scholarly journals Molecular basis for SPIN·DOC-Spindlin1 engagement and its role in transcriptional inhibition

2021 ◽  
Author(s):  
Fan Zhao ◽  
Fen Yang ◽  
Fan Feng ◽  
Bo Peng ◽  
Mark T. Bedford ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Transcriptional Coactivator ◽  
Inhibitory Effects ◽  
Binding Studies ◽  
Transcriptional Inhibition ◽  
Aromatic Cage ◽  
Hydrophobic Motif ◽  
Qpcr Experiment

ABSTRACTSpindlin1 is a transcriptional coactivator with three Tudor-like domains, of which the first and second Tudors are engaged in histone methylation readout, while the function of the third Tudor is largely unknown. Recent studies revealed that the transcriptional co-activator activity of Spindlin1 could be attenuated by SPIN•DOC. Here we solved the crystal structure of SPIN•DOC-Spindlin1 complex, revealing that a hydrophobic motif, DOCpep3 (256-281), of SPIN•DOC interacts with Tudor 3 of Spindlin1 and completes its β-barrel fold. Massive hydrophobic contacts and hydrogen bonding interactions ensure a high affinity DOCpep3-Spindlin1 engagement with a binding Kd of 30 nM. Interestingly, we characterized two more K/R-rich motifs of SPIN•DOC, DOCpep1 (187-195) and DOCpep2 (228-239), which bind to Spindlin1 at lower affinities with Kd values of 78 μM and 31 μM, respectively. Structural and binding studies revealed that DOCpep1 and DOCpep2 competitively bind to the aromatic cage of Spindlin1 Tudor 2 that is responsible for H3K4me3 readout. Although DOCpep3-Spindlin1 engagement is compatible with histone readout, an extended SPIN•DOC fragment containing DOCpep1 and DOCpep2 inhibits histone or TCF4 binding by Spindin1 due to introduced competition. This inhibitory effect is more pronounced for weaker binding targets but not for strong ones such as H3 “K4me3-K9me3” bivalent mark. Our RT-qPCR experiment showed that the removal of the hydrophobic motif or the K/R-rich region compromised the inhibitory effects of SPIN•DOC on Spindlin1-mediated transcriptional activation. In sum, here we revealed multivalent engagement between SPIN•DOC and Spindlin1, in which a hydrophobic motif acts as the primary binding site for stable SPIN•DOC-Spindlin1 association, while two more neighboring K/R-rich motifs further modulate the target selectivity of Spindlin1 via competitive inhibition, therefore attenuating the transcriptional co-activator activities of Spindlin1 through affecting its chromatin association.

Inhibition of Yeast Growth by Tryptamine and Recovery with Tryptophan

2020 ◽  
Vol 16 (1) ◽  
pp. 48-52 ◽  
Author(s):  
Chandrika Kadkol ◽  
Ian Macreadie
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Carbon Source ◽  
Competitive Inhibition ◽  
Yeast Species ◽  
Inhibitory Effect ◽  
The Body ◽  
Inhibitory Effects ◽  
Trna Synthetases ◽  
Fermentative Growth ◽  
Biogenic Monoamine

Background: Tryptamine, a biogenic monoamine that is present in trace levels in the mammalian central nervous system, has probable roles as a neurotransmitter and/or a neuromodulator and may be associated with various neuropsychiatric disorders. One of the ways tryptamine may affect the body is by the competitive inhibition of the attachment of tryptophan to tryptophanyl tRNA synthetases. Methods: This study has explored the effects of tryptamine on growth of six yeast species (Saccharomyces cerevisiae, Candida glabrata, C. krusei, C. dubliniensis, C. tropicalis and C. lusitaniae) in media with glucose or ethanol as the carbon source, as well as recovery of growth inhibition by the addition of tryptophan. Results: Tryptamine was found to have an inhibitory effect on respiratory growth of all yeast species when grown with ethanol as the carbon source. Tryptamine also inhibited fermentative growth of Saccharomyces cerevisiae, C. krusei and C. tropicalis with glucose as the carbon source. In most cases the inhibitory effects were reduced by added tryptophan. Conclusion: The results obtained in this study are consistent with tryptamine competing with tryptophan to bind mitochondrial and cytoplasmic tryptophanyl tRNA synthetases in yeast: effects on mitochondrial and cytoplasmic protein synthesis can be studied as a function of growth with glucose or ethanol as a carbon source. Of the yeast species tested, there is variation in the sensitivity to tryptamine and the rescue by tryptophan. The current study suggests appropriate yeast strains and approaches for further studies.

