Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.11.11 (AMPK)
12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphorylation of the cAMP response element binding protein (CREB) by the catalytic subunit of cAMP-dependent protein kinase (cAK) has been implicated in the cAMP-dependent stimulation of gene transcription. delta-CREB, a spliced variant of CREB, and CREBtide (KRREILSRRPSYR), a synthetic peptide based on the phosphorylation sequence in delta-CREB, were tested as substrates of cAK. Phosphorylation of delta-CREB (0.17 microM) was stoichiometric within 30 s when using a concentration of cAK which approximated the intracellular level (0.2 microM). The rate of phosphorylation of delta-CREB was comparable to the rates of the best physiological substrates of cAK tested. The rate of CREBtide phosphorylation was at least as great as that of delta-CREB, indicating that the peptide retained the determinants of delta-CREB which were responsible for substrate efficacy. The apparent Km of CREBtide phosphorylation by cAK was 3.9 microM, which is 10-fold lower than that of kemptide (Km = 39 microM), the synthetic peptide substrate most often employed for cAK measurement. The Vmax values were 12.4 mumol/(min.mg) for CREBtide and 9.8 mumol/(min.mg) for kemptide. The apparent Km of CREBtide phosphorylation by cGMP-dependent protein kinase (cGK) was 2.9 microM and the Vmax value was 3.2 mumol/(min.mg). Both delta-CREB and CREBtide were phosphorylated at a much slower rate by cGK as compared with cAK, implying that the high cAK/cGK specificity exhibited by delta-CREB was retained by the peptide. Taken together, the results indicated that delta-CREB and CREBtide are among the best substrates tested for cAK and suggested that phosphorylation of CREB by this enzyme could occur in intact cells.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:cAMP-dependent protein kinase, but not the cGMP-dependent enzyme, rapidly phosphorylates delta-CREB, and a synthetic delta-CREB peptide. 133 14

The cAMP response element-binding protein (CREB) mediates transcriptional activation of genes in response to the cAMP signal transduction pathway. There are two different isoforms of CREB, which are generated by alternative RNA splicing. There is evidence that the two isoforms may have different biological activities. As the longer isoform (CREB341) contains a potential phosphorylation site that is not present in the shorter isoform (CREB327), we examined the possible differential phosphorylation of the two CREB isoforms. Recombinant CREB was prepared and used as substrate for phosphorylation by the cAMP-dependent protein kinase in vitro. Phosphopeptide mapping and mutagenesis studies demonstrated that CREB341 contains two sites, serine 133 and serine 98, that can be phosphorylated in vitro by the catalytic subunit of the cAMP-dependent protein kinase. In contrast, CREB327 contains only a single phosphorylation site at serine 119 (equivalent position to serine 133 in CREB341). A kinase titration experiment demonstrated that serine 98 of CREB341 was phosphorylated only at relatively high concentrations of the cAMP-dependent protein kinase. Transient transfection studies were used to test for any possible function of the phosphorylation of serine 98 of CREB341. These studies used GAL4-CREB fusion proteins. We found that mutation of serine 98 to alanine (which would block phosphorylation) has little or no effect on the ability of the CREB fusion protein to activate transcription. These findings suggest that differences in the biological activity of the two CREB isoforms are probably not mediated by differential phosphorylation by the cAMP-dependent protein kinase.
...
PMID:Phosphorylation of cyclic adenosine 3',5'-monophosphate (cAMP) response element-binding protein isoforms by the cAMP-dependent protein kinase. 148 Jan 75

We applied Southwestern and Western blotting and gel retardation techniques to investigate the changes that occur in the cyclic adenosine monophosphate (cAMP)-responsive element (CRE) binding (CREB) proteins in rapidly growing, chemically induced 5123tc and 5123D Morris hepatomas. Using the CRE sequences from the c-fos, E2A, and somatostatin gene promoters, we identified in the nuclear proteins from normal unstimulated or proliferating rat liver cells six different protein factors of Mr 34,000, 36,000, 40,000, 47,000, 56,000, and 72,000 capable of binding to the element. The Mr 47,000 protein had the highest specificity for the core CRE, suggesting its importance in cAMP-mediated gene expression. We could not find the Mr 47,000 CREB protein in the 5123tc and 5123D hepatomas. Our efforts to detect this protein in the tumors by (a) using the CRE sequence from different gene promoters, (b) altering the protocol for extracting nuclear proteins, or (c) attempting to restore its DNA-binding property by phosphorylation [with endogenous protein kinase(s), a catalytic subunit of cAMP-dependent protein kinase, and protein kinase C/dephosphorylation (with alkaline phosphatase)] were unsuccessful. The loss of tje Mr 47,000 CREB protein from solid tumors of the Morris hepatoma is likely to be related to the neoplastic properties of the tumor cell rather than to cell growth because the level of this protein remained unchanged during a 6-day period of liver regeneration. The nuclear extract from the Morris hepatoma that did not have the Mr 47,000 CRE-binding factor contained proteins immunologically related to the CREB, c-Jun, and c-Fos proteins. We conclude that the Mr 47,000 factor represents a distinct member of the CRE-binding protein family and that its absence from the hepatomas may lead to aberrant expression of cAMP-inducible genes.
...
PMID:Changes in cyclic adenosine monophosphate-responsive element binding proteins in rat hepatomas. 182 83

