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 cDNA encoding a serotonin transporter (5-HTT) in the human dorsal raphe nucleus was isolated and sequenced using cross-species amplification of human 5-HTT partial cDNA by the polymerase chain reaction (PCR) and the RACE-PCR procedure, designed for rapid amplification of 3' and 5' cDNA ends. The cDNA contains an open reading frame encoding a hydrophobic polypeptide of 630 amino acids with a calculated molecular weight of approximately 70 kDa. The human 5-HTT is approximately 92% homologous to the rat protein but contains an additional consensus phosphorylation site for cAMP-dependent protein kinase recognition located in the cytoplasmic N-terminal region, while a potential protein kinase C phosphorylation site identified in the rat homolog is not conserved in the human 5-HTT. Hydropathicity analysis revealed twelve membrane spanning segments, a topology proposed for other cloned sodium-dependent transporters.
J Neural Transm Gen Sect 1993
PMID:Isolation of a cDNA encoding the human brain serotonin transporter. 845 85

Biochemical and physiological studies have implicated cAMP and cAMP-dependent protein kinase (PKA) in a plethora of essential cellular processes. Here we show that yeast cells partially depleted of PKA activity (due to a tpkw mutation) and bearing a lesion in a Golgi-localized Ca2+ pump (Pmr1), arrest division with a small bud. The bud morphology of the arrested tpk1w pmr1 mutant cells is characteristic of cells in S phase; however, the terminal phenotype of processes such as DNA replication and nuclear division suggests arrest at the G2/M boundary. This small bud, G2-arrest phenotype is similar to that of strains with a defect in cell wall biosynthesis (pkc1) or membrane biogenesis (och1); however, the biochemical defect may be different since the tpk1w pmr1 double mutants retain viability. The growth defect of the tpk1w pmr1 mutant can be alleviated by preventing the increase in cellular cAMP levels that is known to be associated with a decrease in PKA activity, or by supplementing the medium with millimolar amounts of Ca2+. Although the biochemical consequences of this increase in cAMP concentration are not known, the small-bud phenotype of the double mutant and the known protein processing defect of the pmr1 lesion suggest that the localization or function of some membrane component might be compromised and susceptible to perturbations in cellular cAMP levels. One candidate for such a protein is the cAMP-binding membrane ectoprotein recently described in yeast.
Mol Gen Genet 1996 Jul 19
PMID:cAMP inhibits bud growth in a yeast strain compromised for Ca2+ influx into the Golgi. 870 62

The effects of cyclic AMP (cAMP) on intracellular Na+ concentration ([Na+]i), membrane depolarization and intracellular Ca2+ concentration ([Ca2+]i) and the involvement of cAMP in acetylcholine (ACh)-induced such cellular events and catecholamine (CA) release were studied in cultured bovine adrenal medullary chromaffin cells. 8-Bromo-cyclic AMP (8Br-cAMP) and forskolin caused a rise in [Na+]i, membrane depolarization and a rise in [Ca2+]i and potentiated these responses and CA release to ACh. The effects of 8Br-cAMP or forskolin on ACh-induced changes of but not on basal level of [Na+]i, membrane potential and [Ca2+]i were blocked by tetrodotoxin (TTX, 1 microM). In Na+ deprivated medium, forskolin failed to produce an increase in basal [Ca2+]i level and to potentiate ACh-induced rise. The similar results as in 8Br-cAMP and forskolin were obtained using ouabain, and 8Br-cAMP or foskolin produced no further effects in the presence of ouabain. Inhibitors of cAMP-dependent protein kinase not only blocked the effects of 8Br-cAMP and forskolin on membrane depolarization, [Ca2+]i rise and CA release, but also reduced these responses to ACh. From the similarity between the effects of cAMP and those of ouabain on the cellular events and the counteraction of the effects of cAMP by ouabain, it may be suggested that cAMP produces its effects on ion fluxes and CA release probably via an inhibition of Na+, K(+)-ATPase in intact chromaffin and cAMP may participate in the responses to ACh.
J Neural Transm Gen Sect 1995
PMID:Cyclic AMP enhances acetylcholine (ACh)-induced ion fluxes and catecholamine release by inhibiting Na+, K(+)-ATPase and participates in the responses to ACh in cultured bovine adrenal medullary chromaffin cells. 874 60

