Glycoprotein Biosynthesis: Stimulation of N-Acetylglucosaminyltransferase Activity by Cytidiee 5′-Diphosphocholine

1972 ◽  
Vol 50 (10) ◽  
pp. 1082-1093 ◽  
Author(s):  
Sailen Mookerjea
Keyword(s):  
Enzyme Activity ◽  
Phospholipase C ◽  
Inhibitory Action ◽  
Inhibitory Effect ◽  
Nucleotide Sugar ◽  
Inorganic Pyrophosphate ◽  
Golgi Membranes ◽  
Cationic Detergents ◽  
Better Than ◽  
Stimulation Of

The stimulatory effect of CDP-choline on N-acetylglucosaminyltransferase activity is marked in rough microsomes but is almost absent in Golgi-rich membranes or in serum. The marked CDP-choline effect on the enzyme is evident even when the nucleotide–sugar substrate concentration is raised to near saturation. Diglyceride has an inhibitory action on the enzyme which is effectively reversed by further addition of CDP-choline. Of the other different lipid factors tested only CDP-ethanolamine has a stimulatory effect similar to CDP-choline. CDP-choline alone activates the enzyme better than Triton. CDP-choline and Triton, in different combinations of doses, show a marked synergistic effect. Cationic detergents do not activate the enzyme and inorganic pyrophosphate almost completely inhibits the enzyme activity. Phospholipase A has an inhibitory effect in the presence of CDP-choline. Phospholipase C, by itself, stimulates the enzyme activity. In the presence of CDP-choline, a higher concentration of phospholipase C partially abolishes the CDP-choline effect on the enzyme. Phosphorylcholine from labeled CDP-choline is rapidly incorporated into lecithin in the assay system used for measuring N-acetylglucosaminyltransferase activity. Capacity for lecithin synthesis is poor in Golgi membranes. However, lecithin synthesis is stimulated by adding exogenous diglyceride, but CDP-choline plus diglyceride failed to activate N-acetylglucosaminyltransferase in Golgi membranes. Finally, various possibilities have been discussed to explain the mechanism of action of CDP-choline on the enzyme.

Adenosine A1 receptor-mediated inhibition of myocardial norepinephrine release involves neither phospholipase C nor protein kinase C but does involve adenylyl cyclase

2006 ◽  
Vol 84 (5) ◽  
pp. 573-577 ◽  
Author(s):  
Frank Schütte ◽  
Christof Burgdorf ◽  
Gert Richardt ◽  
Thomas Kurz
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Adenylyl Cyclase ◽  
Phospholipase C ◽  
Suppressive Effect ◽  
Inhibitory Effect ◽  
Direct Stimulation ◽  
Kinase C ◽  
Gf 109203X ◽  
Stimulation Of

Stimulation of adenosine A1 receptors in the heart exerts cardioprotective effects by inhibiting norepinephrine (NE) release from sympathetic nerve endings. The intraneuronal signal transduction triggered by presynaptic adenosine A1 receptors is still not completely understood. The objective of the present study was to determine whether phospholipase C (PLC), protein kinase C (PKC), and adenylyl cyclase (AC) are involved in the adenosine A1 receptor-mediated inhibition of endogenous (stimulation-induced) NE release in isolated Langendorff-perfused rat hearts as an approach to elucidate their role in the cardiovascular system. Activation of adenosine A1-receptors with 2-chloro-N6-cyclopentyladenosine (CCPA) decreased cardiac NE release by ~40%. Inhibition of PLC with 1-[6-[[(17b)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U 73122) as well as inhibition of PKC with 2-[1-(3-dimethylaminopropyl)indol-3-yl]-3-(indol-3-yl)maleimide (GF 109203X) slightly but significantly decreased NE release; however, the suppressive effect of CCPA on NE release was not modulated by U 73122 or GF 109203X. Blockade of AC with 9-(tetrahydro-2′-furyl)adenine (SQ 22536) reversed the inhibitory effect of CCPA on sympathetic neurotransmitter release irrespective of whether PKC was pharmacologically activated by phorbol 12-myristate 13-acetate or was not activated, indicating a PKC-independent but AC-dependent mechanism. Direct stimulation of AC with forskolin increased NE release by ∼20%; an effect that was antagonized by either CCPA or SQ 22536. These data suggest that the adenosine A1 receptor-mediated inhibition of NE release does not involve PLC or PKC but does involve AC.

