Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A comparison of the sequences of the mammalian and Dictyostelium catalytic subunits of cAMP-dependent protein kinase revealed extensive sequence similarities through the catalytic core and the carboxy terminal tail. The amino terminal sequences however differ dramatically. The large difference in size, 73 kDa for the Dictyostelium enzyme versus 40 kDa is due to an extension in the N-terminus. The mouse enzyme has at its amino-terminus a long amphipatic helix, the A-helix, that precedes the catalytic core, covering the surface of both lobes of the enzyme. Dictyostelium does in fact, have a similar motif but it is remote from the catalytic core, in the N-terminal extension. On the basis of molecular modeling, it is proposed that residues 77-98 correspond to a structural motif similar to the A-helix in mouse catalytic subunit. Sequences encoding similar putative motifs contiguous to the catalytic core can be recognized in many other protein kinases and is particularly prominent in all of the non-receptor tyrosine kinases. In the case of Src, this A-helix motif appears to serve as the linker between the conserved catalytic core and the SH2 domain. The interaction between the A-helix motif and the core is described, and the general occurrence of this structure within the protein kinase family is discussed.
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PMID:Protein kinases share a common structural motif outside the conserved catalytic domain. 798 16

Dictyostelium discoideum cells use cyclic AMP (cAMP) for chemotactic signaling as well as for differentiation. The precise regulation of the cytosolic Ca2+ concentration ([Ca2+]i) seems to play a key role for both processes. We performed single cell measurements of [Ca2+]i in amoebae that were starved in suspension for various times and scrape-loaded with the Ca2+ indicator fura-2. Stimulation of cells with cAMP at the concentration required to induce gene expression (> or = 100 microM) elicited a global transient increase in [Ca2+]i that depended on the presence of external Ca2+. Both vegetative and aggregation-competent cells displayed a rise in [Ca2+]i, with aggregation-competent cells responding more often than vegetative cells. Basal [Ca2+]i in the presence of Ca2+ was high in vegetative cells and declined during development; the cAMP-induced rise in [Ca2+]i was higher and lasted longer in vegetative cells than in aggregative cells. The addition of 2'-deoxy-cAMP, which binds to the cAMP receptor, induced an increase in [Ca2+]i, whereas the membrane-permeant analogue 8-bromo-cAMP that has a low affinity for the receptor but activates cAMP-dependent protein kinase had no effect. This indicates that the change in [Ca2+]i is mediated by the cell surface cAMP receptor. Since HC85 mutant cells, which lack the G alpha 2 subunit of the G-protein that couples the receptor to phospholipase C, also responded to stimulation with cAMP, the Ca2+ influx does not seem to be triggered by the phosphoinositide signaling cascade.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Challenge with high concentrations of cyclic AMP induces transient changes in the cytosolic free calcium concentration in Dictyostelium discoideum. 798 72

Dictyostelium slugs expressing a dominant inhibitor of the cAMP-dependent protein kinase (PKA) selectively in prestalk cells are insensitive to the environmental signals that normally induce culmination (Harwood et al., 1992a). When such slugs do, eventually, attempt to culminate they are unable to activate stalk-specific gene expression and they become arrested in their development. We show here that they are also about half the size of normal slugs and that they move at about half normal speed, even after their size difference has been taken into account. They are also less accurate in orienting their direction of movement towards the light. Thus, in addition to its role in cellular differentiation, PKA is required for several important aspects of slug behaviour.
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PMID:Inhibition of cAMP-dependent protein kinase in Dictyostelium prestalk cells impairs slug migration and phototaxis. 802 34

During formation of the Dictyostelium slug extracellular cAMP signals direct the differentiation of prespore cells and DIF, a chlorinated hexaphenone, induces the differentiation of prestalk cells. At culmination the slug transforms into a fruiting body, composed of a stalk supporting a ball of spores. A dominant inhibitor of cAMP-dependent protein kinase (PKA) expressed under the control of a prestalk-specific promoter blocks the differentiation of prestalk cells into stalk cells. Analysis of a gene specifically expressed in stalk cells suggests that PKA acts to remove a repressor that prevents the premature induction of stalk cell differentiation by DIF during slug migration. PKA is also necessary for the morphogenetic movement of prestalk cells at culmination. Expression of the PKA inhibitor under control of a prespore-specific promoter blocks the accumulation of prespore mRNA sequences and prevents terminal spore cell differentiation. Thus PKA is essential for progression along both pathways of terminal differentiation but with different mechanisms of action. On the stalk cell pathway it acts to regulate the action of DIF while on the spore cell pathway PKA itself seems to act as the inducer of spore cell maturation. Ammonia, the extracellular signal which regulates the entry into culmination, acts by controlling the intracellular concentration of cAMP and thus exerts its effects via PKA. The fact that PKA is necessary for both prespore and spore gene expression leads us to postulate the existence of a signalling mechanism which converts the progressive rise in cAMP concentration during development into discrete, PKA-regulated gene activation events.
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PMID:Regulation of Dictyostelium morphogenesis by cAMP-dependent protein kinase. 810 33