In the goldfish, it has been proposed that gonadotropin (GTH) release induced by GTH-releasing hormone (GnRH) involves Ca2+ entry through voltage-sensitive Ca2+ channels (VSCC), protein kinase C (PKC) activation, and arachidonic acid (AA) metabolism, but not cyclic AMP (cAMP) action. However, cAMP appears to mediate GnRH action in other teleosts. In this study, the relative importance of PKC and cAMP in mediating GnRH action in goldfish was studied using primary cultures of dispersed pituitary cells. Consistent with an involvement of PKC in GnRH action, the GTH responses to the PKC activating tetradecanoyl phorbol acetate (TPA), salmon (s)GnRH, and chicken (c)GnRH-II were inhibited by two selective PKC inhibitors, calphostin C, and staurosporine. Furthermore, GTH release responses induced by sGnRH or cGnRH-II were not additive to responses stimulated by the PKC-activating diglyceride DiC8, in either long-term static incubation or acute perifusion experiments. In static incubation studies, the GTH responses to sGnRH and DiC8 were potentiated by the VSCC agonist Bay K 8644, suggesting that VSCC participates in both PKC and GnRH action. Concentrations of K+ < 100 mM did not elicit GTH secretion when tested alone, but were effective in stimulating GTH release in the presence of subthreshold doses of DiC8 or TPA. This suggests that minimal activation of PKC greatly enhances the effectiveness of Ca2+ influx to increase GTH secretion. Taken together, these results indicate that PKC is an important mediator of GnRH-induced, VSCC-dependent GTH release. In contrast to the involvement of PKG, cAMP-dependent mechanisms showed no evidence of direct participation in GnRH-induced GTH release in goldfish. In static incubation studies, the GTH responses to sGnRH and cGnRH-II were not affected by H89, a cAMP-dependent protein kinase (PKA) inhibitor. Furthermore, the GTH release stimulated by cAMP was additive to the response to sGnRH, cGnRH-II, DiC8, TPA, or AA. However, compared to the response to forskolin or TPA alone, combinations of forskolin and TPA resulted in a potentiated increase in GTH release. The acute GTH response to forskolin was also enhanced by DiC8. Thus, cAMP-dependent mechanisms may constitute an independent pathway that interacts positively with GnRH-dependent mechanisms in the regulation of GTH release.
Gen Comp Endocrinol 1996 Jun
PMID:Interactions between signaling pathways in mediating GnRH-stimulated GTH release from goldfish pituitary cells: protein kinase C, but not cyclic AMP is an important mediator of GnRH-stimulated gonadotropin secretion in goldfish. 880 63

Transcription of genes for peroxisomal proteins is repressed by glucose and induced by oleate. At least for the peroxisomal thiolase gene (POT1) there is a third regulatory mechanism, mediated by the transcription factor Adr1p, which is responsible for the high-level expression of the gene in stationary phase. Here we show that a region in the POT1 promoter that extends from positions -238 to -152 mediates this mechanism, and we suggest that Adr1p acts indirectly on POT1. We have also analyzed the role of the cAMP-dependent protein kinase (PKA) in the transcriptional regulation of POT1. PKA exerts a negative control: the high, unregulated PKA activity in a bcy1 mutant maintains POT1 transcription at the repressed level. In a ras2 mutant, which has low PKA activity, glucose repression is not alleviated but in non-repressing conditions POT1 regulation is perturbed and expression prematurely increases during exponential phase. This suggests that the PKA signalling pathway controls the regulation of POT1 in stationary phase. Finally, we have found that Adr1p-dependent expression in stationary phase and induction by oleate are both abolished when respiration is blocked. Utilization of fatty acids as carbon source requires respiration. Our result points to the existence of mechanisms that co-ordinate the level of expression of thiolase and the functional state of the mitochondria.
Mol Gen Genet 1996 Sep 25
PMID:Respiration and low cAMP-dependent protein kinase activity are required for high-level expression of the peroxisomal thiolase gene in Saccharomyces cerevisiae. 887 46