The transcription regulation of many hormone genes is modulated by intracellular second messengers such as cAMP. The cAMP response element binding protein, CREB, binds to the 8 base pair CRE enhancer, TGACGTCA, that is found in the 5'-flank of certain genes including those for somatostatin and the alpha-subunit of human chorionic gonadotropin. The recent characterization of CREB and CREB-related cDNA clones, combined with Southwesterns and Northern blot analyses, reveals a family of transcription factors that dimerize via a leucine zipper motif and bind to the CRE through positively charged basic regions. The CREB cDNA encoding a 327 residue protein is transcriptionally activated via phosphorylation by protein kinases, including the cAMP-dependent protein kinase-A.
...
PMID:Characterization of a cAMP-regulated enhancer-binding protein. 214 88

Cyclic AMP regulates the expression of a number of genes through a conserved promoter element, the CRE1. Moreover, transcriptional induction by cAMP requires the activation of cAMP-dependent protein kinase (protein kinase A). We have previously characterized the cAMP response element binding protein (CREB) in PC12 cells and brain tissue as a nuclear factor, of relative molecular mass 43,000, whose transcriptional efficacy is regulated by protein kinase A phosphorylation. CREB stimulates transcription on binding to the CRE as a dimer. Experiments suggesting that the dimerization and transcriptional efficacy of CREB are each stimulated by phosphorylation at distinct sites prompted us to suggest that CREB is regulated by multiple kinases in vivo. We now report the isolation of a cDNA clone for rat CREB using amino-acid sequence information from purified CREB protein. Sequence analysis of this CREB cDNA predicts a cluster of protein kinase A, protein kinase C and casein kinase II consensus recognition sites near the N terminus of the protein. The proximity of these potential phosphorylation sites to one another indicates that they may interact either positively or negatively to regulate CREB bioactivity.
...
PMID:A cluster of phosphorylation sites on the cyclic AMP-regulated nuclear factor CREB predicted by its sequence. 252 22

Many hormones act on neuroendocrine cells by activating second messenger pathways. Two of these, the phosphoinositol and cAMP-dependent pathways, cause changes in cellular activity through specific protein kinases. By phosphorylating cytoplasmic and nuclear proteins, these kinases apparently coordinate cellular processes, including the biosynthesis and release of neuropeptides. Somatostatin biosynthesis and release, for example, are both positively regulated by the second messenger cAMP in hypothalamic cells, and cAMP also induces somatostatin gene transcription 8-10-fold in transfected PC12 pheochromocytoma cells. Transcriptional induction requires a 30-nucleotide cAMP response element (CRE) which is conserved in other cAMP-responsive genes. This element also confers cAMP responsiveness when placed upstream of the heterologous simian virus 40 (SV40) promoter. The somatostatin gene does not, however, respond to cAMP in mutant PC12 cells which lack cAMP-dependent protein kinase type II activity. Activation of somatostatin gene transcription may consequently require the phosphorylation of a nuclear protein which binds to the CRE. Using a DNase I protection assay, we have characterized a nuclear protein in PC12 cells which binds selectively to the CRE in the somatostatin gene. We have purified this protein which is of relative molecular mass 43,000 (Mr 43K) by sequence-specific DNA affinity chromatography. This 43K CRE binding protein (CREB) is phosphorylated in vitro when it is incubated with the catalytic subunit of cAMP-dependent protein kinase. Stimulating PC12 cells with forskolin, an activator of adenyl cyclase, causes a 3-4-fold increase in the phosphorylation of this protein. We conclude that the cAMP-dependent pathway may regulate gene transcription in response to hormonal stimulation by phosphorylating this CREB protein.
...
PMID:Binding of a nuclear protein to the cyclic-AMP response element of the somatostatin gene. 288 56