066 Noradrenaline and acetylcholine inhibit sleep-promoting neurons of ventrolateral preoptic area through a local GABAergic circuit

SLEEP ◽  
2021 ◽  
Vol 44 (Supplement_2) ◽  
pp. A27-A28
Author(s):  
Roberto De Luca ◽  
Stefano Nardone ◽  
Lin Zhu ◽  
Elda Arrigoni
Keyword(s):  
Muscarinic Receptors ◽  
Inhibitory Action ◽  
Preoptic Area ◽  
Brain Slices ◽  
Inhibitory Effect ◽  
Gabaergic Neurons ◽  
Optogenetic Stimulation ◽  
Direct Inhibitory Effect ◽  
Afferent Inputs ◽  
Stimulation Of

Abstract Introduction The ventrolateral preoptic (VLPO) nucleus is a key area involved in the initiation and maintenance of sleep. During wakefulness, sleep-promoting galanin neurons in the VLPO are directly inhibited by arousal signals including noradrenaline and acetylcholine. We have found that while these neurotransmitters directly inhibit VLPO galanin neurons, they also activate GABAergic neurons in the VLPO that do not express galanin. We propose that when activated by monoaminergic and cholinergic inputs, these local VLPO GABAergic neurons provide an additional inhibition of the VLPO galanin sleep-promoting neurons. We tested this model in brain slices in mice. Methods We studied VLPO galanin neurons in mouse brain slices using patch-clamp recordings. We recorded from fluorescently labeled VLPO galanin neurons following the injection of a cre-dependent AAV encoding for mCherry, into the VLPO of Gal-cre mice. For the optogenetic studies we expressed channelrhodopsin-2 (ChR-2) in VLPO VGAT neurons and mCherry in galanin neurons by injecting a flp-dependent and a cre-dependent AAV encoding respectively for ChR2 and mCherry into the VLPO of VGAT-flp::Gal-cre mice. We photo-stimulated local GABAergic neurons and recorded from labeled VLPO galanin neurons. Noradrenaline, carbachol and receptor antagonists were bath-applied. Results Noradrenaline and carbachol inhibited VLPO galanin neurons by alpha-2 and muscarinic receptors and these effects were maintained in the presence of tetrodotoxin (TTX) indicating, as previously proposed, a direct inhibitory effect of noradrenaline and carbachol on VLPO galanin neurons. In addition, both noradrenaline and carbachol increased the frequency of spontaneous inhibitory post-synaptic currents (sIPSCs) of VLPO galanin neurons, suggesting an additional inhibitory action on VLPO galanin neurons. Finally, optogenetic stimulation of local VLPO GABAergic neurons produced short latency, TTX-resistant, opto-evoked IPSCs in VLPO galanin neurons. Both noradrenaline and carbachol increased the amplitude of these opto-evoked IPSCs by the activation of alpha-1 and muscarinic receptors. Conclusion Our results demonstrate that noradrenaline and acetylcholine inhibit VLPO galanin neurons directly and indirectly. Both noradrenaline and acetylcholine increase GABAergic afferent inputs to VLPO galanin neurons by activating local GABAergic neurons. We propose that during wakefulness this feedforward inhibition provides additional inhibition of VLPO galanin sleep-promoting neurons. Support (if any) NS091126 and HL149630

scholarly journals Retinyl phosphate mannose synthesis in rat liver membranes. Phospholipase sensitivity and phospholipid requirement

1983 ◽  
Vol 216 (3) ◽  
pp. 727-735
Author(s):  
Y Shidoji ◽  
C S Silverman-Jones ◽  
L M De Luca
Keyword(s):  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Phospholipase C ◽  
Rat Liver ◽  
Membrane Fraction ◽  
Inhibitory Effect ◽  
Synthetic Activity ◽  
Dolichyl Phosphate ◽  
Liver Membranes ◽  
Endogenous Lipids