When Dictyostelium slugs are disaggregated and shaken in suspension prespore mRNAs disappear from the cells very rapidly but in the presence of extracellular cAMP the loss of prespore mRNA sequences is retarded. In a mutant which lacks a functional regulatory subunit of the cAMP-dependent protein kinase (PKA), and where the catalytic subunit is thereby rendered constitutively active, two prespore mRNA sequences persist for extended times after cellular disaggregation. Thus PKA is a component of the signaling pathway that allows prespore cells rapidly to dedifferentiate when extracellular cAMP signaling is disrupted. Analysis of cells expressing a dominant inhibitor of PKA shows there to be both a PKA-requiring and a non-PKA-requiring intracellular signaling pathway directing prespore-specific gene transcription and suggests that there may also be post-transcriptional regulation by PKA.
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PMID:A role for cAMP-dependent protein kinase in determining the stability of prespore cell differentiation in Dictyostelium. 817 84

Cell movement and cell-type-specific gene expression during Dictyostelium development are regulated by cAMP, which functions both as an extracellular hormone-like signal and an intracellular second messenger. Previous data indicated that aca- mutants, which lack adenylyl cyclase activity, fail to aggregate and do not express cell-type-specific genes. We show here that overexpression of ACG, a constitutively active adenylyl cyclase, which in wild-type cells is only expressed during spore germination, partially restores the coordination of cell movement and completely restores developmental gene expression. The aca- cells can also be induced to develop into viable spores by synergy with wild-type cells and, furthermore, form small but normal fruiting bodies, after a developmentally relevant regimen of stimulation with nanomolar cAMP pulses followed by micromolar cAMP concentrations. 2'-Deoxy cAMP, a cAMP analog that activates the cell-surface cAMP receptors but not cAMP-dependent protein kinase (PKA), also induces fruiting body formation as well as expression of prespore-specific and prestalk-enriched genes in aca- cells. Intracellular cAMP levels were not altered in aca- cells after stimulation with 2'-deoxy cAMP. Our data indicate that ACA is not required to provide intracellular cAMP for PKA activation but is essential to produce extracellular cAMP for coordination of cell movement during all stages of development and for induction of developmental gene expression.
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PMID:Extracellular cAMP is sufficient to restore developmental gene expression and morphogenesis in Dictyostelium cells lacking the aggregation adenylyl cyclase (ACA). 822 44

The ecmA and ecmB genes of Dictyostelium encode related extracellular matrix proteins and both are induced by DIF, the stalk cell-specific morphogen. The ecmA gene is expressed throughout the prestalk region of the migrating slug but only later, at culmination, do the prestalk cells express the ecmB gene. Expression of the ecmB gene is induced at the entrance to the stalk tube and we have identified two, apparently redundant, promoter elements that control this process. They act as repressors, preventing transcription in the tip of the migrating slug and the apical papilla of the culminant. They have a semi-palindromic consensus sequence TTGnCAA, where n is in one case 2 and in the other 4 bp. Either element alone is able to repress ecmB promoter activity in prestalk cells. Introduction of a single repressor element into the promoter of the ecmA gene changes its expression pattern to resemble that of the ecmB gene. Mutant elements, where n is altered, cause repression during the slug stage but allow premature ecmB expression during culmination; suggesting that the effective strength of the inductive signal may increase during culmination. Inhibition of cAMP-dependent protein kinase (PKA) in prestalk cells blocks both stalk cell maturation and ecmB gene expression. We show that the block to gene expression correlates precisely with the presence of a functional repressor element and this is consistent with the notion that expression of the ecmB gene is controlled by a PKA-dependent release from transcriptional repression.
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PMID:A repressor controls the timing and spatial localisation of stalk cell-specific gene expression in Dictyostelium. 826 39

