Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The function of the pars tuberalis as a mediator of the action of melatonin remains elusive. As a direct method of assessing the potential role of secretory proteins, ovine pars tuberalis cells have been cultured and radiolabelled with 35S-methionine, and the accumulation of specific radioactive products in the medium, measured after separation by SDS-PAGE and fluorography. The synthesis and secretion of a number of labelled proteins are increased by forskolin (1 microM) and inhibited dose dependently by melatonin (IC50, 300 pM), although consistently a 72-kD protein (p72), is the most intensely labelled of these. Thus, 72 acts as a useful marker of cellular activity for melatonin, whereas prolactin (p23) provides a melatonin non-responsive marker in ovine pars tuberalis cell cultures. The synthesis and secretion of p72 and other melatonin-sensitive proteins is regulated through the cyclic AMP/protein kinase A second-messenger pathway, as analogues of cyclic AMP mimic the action of forskolin, yet 1,9-dideoxyforskolin, a forskolin analogue that is not active on adenylate cyclase, has no effect. However, the phorbol ester, phorbol-12,13-myristate acetate, also regulates the synthesis and secretion of the same profile of proteins as forskolin indicating a potential role for protein kinase C, which occurs through an independent rather than a synergistic pathway. The differential effects of nocadazole (1 microM) and extracellular calcium depletion upon p72 and prolactin secretion indicates that p72 is secreted by a calcium and microtubule independent pathway, in contrast to prolactin. These observations in conjunction with the absence of dense-core storage vesicles in melatonin-responsive cells of the ovine PT are consistent with constitutive secretion of p72 from the latter and regulated secretion of prolactin from melatonin non-responsive cells. Using immunoprecipitation de novo synthesis and secretion of either LH or LH-like proteins from ovine pars tuberalis cells could not be detected under the conditions used. The absence of 125I-(Des-Gly10[D-Ala6]-LHRH-ethylamide) binding over most, but not all, of the ovine pars tuberalis supports the contention that the majority of the cells of the ovine pars tuberalis are not gonadotrophs. These results provide further support for the unique function for the pars tuberalis.
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PMID:p72, a marker protein for melatonin action in ovine pars tuberalis cells: its regulation by protein kinase A and protein kinase C and differential secretion relative to prolactin. 820 12

We have previously shown that direct activation of protein kinase A (PKA) and protein kinase C (PKC) induced changes in the expression of genes coding for PKA RII beta and C alpha subunit isoforms in cultured anterior pituitary cells, suggesting the possibility of interconnected regulation at this point. To evaluate whether the cell content of PKA protein subunits could be similarly altered, the catalytic (C) and regulatory type I (RI) and type II (RII) subunits were identified by Western blot analysis using specific immunoaffinity-purified antibodies. Activation of PKA by the permeant cyclic adenosine monophosphate (cAMP) analogue 8-Br-cAMP induced a dramatic time- and concentration-dependent decline of C subunit to a residual level that may represent 10-15% of that in untreated cells. The most profound decrease occurred during the first 5 h following treatment with 0.5-2 mM analogue (by 65 +/- 14 and 79 +/- 5%, respectively). Under identical conditions, RII was increased by about 40% at the higher concentrations, while RI increased slightly, but only at low concentrations (below 1 mM 8-Br-cAMP), and then gradually decreased. Exposure of cells to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) also resulted in decreased levels of the PKA C subunit, however, with a different concentration-dependent profile. In particular, a decline in PKA C was most pronounced (60%) at a low concentration of TPA (10 nM) as compared with the concentrations equal to or above 20 nM (40% decrease). TPA at 10 nM also depressed notably (by 25%) the level of RII subunit, but higher concentrations were essentially ineffective, although a slight and statistically not significant elevation of the cell subunit content was observed as for RI. Simultaneous activation of both PKA and PKC pathways resulted in further depletion of PKA C and an important loss (50%) of RII, a subunit which was enhanced by the activation of either system alone. Finally, gonadotropin-releasing hormone, a neuropeptide that has the potentiality to activate both PKA and PKC signaling in gonadotropes, was able to alter PKA subunit cell content: PKA C was significantly reduced at either a subliminal (0.1 nM) or maximal (10 nM) concentration, whereas RII increased at the low concentration and decreased at the high concentration. In conclusion, these data demonstrate that the pituitary cell contents of RI, RII, and C subunits of PKA are regulated under the activation of PKA itself as well as PKC in a manner that can exhibit further alteration when both systems come simultaneously into play. Changes in the PKA subunit levels in certain cases may correlate with a variation of the mRNAs suggesting multiple control mechanisms, including an alteration of gene expression and changes in subunit degradation, synthesis, and/or turnover. These data, together with those obtained in the presence of gonadotropin-releasing hormone, provide further support for a hormonally induced interplay between PKA and PKC signaling pathways at the crucial level of PKA in the pituitary gland including gonadotropes.
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PMID:Modulation of regulatory and catalytic subunit levels of cAMP-dependent protein kinase A in anterior pituitary cells in response to direct activation of protein kinases A and C or after GnRH stimulation. 855 83

