Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have attempted to elucidate the effect of thyroid hormone on phospholipase C-linked inositol phospholipid hydrolysis in the rat hypothalamus. Hypothalamic slices of each animal, euthyroid control, hypothyroid, and thyroxine (T4)-supplemented hypothyroid rats were labeled with [3H]myoinositol in the presence of 5 mM LiCl, and then incubated for 60 min in KHG buffer containing either vehicle or 1 mM ouabain, a Na-K ATPase inhibitor. Hypothyroidism caused a significant increase in both basal and ouabain-stimulated accumulation of [3H]inositol phosphate ([3H]IP) in hypothalamic slices, whereas supplement with T4 to hypothyroid rats resulted in a complete restoration of hypothalamic [3H]IP formation to the value of euthyroid control. The present results indicate that thyroid hormone affects phospholipase C-linked inositol phospholipid hydrolysis in the hypothalamus, suggesting that negative feedback action of thyroid hormone may occur at a post-receptor site in the hypothalamus.
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PMID:Thyroid hormone affects the hydrolysis of inositol phospholipids in the rat hypothalamus. 131 27

FRTL-5 thyroid cells express a muscarinic receptor which inhibits the phospholipase C activity in a pirenzepine-insensitive manner. We here report that the cholinergic agonist carbachol decreases in these cells the steady-state iodide content, an effect correlated with the iodination of thyroglobulin and with thyroid hormone formation. Several signal pathways may be involved in this phenomenon since carbachol in addition to inhibiting phospholipase C, increased the arachidonic acid release and modified the adenylyl cyclase activity. In FRTL-5 cells, arachidonic acid is released via the direct stimulation of phospholipase A2 by a pirenzepine-sensitive muscarinic receptor coupled to a GTP binding protein sensitive to pertussis toxin. Regarding adenylyl cyclase, carbachol potentiated the thyrotropin-induced stimulation of the enzyme, whereas it did not affect the basal levels of cAMP. In vitro binding studies revealed the presence of two muscarinic binding sites. To summarize, the analysis of signal pathways and of in vitro binding sites indicates a complex muscarinic regulation of thyroid function, which includes the modulation of iodide fluxes.
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PMID:Muscarinic regulation of phospholipase A2 and iodide fluxes in FRTL-5 thyroid cells. 165 22

Deoxycytidine kinase (dC kinase) is the rate-limiting enzyme in the anabolism of important anticancer and retroviral nucleoside derivatives. Its activity is often decreased in resistance to these drugs. To analyze the structure, function, and control of this clinically important enzyme we isolated 15 cDNA clones for human deoxycytidine kinase from lambda gt11 thymus and Molt 4 libraries. Four clones were sequenced. The largest clone is 2.9 kilobases and codes for a 626-amino acid open reading frame. The DNA and deduced amino acid sequence of the human dC kinase clones are homologous with a previously unidentified murine cDNA clone p3.4J (EMBL:MM34j) reported to be related to granulocyte-macrophage colony-stimulating factor. Deoxycytidine kinase also has cysteine-rich regions that are homologous with thioredoxin, the beta subunit of prolyl 4-hydroxylase, phosphoinositide-specific phospholipase C, thyroid hormone-binding protein, and protein disulfide isomerase. No differences were seen in the amount and size of deoxycytidine kinase protein and mRNA between CCRF/CEM and L1210 leukemic cell lines that express and do not express enzyme activity. Genomic restriction fragments were similar between the active and inactive CCRF/CEM cell lines. These data suggest that the cells deficient in dC kinase activity have a small defect in the structural gene.
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PMID:Human deoxycytidine kinase. Sequence of cDNA clones and analysis of expression in cell lines with and without enzyme activity. 200 68

We investigated the effect of thyroid hormone on phosphatidylinositol-specific phospholipase C activity in rat liver. Thyroidectomy increased the activity of the enzyme. Thyroid hormone (T4, 40 micrograms) administration to thyroidectomized-rats decreased phospholipase C activity. The inhibition induced by thyroid hormone was of a non-competitive type. The higher concentration of Ca2+ strongly inhibited the activity of the enzyme obtained from thyroidectomized-rats' liver in vitro. The diminished activity of the enzyme obtained from thyroxine-treated-thyroidectomized-rats was recovered by pretreatment of the enzyme with EGTA. The activity of the enzyme derived from thyroidectomized-rats was not affected by EGTA treatment. These results suggest that thyroid hormone decreases the activity of phosphatidylinositol-specific phospholipase C activity through the mobilization of Ca2+ in the intracellular space.
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PMID:Thyroid hormone inhibition of phosphatidylinositol-specific phospholipase C in rat liver. 300 70