A remarkable and immediate decrease in GDP-mannose:retinyl phosphate mannosyltransferase activity was found on pre-incubation of rat liver postnuclear membranes with phospholipase A2 or phospholipase C. Under the same conditions of pre-incubation (1 min at 37 degrees C) trypsin did not affect the enzyme activity, whereas pre-incubation for 30 min with trypsin and Pronase abolished enzyme activity. The lipid extract of untreated rat liver membranes partially restored enzyme activity after phospholipase treatment. Sphingomyelin was as active as the endogenous lipids. Other phospholipids were less active in the following order: phosphatidylcholine greater than phosphatidylethanolamine greater than phosphatidylinositol = phosphatidylserine. Dolichyl phosphate mannose synthesis was inhibited less (33%) by phospholipase C than was Ret-P-Man synthesis (98.5%) under identical conditions of incubation, which included 0.025% Triton. However, retinyl phosphate mannose synthesis by purified endoplasmic reticulum was found to be resistant to phospholipase C. Mixing experiments failed to demonstrate an inhibitory effect of the phospholipase-treated postnuclear membrane fraction on the synthetic activity of the endoplasmic reticulum, thus excluding the release of an inhibitory factor from the postnuclear membranes.

Inhibitory Action of Bulbar and Suprabulbar Reticular Formation on the Spinal Reflex Pathway

1956 ◽  
Vol 184 (3) ◽  
pp. 497-504 ◽  
Author(s):  
Chandler McC. Brooks ◽  
Kiyomi Koizumi ◽  
Arthur A. Siebens
Keyword(s):  
Reticular Formation ◽  
Inhibitory Action ◽  
Inhibitory Effect ◽  
Spinal Reflex ◽  
Reciprocal Effect ◽  
Reflex Pathway ◽  
Reflex Pathways ◽  
Post Tetanic Potentiation ◽  
Afferent Terminals ◽  
Stimulation Of

Inhibitory action of bulbar and suprabulbar reticular formation on spinal flexor and extensor reflex pathways was studied. In some instances a reciprocal effect was obtained but usually a generalized inhibition resulted. Inhibition varied in magnitude but was always present during reticular formation stimulation. In a high percentage of cases inhibition persisted for a period of 2–3 minutes after cessation of stimulation. Stimulations which blocked the reflex occasionally also had an inhibitory effect on the antidromic potential evoked by stimulation of the motor fibers involved in the reflex but in many instances the antidromic potential was actually augmented. The inhibitory stimulation also did not prevent facilitation of the antidromic potential by orthodromic stimuli. Post-tetanic potentiation was not prevented nor terminated by stimulation of the inhibitory areas of the reticular formation. This data suggest that inhibition from the reticular formation does not block afferent terminals but acts postsynaptically in such a manner, however, as not to increase axon hillock block of antidromic invasion of the soma. Effects of certain anesthetics and drugs on these phenomena were studied.

scholarly journals Guanine nucleotides mediate stimulatory and inhibitory effects on cerebral-cortical membrane phospholipase C activity

1989 ◽  
Vol 261 (1) ◽  
pp. 245-251 ◽  
Author(s):  
I Litosch
Keyword(s):  
Phospholipase C ◽  
Pertussis Toxin ◽  
Inhibitory Effect ◽  
Guanine Nucleotides ◽  
Regulatory Effect ◽  
Inhibitory Effects ◽  
Gtp Binding ◽  
Maximum Inhibition ◽  
Cortical Membranes ◽  
Stimulation Of

