scholarly journals The antidepressant drug vilazodone is an allosteric inhibitor of the serotonin transporter

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Per Plenge ◽  
Dongxue Yang ◽  
Kristine Salomon ◽  
Louise Laursen ◽  
Iris E. Kalenderoglou ◽  
...  
Keyword(s):  
Serotonin Transporter ◽  
Selective Serotonin Reuptake Inhibitors ◽  
Competitive Inhibition ◽  
Common Mental Disorder ◽  
Antidepressant Drug ◽  
Binding Pocket ◽  
Competitive Inhibitor ◽  
Limited Information ◽  
Allosteric Site ◽  
Binding Characteristics

AbstractDepression is a common mental disorder. The standard medical treatment is the selective serotonin reuptake inhibitors (SSRIs). All characterized SSRIs are competitive inhibitors of the serotonin transporter (SERT). A non-competitive inhibitor may produce a more favorable therapeutic profile. Vilazodone is an antidepressant with limited information on its molecular interactions with SERT. Here we use molecular pharmacology and cryo-EM structural elucidation to characterize vilazodone binding to SERT. We find that it exhibits non-competitive inhibition of serotonin uptake and impedes dissociation of [3H]imipramine at low nanomolar concentrations. Our SERT structure with bound imipramine and vilazodone reveals a unique binding pocket for vilazodone, expanding the boundaries of the extracellular vestibule. Characterization of the binding site is substantiated with molecular dynamics simulations and systematic mutagenesis of interacting residues resulting in decreased vilazodone binding to the allosteric site. Our findings underline the versatility of SERT allosteric ligands and describe the unique binding characteristics of vilazodone.

An Amperometric Cytochrome P450-2D6 Biosensor System for the Detection of the Selective Serotonin Reuptake Inhibitors (SSRIs) Paroxetine and Fluvoxamine

2016 ◽  
Vol 44 ◽  
pp. 208-228 ◽  
Author(s):  
Rachel Fanelwa Ajayi ◽  
Ezo Nxusani ◽  
Samantha F. Douman ◽  
Anovuyo Jonnas ◽  
Priscilla Gloria Lorraine Baker ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Serotonin Reuptake ◽  
Selective Serotonin Reuptake Inhibitors ◽  
Competitive Inhibition ◽  
Plasma Concentrations ◽  
Antidepressant Drug ◽  
Selective Serotonin ◽  
Cytochrome P450 2D6 ◽  
Biosensor System ◽  
P450 2D6

Paroxetine is the second most prescribed selective serotonin reuptake inhibitor (SSRI) antidepressant drug, characterized by extensive inter-individual variation in steady state plasma concentrations resulting in drug toxicity amongst patinets. A nanopolymeric biosensor for studying the biotransformation of paroxetine is presented. The bioelectrode system consists of cytochrome P450-2D6 enzyme encapsulated in nanotubular poly (8-anilino-1-napthalene sulphonic acid) electrochemically deposited on gold. The biosensing procedure involved the determination of the extent of modulation of fluvoxamine responses to the P450-2D6 enzyme electrode after incubation in paroxetine standard solutions. Paroxetine inhibited the activity of cytochrome P450-2D6 (CYP2D6) resulting in a decrease in the fluvoxamine signal of the biosensor. The biosensor gave a linear analytical response for the paroxetine in the interval 0.005 and 0.05 μM, with a detection limit of 0.002 μM and a response time of 30 s. Electrochemical Michaelis–Menten kinetics of the reversible competitive inhibition of the fluvoxamine responses of the biosensor by 0, 0.05 and 0.1 μM paroxetine gave apparent Michaelis–Menten constant (KMapp) values of 1.00 μM, 1.11 μM and 1.25 μM, respectively. The corresponding value for the maximum response, IMAX was 0.02 A. The dissociation constant, KI, value evaluated from Dixon analysis of the paroxetine modulation data was estimated to be-0.02 μM while Cornish-Bowden analysis confirmed the competitive inhibitory characteristics of the enzyme.

