaction mixture, suggesting that MAPK as well as Akt acts upstream of PDE3. The activation of PDE3 by insulin was independent of a transient increase in the MAPK activity, probably due to the dephosphorylated inactivation mediated by the induced activation of MAPK phosphatases (MKPs). Vanadate did not affect the MKP activity. These results indicate that vanadate stimulates the particulate PDE3 activity by activating mainly p44 MAPK via a PKA-dependent process, and that it differs from insulin with regard to a phosphorylation cascade of PDE3 activation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2005

Identification of human myometrial target genes of the cAMP pathway: the role of cAMP-response element binding (CREB) and modulator (CREMalpha and CREMtau2alpha) proteins.

cAMP-response element (CRE) binding (CREB) and modulator (CREM) proteins, activated by protein kinase A-mediated phosphorylation, bind as homo- and heterodimers to promoters containing CRE and activator protein 1 (AP-1) sites to alter target-gene expression. We have previously reported differential expression of CREB and CREM splice variants CREMalpha and CREMtau2alpha in human myometrium during pregnancy and labour. Via microarray studies with cultured myometrial cells stably transfected with CREB, CREMalpha and CREMtau2alpha cDNAs, CREB affected the expression of 958 genes; 522 being up-regulated and 436 down-regulated. CREMalpha altered the expression of 118 genes; 71 were increased and 47 decreased. CREMtau2alpha affected 220 genes; 148 were activated and 72 repressed. Notably, genes affected by CREB, CREMalpha and CREMtau2alpha belong to largely discrete groups: less than 9% were affected by more than one factor. Genes involved in regulation of cell death and apoptosis, growth and maintenance, signal transduction, physiological and developmental processes, protein kinase cascades, extracellular matrix, cytoskeleton, cell-cycle regulation, transport, and a variety of enzymes, intracellular components and nucleic acid-binding proteins have been described, many of which are involved in the modulation of myometrial activity during pregnancy and parturition.

Cyclic AMP↗