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)

ras-Transformed NIH3T3 (R3T3) cells were transfected with expression vectors for the RII alpha and RII beta regulatory subunits of the type II isozyme of cAMP-dependent protein kinase, and the effects on gene activation by corticotropin-releasing factor (CRF) and prostaglandin E1 (PGE1) were analyzed. In RII alpha and RII beta-overexpressing cells, type II isozyme levels were increased, and type I isozyme levels were eliminated, demonstrating that both RII regulatory subunits compete efficiently with RI for catalytic subunit. The type II isozyme separated into three peaks on high performance liquid chromatography, referred to as A, B, and C. Western blot analysis strongly suggests that peak A and peak C correspond to holoenzymes containing RII beta and RII alpha, respectively. Overexpression of RII alpha resulted in the loss of peak A and a dramatic reduction in RII beta protein with no change in RII beta mRNA, indicating that the level of RII beta protein is controlled posttranscriptionally and that RII beta protein may become unstable when displaced from C. The role of type I and II kinases in transcriptional activation was investigated by comparing the response of control and RII expressing clones to site-selective cAMP analogs and the hormones, CRF and PGE1. The site-selective analogs demonstrated that either type I or type II kinase could activate the cAMP-responsive alpha-subunit promoter. The response to various concentrations of CRF or PGE1 was identical in control cells and transfected clones containing very little type I kinase. These experiments suggest that in the CRF and PGE1 response pathways leading to gene induction, the magnitude and sensitivity of the response are not influenced by the presence or absence of type I cAMP-dependent protein kinase.
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PMID:Hormonal activation of gene transcription in ras-transformed NIH3T3 cells overexpressing RII alpha and RII beta subunits of the cAMP-dependent protein kinase. 174 4

Previous work has shown that prolonged pretreatment of a mouse anterior pituitary cell line, AtT-20 cells, with the cytokine interleukin 1 (IL-1) stimulates beta-endorphin release and potentiates the secretion induced by many secretagogues. Desensitization of protein kinase C (PKC) by pretreatment with phorbol ester [phorbol 12-tetradecanoate 13-acetate (TPA)] for 8 hr abolished the secretion induced by TPA as well as the enhancement of TPA-induced beta-endorphin release produced by IL-1. Desensitization of PKC only partly abolished the potentiating effects of IL-1 on corticotropin-releasing factor-induced beta-endorphin secretion. In contrast, IL-1-induced beta-endorphin release was independent of PKC. We observed that treatment of AtT-20 cells with IL-1 markedly phosphorylated 19-, 20-, and 60-kDa proteins within minutes, presumably by early activation of protein kinases. Prolonged treatment with TPA, which was shown to desensitize an 87-kDa protein (a substrate for PKC), had no effect on IL-1-induced phosphorylation of 20-, 60-, and 87-kDa proteins, indicating that the phosphorylation of these proteins does not involve PKC. IL-1 does not generate cAMP in AtT-20 cells, suggesting that a cAMP-dependent protein kinase is also not involved. Prolonged treatment with IL-1 abolishes the capacity of cytokine to induce the phosphorylation of 20- and 60-kDa proteins. The presence of IL-1 was required initially only for a short time to induce late secretion in AtT-20 cells. These observations indicate that once IL-1 generates an early signal, its presence is no longer necessary for the subsequent secretion of beta-endorphin.
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PMID:Interleukin 1 induces early protein phosphorylation and requires only a short exposure for late induced secretion of beta-endorphin in a mouse pituitary cell line. 215 4