scholarly journals A Functional Interaction Between the SARS-CoV-2 Spike Protein and the Human α7 Nicotinic Receptor

2021 ◽  
Author(s):  
Juan Facundo Chrestia ◽  
Ana Sofia Oliveira ◽  
Adrian J. Mulholland ◽  
Timothy Gallagher ◽  
Isabel Bermúdez ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Competitive Inhibition ◽  
Binding Pocket ◽  
Competitive Inhibitor ◽  
Host Cells ◽  
Spike Protein ◽  
Potential Contribution ◽  
Functional Interaction ◽  
S Protein ◽  
Α7 Nachr

Abstract Coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Infection relies on the binding of the viral spike protein (S) to angiotensin-converting enzyme 2 in host cells. The S protein has been suggested to interact with nicotinic acetylcholine receptors (nAChRs), and a potential contribution of nAChRs to COVID-19 pathophysiology has been proposed. α7 nAChR is an interesting candidate target since it is present in neuronal and non-neuronal cells, including immune cells, and has anti-inflammatory actions. We here identified a novel direct functional interaction between the α7 nAChR and the Y674-R685 S region. The S fragment exerts a dual effect, acting as a low-efficacy agonist and a non-competitive inhibitor. It activates the α7 nAChR, in line with our previous molecular dynamics simulations showing favorable binding of this accessible region of the S protein to the nAChR agonist binding pocket. However, activation requires the presence of positive allosteric modulators that enhance channel opening probability, indicating very low activation efficacy. The S fragment also induces an overlapped non-competitive inhibition, which may be the predominant effect on α7 responses. This study provides unequivocal evidence supporting a functional α7-S protein interaction, which opens doors for exploring the involvement of nAChRs in COVID-19 pathophysiology.

Kinetic Aspects of the Interaction of Blood Clotting Enzymes

1968 ◽  
Vol 19 (03/04) ◽  
pp. 364-367 ◽  
Author(s):  
H. C Hemker ◽  
P. W Hemker
Keyword(s):  
Enzyme Kinetics ◽  
Blood Clotting ◽  
Competitive Inhibition ◽  
Competitive Inhibitor ◽  
Kinetics Of

SummaryThe enzyme kinetics of competitive inhibition under conditions prevailing in clotting tests are developed and a method is given to measure relative amounts of a competitive inhibitor by means of the t — D plot.

Structural Insights into Azole-based Inhibitors of Heme Oxygenase-1: Development of Selective Compounds for Therapeutic Applications

2019 ◽  
Vol 25 (42) ◽  
pp. 5803-5821 ◽  
Author(s):  
Mona N. Rahman ◽  
Dragic Vukomanovic ◽  
Jason Z. Vlahakis ◽  
Walter A. Szarek ◽  
Kanji Nakatsu ◽  
...  
Keyword(s):  
Heme Oxygenase ◽  
Competitive Inhibition ◽  
Cytochromes P450 ◽  
Structural Similarity ◽  
Binding Pocket ◽  
Initial Study ◽  
Structural Basis ◽  
Heme Oxygenase 1 ◽  
Design Strategies ◽  
Inhibitor Binding

The development of isozyme-selective heme oxygenase (HO) inhibitors promises powerful pharmacological tools to elucidate the regulatory characteristics of the HO system. It is already known that HO has cytoprotective properties with a role in several disease states; thus, it is an enticing therapeutic target. Historically, the metalloporphyrins have been used as competitive HO inhibitors based on their structural similarity to the substrate, heme. However, heme’s important role in several other proteins (e.g. cytochromes P450, nitric oxide synthase), results in non-selectivity being an unfortunate side effect. Reports that azalanstat and other non-porphyrin molecules inhibited HO led to a multi-faceted effort over a decade ago to develop novel compounds as potent, selective inhibitors of HO. The result was the creation of the first generation of non-porphyrin based, non-competitive inhibitors with selectivity for HO, including a subset with isozyme selectivity for HO-1. Using X-ray crystallography, the structures of several complexes of HO-1 with novel inhibitors have been elucidated and provided insightful information regarding the salient features required for inhibitor binding. This included the structural basis for non-competitive inhibition, flexibility and adaptability of the inhibitor binding pocket, and multiple, potential interaction subsites, all of which can be exploited in future drug-design strategies. Notably, HO-1 inhibitors are of particular interest for the treatment of hyperbilirubinemia and certain types of cancer. Key features based on this initial study have already been used by others to discover additional potential HO-1 inhibitors. Moreover, studies have begun to use selected compounds and determine their effects in some disease models.

