The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
Jacques Emile Dumont - One of the best experts on this subject based on the ideXlab platform.
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relative contribution of phosphoinositides and phosphatidylcholine hydrolysis to the actions of carbamylcholine thyrotropin and phorbol esters on dog thyroid slices regulation of Cytidine Monophosphate phosphatidic acid accumulation and phospholipase
Endocrinology, 1994Co-Authors: Claudine Lejeune, J Mockel, Jacques Emile DumontAbstract: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...
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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 phos
Endocrinology, 1994Co-Authors: Claudine Lejeune, J Mockel, Jacques Emile DumontAbstract: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.
Ken Kitajima - One of the best experts on this subject based on the ideXlab platform.
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development of a simple and efficient method for assaying Cytidine Monophosphate sialic acid synthetase activity using an enzymatic reduced nicotinamide adenine dinucleotide oxidized nicotinamide adenine dinucleotide converting system
Analytical Biochemistry, 2005Co-Authors: Akiko Fujita, Chihiro Sato, Anjak Munsterkuhnel, Rita Gerardyschahn, Ken KitajimaAbstract:Abstract A new reliable method to assay the activity of Cytidine Monophosphate sialic acid (CMP-Sia) synthetase (CSS) has been developed. The activation of sialic acids (Sia) to CMP-Sia is a prerequisite for the de novo synthesis of sialoglycoconjugates. In vertebrates, CSS has been cloned from human, mouse, and rainbow trout, and the crystal structure has been resolved for the mouse enzyme. The mouse and rainbow trout enzyme have been compared with respect to substrate specificity, demonstrating that the mouse enzyme exhibits a pronounced specificity for N -acetylneuraminic acid (Neu5Ac), while the rainbow trout CSS is equally active with either of three Sia species, Neu5Ac, N -glycolylneuraminic acid (Neu5Gc), and deaminoneuraminic acid (KDN). However, molecular details that explain the pronounced substrate specificities are unknown. Understanding the catalytic mechanisms of these enzymes is of major importance, since CSSs play crucial roles in cellular sialylation patterns and thus are potential drug targets in a number of pathophysiological situations. The availability of the cDNAs and the obtained structural data enable rational approaches; however, these efforts are limited by the lack of a reliable high-throughput assay system. Here we describe a new assay system that allows product quantification in a reduced nicotinamide adenine dinucleotide (NADH)-dependent color reaction. The activation reaction catalyzed by CSS, CTP + Sia → CMP-Sia + pyrophosphate, was evaluated by a consumption of Sia, which corresponds to that of NADH on the following two successive reactions: (i) Sia → pyruvate + ManNAc (or Man), catalyzed by a sialic acid lyase (SAL), and (ii) pyruvate + NADH → lactate + oxidized nicotinamide adenine dinucleotide (NAD + ), catalyzed by a lactate dehydrogenase (LDH). Consumption of NADH can be photometrically monitored on a microtiter plate reader for a number of test samples at the same time. Furthermore, based on the quantification of CSS used in the SAL/LDH assay, relative activities toward Sia derivatives have been obtained. The preference of mouse CSS toward Neu5Ac and the ability of the rainbow trout enzyme to activate both KDN and Neu5Ac were confirmed. Thus, this simple and time-saving method is suitable for a systematic comparison of enzyme activity of structurally mutated enzymes based on the relative specific activity.
Yi Zhang - One of the best experts on this subject based on the ideXlab platform.
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pigment epithelium derived factor facilitates nlrp3 inflammasome activation through downregulating Cytidine Monophosphate kinase 2 a potential treatment strategy for missed abortion
International Journal of Molecular Medicine, 2020Co-Authors: Xi Zhang, Kun Zhang, Yi ZhangAbstract:A number of conditions may underlie the occurrence of missed abortion (MA), including inflammation. Pigment epitheliumderived factor (PEDF) is a novel mediator of the inflammationrelated nucleotidebinding oligomerization domainlike receptor protein 3 (NLRP3) inflammasome, which is associated with several human diseases. However, the association between MA and NLRP3 inflammasome, and whether PEDF is reduced in MA, remain unknown. In the present study, the decidua and chorion tissues of patients who had suffered a MA were examined, and a lipopolysaccharide (LPS)induced human chorionic trophoblast HTR8/SVneo cell model was established to mimic MA in vitro. The results revealed that Cytidine Monophosphate kinase 2 (CMPK2) expression and NLRP3 inflammasome activation, downstream proIL18 and proIL1beta expression, and IL18 and IL1beta release, were all significantly increased in MA tissues or LPSinduced HTR8/SVneo cells. PEDF reversed the increase in CMPK2 expression and activation of the NLRP3 inflammasome axis and, thus, downregulated the production of mitochondrial reactive oxygen species and mitochondrial DNA release, resulting in reduced lactate dehydrogenase release, and a resultant decrease in cell viability. Recovery of CMPK2 expression abolished all the effects of PEDF, indicating that CMPK2 may be an effector downstream of PEDF. PEDF reduced CMPK2 protein levels but did not affect the mRNA levels, and treatment with the proteasomal inhibitor MG132 significantly reversed this reduction in CMPK2 protein levels. Furthermore, a ubiquitination assay of immunoprecipitation demonstrated that CMPK2 was polyubiquitinated in the presence of LPS, PEDF and MG132. These results indicated that the NLRP3 inflammasome is implicated in the pathogenesis of MA, and PEDF may reduce MA through ubiquitindependent proteasomal degradation of CMPK2 to inhibit NLRP3 activation, which may serve as a novel strategy for preventing or reducing the risk of MA.