The key roles of the excitatory neurotransmitter glutamate and its second messengers, nitric oxide (NO) and cGMP, in long-term potentiation and neural plasticity are well documented. However, complex functions such as memory are likely to require long term changes in synaptic efficacy which require gene expression and protein synthesis. Here we demonstrate that the glutamate receptor agonist, N-methyl-D-aspartic acid (NMDA), nitric oxide (NO) and cGMP each repress expression of the gonadotropin-releasing hormone (GnRH) gene in the hypothalamic cell line, GT1. This repression is dependent upon signals from NMDA receptors activating NO synthase to synthesize NO. In turn NO induces guanylyl cyclase to synthesize cGMP, activating cGMP- dependent protein kinase. Repression requires elevation of calcium because it only occurs in the presence of calcium ionophore or with release of intracellular calcium. Repression also requires protein synthesis. Activation of this pathway specifically represses expression of a reporter gene containing the regulatory region of the GnRH gene in transfected GT1 cells, indicating that repression occurs at the transcriptional level. Furthermore the target for transcriptional repression is a 300 bp neuron-specific enhancer found 1.5 kb upstream of the GnRH gene which is sufficient to confer repression to a heterologous promoter. Thus the NMDA/NO/cGMP neurotransmitter signal transduction pathway controls not only synaptic function but also neuron-specific gene expression.
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PMID:NMDA and nitric oxide act through the cGMP signal transduction pathway to repress hypothalamic gonadotropin-releasing hormone gene expression. 859 37

The prostaglandin endoperoxide synthase-2 (PGS-2) gene encodes an isoform of prostaglandin synthase that is transiently induced by protein kinase A (luteinizing hormone/cAMP) and protein kinase C (gonadotropin-releasing hormone) agonists in granulosa cells of ovulating follicles. The promoter of the rat PGS-2 gene contains a CAAT enhancer-binding protein consensus site (CAAT box) which can confer hormone inducibility to a PGS-2.CAT reporter gene, as well as a putative E-box region. To determine if the E-box region was involved in hormone induced trans-activation of the rat PGS-2 gene, constructs with the CAAT box and E-box regions (-192 PGS-2.CAT), only the putative E-box (-110 PGS-2.CAT), or neither region (-52 PGS-2.CAT) were transiently transfected into rat granulosa cell cultures. CAT activity was induced in both the -192 and -110 PGS-2*CAT vectors by luteinizing hormone (10-fold) and gonadotropin-releasing hormone (6-fold), whereas CAT activity of the -52 PGS-2.CAT construct did not differ from the promoterless vector (pCAT-Basic). Deletion of 1 base pair from the E-box within the -110 PGS-2.CAT construct, as well as point mutations within the CAAT box, E-box, or both regions of the -192 PGS-2.CAT construct, demonstrated that the E-box is critical for basal transcription, and that regions, in addition to the CAAT box, are involved in hormone induction of the PGS-2 gene. An oligonucleotide spanning the rat PGS-2 E-box bound two specific protein complexes which were supershifted in the presence of antibody specific for the upstream stimulatory factor. Thus, in rat granulosa cells, the PGS-2 E-box region appears to interact with upstream cis-acting elements other than the CAAT box to confer hormonal regulation of the gene. The E-box region of the rat PGS-2 promoter does not contain ATF/CRE activity found in the human and mouse PGS-2 promoters, but is critical for basal transcription of the PGS-2 gene in rat granulosa cells and binds the upstream stimulatory factor (as do E-box regions of other genes regulated in the ovary).
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PMID:An E-box region within the prostaglandin endoperoxide synthase-2 (PGS-2) promoter is required for transcription in rat ovarian granulosa cells. 866 19