scholarly journals EPID-36. ANTIDEPRESSANT DRUG USE IN GLIOBLASTOMA PATIENTS: AN EPIDEMIOLOGICAL VIEW

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii86-ii86
Author(s):  
Dorothee Gramatzki ◽  
James Rogers ◽  
Marian Neidert ◽  
Caroline Hertler ◽  
Emilie Le Rhun ◽  
...  
Keyword(s):  
Overall Survival ◽  
Multivariate Analysis ◽  
Drug Use ◽  
Survival Data ◽  
Selective Serotonin Reuptake Inhibitors ◽  
Methylation Status ◽  
Antidepressant Drug ◽  
Antidepressant Drugs ◽  
Population Level ◽  
Disease Course

Abstract PURPOSE Antidepressant drugs have shown anti-tumor activity in preclinical glioblastoma studies. Antidepressant drug use, as well as its association with survival, in glioblastoma patients has not been well characterized on a population level. METHODS Patient characteristics, including the frequency of antidepressant drug use, were assessed in a glioblastoma cohort diagnosed in a 10-year time-frame between 2005 and 2014 in the Canton of Zurich, Switzerland. Cox proportional hazards regression models were applied for multivariate analysis. Kaplan-Meier survival curves were used to estimate overall survival data and the log-rank test was performed for comparisons. RESULTS Four hundred four patients with isocitrate dehydrogenase (IDH) wildtype glioblastoma were included in this study. Sixty-five patients (16.1%) took antidepressant drugs at some point during the disease course. Patients were most commonly prescribed selective serotonin reuptake inhibitors at any time (N=46, 70.8%). Nineteen patients (29.2%) were on antidepressant drugs at the time of their tumor diagnosis. No differences were observed in overall survival between those patients who had taken antidepressants at some point in their disease course and those who had not (p=0.356). These data were confirmed in a multivariate analysis including age, Karnofsky performance status, gender, extent of resection, O6-methylguanine DNA methyltransferase (MGMT) promoter methylation status, and first-line treatment as cofounders (p=0.315). Also, there was no association of use of drugs modulating voltage-dependent potassium channels (citalopram; escitalopram) with survival (p=0.639). CONCLUSIONS This signal-seeking study does not support the hypothesis that antidepressants have antitumor efficacy in glioblastoma on a population level.

scholarly journals Advances in Nano-Enabled Platforms for the Treatment of Depression

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1431
Author(s):  
Fadzai P. Mutingwende ◽  
Pierre P. D. Kondiah ◽  
Philemon Ubanako ◽  
Thashree Marimuthu ◽  
Yahya E. Choonara
Keyword(s):  
Drug Delivery ◽  
Drug Toxicity ◽  
Common Mental Disorder ◽  
Antidepressant Drug ◽  
Chemical Properties ◽  
Controlled Drug Release ◽  
Routes Of Administration ◽  
Antidepressant Efficacy ◽  
High Doses ◽  
The Brain