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Pigment epithelium‑derived factor facilitates NLRP3 inflammasome activation through downregulating Cytidine Monophosphate kinase 2: A potential treatment strategy for missed abortion
International Journal of Molecular Medicine, 2020Co-Authors: Xi Zhang, Kun Zhang, Yi ZhangAbstract:A number of conditions may underlie the occurrence of missed abortion (MA), including inflammation. Pigment epithelium‑derived factor (PEDF) is a novel mediator of the inflammation‑related nucleotide‑binding oligomerization domain‑like receptor protein 3 (NLRP3) inflammasome, which is associated with several human diseases. However, the association between MA and NLRP3 inflammasome, and whether PEDF is reduced in MA, remain unknown. In the present study, the decidua and chorion tissues of patients who had suffered a MA were examined, and a lipopolysaccharide (LPS)‑induced human chorionic trophoblast HTR8/SVneo cell model was established to mimic MA in vitro. The results revealed that Cytidine Monophosphate kinase 2 (CMPK2) expression and NLRP3 inflammasome activation, downstream pro‑IL‑18 and pro‑IL‑1β expression, and IL‑18 and IL‑1β release, were all significantly increased in MA tissues or LPS‑induced HTR8/SVneo cells. PEDF reversed the increase in CMPK2 expression and activation of the NLRP3 inflammasome axis and, thus, downregulated the production of mitochondrial reactive oxygen species and mitochondrial DNA release, resulting in reduced lactate dehydrogenase release, and a resultant decrease in cell viability. Recovery of CMPK2 expression abolished all the effects of PEDF, indicating that CMPK2 may be an effector downstream of PEDF. PEDF reduced CMPK2 protein levels but did not affect the mRNA levels, and treatment with the proteasomal inhibitor MG132 significantly reversed this reduction in CMPK2 protein levels. Furthermore, a ubiquitination assay of immunoprecipitation demonstrated that CMPK2 was polyubiquitinated in the presence of LPS, PEDF and MG132. These results indicated that the NLRP3 inflammasome is implicated in the pathogenesis of MA, and PEDF may reduce MA through ubiquitin‑dependent proteasomal degradation of CMPK2 to inhibit NLRP3 activation, which may serve as a novel strategy for preventing or reducing the risk of MA.
Tatsuji Seki - One of the best experts on this subject based on the ideXlab platform.
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cloning and characterization of Cytidine Monophosphate 3 deoxy d manno octulosonate synthetase from arabidopsis thaliana
Journal of Bioscience and Bioengineering, 2009Co-Authors: Ryo Misaki, Hiroyuki Kajiura, Kenji Fujii, Kazuhito Fujiyama, Tatsuji SekiAbstract:Abstract The function and metabolic pathway of 3-deoxy- d -manno-octulosonate (KDO) are unclear in plants although it is an essential component in plant cell wall. Here we cloned and characterized a putative Arabidopsis thaliana Cytidine Monophosphate-KDO synthetase to understand synthetic pathways of KDO. It showed a ubiquitous expression, the activity at an optimal pH of 8.0, and a requirement of Mg2+.
Claudine Lejeune - One of the best experts on this subject based on the ideXlab platform.
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relative contribution of phosphoinositides and phosphatidylcholine hydrolysis to the actions of carbamylcholine thyrotropin and phorbol esters on dog thyroid slices regulation of Cytidine Monophosphate phosphatidic acid accumulation and phospholipase
Endocrinology, 1994Co-Authors: Claudine Lejeune, J Mockel, Jacques Emile DumontAbstract: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...
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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 phos
Endocrinology, 1994Co-Authors: Claudine Lejeune, J Mockel, Jacques Emile DumontAbstract: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.