L-Thyroxine (T4) and 3,3',5-L-triiodothyronine (T3) potentiate the antiviral state induced by interferon-gamma(IFN-gamma) in homologous cells by a mechanism that is dependent upon calcium/phospholipid-dependent protein kinase (PKC). L-T4 and T3 also potentiate induction by IFN-gamma of MHC class II HLA-DR antigen expression in HeLa cells. In the present studies of HLA-DR expression, the PKC inhibitor staurosporine (0.1-1 nM) enhanced the expression of HLA-DR when the inhibitor was added simultaneously with IFN-gamma, 100 IU/ml. In the presence of IFN-gamma and 10(-7) M T4, the same concentrations of staurosporine inhibited potentiation of HLA-DR expression by thyroid hormone. A more specific PKC inhibitor, CGP41251 (0.5-5 nM), similarly enhanced HLA-DR expression in the presence of IFN-gamma but inhibited thyroid hormone potentiation of antigen expression. Both actions of CGP41251 were suppressed when cells were also treated with phorbol 12-myristate 13-acetate (PMA). A phospholipase C inhibitor, U73122 (1-1000 nM), did not alter the potentiating ability of T4, although it inhibited in a concentration-dependent manner the expression of HLA-DR induced by IFN-gamma. The potentiating effect of T4 was much more sensitive to a cyclic AMP-dependent protein kinase (PKA) inhibitor,KT5720 (1-1000nM), than was the induction of HLA-DR by IFN-gamma. The inhibitory effects of KT5720 were reversed by concurrent 8-bromo-cAMP treatment. The calmodulin antagonist W-7 (5-50 microM) did not alter IFN-gamma induction of HLA-DR in either the presence or absence of T4. HLA-DR expression in HeLa cells appears to be under PKC-associated inhibition; IFN-gamma reverses this inhibition to promote the appearance of the DR antigen. In contrast, potentiation by T4 of induction of HLA-DR by IFN-gamma requires activation of PKC. PKA is involved both in DR induction by IFN-gamma and in potentiation of the latter by T4. Thus, PKA and PKC have discrete roles in IFN-gamma-induced MHC class II antigen expression and its modulation by thyroid hormone.
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PMID:Potentiation by thyroxine of interferon-gamma-induced HLA-DR expression is protein kinase A- and C-dependent. 864 Apr 46

Added to HeLa cells previously exposed to recombinant human interferon (IFN)-gamma for 20 h, thyroid hormone [L-thyroxine (T4)] in physiological concentrations potentiates the antiviral action of IFN-gamma by more than 100-fold in 4 h. We examined protein kinase activities for their contributions to the mechanism of this posttranslational effect of thyroid hormone. Added concurrently with thyroid hormone, the protein kinase C (PKC) inhibitor CGP-41251 (5 nM) blocked T4 potentiation of IFN-gamma action. Coincubated with CGP-41251, phorbol 12-myristate 13-acetate (PMA) reversed the effect of the inhibitor on thyroid hormone action. U-73122 (10 nM), a phospholipase C inhibitor, also blocked hormone potentiation. KT-5720 (500 nM), a protein kinase A (PKA) inhibitor, completely inhibited the T4 effect, whereas 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) restored hormone action in the presence of KT-5720. In the absence of T4, 8-BrcAMP and PMA, added together to cells in the 4-h paradigm, fully reproduced hormone potentiation of the antiviral effect of IFN-gamma. Incubated individually with IFN-gamma-treated cells, the two agonists had no potentiating action. Thyroid hormone apparently must activate both PKA and PKC in the nongenomic pathway of IFN-gamma action to enhance antiviral activity in HeLa cells.
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PMID:Potentiation by thyroxine of interferon-gamma-induced antiviral state requires PKA and PKC activities. 889 32

Tumor necrosis factor-alpha (TNF-alpha) has been suggested to be related to the pathogenesis of autoimmune thyroid diseases, nonthyroid illness, and other thyroid dysfunctions induced by infectious diseases. In relation to these, in vitro studies demonstrated that TNF-alpha influences growth and/or differentiated functions mediated by thyroid-stimulating hormone (TSH), including 125I organification. In the present study, we found that TNF-alpha inhibits TSH-induced H2O2 production, which is an inevitable process for iodide organification, and hence thyroid hormone synthesis, in FRTL-5 thyroid cells. In the cells, TNF-alpha induced ceramide production and the addition of exogenous ceramide or sphingomyelinase treatment of the cells simulated TNF-alpha actions. Although TSH stimulation of H2O2 production is mediated by the phospholipase C (PLC)-Ca2+ pathway, TNF-alpha and exogenous and endogenous ceramide affected neither TSH-dependent PLC activation and Ca2+ mobilization nor TSH-induced cAMP accumulation but attenuated Ca(2+)-induced H2O2 production. We conclude that TNF-alpha, through a sphingomyelinase-ceramide pathway, regulates TSH-induced H2O2 production at steps beyond the Ca2+ mobilization step in the PLC-Ca2+ signaling pathway coupled to TSH. This suggests participation of TNF-alpha in thyroid disorder in hormone synthesis induced by thyroid disease associated with the activation of immune systems.
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PMID:Inhibition of TSH-induced hydrogen peroxide production by TNF-alpha through a sphingomyelinase signaling pathway. 931 56