Nanotechnology has aided in the advancement of drug delivery for the treatment of several neurological disorders including depression. Depression is a relatively common mental disorder which is characterized by a severe imbalance of neurotransmitters. Several current therapeutic regimens against depression display drawbacks which include low bioavailability, delayed therapeutic outcome, undesirable side effects and drug toxicity due to high doses. The blood–brain barrier limits the entry of the drugs into the brain matrix, resulting in low bioavailability and tissue damage due to drug accumulation. Due to their size and physico-chemical properties, nanotechnological drug delivery systems present a promising strategy to enhance the delivery of nanomedicines into the brain matrix, thereby improving bioavailability and limiting toxicity. Furthermore, ligand-complexed nanocarriers can improve drug specificity and antidepressant efficacy and reduce drug toxicity. Biopolymers and nanocarriers can also be employed to enhance controlled drug release and reduce the hepatic first-pass effect, hence reducing the dosing frequency. This manuscript reviews recent advances in different biopolymers, such as polysaccharides and other nanocarriers, for targeted antidepressant drug delivery to the brain. It probes nano-based strategies that can be employed to enhance the therapeutic efficacy of antidepressants through the oral, intranasal, and parenteral routes of administration.

scholarly journals Structural basis for subtype-specific inhibition of the P2X7 receptor

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Akira Karasawa ◽  
Toshimitsu Kawate
Keyword(s):  
P2x7 Receptor ◽  
Hydrophobic Interactions ◽  
Binding Pocket ◽  
Drug Binding ◽  
Structural Basis ◽  
Atp Binding ◽  
Allosteric Site ◽  
Channel Opening ◽  
A Site ◽  
Novel Drug

The P2X7 receptor is a non-selective cation channel activated by extracellular adenosine triphosphate (ATP). Chronic activation of P2X7 underlies many health problems such as pathologic pain, yet we lack effective antagonists due to poorly understood mechanisms of inhibition. Here we present crystal structures of a mammalian P2X7 receptor complexed with five structurally-unrelated antagonists. Unexpectedly, these drugs all bind to an allosteric site distinct from the ATP-binding pocket in a groove formed between two neighboring subunits. This novel drug-binding pocket accommodates a diversity of small molecules mainly through hydrophobic interactions. Functional assays propose that these compounds allosterically prevent narrowing of the drug-binding pocket and the turret-like architecture during channel opening, which is consistent with a site of action distal to the ATP-binding pocket. These novel mechanistic insights will facilitate the development of P2X7-specific drugs for treating human diseases.

scholarly journals Mitochondrial adenosine triphosphatase from human placenta--inhibition by free magnesium ions of ITP hydrolysis.

1994 ◽  
Vol 41 (1) ◽  
pp. 39-44 ◽  
Author(s):  
Z Aleksandrowicz
Keyword(s):  
Competitive Inhibition ◽  
Competitive Inhibitor ◽  
Hill Coefficient ◽  
Negative Cooperativity ◽  
Magnesium Ions ◽  
Beef Liver ◽  
Bicarbonate Ions ◽  
The Hill ◽  
Kinetics Of ◽  
Free Magnesium

The effects of Mg2+ and bicarbonate on the kinetics of ITP hydrolysis by soluble ATPase (F1) from human placental mitochondria were studied. Increasing amounts of Mg2+ at fixed ITP concentration, caused a marked activation of F1 followed by inhibition at higher Mg2+ concentration. The appropriate substrate for the mitochondrial F1 seems to be the MgITP complex as almost no ITP was hydrolysed in the absence of magnesium. Mg2+ behaved as a competitive inhibitor towards the MgITP complex. In this respect the human placental enzyme differ from that from other sources such as yeast, beef liver or rat liver. The linearity of the plot presenting competitive inhibition by free Mg2+ of MgITP hydrolysis (in the presence of activating bicarbonate anion) suggests that both Mg2+ and MgITP bind to the same catalytic site (Km(MgITP) = 0.46 mM, Ki(Mg) = 4 mM). When bicarbonate was absent in the ITPase assay, placental F1 exhibited apparent negative cooperativity in the presence of 5 mM Mg2+, just as it did with MgATP as a substrate under similar conditions. Bicarbonate ions eliminated the negative cooperativity with respect to ITP (as the Hill coefficient of 0.46 was brought to approx. 1), and thus limited inhibition by free Mg2+. The results presented suggest that the concentration of free magnesium ions may be an important regulatory factor of the human placental F1 activity.

