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 actions of carbamylcholine (Cchol), the ionophores A23187 and thapsigargin, and TSH on [3H]cytidine monophosphate-phosphatidic acid ([3H]CAMP-PA) accumulation were studied in prelabeled dog thyroid slices to evaluate phosphatidic acid (PA) generation and inositol recycling by phosphatidylinositol (PtdIns) synthesis. The effects of the same agonists were also measured on phosphatidylbutanol generation in [3H]palmitate- or [3H]myristate-prelabeled slices to assess the activity of phospholipase-D (PLD) and on the effluxes of myo-[3H]inositol and [3H]choline induced by these agents from prelabeled slices. Cchol (10(-6)-10(-4) M) increased inositol phosphate (InsP) generation, with no change in inositol efflux, and contracted the intracellular inositol pool. This suggests a stimulation of PtdIns synthesis as well as hydrolysis. The muscarinic agonist provoked a dramatic accumulation of CMP-PA in the presence of lithium chloride (10 mM), which suggests that when InsP hydrolysis is inhibited, inositol limits the rate of CMP-PA incorporation into PtdIns. Cchol also increased phosphatidylbutanol formation. The latter two actions of Cchol were reproduced by A23187 (10(-5) M) and thapsigargin (2 x 10(-6) M) and were inhibited by calphostin-C, an inhibitor of the regulatory site of protein kinase-C. Cchol also induced increased free choline efflux, with a decreased choline phosphate relative content of the medium. TSH (10 mU/ml) stimulated free inositol efflux and induced a slight and proportional increase in [3H]inositol incorporation in phosphoinositides and InsP. The hormone also increased PA and CMP-PA accumulation exclusively in the presence of the PA phosphatase inhibitor propranolol (10(-4) M), but had no detectable action on PLD activity. None of these effects of TSH was reproduced by forskolin or potentiated by lithium chloride (10 mM). The data demonstrate the existence in thyroid tissue of a PLD-hydrolyzing phosphatidylcholine that was stimulated by Cchol and increased intracellular Ca2+, but not by TSH. The results obtained, besides confirming that TSH does not stimulate PtdInsP2-PLC or affect phosphatidylcholine hydrolysis, suggest that the hormone, instead, stimulates de novo PtdIns synthesis and/or inositol transport. The physiological relevance of these actions of Cchol, increased intracellular Ca2+, and TSH in thyroid metabolism could be related to their divergent effects on thyroid cell metabolism.
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PMID:Relative contribution of phosphoinositides and phosphatidylcholine hydrolysis to the actions of carbamylcholine, thyrotropin (TSH), and phorbol esters on dog thyroid slices: regulation of cytidine monophosphate-phosphatidic acid accumulation and phospholipase-D activity. I. Actions of carbamylcholine, calcium ionophores, and TSH. 798 36

The chimeric chloramphenicol acetyltransferase (CAT) construct, pTRCAT5'-199, containing the TSH receptor (TSHR) minimal promoter, -199 to -39 base pairs (bp), exhibits the thyroid specificity and TSH/cAMP autoregulation evident in TSHR gene expression. The present report shows that a cis-acting element between -189 and -175 bp, which binds thyroid transcription factor-1 (TTF-1), is involved in both activities. The 22 bp between -199 and -178 contains a positive element important for expression of the TSHR minimal promoter in rat FRTL-5 thyroid cells. DNAase I footprinting shows that extracts from functioning FRTL-5, but not non-functioning FRT thyroid or Buffalo rat liver (BRL) cells, protect a region between -189 and -175 bp. The protection is duplicated by TTF-1, and the protected element has only a two-base mismatch from the consensus TTF-1 element identified in the thyroglobulin (TG) and thyroid peroxidase minimal promoters. Gel mobility shift analyses reveal that FRTL-5 thyroid cell nuclear extracts form a specific protein/DNA complex with this region, which is prevented by the TTF-1 binding element from the TG promoter; FRT and BRL cell nuclear extracts do not have TTF-1 and do not form this complex. A role for the TSHR/TTF-1 binding element in thyroid-specific expression of the TSHR gene is evidenced as follows. Overexpression of TTF-1 in FRT or BRL cells, which have no TTF-1, increased the activity of pTRCAT5'-199, but not pTRCAT5'-177, which has no TTF-1 binding element. A nonsense mutation of the TTF-1 binding element eliminated TTF-1-induced activation of TSHR promoter activity in FRT or BRL cells and reduced TSHR promoter activity in FRTL-5 thyroid cells. In contrast, mutation of this element to the TTF-1 consensus sequence of the TG or thyroid peroxidase promoter had no significant influence on TSHR promoter activity. The activity of the TSHR/TTF-1 binding element requires a functioning cAMP response element (CRE). Thus, TTF-1 activity is lost when the CRE site is mutated to a nonfunctional, nonpalindromic sequence; it is, in contrast, maximized when CRE activity is maximized by its mutation to a consensus AP1 element. TTF-1 phosphorylation is important for binding and activity. Thus, binding of TTF-1 to the TSHR/TTF-1 element is phosphatase-sensitive and is increased by treating nuclear extracts with the catalytic subunit of protein kinase A. Overexpression of the catalytic subunit of PKA enhances TTF-1-increased activity of the TSHR minimal promoter.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Thyroid-specific expression and cyclic adenosine 3',5'-monophosphate autoregulation of the thyrotropin receptor gene involves thyroid transcription factor-1. 799 32