The possible involvement of extracellular Ca2+ ([Ca2+]o) in mediating the acute gonadotropin (GtH) response to salmon gonadotropin-releasing hormone (sGnRH) and chicken gonadotropin-releasing hormone-II (cGnRH-II) in goldfish was examined using dispersed pituitary cells in perifusion. Perifusion with Ca(2+)-deficient medium reduced the GtH responses to 5-min pulses of either GnRH, indicating the participation of [Ca2+]o in acute GnRH action. Using a 10-min GnRH pulse application protocol, the dependence of the acute GtH responses to the two GnRHs on [Ca2+]o entry through voltage-sensitive Ca2+ channels (VSCC) was examined using the dihydropyridine VSCC blocker nifedipine and the cation Co2+. Treatment with nifedipine consistently reduced the acute GtH response to either sGnRH or cGnRH-II. Similarly, perifusion with CoCl2 reduced the sGnRH-induced GtH release. In contrast to its effects on sGnRH, CoCl2 abolished the cGnRH-II-induced GtH release. These results indicate that [Ca2+]o entry through VSCC participates in the acute GtH response to both native GnRHs; however, the cGnRH-II-stimulated acute release is relatively more dependent on [Ca2+]o and VSCC functions than sGnRH-induced secretion. The involvement of calmodulin (CaM) in mediating GnRH action was also examined. Treatment with a CaM antagonist, calmidazolium, or with a Ca2+/CaM-dependent protein kinase II inhibitor, KN62, reduced GtH responses to sGnRH and cGnRH-II in 2-hr static incubation, but not in perifusion studies with dispersed goldfish pituitary cells using 5- or 10-min GnRH pulses. These results suggest that CaM-dependent mechanisms participate in mediating the long-term, but not the acute, GtH response to GnRH. Compared to sGnRH, cGnRH-II-induced GtH release was more sensitive to inhibition by KN62, indicating a higher degree of dependence of cGnRH-II action on CaM. These results extend our understanding of the differential involvement of [Ca2+]o and CaM in mediating the short-term and long-term actions of the two native GnRH peptides on GtH release in goldfish.
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PMID:Roles of calcium and calmodulin in the mediation of acute and sustained GnRH-stimulated gonadotropin secretion from dispersed goldfish pituitary cells. 871 48

Unstable expansion of the CTG repeats in the 3' untranslated region encoding a member of the protein kinase family in the q13.3 band on chromosome 19 is a mutation specific for myotonic dystrophy. To examine the correlation between clinical expression and CTG trinucleotide repeat length, we carried out Southern blot analysis in a family with myotonic dystrophy. In this pedigree, the expanded CTG repeats were transmitted maternally. The mother had three female children. The mother had about 200 CTG repeats, and the number of repeats for each child was about 800, 1500 and 1600 in birth order. The mother and the patient with 800 repeats were unaware of muscle weakness or myotonia. Symptoms were present from age 3 years in the patient with 1500 repeats and from birth in the one with 1600 repeats. Although the mother menstruated regularly, the patients with 800 and 1500 repeats both menstruated irregularly, and the one with 1600 repeats has never menstruated. The age of onset and severity of the disease were correlated with the size of the expanded repeats. Endocrinological studies revealed that the basal levels of the gonadotropins, PRL and E2 were within normal range, and a pituitary response to LHRH was observed. These data suggest that the amenorrhea and menstrual irregularities were caused by a suprahypophyseal dysfunction. When expanded CTG repeats are transmitted maternally, abnormal products resulting from the metabolic disturbance in the affected mother may harm the fetus in utero. A heterozygous fetus, who has more CTG repeats, may be unable to metabolize the pathologic products sufficiently and therefore may become more severely affected. This may explain the exclusive maternal transmission of congenital myotonic dystrophy.
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PMID:CTG trinucleotide repeat length and clinical expression in a family with myotonic dystrophy. 873 4