scholarly journals Structure–function analysis of water-soluble inhibitors of the catalytic domain of exotoxin A from Pseudomonas aeruginosa

2005 ◽  
Vol 385 (3) ◽  
pp. 667-675 ◽  
Author(s):  
Susan P. YATES ◽  
Patricia L. TAYLOR ◽  
René JØRGENSEN ◽  
Dana FERRARIS ◽  
Jie ZHANG ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Diphtheria Toxin ◽  
Catalytic Domain ◽  
Competitive Inhibition ◽  
Function Analysis ◽  
Binding Pocket ◽  
Ring Structure ◽  
Water Soluble ◽  
Exotoxin A ◽  
Ic50 Values

The mono-ADPRT (mono-ADP-ribosyltransferase), Pseudomonas aeruginosa ETA (exotoxin A), catalyses the transfer of ADP-ribose from NAD+ to its protein substrate. A series of water-soluble compounds that structurally mimic the nicotinamide moiety of NAD+ was investigated for their inhibition of the catalytic domain of ETA. The importance of an amide locked into a hetero-ring structure and a core hetero-ring system that is planar was a trend evident by the IC50 values. Also, the weaker inhibitors have core ring structures that are less planar and thus more flexible. One of the most potent inhibitors, PJ34, was further characterized and shown to exhibit competitive inhibition with an inhibition constant Ki of 140 nM. We also report the crystal structure of the catalytic domain of ETA in complex with PJ34, the first example of a mono-ADPRT in complex with an inhibitor. The 2.1 Å (1 Å=0.1 nm) resolution structure revealed that PJ34 is bound within the nicotinamide-binding pocket and forms stabilizing hydrogen bonds with the main chain of Gly-441 and to the side-chain oxygen of Gln-485, a member of a proposed catalytic loop. Structural comparison of this inhibitor complex with diphtheria toxin (a mono-ADPRT) and with PARPs [poly(ADP-ribose) polymerases] shows similarity of the catalytic residues; however, a loop similar to that found in ETA is present in diphtheria toxin but not in PARP. The present study provides insight into the important features required for inhibitors that mimic NAD+ and their binding to the mono-ADPRT family of toxins.

scholarly journals Surface Epitope Coverage Affects Binding Characteristics of Bisphenol-A Functionalized Nanoparticles in a Competitive Inhibition Assay

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Yang Lu ◽  
Joshua Richard Peterson ◽  
Erwann Luais ◽  
John Justin Gooding ◽  
Nanju Alice Lee
Keyword(s):  
Bisphenol A ◽  
Binding Sites ◽  
Competitive Inhibition ◽  
Limit Of Detection ◽  
Molar Concentration ◽  
Inhibition Assay ◽  
Binding Characteristics ◽  
Sensor Performance ◽  
Reliable Detection ◽  
Minimum Number

The biomolecule interface is a key element in immunosensor fabrication, which can greatly influence the sensor performance. This paper explores the effects of surface epitope coverage of small molecule functionalized nanoparticle on the apparent affinity (avidity) of antibody in a competitive inhibition assay using bisphenol-A (BPA) as a model target. An unconventional two-antibody competitive inhibition ELISA (ci-ELISA) using thiolated BPA modified gold nanoparticles (cysBPAv-AuNP) as a competing reagent was devised for this study. It was shown that the antibody complexation with cysBPAv-AuNPs required a minimum number of surface epitopes on the nanoparticle to form a sufficiently strong interaction and reliable detection. The binding of cysBPAv-AuNP to anti-BPA antibodies, for limited antibody binding sites, was enhanced by a greater number of epitope-modified nanoparticles (cysBPAv-AuNP) as well as with higher epitope coverage. Increasing the molar concentration of epitope present in an assay enhanced the binding between anti-BPA antibodies and cysBPAv-AuNP. This implies that, to increase the limit of detection of a competitive inhibition assay, a reduced molar concentration of epitope should be applied. This could be achieved by either lowering the epitope coverage on each cysBPAv-AuNP or the assay molar concentration of cysBPAv-AuNP or both of these factors.

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