L-T3 and L-T4 activated the Na+/H+ exchanger of L-6 myoblasts, with a fast nongenomic mechanism, both in the steady state and when cells undergo acid loading with ammonium chloride. Monitored with the intracellular pH-sensitive fluorescent probe 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, activation of the exchanger appeared to be initiated at the plasma membrane, because T3-agarose reproduced the effect of L-T3, and triiodothyroacetic acid, a hormone analog previously shown to inhibit membrane actions of thyroid hormone, blocked the action of L-T3 on the exchanger. We show here for the first time that transduction of the hormone signal in this nongenomic response requires tyrosine kinase-dependent phospholipase C activation and two different signaling pathways: 1) mobilization of intracellular calcium, assessed by the fluorescent probe fura-2, through activation of inositol trisphosphate receptors and without contributions from extracellular calcium or ryanodine receptors; and 2) protein phosphorylation involving protein kinase C and MAPK (ERK1/2), as shown by the use of kinase inhibitors and by immunoblotting for activated kinases.
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PMID:Rapid nongenomic effects of 3,5,3'-triiodo-L-thyronine on the intracellular pH of L-6 myoblasts are mediated by intracellular calcium mobilization and kinase pathways. 1534 78

Endocytosis is a distinctive property of all eukaryotic cells. Polarized cells face two different worlds by membranes of distinct composition: the basolateral membrane is exposed to the constant internal medium, whereas the apical membrane is exposed to variable environments. Endocytosis on both aspects also depends on different machineries. This short review illustrates the molecular basis and physiopathological implications of apical endocytosis. In a cultured epithelial cell line, Src selectively triggers apical macropinocytosis by activating the actin cytocortex via signalling membrane lipids generated by an amplification cascade involving phosphoinositide 3-kinase, phospholipase C and phospholipase D. Several actors of Src response are also activated by enteroinvasive bacteria, to trigger their entry into enterocytes. In the thyroid gland, the rates of thyroglobulin apical micropinocytosis and transfer to lysosomes determine the level of thyroid hormone production, by controlling the encounter of the prohormone with converting hydrolases. TSH selectively promotes the encounter, by inducing the expression of rate-limiting catalysts, the small GTPases Rab5 and Rab7, and of their exchange factor(s). This induction is constitutive in autonomous adenomas. In kidney proximal tubular cells, apical receptor-mediated endocytosis ensures full recapture of ultrafiltrated proteins. Inactivating mutations of the endosomal chloride channel, ClC-5, that are responsible for Dent's disease, cause a loss of surface receptors leading to proteinuria. These examples illustrate how three levels of regulation of apical endocytosis, namely the mode of entry, the rate of vesicular trafficking and the subcellular addressing account for a variety of human diseases.
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PMID:[Apical endocytosis: molecular controls and physiopathologic implications]. 1639 73

Thyroperoxidase-catalyzed iodination of thyroglobulin and subsequent oxidative coupling of iodinated tyrosyl residues to protein-bound iodothyronines are the key reactions in thyroid hormone biosynthesis. Under sufficient iodine supply, both synthesis steps are rate-limited by the availability of hydrogen peroxide (H(2)O(2)), which is required as final electron acceptor. The primary enzyme feeding H(2)O(2) to thyroid peroxidase is a heterodimeric NADPH oxidase complex of dual oxidase 2 (DUOX2) and DUOX maturation factor 2 (DUOXA2) at the apical plasma membrane. While the thyrotropin receptor mediates most biological effects through the Gs/adenyl cyclase/cAMP pathway, the Gq/phospholipase C-beta cascade induces H(2)O(2) generation via synergistic effects of increased intracellular calcium and protein kinase C activation on DUOX2/DUOXA2. Defects in thyroidal H(2)O(2) generation have been identified in a subset of patients with congenital hypothyroidism. These include loss-of-function mutations in DUOX2 and DUOXA2. Thyrotropin receptor mutations with preferential loss of Gq-coupling may indirectly affect H(2)O(2) production. Expressivity of the defects can be highly variable owning to the presence of genetic modifiers (e.g., the paralogs DUOX1 and DUOXA1), and environmental factors particularly nutritional iodide intake.
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PMID:Defects of thyroidal hydrogen peroxide generation in congenital hypothyroidism. 2012 87


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