In cultured pituitary cells of tilapia, gonadotropin-releasing hormone (GnRH; 10 nM 4-24 h), elevation of cyclic AMP (by 10 microM forskolin or 0.2 mM 3-isobutyl-1-methylxanthine: IBMX 0.5-36 h) or activation of protein kinase C (PKC; by 12.5 nM tetradecanoyl phorbol-13-acetate: TPA, 0.5-24 h) all increased gonadotropin (GtH) II beta steady state mRNA levels by three to four-fold. The involvement of PKA and PKC in the GnRH stimulatory effect on both GtH release and GtH II beta mRNA levels was corroborated by use of the PKA and PKC inhibitors, H89 and GF109203X, respectively (100 nM) which attenuated the GnRH effect. Incubation with actinomycin D (8 microM, 4-21 h) after preexposure for 24 h to either forskolin (10 microM) or TPA (12.5 nM), revealed that rates of transcript degradation were slower in forskolin-treated cells (T 1/2 = 14.1 h) than in control or TPA-treated cells (T 1/2 = 8.47 or 8.38 h), suggesting a stabilizing effect on the mRNA. Dopamine (DA; 10 microM, 4-36 h) had no apparent effect on steady state mRNA levels of GtH II beta, but reduced GtH release by as much as 75%. Steady state levels of growth hormone (GH) mRNA were not affected by exposure to GnRH (10 nM, 4-24 h), although GH release was more than doubled. Similarly, activation of PKC (by TPA 12.5 nM, 1.5-36 h), which was shown to be essential for the GnRH-stimulatory effect on GH release, did not alter levels of the GH transcript, but increased GH release by more than fivefold. DA (10 microM, 4-24 h) moderately increased GH transcript levels (160%) with similar kinetics but lower potency than direct elevation of cAMP (by 10 microM forskolin or 0.2 mM IBMX, 0.5-36 h) which increased transcript levels by more than fourfold. The involvement of PKA in the DA effect was confirmed when the PKA inhibitor H89 (100 nM, 15 min prior to DA exposure) attenuated the DA effect on GH mRNA levels. Exposure of cells to actinomycin D (8 microM, 2-16 h) after treatment with forskolin (10 microM, 24 h) led to a slower rate of transcript degradation than in control cells (T 1/2 = 6.5 h vs. T 1/2 = 4.36 h), suggesting that cAMP also elicits a stabilizing effect on GH mRNA. Somatostatin (100 nM, 0.5-36 h) had no clear effect on GH transcript levels, but reduced GH release by as much as 90%. These results suggest that activation of either cAMP-PKA or PKC pathways can, possibly by different mechanisms, stimulate mRNA levels of the GtH II beta gene, but that only the cAMP-PKA pathway stimulates GH mRNA levels. It would appear therefore that GnRH, although stimulating GH release, does not regulate GH transcription in this fish.
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PMID:Differential effects of gonadotropin-releasing hormone, dopamine and somatostatin and their second messengers on the mRNA levels of gonadotropin II beta subunit and growth hormone in the teleost fish, tilapia. 889 62

Aromatase (CYP19) mRNA is induced by follicle-stimulating hormone (FSH) in granulosa cells of preovulatory follicles and subsequently is rapidly diminished as a consequence of the luteinizing hormone (LH) surge. Primary cultures of rat granulosa cells were used to identify some of the cellular mechanisms by which FSH increases and LH decreases steady-state levels of aromatase mRNA. Induction of aromatase mRNA by FSH was increased by cycloheximide but was blocked by alpha-amanitin and the C-kinase activators gonadotropin-releasing hormone (GnRH) and phorbol 12-myristate 13-acetate (PMA). In contrast, the decrease in steady-state levels of aromatase mRNA by LH was mimicked by A-kinase (forskolin) and C-kinase (PMA or GnRH) activators. The decrease in aromatase mRNA was associated with decreased amounts of mRNA and protein for steroidogenic factor-1 (SF-1), a nuclear orphan receptor that binds and trans-activates the aromatase promoter, and with the A-kinase subunit type II (RII beta), which is required for mediating cAMP action in these cells. The down-regulation of aromatase, SF-1, and RII beta by each kinase activator and alpha-amanitin was prevented by cycloheximide when the drug was added in combination with the activator. If, however, cycloheximide was added 2 h after PMA (or LH), the drug did not prevent the rapid loss of mRNA. When granulosa cells were transfected with an aromatase CAT transgene, CAT activity was stimulated 10- to 20-fold by FSH and forskolin but not by PMA. Taken together, these results indicate that the A-kinase but not the C-kinase pathway can trans-activate the aromatase gene in immature granulosa cells, whereas the C-kinase, as well as A-kinase pathways, mimic the LH surge to decrease aromatase mRNA in preovulatory cells. By increasing degradation of aromatase mRNA and by inhibiting transcription, the LH surge rapidly terminates the granulosa cell pattern of gene expression while reprogramming the cells to express genes associated with ovulation and luteinization.
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PMID:Expression of aromatase in the ovary: down-regulation of mRNA by the ovulatory luteinizing hormone surge. 902 37