Bovine adrenal zona fasciculata (AZF) cells express a noninactivating K+ current (IAC) that is inhibited by adrenocorticotropic hormone (ACTH) at picomolar concentrations. Inhibition of IAC may be a critical step in depolarization-dependent Ca2+ entry leading to cortisol secretion. In whole-cell patch clamp recordings from AZF cells, we have characterized properties of IAC and the signalling pathway by which ACTH inhibits this current. IAC was identified as a voltage-gated, outwardly rectifying, K(+)-selective current whose inhibition by ACTH required activation of a pertussis toxin-insensitive GTP binding protein. IAC was selectively inhibited by the cAMP analogue 8-(4-chlorophenylthio)-adenosine 3':5'-cyclic monophosphate (8-pcpt-cAMP) with an IC50 of 160 microM. The adenylate cyclase activator forskolin (2.5 microM) also reduced IAC by 92 +/- 4.7%. Inhibition of IAC by ACTH, 8-pcpt-cAMP and forskolin was not prevented by the cAMP-dependent protein kinase inhibitors H-89 (5 microM), cAMP-dependent protein kinase inhibitor peptide (PKI[5-24]) (2 microM), (Rp)-cAMPS (500 microM), or by the nonspecific protein kinase inhibitor staurosporine (100 nM) applied externally or intracellularly through the patch pipette. At the same concentrations, these kinase inhibitors abolished 8-pcpt-cAMP-stimulated A-kinase activity in AZF cell extracts. In intact AZF cells, 8-pcpt-cAMP activated A-kinase with an EC50 of 77 nM, a concentration 2,000-fold lower than that inhibiting IAC half maximally. The active catalytic subunit of A-kinase applied intracellularly through the recording pipette failed to alter functional expression of IAC. The inhibition of IAC by ACTH and 8-pcpt-cAMP was eliminated by substituting the nonhydrolyzable ATP analogue AMP-PNP for ATP in the pipette solution. Penfluridol, an antagonist of T-type Ca2+ channels inhibited 8-pcpt-cAMP-induced cortisol secretion with an IC50 of 0.33 microM, a concentration that effectively blocks Ca2+ channel in these cells. These results demonstrate that IAC is a K(+)-selective current whose gating is controlled by an unusual combination of metabolic factors and membrane voltage. IAC may be the first example of an ionic current that is inhibited by cAMP through an A-kinase-independent mechanism. The A-kinase-independent inhibition of IAC by ACTH and cAMP through a mechanism requiring ATP hydrolysis appears to be a unique form of channel modulation. These findings suggest a model for cortisol secretion wherein cAMP combines with two separate effectors to activate parallel steroidogenic signalling pathways. These include the traditional A-kinase-dependent signalling cascade and a novel pathway wherein cAMP binding to IAC K+ channels leads to membrane depolarization and Ca2+ entry. The simultaneous activation of A-kinase- and Ca(2+)-dependent pathways produces the full steroidogenic response.
J Gen Physiol 1996 Oct
PMID:Adrenocorticotropic hormone and cAMP inhibit noninactivating K+ current in adrenocortical cells by an A-kinase-independent mechanism requiring ATP hydrolysis. 889 75

1. The effect of zeranol (3-100 microM) on rat uterus contractions induced by KCl (60 mM) and CaCl2 (30 microM-10 mM) has been assayed. 2. Zeranol relaxed the tonic contraction induced by KCl in a concentration-dependent manner (IC50 15.62 +/- 2.66 microM). CaCl2 (0.1-10 mM) did not counteract the relaxing effect of zeranol. 3. CaCl2 (30 microM -10 mM) produced a concentration-dependent contraction of rauuterus in medium lacking calcium plus KCl (60 mM) (EC50 0.34 +/- 0.03 mM). Zeranol (8 microM) displaced the CaCl2 concentration-response curve to the right and increased the EC50 to 1.27 +/- 0.57 mM (P < 0.05) without modifying the Emax. 4. The antiestrogen tamoxifen (1 microM) and the inhibitor of cAMP-dependent protein kinase TPCK (3 microM) did not modify the effect of zeranol. However, the inhibitors of transcription (actinomycin D, 4 microM), protein synthesis (cycloheximide, 100 microM), and ornithine-decarboxilase (alpha-difluoromethyl-ornithine, 10 mM)) antagonized the effect of zeranol, increasing the IC50 to 50.2 +/- 6.2 microM, 122 +/- 6.9 microM, and 23.51 +/- 1.14 microM, respectively. 5. Our results suggest that the relaxing effect of zeranol on rat uterus smooth muscle is produced by mechanisms unrelated to cAMP and estrogen receptors, but involves transcriptional effects and polyamine synthesis.
Gen Pharmacol 1997 Apr
PMID:Transcriptional mechanisms involved in the relaxant effect of zeranol on isolated rat uterus. 914 25