We examined the effect of cAMP on the phosphorylation of intracellular proteins in cultured chondroblasts to understand the stimulatory role of intracellular cAMP in chondrogenesis of chick limb bud mesenchymal cells. A 40-kDa protein was remarkably phosphorylated by cAMP and the phosphorylation was completely blocked by an inhibitor of cAMP-dependent protein kinase. The phosphorylation of the 40-kDa protein was maximum at early stage of chondrogenesis (i.e., 24 hr of culture) which is consistent with the changes in the level of intracellular cAMP. The 40-kDa phosphoprotein was exclusively located in the nuclear parts of chondroblast but distinct from cAMP response element binding protein.
...
PMID:cAMP induces phosphorylation of a 40-kDa nuclear protein which is distinct from CREB during chondrogenesis of chick limb bud mesenchymal cells in vitro. 761 1

Cyclic AMP, via activation of cAMP-dependent protein kinase (PKA) and subsequent protein phosphorylation, regulates a number of cellular and tissue responses that are critical to normal development of the mammalian palate. The present study examines the expression, distribution, and phosphorylation in the developing murine palate of a substrate for PKA known as the cAMP-response element binding protein (CREB). This 43 x 10(3) M(r) protein functions as a regulator of cAMP-inducible gene expression. CREB is expressed constituitively throughout the palatal morphogenetic period and is ubiquitously distributed throughout palatal tissue. Immunofluorescent staining of palatal cells and tissues with an anti-CREB antibody revealed CREB to be localized to cell nuclei. Western blot analysis of extracts of staged palatal shelves with an antibody specific for phospho-ser 133-CREB demonstrated a steady increase in CREB phosphorylation at this residue during palate development. These observations show a temporal correlation with expression levels of cAMP-regulated genes in palate cells. The data indicate that CREB activity in the developing palate is most likely to be regulated at the level of protein phosphorylation as opposed to changes in levels of CREB protein expression.
...
PMID:Developmental changes in phosphorylation of the transcription factor CREB in the embryonic murine palate. 762 77

The cAMP response element binding protein (CREB) mediates transcriptional activation in response to the cAMP signaling pathway. Several recent studies have suggested that phosphorylation-dependent interaction of CREB with a co-activator designated CREB binding protein (CBP) is a crucial step in mediating transcriptional responses to cAMP. In the present study we have determined that replacement of Ser142 of CREB with Asp greatly decreases the ability of the cAMP-dependent protein kinase to activate CREB. As Ser142 is located within the region of CREB that interacts with CBP, it seemed quite likely that mutations at this site might interfere with binding to CBP. However, both in vitro and in vivo protein-protein interaction assays revealed that replacement of Ser142 with Asp does not interfere with the binding of CREB to CBP. These studies argue strongly that although the binding of CREB to CBP is necessary, it is not sufficient for transcriptional responses to cAMP.
...
PMID:An inactivating point mutation demonstrates that interaction of cAMP response element binding protein (CREB) with the CREB binding protein is not sufficient for transcriptional activation. 770 40

The cAMP-dependent protein kinase (PKA) phosphorylates CREB327/341 at a single serine residue, Ser119/133, respectively. Phosphorylation at this site creates the sequence motif SXXXS(P), a consensus site of the glycogen synthase kinase-3 (GSK-3) enzyme (Fiol, C.J., Mahrenholz, A.M., Wang, Y., Roeske, R.W., and Roach, P.J. (1987) J. Biol. Chem. 262, 14042-14048). We examined the phosphorylation of CREB at the SXXXS(P) consensus site and its role in CREB transactivation to cAMP induction. Neither isoform of the GSK-3 enzyme (GSK-3 alpha or beta) utilizes CREB as its substrate unless CREB is already phosphorylated at Ser119/133. A 13-amino acid peptide containing the sequence surrounding Ser119/133 was phosphorylated by GSK-3, at Ser115/129, only after the primary phosphorylation of the peptide by PKA (at Ser119/133), suggesting that Ser115/129 is a GSK-3 phosphoacceptor site. Mutant CREB327/341 proteins containing Ser-->Ala substitutions confirmed Ser115/129 as the only GSK-3 phosphorylation site. Transfection assays of wild type and mutant Gal4-CREB fusion proteins in PC12 cells demonstrated that Ser-->Ala substitution of residue 129 of CREB341 impairs the transcriptional response to cAMP induction. Analogous mutation in CREB327 results in 70% decrease in its transactivation response to cAMP. In undifferentiated F9 cells, which are refractory to cAMP induction, transfected GSK-3 beta kinase induces a 60-fold increase in cyclic AMP response element-dependent transcription, mediated via the endogenous CREB protein. We propose that the hierarchical phosphorylation at the PKA and GSK-3 sites of CREB are essential for cAMP control of CREB.
...
PMID:A secondary phosphorylation of CREB341 at Ser129 is required for the cAMP-mediated control of gene expression. A role for glycogen synthase kinase-3 in the control of gene expression. 779 17


1 2 3 4 Next >>

---