The pulsatile release of gonadotropin-releasing hormone (GnRH) into the portal vasculature is responsible for the maintenance of reproductive function. Levels of GnRH decapeptide available for this process can be regulated at transcriptional, posttranscriptional, and posttranslational levels. In the immortalized neuronal GT1 cell lines which synthesize and secrete GnRH, regulation of GnRH biosynthesis has been studied using activators of the protein kinase A (PKA), protein kinase C (PKC), and calcium second messenger systems. These substances, while stimulating GnRH release, cause a universal inhibition of all biosynthetic indices measured to date, including decreases in transcription of the proGnRH gene, GnRH mRNA levels, mRNA stability, and translational efficiency. In contrast, in the animal, the mechanism for the regulation of GnRH gene expression appears to be primarily posttranscriptional, since changes in GnRH mRNA levels often occur in the absence of changes in GnRH primary transcript levels an index of GnRH gene transcription. For example, GnRH mRNA levels increase in response to stimulation with glutamate analogs, while GnRH primary transcript levels are unchanged. However, parallel changes in GnRH mRNA and primary transcript have been observed on proestrus prior to the LH/GnRH surge, suggesting that the regulation of GnRH mRNA levels in vivo involves a complex interplay of transcriptional and posttranscriptional processes.
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PMID:Regulation of gonadotropin-releasing hormone gene expression in vivo and in vitro. 910 Dec 60

In species that ovulate spontaneously, two key events mediate the stimulation of preovulatory gonadotropin surges: 1) neurosecretion of a preovulatory LHRH surge and 2) an acute increase in responsiveness of the pituitary gland to the LHRH neurosecretory trigger. These processes, in turn, depend upon both the positive feedback actions of preovulatory estrogen secretions and specific neural signals for initiation of the surge. In female rats, the neural signals for the surge are principally derived from the 24-h neural clock, thereby limiting the timing of surges to the afternoon of proestrus. It remains unclear, however, how neural signals converge with endocrine signals (estrogen) in specific brain cells and how their cellular integration leads to appropriate secretion of gonadotropin surges. Previous work has suggested that estrogen may exert its facilitatory actions by opening a neural "gate," thereby allowing transmission of the daily neural signal to surge-initiating neuronal groups. How may estrogen act to render a neural pathway patent? A conventional view holds that steroid hormones can exert permissive effects on signaling efficacy by modulating neurotransmitter receptor expression, intracellular second messenger production, and protein kinase activity. However, recent evidence has suggested that estrogen may also have the capacity to permit cross-talk between neurotransmitter signaling pathways and parallel transcriptional regulatory pathways. The progesterone receptor is an estrogen-inducible transcription factor that has been shown to be transactivated--even in the absence of its cognate ligand--after stimulation of neurotransmitter receptors coupled to adenylate cyclase stimulation. Thus, the convergence of neural and endocrine signals for the stimulation of gonadotropin surges could occur at the level of the progesterone receptor: estrogen may stimulate expression of progesterone receptors, which in turn may be initially transactivated by synaptic signals. Activated progesterone receptors may thereafter regulate transcription of target genes that control transmitter synthesis and release in neural circuitries governing LHRH gene expression and/or pulsatile LHRH release. An analogous mechanism may operate in pituitary gonadotrophs, in which ligand-independent transactivation of progesterone receptors mediates integration of neurosecretory and estrogen positive feedback signals, leading to increased pituitary responsiveness to LHRH. It is proposed that the "seeding" of specific neuronal groups and pituitary gonadotrophs with progesterone receptors, and perhaps other inducible transcription factors, comprises an important basis of estrogen's permissive role in the stimulation of gonadotropin surges. The validity of this integrative model remains to be confirmed, as does its possible importance in generating gonadotropin surges in other species.
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PMID:New concepts of the neuroendocrine regulation of gonadotropin surges in rats. 911 24


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