In cerebral-cortical membranes, hydrolysis-resistant guanine nucleotides exert a dual regulatory effect on phospholipase C activity. Nanomolar concentrations of guanosine 5′-[beta gamma-imido]triphosphate (p[NH]ppG) or guanosine 5′-[gamma-thio]triphosphate (GTP[S]) inhibited basal phospholipase C activity, with a maximum inhibition of 30% at 10 nM. Increasing the concentration of p[NH]ppG or GTP[S] to over 10 nM resulted in a reversal of the inhibitory effect and onset of stimulation of phospholipase C activity. These inhibitory effects were blocked by 100 microM-guanosine 5′-[beta-thio]diphosphate. GTP was relatively ineffective in producing either stimulation or inhibition of phospholipase C activity. Similarly, ATP, adenosine 5′-[beta gamma-imido]triphosphate and GDP were also ineffective. Expression of the dual effects of guanine nucleotides was affected by the Mg2+ concentration. At 0.3 mM-Mg2+, both the inhibitory and the stimulatory components of p[NH]ppG action were evident. At 2.5 mM-Mg2+, only p[NH]ppG stimulation was observed. Pertussis-toxin treatment blocked the p[NH]ppG-mediated inhibition of phospholipase C activity. These results demonstrate that non-hydrolysable guanine nucleotides exert both a stimulatory and an inhibitory effect on membrane phospholipase C activity. These effects may be mediated through distinct GTP-binding proteins.

Phospholipase C from Clostridium Perfringens Induces Human Platelet Aggregation in Plasma

1988 ◽  
Vol 59 (02) ◽  
pp. 236-239 ◽  
Author(s):  
Giovanna Barzaghi ◽  
Chiara Cerletti ◽  
Giovanni de Gaetano
Keyword(s):  
Platelet Aggregation ◽  
Receptor Antagonist ◽  
Phospholipase C ◽  
Clostridium Perfringens ◽  
Human Platelet ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Platelet Activating Factor ◽  
Inhibitory Effect ◽  
Thromboxane Receptor Antagonist

SummaryWe studied the aggregating effect of different concentrations of phospholipase C (PLC) (extracted from Clostridium perfringens) on human platelet-rich plasma (PRP). PRP was preincubated with PLC for 3 min at 37° C and the platelet aggregation was followed for 10 min. The threshold aggregating concentration (TAG) of PLC was 3-4 U/ml.We also studied the potentiation of PLC with other stimuli on platelet aggregation. Potentiating stimuli, such as arachidonic acid (AA), ADP. Platelet Activating Factor (PAF) and U-46619 (a stable analogue of cyclic endoperoxides) were all used at subthreshold concentrations. We also studied the possible inhibitory effect of aspirin, apyrase, TMQ, a prostaglandin endoper- oxide/thromboxane receptor antagonist and BN-52021, a PAF receptor antagonist. Only aspirin and apyrase were able to reduce aggregation induced by PLC alone and PLC + AA and PLC + ADP respectively. TMQ and BN-52021 were inactive. In ex vivo experiments oral aspirin (500 mg) partially inhibited platelet aggregation induced by PLC alone, PLC + AA and PLC + ADP 2 and 24 h after administration. Aspirin 20 mg for 7 days also reduced aggregation induced by PLC + AA.

Inhibition of ADP-Induced Responses in Human Platelets by Agents Elevating the Cyclic AMP Level: Comparison of Aggregation and Shape Change

1984 ◽  
Vol 52 (03) ◽  
pp. 333-335 ◽  
Author(s):  
Vider M Steen ◽  
Holm Holmsen
Keyword(s):  
Inhibitory Action ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Inhibitory Effects ◽  
Early Step ◽  
Stimulus Response ◽  
Sequential Relationship

SummaryThe inhibitory effect of cAMP-elevating agents on shape change and aggregation in human platelets was studied to improve the understanding of the sequential relationship between these two responses.Human platelet-rich plasma was preincubated for 2 min at 37° C with prostaglandin E1 or adenosine, agents known to elevate the intracellular level of cAMP. Their inhibitory effects on ADP-induced shape change and aggregation were determined both separately and simultaneously. The dose-inhibition patterns for shape change and aggregation were similar for both PGE1 and adenosine. There was no distinct difference between the inhibitory action of these two inhibitors.These observations suggest that elevation of the intracellular concentration of cAMP interferes with an early step in the stimulus-response coupling that is common for aggregation and shape change.