Protein iodination by the dog thyrocyte (a marker of thyroid hormone synthesis) is stimulated by the Ca(2+)-phosphatidylinositol and cAMP cascades. We have shown previously that H2O2 generation, a limiting step of thyroid hormone synthesis, is modulated by these two cascades. In this work, we show that the I- release from preloaded thyrocytes is also activated by agents activating the Ca(2+)-phosphatidylinositol cascade and by Ca2+ ionophores, especially in synergy with 12-O-tetradecanoylphorbol 13-acetate, a potent activator of protein kinase-C. The effect of carbachol is reduced when the extracellular Ca2+ is depleted. Thus, both arms of the Ca(2+)-phosphatidylinositol cascade, Ca2+ and diacylglycerol, acutely and synergistically activate dog thyrocyte I- release. This I- release was also accelerated by acute and chronic exposure to TSH, forskolin, or (BU)2cAMP. The chronic stimulation of I- release by TSH exposure was diminished by chronic epidermal growth factor treatment (which dedifferentiates the thyrocytes). In addition, the chronic stimulation of I- release by forskolin was not affected by withdrawal of the agent up to 4 h before the experiment, in contrast to the acute effect of forskolin, which vanished within 16 min after forskolin withdrawal. These results suggest that the chronic stimulation of I- release by TSH or forskolin involves a stable mechanism. The I- transport system causing the release of I- from the dog thyrocyte is almost insensitive to inhibition by NaClO4 and KSCN. Hence, the iodide release cannot be due to the action of the basolateral Na+/I- cotransporter. In addition, we show that I- release was less sensitive than I- uptake to the inhibition by dysidenin, a marine toxin isolated from the sponge, Dysidea herbacea, known to inhibit I- uptake by dog thyroid slices. In summary, this work suggests that in a well defined model of the thyroid, the dog thyrocyte in primary culture, an I- transport system distinct from the basolateral Na+/I- cotransporter, is responsible for the observed I- release. The complex modulation of this transport system, involving at least the Ca(2+)-phosphatidylinositol and cAMP cascades, parallels the regulation of protein iodination, which itself reflects thyroid hormone synthesis.
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PMID:Control of the dog thyrocyte plasma membrane iodide permeability by the Ca(2+)-phosphatidylinositol and adenosine 3',5'-monophosphate cascades. 807 Mar 94