Selective aromatase inhibition by pyridoglutethimide, an analogue of aminoglutethimide

1990 ◽  
Vol 122 (5) ◽  
pp. 592-598 ◽  
Author(s):  
Jo Kitawaki ◽  
Takara Yamamoto ◽  
Mamoru Urabe ◽  
Takaya Tamura ◽  
Shigeo Inoue ◽  
...  
Keyword(s):  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Side Chain ◽  
Aromatase Activity ◽  
Inhibitory Effects ◽  
Metabolizing Enzymes ◽  
Chain Cleavage ◽  
Steroid Hydroxylases ◽  
Cytochrome P 450

Abstract. The inhibitory effects of pyridoglutethimide (3-ethyl-3-(4-pyridyl)piperidine-2,6-dione), an analogue of aminoglutethimide, on aromatase and other cytochrome P-450-dependent steroid-metabolizing enzymes were studied in vitro. Pyridoglutethimide and aminoglutethimide showed competitive inhibition of human placental aromatase activity with apparent Ki values of 1.7 and 0.7 μmol/l, respectively. Both pyridoglutethimide and aminoglutethimide inhibited the aromatase activity of uterine leiomyoma and cultured choriocarcinoma Enami cells as well as immunopurified human placental aromatase cytochrome P-450 by more than 90%, with IC50 values of 10–19 and 5–7 μmol/l, respectively. These results might suggest that the inhibitors interacted directly with the aromatase cytochrome P-450 of these tissues. Aminoglutethimide inhibited bovine adrenal cholesterol side-chain cleavage activity with an IC50 value of 40 μmol/l and inhibited 21-hydroxylase activity slightly, but did ot inhibit 17α-, 1 1β- and 18-hydroxylase at concentrations up to 100 μmol/l. On the other hand, pyridoglutethimide had no inhibitory effect on any of these enzymes at concentrations up to 50 μmol/l, although it inhibited 11β- and 18-hydroxylase slightly at 100 μmol/l. These results indicated that pyridoglutethimide was an aromatase inhibitor of a comparable potency to aminoglutethimide, but that it did not inhibit other steroid hydroxylases.

scholarly journals Effects of thia-substituted fatty acids on mitochondrial and peroxisomal β-oxidation. Studies in vivo and in vitro

1990 ◽  
Vol 270 (1) ◽  
pp. 167-173 ◽  
Author(s):  
R Hovik ◽  
H Osmundsen ◽  
R Berge ◽  
A Aarsland ◽  
S Bergseth ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Inhibitory Effects ◽  
Duration Of Treatment ◽  
Acyl Coa Oxidase ◽  
Dose Dependent

1. The effects of 3-, 4- and 5-thia-substituted fatty acids on mitochondrial and peroxisomal β-oxidation have been investigated. When the sulphur atom is in the 4-position, the resulting thia-substituted fatty acid becomes a powerful inhibitor of β-oxidation. 2. This inhibition cannot be explained in terms of simple competitive inhibition, a phenomenon which characterizes the inhibitory effects of 3- and 5-thia-substituted fatty acids. The inhibitory sites for 4-thia-substituted fatty acids are most likely to be the acyl-CoA dehydrogenase in mitochondria and the acyl-CoA oxidase in peroxisomes. 3. The inhibitory effect of 4-thia-substituted fatty acids is expressed both in vitro and in vivo. The effect in vitro is instantaneous, with up to 95% inhibition of palmitoylcarnitine oxidation. The effect in vivo, in contrast, is dose-dependent and increases with duration of treatment. 4. Pretreatment of rats with a 3-thia-substituted fatty acid rendered mitochondrial β-oxidation less sensitive to inhibition by 4-thia-substituted fatty acids.

scholarly journals Inhibitory Effects of Eight Green Tea Catechins on Cytochrome P450 1A2, 2C9, 2D6, and 3A4 Activities

2016 ◽  
Vol 19 (2) ◽  
pp. 188 ◽  
Author(s):  
Takashi Satoh ◽  
Haruka Fujisawa ◽  
Ami Nakamura ◽  
Natsuko Takahashi ◽  
Kazuhiro Watanabe
Keyword(s):  
Cytochrome P450 ◽  
Green Tea ◽  
Competitive Inhibition ◽  
Liver Microsomes ◽  
Inhibitory Effect ◽  
Dietary Habit ◽  
Inhibitory Effects ◽  
Tea Catechins ◽  
Green Tea Catechins ◽  
High Concentrations