This study was undertaken to define the roles of corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) in the regulation of adrenocorticotropin (ACTH) release and biosynthesis in cultured ovine anterior pituitary cells and to define the intracellular mechanisms responsible for their action. At 4 h, CRF and AVP increased both ACTH release and total ACTH content, with AVP clearly the more potent agonist (maximal ACTH release: AVP, 22.8-fold; CRF, 7.6-fold; maximal increment in total ACTH content: AVP, 1.9-fold; CRF, 1.1-fold; EC50 for ACTH release: AVP, 2.3 +/- 0.5 nM; CRF, 9.2 +/- 5.0 nM). The increase in total ACTH content was interpreted to reflect an augmentation of ACTH biosynthesis since it was abolished by 10 microM cycloheximide. Exposure of the anterior pituitary cells to increasing concentrations of forskolin or 8-bromo-cAMP elicited increases in ACTH release and total ACTH content that were similar to those caused by CRF. A 30-min incubation with phorbol 12-myristate 13-acetate (PMA) caused a dose-related translocation of protein kinase C from the cytosol to the cell membrane; after 4 h, the increases in ACTH release and total ACTH content in response to increasing concentrations of PMA were similar to those caused by AVP. Chronic (24 h) exposure to 150 nM PMA caused an almost total depletion of both cytosolic and membrane-bound protein kinase C activities. When protein kinase C-depleted cells were subsequently exposed to AVP, the increases in ACTH release and total ACTH content were markedly attenuated, but the responses to CRF were preserved. Finally, the combination of CRF and AVP, CRF and PMA, or AVP and 8-bromo-cAMP increased ACTH release and total ACTH content in a synergistic manner. We conclude that: 1) in ovine anterior pituitary cells, AVP is the predominant regulator of ACTH secretion and biosynthesis; 2) the action of AVP is predominantly mediated by activation of protein kinase C, whereas the action of CRF is likely to be mediated by activation of the cAMP-dependent protein kinase (protein kinase A); and 3) the ability of CRF and AVP to increase total ACTH content and secretion in a synergistic manner provides a demonstration in normal pituitary cells that protein kinases C and A may interact in a unidirectional manner to regulate ACTH biosynthesis in addition to ACTH release. This interaction may take place within, or between, individual corticotropes.
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PMID:The biosynthesis and secretion of adrenocorticotropin by the ovine anterior pituitary is predominantly regulated by arginine vasopressin (AVP). Evidence that protein kinase C mediates the action of AVP. 216 7

The effects of the protein kinase C activator, phorbol myristate acetate (PMA), on cytosolic calcium levels and adrenocorticotropin (ACTH) release from the mouse anterior pituitary tumor cell line, AtT-20, were compared to those induced by the hormone, corticotropin-releasing factor (CRF), a stimulant of cAMP-dependent protein kinase activity. Cytosolic calcium levels were measured using the fluorescence probe Quin 2. PMA induced a time- and concentration-dependent rise in cytosolic calcium levels and ACTH release from AtT-20 cells that was blocked by verapamil and nifedipine, antagonists of voltage-regulated calcium channels, and tetraethylammonium (TEA), a K+ channel antagonist. The inactive phorbol ester, 4-phorbol 12,13-didecanoate, did not alter cytosolic calcium levels or ACTH release. Several minutes after the initial stimulation of calcium influx by PMA, cytosolic calcium levels returned to basal levels despite the continued presence of the phorbol ester. A short pretreatment (2-4 min) of AtT-20 cells with PMA abolished the ability of K+, CRF, and forskolin to raise intracellular calcium levels. These findings indicate that phorbol esters induce a secondary inhibition of calcium influx after an initial stimulation. In contrast to the effects of PMA, CRF induced a sustained rise in cytosolic calcium levels and did not reduce the subsequent stimulation of calcium influx by K+ or PMA. CRF-stimulated calcium influx was blocked by verapamil but not TEA. The ability of CRF to elevate cytosolic calcium levels was mediated by cAMP-dependent protein kinase because the insertion of a synthetic peptide inhibitor of cAMP-dependent protein kinase activity into AtT-20 cells attenuated the ability of CRF and forskolin but not PMA to raise cytosolic calcium levels. The results suggest that activators of protein kinase C and cAMP-dependent protein kinase regulate intracellular calcium levels in AtT-20 cells through different mechanisms.
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PMID:Activators of protein kinase C and cyclic AMP-dependent protein kinase regulate intracellular calcium levels through distinct mechanisms in mouse anterior pituitary tumor cells. 282 94

Corticotropin-releasing factor (CRF) is the most potent and effective natural stimulant of corticotropin (ACTH) secretion. In a tumor cell line of the mouse anterior pituitary (AtT-20/D16-16) consisting of a homogeneous population of corticotrophs, CRF is known to increase adenylate cyclase and cAMP-dependent protein kinase activities as well as to release ACTH. To determine whether activation of cAMP-dependent protein kinase is essential for CRF to evoke the secretion of ACTH, an inhibitor (PKI) of this kinase was inserted into AtT-20 cells. This was accomplished by first encapsulating PKI into liposomes and then covalently coupling them to protein A for binding to antibodies directed against an AtT-20 cell surface antigen, N-CAM (neural cell adhesion molecule). The binding of the liposomes to the anti-N-CAM antibodies led to the internalization of the PKI into the tumor cells. The PKI treatment greatly attenuated CRF-stimulated ACTH release as well as the secretory response to beta-adrenergic agonists. However, ACTH release in response to caerulein, an agonist of cholecystokinin 8 receptors, was not altered by the PKI treatment. CRF treatment also increased the levels of mRNA for proopiomelanocortin (POMC), the precursor for ACTH in AtT-20 cells. Application of liposomes containing PKI to AtT-20 cells blocked the ability of CRF and 8-bromo-cAMP, but not phorbol ester, to increase POMC mRNA levels. The results revealed an essential role for cAMP in mediating the effect of CRF on ACTH release and POMC gene expression.
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PMID:Corticotropin-releasing factor-induced adrenocorticotropin hormone release and synthesis is blocked by incorporation of the inhibitor of cyclic AMP-dependent protein kinase into anterior pituitary tumor cells by liposomes. 299 99