We studied the effect of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), and interferon-gamma (IFN-gamma) on the function of thyroid cells and pituitary thyrotrophs. In FRTL-5 rat thyroid cells, both human and murine TNF-alpha inhibited basal and TSH-stimulated [125I]iodide transport. IL-1 shared this action with TNF-alpha, but was less potent. IL-1 and IFN-gamma did not cause a further reduction of TNF-alpha-induced inhibition of [125I]iodide transport. TNF-alpha, phorbol ester 12-myristate 13-acetate (PMA), and calcium ionophore (CI) A23817 all inhibited [125I]iodide transport, but high doses of PMA and CI also blocked the inhibitory action of TNF-alpha on [125I]iodide transport. Inhibition of protein kinase A and protein kinase C by H7 or HA inhibited TSH-stimulated iodide transport, but did not block the TNF-alpha action, suggesting that the mechanism of TNF-alpha action on thyroid cells is independent of protein kinase A and C. In pituitary cells, both human and murine TNF-alpha did not affect basal TSH secretion, but TNF-alpha reduced TRH-stimulated TSH secretion. This study provides further in vitro evidence that TNF-alpha inhibits the function of the hypothalamus-pituitary-thyroid axis acting directly on both the pituitary and thyroid glands.
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PMID:Suppression of rat thyrotroph and thyroid cell function by tumor necrosis factor-alpha. 811 27

The signal transduction of TSH in invasion and growth of FTC 133, a human follicular thyroid cancer cell line, was investigated. TSH (0.01-1 mIU/ml) stimulated invasion of FTC 133 by 21% and growth by 20% of basal. Cyclic AMP-stimulators and inhibitors had no effect at any concentration. The PKC-agonist TPA enhanced invasion and growth by 15%, whereas staurosporine, a PKC-antagonist, inhibited them by 32% and 60%, respectively. The latter also reversed TSH stimulation. EGF enhanced invasion (42%) and growth of FTC 133 (25%). Staurosporine did not reverse EGF stimulation. The tyrosine kinase antagonist genistein reversed EGF, but not TSH stimulation. Pertussis toxin inhibited invasion (18%) and growth (22%). Cholera toxin was less inhibitive. We demonstrated for the first time, that TSH stimulates invasion and growth of human thyroid cancer cells in vitro by PKC- rather than PKA-stimulation.
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PMID:Thyrotropin stimulates invasion and growth of follicular thyroid cancer cells via PKC- rather than PKA-activation. 821 54

The actin/myosin II cytoskeleton and its role in phagocytosis were examined in primary cultures of dog thyroid cells. Two (19 and 21 kD) phosphorylated light chains of myosin (P-MLC) were identified by two-dimensional gel electrophoresis of antimyosin immunoprecipitates, and were associated with the Triton X-100 insoluble, F-actin cytoskeletal fraction. Analyses of Triton-insoluble and soluble 32PO4-prelabeled protein fractions indicated that TSH (via cAMP) or TPA treatment of intact cells decreases the MLC phosphorylation state. Phosphoamino acid and tryptic peptide analyses of 32P-MLCs from basal cells showed phosphorylation primarily at threonine and serine residues; most of the [32P] appeared associated with a peptide containing sites typically phosphorylated by MLC kinase. Even in the presence of the agents which induced dephosphorylation, the phosphatase inhibitor, calyculin A, caused a severalfold increase in MLC phosphorylation at several distinct serine and threonine sites which was also associated with actomyosin and cell contraction. Phosphorylation of cell homogenate proteins or the cytoskeletal fraction with [gamma-32P]ATP indicated that Ca2+, EGTA, or trifluoperazine (TFP) has little effect on the phosphorylation of MLC. Both fluorescent phalloidin and antimyosin staining of cells showed distinct dorsal and ventral stress fiber complexes which were disrupted within 30 min by TSH and cAMP; TPA appeared to cause disruption of dorsal, and rearrangement of ventral complexes. Concomitant with MLC dephosphorylation and stress fiber disruption, TSH/cAMP, but not TPA, induced dorsal phagocytosis of latex beads. While stimulation of either A or C-kinase disrupts dorsal stress fibers and rearranges actomyosin, another event(s) mediated by A-kinase appears necessary for phagocytic activity.
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PMID:Phagocytosis induced by thyrotropin in cultured thyroid cells is associated with myosin light chain dephosphorylation and stress fiber disruption. 831 42