PURPOSE: Green tea is a traditional beverage that has been enjoyed by the Japanese to this day. Recently, there has been an increase in the consumption of green tea beverage having high concentrations of catechins, such as (-)-epigallocatechin-3-O-gallate (EGCG). Many people tend to ingest large amounts of catechins through the frequent consumption of green tea beverage, and this dietary habit may lead to unwanted interactions between the catechins in green tea and medicinal drug. METHODS: The inhibitory effects of eight green tea catechins on drug metabolizing enzymes, cytochrome P450 (CYP) 1A2, 2C9, 2D6, and 3A4, were investigated in human liver microsomes. Incubation was initiated by the addition of cocktail probe drugs that served as specific substrates for each CYP, and the resulting metabolites were analyzed by LC-MS. RESULTS: From a comparison of the fifty percent inhibitory concentration (IC50) values of the eight green tea catechins, it was found that non-gallated catechins did not inhibit CYPs, whereas gallated catechins inhibited all CYPs except CYP2D6. Among them, CYP2C9 was most strongly inhibited by (-)-catechin-3-O-gallate (CG) (7.60 µM), and CYP1A2 was most strongly inhibited by EGCG (8.93 µM). Catechin gallate exhibited non-competitive inhibition of CYP2C9, and its Ki value was 9.76 ± 0.47µM. The present study is the first to report the inhibitory effect of CG on CYP2C9. In contrast, EGCG showed competitive inhibition of CYP1A2, and its Ki value was 14.3 ± 0.09 µM. CONCLUSION: Previous reports had predicted that plasma EGCG concentration reached 7.4 µM after ingesting green tea having high concentrations of catechins. That concentration of EGCG is equivalent to one-half to one-third of its Ki value for CYP1A2 and CYP3A4 in this study. The ingestion of beverages containing large amounts of green tea catechins together with drugs that are metabolized by CYP1A2, CYP2C9, and CYP3A4 should be avoided. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

Itanoxone, An Inhibitor Of Cyclo-Oxygenase, Acts Preferentially On Platelet Than On Vascular Enzyme

1981 ◽  
Author(s):  
S Villa ◽  
A DeLhon ◽  
C Palmier ◽  
M Livio ◽  
B Maynardier ◽  
...  
Keyword(s):  
Competitive Inhibition ◽  
Cumulative Effect ◽  
Inhibitory Effect ◽  
Prostaglandin Synthesis ◽  
Measurable Effect ◽  
Inhibitory Effects ◽  
Antithrombotic Drug ◽  
Repeated Doses ◽  
Dose Dependent ◽  
Potential Use

Several attaints have been made to dissociate the inhibitory effects of aspirin on platelet and vascular cells, but no definite results have been obtained. Other drugs, presumably acting on cyclo-oxygenase, are therefore being investigated for their relative inhibitory effect on platelet and vascular prostaglandin synthesis.The present study was performed in male CD-COBS rats. Itanoxone [ (chloro-2' -diphenyl) -4-oxo-4 methylene 2-butyric acid ], a newly developed, hypolipidemic and hypouricemic compound with moderate anti-inflanmatory activity, showed a short lived, dose dependent (20-200 mg/kg, orally) apparently competitive inhibition of platelet MDA stimulated by either thrombin or arachidonic acid. Repeated doses did not result in any cumulative effect. At doses which completely blocked MDA production, itanoxone also inhibited thrombin-stimulated thromboxane B2 production in platelets but had no measurable effect on vascular prostacyclin generation measured both by a bioassay and a radioimmunoassay of its stable derivative 6-Keto-PGF1α . Pretreatment with itanoxone partially prevented therrhibitory effect of aspirin on both platelet and vascular prostaglandin synthesis. This suggests that itanoxone - like aspirin - acts at the level of cyclo-oxygenase but has much greater selectivity on the platelet enzyme.This pharmacological activity is of great theoretical interest for potential use of this compound as an antithrombotic drug.