Phosphofructokinase II (PEK II) from Trichoderma reesei was partially purified (247-fold). The calculated Km values for fructose 6-phosphate and ATP were 0.7 mM and 40 microM, respectively. Upon incubation in the presence of [gamma-32P]ATP, the enzyme formed a radioactive phosphoprotein with molecular mass of 67 kDa in autoradiography analysis after SDS-PAGE. Upon incubation in the presence of ATP-Mg and the catalytic subunit of cAMP-dependent protein kinase, its activity was not modified. The same result was obtained when a cell-free extract of T. reesei was incubated with ATP-Mg and cAMP. 2,4-Dinitrophenol caused a transient rise in cAMP levels in the fungal cell. The results provide evidence that the fructose 2,6-bisphosphate level in T. reesei is independent of cAMP concentrations and not related to a cAMP-dependent mechanism, but to the availability of substrate fructose 6-phosphate.
J Gen Microbiol 1993 Jun
PMID:Characterization of phosphofructokinase II and regulation of fructose 2,6-bisphosphate levels in Trichoderma reesei. 919 69

Protein phosphorylation is a primary means of mediating signal transduction events that control cellular processes. Accordingly, the activities of protein kinases and phosphatases are highly regulated. One level of regulation is that the subcellular distribution of several kinases and phosphatases is restricted by association with targeting proteins or subunits. This mechanism promotes rapid and preferential modulation of specific targets within a defined microenvironment in response to diffusible second messengers. The type II cAMP-dependent protein kinase (PKA) is targeted by association of its regulatory subunit (RII) with A-kinase anchoring proteins (AKAPs). To date, 36 unique AKAPs have been identified. Each of these proteins contains a conserved amphipathic helix responsible for AKAP association with cellular structures. Disruption of PKA/AKAP interaction with peptides patterned after the amphipathic helix region blocks certain cAMP responses, including the modulation of glutamate receptor ion-channel activity in neurons and transcription of cAMP-responsive genes. Yeast two-hybrid screening methods have identified neuronal specific AKAP79-binding proteins including the beta isoform of the phosphatase 2B, calcineurin. Biochemical and immunological studies have confirmed the two-hybrid results and identified additional members of this multienzyme signaling complex, including certain protein kinase C isoforms. These findings are consistent with colocalization of CaN, PKC, and type II PKA by AKAP79 and suggest a novel model for reversible phosphorylation in which the opposing kinase and phosphatase actions are colocalized in a signal transduction complex by association with a common anchor protein.
Soc Gen Physiol Ser 1997
PMID:Dissection of protein kinase and phosphatase targeting interactions. 921 Feb 33

It is currently believed that a nonselective cation (NSC) channel, which responds to arginine vasotocin (an antidiuretic hormone) and stretch, regulates Na+ absorption in the distal nephron. However, the mechanisms of regulation of this channel remain incompletely characterized. To study the mechanisms of regulation of this channel, we used renal epithelial cells (A6) cultured on permeable supports. The apical membrane of confluent monolayers of A6 cells expressed a 29-pS channel, which was activated by stretch or by 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of phosphodiesterase. This channel had an identical selectivity for Na+, K+, Li+, and Cs+, but little selectivity for Ca2+ (PCa/PNa < 0.005) or Cl- (PCl/PNa < 0.01), identifying it as an NSC channel. Stretch had no additional effects on the open probability (Po) of the IBMX-activated channel. This channel had one open ("O") and two closed (short "CS" and long "CL") states under basal, stretch-, or IBMX-stimulated conditions. Both stretch and IBMX increased the Po of the channel without any detectable changes in the mean open or closed times. These observations led us to the conclusion that a kinetic model "CL <--> CS <--> O" was the most suitable among three possible linear models. According to this model, IBMX or stretch would decrease the leaving rate of the channel for CL from CS, resulting in an increase in Po. Cytochalasin D pretreatment abolished the response to stretch or IBMX without altering the basal activity. H89 (an inhibitor of cAMP-dependent protein kinase) completely abolished the response to both stretch and IBMX, but, unlike cytochalasin D, also diminished the basal activity. We conclude that: (a) the functional properties of the cAMP-activated NSC channel are similar to those of the stretch-activated one, (b) the actin cytoskeleton plays a crucial role in the activation of the NSC channel induced by stretch and cAMP, and (c) the basal activity of the NSC channel is maintained by PKA-dependent phosphorylation but is not dependent on actin microfilaments.
J Gen Physiol 1997 Sep
PMID:Activation of Na+-permeant cation channel by stretch and cyclic AMP-dependent phosphorylation in renal epithelial A6 cells. 927 57


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