Microinjection of a dominant interfering mutant of Ras (N17 Ras) caused a significant reduction in thyrotropin (thyroid-stimulating hormone [TSH])-stimulated DNA synthesis in rat thyroid cells. A similar reduction was observed following injection of the heat-stable protein kinase inhibitor of the cyclic AMP-dependent protein kinase. Coinjection of both inhibitors almost completely abolished TSH-induced DNA synthesis. In contrast to TSH, overexpression of cellular Ras protein did not stimulate the expression of a cyclic AMP response element-regulated reporter gene. Similarly, injection of N17 Ras had no effect on TSH-stimulated reporter gene expression. Moreover, overexpression of cellular Ras protein stimulated similar levels of DNA synthesis in the presence or absence of the heat-stable protein kinase inhibitor. Together, these results suggest that in Wistar rat thyroid cells, a full mitogenic response to TSH requires both Ras and cyclic APK-dependent protein kinase.
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PMID:Inhibition of thyrotropin-stimulated DNA synthesis by microinjection of inhibitors of cellular Ras and cyclic AMP-dependent protein kinase. 833 96

We studied the effects of interleukin-6(IL-6) on DNA synthesis and cyclic AMP production in rat thyroid FRTL-5 cells. When cells were incubated with IL-6 in the presence or absence of IGF-I, cell proliferation was not observed. By contrast, IL-6 stimulated DNA synthesis in a dose dependent manner when TSH was added concomitantly. On the other hand, IL-6 did not modulate the cAMP accumulation in the presence or absence of TSH. These data demonstrate that, like IGF-I, IL-6 may be able to act as a growth factor through activation of a mitogenic signal transduction pathway different from A-kinase in FRTL-5 cells.
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PMID:Effect of interleukin-6 on cell proliferation of FRTL-5 cells. 838 10

The hypothalamic neuropeptide TRH, through G-protein-coupled transmembrane pituitary receptors, rapidly stimulates intracellular signaling events that, in turn, stimulate gene transcription. Our previous studies in transfected pituitary tumor cells indicated that TRH stimulation of thyrotropin beta-subunit (TSH beta) gene expression involves both calcium mobilization and protein kinase-C activation. To characterize the gene-proximal elements of the intracellular signaling pathways involved, we examined the effects of TRH, ionomycin, and phorbol ester (TPA) on cellular protooncogenes (c-jun and c-fos) known to be responsive to calcium mobilization and protein kinase-C activation. TRH stimulated a 3-fold increase in both c-jun and c-fos mRNA levels within 1 h, followed by a rapid decline in steady state mRNA levels. A secondary response to the single administration was noted, culminating in a 5-fold stimulation at 20 h. The increase in c-jun and c-fos mRNA levels occurred before the increased steady state mRNA levels of both PRL and TSH beta chimera in transfected pituitary GH3 cells. Furthermore, we examined the role of calcium in these effects using the ionophore ionomycin to elevate and TMB-8 to decrease intracellular calcium. We used the phorbol ester TPA to investigate the effects of increased protein kinase-C activity and H7 or pretreatment with TPA to monitor the decreased kinase activity. Our data indicate that calcium mobilization and protein kinase activation represent distinct components of the signaling events initiated by TRH resulting in increased c-jun and c-fos mRNA levels. Only c-fos mRNA is increased by all three factors, suggesting that c-fos may be a key element in mediating the intracellular processes reflecting TRH action.
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PMID:Thyrotropin-releasing hormone stimulates c-jun and c-fos messenger ribonucleic acid levels: implications for calcium mobilization and protein kinase-C activation. 840 12

We studied the role of various intracellular pathways in thyroglobulin secretion. The P2 agonists (ATP, ADP, GTP), 12-O-tetradecanoylphorbol-13-acetate (TPA), and protein kinase A activators stimulate thyroglobulin secretion in cells grown without TSH. The effects of these agents are additive. Pertussis toxin partially inhibits the effect of ATP but has no effect on the action of GTP. ATP and GTP increase cytosolic calcium (279 +/- 16% and 302 +/- 22%, respectively) while TPA and TSH (1 mU/ml) do not. Thus, both the protein kinase A and kinase C pathways regulate thyroglobulin secretion in FRTL-5 cells.
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PMID:P2 purinergic agonists and 12-O-tetradecanoylphorbol-13-acetate, as well as protein kinase A activators, stimulate thyroglobulin secretion in FRTL-5 cells. 846 Sep 98


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