We and others have previously shown that cAMP-dependent protein kinase (PKA) activity is essential for aggregation, induction of prespore gene expression and multicellular development in Dictyostelium. In this manuscript, we further examine this regulatory role. We have overexpressed the Dictyostelium PKA catalytic subunit (PKAcat) in specific cell types during the multicellular stages, using prestalk and prespore cell-type-specific promoters to make PKA activity constitutive in these cells (independent of cAMP concentration). To examine the effects on cell-type differentiation, we cotransformed the PKAcat-expressing vectors with reporter constructs expressing lacZ from four cell-type-specific promoters: ecmA (specific for prestalk A cells); ecmB (specific for prestalk B and anterior-like cells in the slug); ecmB delta 89 (specific for stalk cells); and SP60 (prespore-cell-specific). By staining for beta-galactosidase expression histologically at various stages of development in individual strains, we were able to dissect the morphological changes in these strains, examine the spatial localization of the individual cell types, and understand the possible roles of PKA during multicellular development. Expression of PKAcat from either the ecmA or ecmB prestalk promoters resulted in abnormal development that arrested shortly after the mound stage, producing a mound with a round apical protrusion at the time of tip formation. Prestalk A and prestalk B cells were localized in the central region and the apical mound in the terminal differentiated aggregate, while prespore cells showed an aberrant spatial localization. Consistent with a developmental arrest, these mounds did not form either mature spores or stalk cells and very few cells expressed a stalk-cell-specific marker. Expression of PKAcat from the prespore promoter resulted in abnormal morphogenesis and accelerated spore cell differentiation. When cells were plated on agar, a fruiting body was formed with a very large basal region, containing predominantly spores, and a small, abnormal sorocarp. Mature spore cells were first detected by 14 hours, with maximal levels reached by 18-20 hours, in contrast to 24-26 hours in wild-type strains. When cells were plated on filters, they produced an elongated tip from a large basal region, which continued to elongate as a tubular structure and produce a 'slug-like' structure at the end. The slug was composed predominantly of prestalk cells with a few prespore cells restricted to the junction between the 'slug' and tube. As the slug migrated, these prespore cells were found in the tube, while new prespore cells appeared at the slug/tube junction, suggesting a continual differentiation of new prespore cells at the slug's posterior.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:cAMP-dependent protein kinase differentially regulates prestalk and prespore differentiation during Dictyostelium development. 827 51

The cAMP-dependent protein kinase (cAPK) plays an essential role during differentiation and fruit morphogenesis in Dictyostelium discoideum. The presence of an open reading frame on the gene, pkaC (previously named either Dd PK2 or Dd PK3 by different groups), predicts a 73-kDa polypeptide with 54% similarity to the catalytic subunits of cAPKs from other organisms. Using anti-peptide antibodies, we show that the pkaC gene product, PkaC, is a 73-kDa polypeptide. Despite the fact that PkaC is about twice the size of its mammalian counterparts, it possesses all of the properties required of a catalytic subunit. It is physically associated with the regulatory subunit, and this association results in an inhibition of the catalytic activity which is reverted by cAMP. PkaC copurifies with cAPK activity, and an increased cAPK activity is observed in cells overexpressing PkaC. We conclude that PkaC is a catalytic subunit of the Dictyostelium discoideum cAPK and discuss the unusual features of this protein with the highest molecular weight of known cAPKs.
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PMID:An unusual catalytic subunit for the cAMP-dependent protein kinase of Dictyostelium discoideum. 837 60

We studied how extracellular cyclic AMP (cAMP) dilates the isolated and perfused canine coronary artery using pharmacological tools. Single injections of cAMP (1-1000 nmol), adenosine 3',5'-cyclic monophosphorothioate Sp-isomer (Sp-cAMPS) (10-1000 nmol, an agonist of the cell surface cAMP receptor in Dictyostelium discoideum and of cAMP-dependent protein kinase), adenosine (0.1-1000 nmol) and 5'-AMP (0.1-1000 nmol) dilated the canine coronary artery dose dependently. The potency order for vasodilation was adenosine > 5'-AMP > cAMP > Sp-cAMPS > 8-bromo-cyclic GMP > 3'-AMP > 8-bromo-cAMP > N6,O2'-dibutyryl-cAMP. 2'-Deoxy-cAMP, 2',3'-cAMP, guanosine, cGMP, 3'-GMP and 5'-GMP did not produce vasodilation. Adenosine antagonists such as aminophylline (1-100 microM, nonselective), 8-phenyltheophylline (0.1-10 microM, A1 selective), 8-cyclopentyl-1,3-dipropylxanthine (0.01-1 microM, A1 selective) and 3,7-dimethyl-1-proparglyxanthine (0.01-1 microM, A2 selective) shifted the dose-response curve of adenosine in parallel to the right, but they shifted that of cAMP to the right and downwards. 8-Phenyltheophylline (1 and 10 microM) inhibited the response to Sp-cAMPS (100 nmol) dose dependently. Aminophylline (10 microM) did not affect isoproterenol- and forskolin-induced vasodilations. Adenosine deaminase (3 U/ml) completely inhibited the response to adenosine, but not those to 5'-AMP, cAMP, 8-bromo-cAMP and Sp-cAMPS. 5'-Nucleotidase inhibitors, adenosine-5'-(alpha,beta-methylene) diphosphate (10 microM) and 5'-GMP (1 mM), inhibited the responses to cAMP and 5'-AMP, but not that to adenosine.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pharmacological analysis of vasodilation induced by extracellular adenosine 3',5'-cyclic monophosphate in the isolated and perfused canine coronary artery. 838 43


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