In a tumor cell line of the mouse anterior pituitary (AtT-20/D16-16) consisting of a homogeneous population of corticotrophs, corticotropin-releasing factor (CRF) activates adenylate cyclase and cAMP-dependent protein kinase. In addition, CRF induces a rise in cytosolic calcium levels in AtT-20/D16-16 cells and stimulates adrenocorticotropin hormone release. To determine whether activation of cAMP-dependent protein kinase is essential for CRF to stimulate calcium mobilization and trigger adrenocorticotropin hormone release, an inhibitor of cAMP-dependent protein kinase was inserted into AtT-20/D16-16 cells using a liposome technique. In control cells, CRF, forskolin (a direct activator of adenylate cyclase) and potassium increased cytosolic calcium levels. Insertion of the protein kinase inhibitor into AtT-20/D16-16 cells greatly attenuated CRF and forskolin-stimulated calcium mobilization although it did not alter the rise in cytosolic calcium induced by potassium. Treatment of the cells with liposomes lacking protein kinase inhibitor (but containing an equivalent amount of bovine serum albumin) had no effect upon the calcium mobilization elicited by any of the agents tested. These results reveal an essential role for cAMP-dependent protein kinase in mediating CRF-stimulated calcium mobilization and suggest that its activation may be an essential molecular event for CRF to evoke adrenocorticotropin hormone secretion.
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PMID:Molecular mechanisms of corticotropin-releasing factor stimulation of calcium mobilization and adrenocorticotropin release from anterior pituitary tumor cells. 303 99

Corticotropin-releasing factor (CRF) stimulates adrenocorticotropin (ACTH) release via the adenylate cyclase/cAMP-dependent protein kinase system. Because calcium is necessary for receptor-mediated release of ACTH, we have examined the effect of CRF on 45Ca2+ uptake in a corticotroph cell line model, AtT-20. Treatment of AtT-20 cells with CRF (10(-9)-10(-6) M) resulted in dose- and time-dependent increases in 45Ca2+ uptake, up to 2.2-fold above control values. The effect was statistically significant at 1 min and persisted for at least 10 min. Treatment with forskolin (1-30 microM), 8-Br-cAMP (0.5 mM), cholera toxin (CT, 100 ng/ml) and K+ (20 mM) also increased cell-associated 45Ca2+. The effect of K+ was completely blocked by nifedipine (100 microM), whereas the effects of CRF (10(-8) M) were only partially inhibited by this calcium channel antagonist. These data suggested a role of voltage-dependent calcium channels in 45Ca2+ uptake. Short term pretreatment (1-2 h) of AtT-20 cells with CRF (10(-8) M) significantly desensitized both CRF-stimulated cAMP accumulation and ACTH release, but did not attenuate CRF-stimulated 45Ca2+ uptake. Pretreatment with CRF (10(-8) M) for 4 h did not alter CT- or forskolin-stimulated cAMP accumulation and ACTH release. This suggests that the molecular mechanisms of desensitization are proximal to adenylate cyclase. Conversely, long term pretreatment (24 h) of AtT-20 cells with CRF (10(-8) M) induced significant desensitization of CRF-stimulated 45Ca2+ uptake. These results indicate that CRF stimulates calcium uptake in AtT-20 cells via cAMP-dependent and cAMP-independent mechanisms, and that the cellular mechanisms involved in desensitization of cAMP accumulation and ACTH release and those involved in desensitization of calcium uptake are qualitatively different.
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PMID:Corticotropin-releasing factor (CRF) stimulates 45Ca2+ uptake in the mouse corticotroph cell line AtT-20. 838 2