Mechanism of the Antiplatelet Action of Dipyridamole in Whole Blood: Modulation of Adenosine Concentration and Activity

1986 ◽  
Vol 55 (01) ◽  
pp. 012-018 ◽  
Author(s):  
Paolo Gresele ◽  
Jef Arnout ◽  
Hans Deckmyn ◽  
Jos Vermylen
Keyword(s):  
Platelet Aggregation ◽  
Adenosine Receptor ◽  
Whole Blood ◽  
Blood Cells ◽  
Inhibitory Action ◽  
Phosphodiesterase Inhibitor ◽  
Inhibitory Effect ◽  
Adenosine Concentration ◽  
Pharmacological Studies

SummaryDipyridamole inhibits platelet aggregation in whole blood at lower concentrations than in plasma. The blood cells responsible for increased effectiveness in blood are the erythrocytes. Using the impedance aggregometer we have carried out a series of pharmacological studies in vitro to elucidate the mechanism of action of dipyridamole in whole blood. Adenosine deaminase, an enzyme breaking down adenosine, reverses the inhibitory action of dipyridamole. Two different adenosine receptor antagonists, 5’-deoxy-5’-methylthioadenosine and theophylline, also partially neutralize the activity of dipyridamole in blood. Enprofylline, a phosphodiesterase inhibitor with almost no adenosine receptor antagonistic properties, potentiates the inhibition of platelet aggregation by dipyridamole. An inhibitory effect similar to that of dipyridamole can be obtained combining a pure adenosine uptake inhibitor (RE 102 BS) with a pure phosphodiesterase inhibitor (MX-MB 82 or enprofylline). Mixing the blood during preincubation with dipyridamole increases the degree of inhibition. Lowering the haematocrit slightly reduces the effectiveness.Although we did not carry out direct measurements of adenosine levels, the results of our pharmacological studies clearly show that dipyridamole inhibits platelet aggregation in whole blood by blocking the reuptake of adenosine formed from precursors released by red blood cells following microtrauma. Its slight phosphodiesterase inhibitory action potentiates the effects of adenosine on platelets.

Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2

Reproduction ◽  
2000 ◽  
pp. 57-68 ◽  
Author(s):  
J Garde ◽  
ER Roldan
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phosphodiesterase Inhibitors ◽  
Dibutyryl Camp ◽  
Camp Phosphodiesterase ◽  
Ram Sperm ◽  
Camp Formation ◽  
Stimulation Of

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.

Synthesis and Assessment of Novel Anti-chlamydial Benzylidene Acylhydrazides Derivatives

2018 ◽  
Vol 15 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Xiaofeng Bao ◽  
Ying Xue ◽  
Chao Xia ◽  
Yin Lu ◽  
Ningjing Yang ◽  
...  
Keyword(s):  
Inhibitory Effect ◽  
Dependent Manner ◽  
Iron Starvation ◽  
Hydrochloride Salt ◽  
Obligate Intracellular ◽  
Biphasic Life Cycle ◽  
Ic50 Value ◽  
Ic50 Values ◽  
Dose Dependent ◽  
Better Than

Background: Chlamydiae, characterized by a unique biphasic life cycle, are a group of Gram-negative obligate intracellular bacterial pathogens responsible for diseases in a range of hosts including humans. Benzylidene acylhydrazide CF0001 could inhibit chlamydiae independent of iron starvation and T3SS inhibition. This finding promoted us to design and synthesize more benzylidene acylhydrazides to find novel anti-chlamydial agents. Methods: The carboxylic acids 1a-1d were coupled with Boc-hydrazide inpresence of EDCI and DMAP to obtain the intermediate 2a-2d in 60-62% yields. N-Boc deprotections were performed to obtain hydrazide hydrochloride salt 3a-3d. Nextly, the hydrazides were subjected to condensation with aldehydes to obtain benzylidene acylhydrazides 4a-4g in 30-52% yields in two steps. Results: Compound 4d exhibited best inhibitory effect on the formation and growth of chlamydial inclusions. The IC50 value of compound 4d for infectious progenies was 3.55 µM, better than 7.30 µM of CF0001. Conclusion: To find novel anti-chlamydial agents, we have designed and synthesized benzylidene acylhydrazides 4a-4g. Compounds 4a, 4d, 4g showed inhibitory activity on C. muridarum with the IC50 values from 3.55-12 µM. The 3,5-dibromo-4-hydroxyl substitutes on ring B are critical to keep their anti-chlamydial activity. Compound 4d inhibited C. muridarum in a dose-dependent manner without apparent cytotoxicity.

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