Chemotactic factor binding by metastatic tumour cells: evidence for a formyl-peptide receptor on a non-myelogenous cell

1985 ◽  
Vol 73 (1) ◽  
pp. 121-134
Author(s):  
W.A. Marasco ◽  
P.A. Ward ◽  
D.E. Feltner ◽  
J. Varani
Keyword(s):  
Binding Sites ◽  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Tumour Cells ◽  
Formyl Peptide Receptor ◽  
Metastatic Tumour ◽  
Binding Studies ◽  
Peptide Receptor ◽  
Formyl Peptide ◽  
Equilibrium Dissociation

Analysis of fMet-Leu-[3H]Phe binding to Walker 256 carcinosarcoma cells demonstrated both saturable and reversible binding, and indicated the presence of a single population of binding sites having an equilibrium dissociation constant: KD = 15.7 +/− 3.3 X 10(−9) M, and with 2425 +/− 204 binding sites per cell. The specificity of the binding site was investigated by competitive inhibition of fMet-Leu-[3H]Phe binding studies using 10 oligoformyl peptides. These results demonstrated an order of peptide reactivity with marked similarity in specificity to the leucocyte binding sites for the formyl-peptides. The most active peptides also had potent agonist activity as determined by their ability to increase the cells' adherence response to nylon-wool fibres. In addition, a competitive antagonist of the formyl-peptide receptor, tert-butoxy-Phe-Leu-Phe-Leu-Phe, completely abolished the adherence response induced by fMet-Leu-Phe, but had no inhibitory effect on the adherence response caused by the tumour-promoting agent, phorbol myristate acetate. These data demonstrate that formyl-peptide receptors may be more common than we have anticipated and may be found on cells not derived from the myeloid series. Furthermore, these studies advance our understanding of stimulus-coupled responses in tumour cells.

scholarly journals Potential Antidiabetic Effects of Extracts from Four Medicinal Plants Used in Burkina Faso by Inhibition of Alpha-Amylase

Diabetology ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 250-258
Author(s):  
Judith N. Semporé ◽  
Mamounata Diao ◽  
Lassina Ouattara ◽  
Paulin Ouoba ◽  
Windmi Kagambega ◽  
...  
Keyword(s):  
Plant Extracts ◽  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Rice Starch ◽  
Inhibitory Effects ◽  
Sclerocarya Birrea ◽  
Dependent Inhibition ◽  
Phytochemical Compounds ◽  
Dose Dependent Inhibition ◽  
Liquid Fractionation

Background: The purpose of this study was to evaluate α-amylase inhibitory effects of hydroethanolic extracts of bark from Daniella oliveri, Sclerocarya birrea, Maranthes polyandra, and Pteleopsis suberosa to fight type-II diabetes. Methods: Compound extractions were performed by hydroethanol maceration followed by liquid-liquid fractionation with solvents. TLC profiling was carried out with different fractions. The inhibitory effects of plant extracts on α-amylase activity were determined using rice starch as a substrate. Results: TLC profiling of different fractions showed different phytochemical compounds. The hydroethanolic plant extracts exhibited dose-dependent inhibition of α-amylase. D. oliveri displayed competitive inhibition, M. polyandra and S. birrea showed uncompetitive inhibition and Pteleopsis suberosa exerted mixed-inhibition. M. polyandra extract exerted the highest inhibitory effect (IC50 = 0.5 mg/mL). Conclusions: The barks of M. polyandra exhibit a remarkable α-amylase inhibitory effect which can be a novel source of antidiabetic molecules.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Effects of Dipyrone on Prostaglandin Production by Human Platelets and Cultured Bovine Aortic Endothelial Cells

1983 ◽  
Vol 49 (02) ◽  
pp. 132-137 ◽  
Author(s):  
A Eldor ◽  
G Polliack ◽  
I Vlodavsky ◽  
M Levy
Keyword(s):  
Endothelial Cells ◽  
Arachidonic Acid ◽  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Ionophore A23187 ◽  
Aortic Endothelial Cells ◽  
Bovine Aortic Endothelial Cells ◽  
Aortic Endothelial

SummaryDipyrone and its metabolites 4-methylaminoantipyrine, 4-aminoantipyrine, 4-acetylaminoantipyrine and 4-formylaminoan- tipyrine inhibited the formation of thromboxane A2 (TXA2) during in vitro platelet aggregation induced by ADP, epinephrine, collagen, ionophore A23187 and arachidonic acid. Inhibition occurred after a short incubation (30–40 sec) and depended on the concentration of the drug or its metabolites and the aggregating agents. The minimal inhibitory concentration of dipyrone needed to completely block aggregation varied between individual donors, and related directly to the inherent capacity of their platelets to synthesize TXA2.Incubation of dipyrone with cultured bovine aortic endothelial cells resulted in a time and dose dependent inhibition of the release of prostacyclin (PGI2) into the culture medium. However, inhibition was abolished when the drug was removed from the culture, or when the cells were stimulated to produce PGI2 with either arachidonic acid or ionophore A23187.These results indicate that dipyrone exerts its inhibitory effect on prostaglandins synthesis by platelets or endothelial cells through a competitive inhibition of the cyclooxygenase system.

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.

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