The immunomodulating properties of a neuropeptide hormone, corticotropin-releasing factor (CRF), led us to investigate its effect on cAMP production by human peripheral blood mononuclear cells (MNC). In response to stimulation with CRF (100 nM), a statistically significant (P = 0.019) increase occurred in the amount of cAMP produced by MNC. Purified monocytes, but not lymphocytes, also displayed a significant (P = 0.01) increase (8- to 10-fold) in intracellular cAMP after treatment with CRF (100 nM). The antagonist alpha-helical CRF9-41 (100 nM) counteracted the cAMP increase induced by CRF (100 nM). The CRF-induced cAMP production was augmented by pretreatment of MNC with a cAMP-dependent protein kinase (PKA) peptide inhibitor (PI20), but was virtually unaffected by the protein kinase C (PKC) inhibitor H7, suggesting a role for cAMP signalling. Moreover, the CRF-stimulated cAMP level was reduced to baseline by intracellular Ca2+ antagonist HA1004, indicating a role for Ca(2+)-signalling. Based on these findings, it is concluded that cAMP and/or Ca2+ play a second messenger role in the CRF signal transduction pathway.
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PMID:Corticotropin-releasing factor-induced production of cyclic AMP by human peripheral blood immunocytes. 839 Apr

Corticotropin-releasing factor (CRF) and vasoactive intestinal polypeptide (VIP) are neuropeptides displaying a variety of short-term effects in the nervous system. It is shown here in transfection experiments of an immortalized noradrenergic locus coeruleus-like cell line that both CRF and VIP also trigger a signaling cascade capable of activating gene transcription. To elucidate the signaling pathway leading to transcriptional induction, cells were transfected with an inhibitor for cAMP-dependent protein kinase, targeted to the nucleus via a nuclear-localization signal. Transcriptional induction of a reporter gene by CRF and VIP was blocked in these cells, indicating that the cAMP-dependent protein kinase is required for transducing CRF and VIP generated signals into the nucleus. Additionally, transfection experiments with a reporter gene containing cAMP response elements in its regulatory region demonstrate that CRF and VIP receptor activation induce transcription through this genetic regulatory element. We conclude that long-term effects of CRF and VIP in neurons are likely to be mediated by the transcriptional regulation of CRF and VIP-responsive genes via the cAMP signaling pathway.
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PMID:Corticotropin-releasing factor and vasoactive intestinal polypeptide activate gene transcription through the cAMP signaling pathway in a catecholaminergic immortalized neuron. 1035 85

We have studied modulation of the slow Ca(2+)-activated K(+) current (I(sAHP)) in CA1 hippocampal pyramidal neurons by three peptide transmitters: corticotropin releasing factor (CRF, also called corticotropin releasing hormone, CRH), vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (CGRP). These peptides are known to be expressed in interneurons. Using whole cell voltage clamp in hippocampal slices from young rats, in the presence of tetrodotoxin (TTX, 0.5 microM) and tetraethylammonium (TEA, 5 mM), I(sAHP) was measured after a brief depolarizing voltage step eliciting inward Ca(2+) current. Each of the peptides CRF (100-250 nM), VIP (400 nM), and CGRP (1 microM) significantly reduced the amplitude of I(sAHP). Thus the I(sAHP) amplitude was reduced to 22% by 100 nM CRF, to 17% by 250 nM CRF, to 22% by 400 nM VIP, and to 40% by 1 microM CGRP. We found no consistent concomitant changes in the Ca(2+) current or in the time course of I(sAHP) for any of the three peptides, suggesting that the suppression of I(sAHP) was not secondary to a general suppression of Ca(2+) channel activity. Because each of these peptides is known to activate the cyclic AMP (cAMP) cascade in various cell types, and I(sAHP) is known to be suppressed by cAMP via the cAMP-dependent protein kinase (PKA), we tested whether the effects on I(sAHP) by CRF, VIP, and CGRP are mediated by PKA. Intracellular application of the PKA-inhibitor Rp-cAMPS significantly reduced the suppression of I(sAHP) by CRF, VIP, and CGRP. Thus with 1 mM Rp-cAMPS in the recording pipette, the average suppression of I(sAHP) was reduced from 78 to 26% for 100 nM CRF, from 83 to 32% for 250 nM CRF, from 78 to 30% for 400 nM VIP, and from 60 to 7% for 1 microM CGRP. We conclude that CRF, VIP, and CGRP suppress the slow Ca(2+)-activated K(+) current, I(sAHP), in CA1 hippocampal pyramidal neurons by activating the cAMP-dependent protein kinase, PKA. Together with the monoamine transmitters norepinephrine, serotonin, histamine, and dopamine, these peptide transmitters all converge on the cAMP cascade modulating I(sAHP).
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PMID:Protein kinase A mediates the modulation of the slow Ca(2+)-dependent K(+) current, I(sAHP), by the neuropeptides CRF, VIP, and CGRP in hippocampal pyramidal neurons. 1075 17


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