scholarly journals Computational Pharmacogenetics of P-Glycoprotein Mediated Antiepileptic Drug Resistance

2016 ◽  
Author(s):  
Ashok Palaniappan ◽  
Sindhu Varghese
Keyword(s):  
Drug Resistance ◽  
Treatment Failure ◽  
Conformational Changes ◽  
Point Mutations ◽  
Active Role ◽  
Docking Studies ◽  
Drug Binding ◽  
Experimental Investigations ◽  
Drug Bioavailability ◽  
P Glycoprotein

AbstractThe treatment of epilepsy using antiepileptogenic drugs is complicated by drug re-sistance, resulting in treatment failure in more than one-third of cases. Human P-glycoprotein (hPGP; MDR1) is a known epileptogenic mediator. Given that experimental investigations have suggested a role for pharmacogenetics in this treatment failure, it would be of interest to study hPGP polymorphisms that might contribute to the emergence of drug resistance. Changes in protein functional activity could result from point mutations as well as altered abundance. Bioinformatics approaches were used to assess and rank the functional impact of 20 missense MDR1 polymorphisms and the top five were selected. The structures of the wildtype and mutant hPGP were modelled based on the mouse PGP structure. Docking studies of the wildtype and mutant hPGP with four standard anti-epileptic drugs were carried out. Our results revealed that the drug binding site with respect to the wildtype protein was uniform. However the mutant hPGP proteins displayed a repertoire of binding sites with stronger binding affinities towards the drug. Our studies indicated that specific polymorphisms in MDR1 could drive conformational changes of PGP structure, facilitating altered contacts with drug-substrates and resulting in drug extrusion. This suggests that MDR1 polymorphisms could play an active role in modifying drug bioavailability, leading to pharmacoresistance in antiepileptic chemotherapy.

scholarly journals Computational Pharmacogenetics of P-Glycoprotein Mediated Antiepileptic Drug Resistance

2018 ◽  
Vol 11 (1) ◽  
pp. 197-207 ◽  
Author(s):  
Sindhu Varghese ◽  
Ashok Palaniappan
Keyword(s):  
Drug Resistance ◽  
Treatment Failure ◽  
Conformational Changes ◽  
Binding Sites ◽  
Docking Studies ◽  
Drug Binding ◽  
Experimental Investigations ◽  
Binding Affinities ◽  
Drug Binding Site ◽  
P Glycoprotein

Background:The treatment of epilepsy using antiepileptogenic drugs is complicated by drug resistance, resulting in treatment failure in more than one-third of cases. Human P-glycoprotein (hPGP;MDR1) is a known epileptogenic mediator.Methods:Given that experimental investigations have suggested a role for pharmacogenetics in this treatment failure, it would be of interest to study hPGP polymorphisms that might contribute to the emergence of drug resistance. Changes in protein functional activity could result from mutations as well as altered abundance. Bioinformatics approaches were used to assess and rank the functional impact of 20 missenseMDR1polymorphisms and the top five were selected. The structures of the wildtype and variant hPGP were modelled based on the mouse PGP structure. Docking studies of the wildtype and variant hPGP with four standard anti-epileptic drugs were carried out.Results:Our results revealed that the drug binding site with respect to the wildtype protein was uniform. However, the variant hPGP proteins displayed a repertoire of binding sites with stronger binding affinities towards the drug.Conclusion:Our studies indicated that specific polymorphisms inMDR1could drive conformational changes of PGP structure, facilitating altered contacts with drug-substrates and thus modifying their bioavailability. This suggests thatMDR1polymorphisms could actively contribute to the emergence of pharmaco-resistance in antiepileptic therapy.

scholarly journals Plasmodium falciparum DHODH inhibitor complexes reveal flexible binding site

2014 ◽  
Vol 70 (a1) ◽  
pp. C1793-C1793
Author(s):  
Paul Rowland ◽  
Onkar SINGH ◽  
Leila Ross ◽  
Francisco Gamo ◽  
Maria Lafuente-Monasterio ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Binding Site ◽  
Crystal Structures ◽  
Point Mutations ◽  
Crystal Form ◽  
Drug Binding ◽  
Binding Modes ◽  
Resistance Mutations ◽  
Drug Binding Site

Malaria is a preventable and treatable disease, yet annually there are still hundreds of thousands of malaria-related deaths. The disease is caused by infection with mosquito-borne Plasmodium parasites. With hundreds of millions of cases each year there is a very high potential for drug resistance and this has compromised many existing therapies. One target under investigation is the enzyme dihydroorotate dehydrogenase (DHODH) which catalyses the rate-limiting step of pyrimidine biosynthesis and is an essential enzyme in the malaria parasite. There are currently several Plasmodium-selective DHODH inhibitors under development. To investigate the potential for drug resistance against DHODH inhibitors in vitro resistance selections were carried out using known inhibitors from different structural classes [1]. These studies identified point mutations in the drug binding site which lead to reduced sensitivity to the inhibitors, and in some cases increased sensitivity to a different inhibitor, suggesting a novel combination therapy approach to combat resistance. To help understand the significance of the inhibitor binding site mutations we determined the crystal structures of P. falciparum DHODH in complex with the inhibitors Genz-669178, IDI-6253 and IDI-6273. Co-crystallisation experiments led to a new crystal form in each case. Here we describe the crystal structures, the binding modes of the inhibitors and the great flexibility of the binding site, which is able to adjust to accommodate different inhibitor series. The structural role of the resistance mutations is also discussed.

scholarly journals Dissection of drug-binding-induced conformational changes in P-glycoprotein

1998 ◽  
Vol 255 (2) ◽  
pp. 383-390 ◽  
Author(s):  
Guichun Wang ◽  
Roxana Pincheira ◽  
Jian-Ting Zhang
Keyword(s):  
Conformational Changes ◽  
Drug Binding ◽  
P Glycoprotein

scholarly journals Unravelling the complex drug–drug interactions of the cardiovascular drugs, verapamil and digoxin, with P-glycoprotein

2016 ◽  
Vol 36 (2) ◽  
Author(s):  
Kaitlyn V. Ledwitch ◽  
Robert W. Barnes ◽  
Arthur G. Roberts
Keyword(s):  
Drug Interactions ◽  
Conformational Changes ◽  
Atp Hydrolysis ◽  
Mechanistic Model ◽  
Cardiovascular Drugs ◽  
Drug Binding ◽  
P Glycoprotein ◽  
Complex Drug

P-glycoprotein (Pgp) plays a major role in promoting drug–drug interactions (DDIs) with verapamil and digoxin. In the present study, we present a comprehensive molecular and mechanistic model of Pgp DDIs encompassing drug binding, ATP hydrolysis, transport and conformational changes.

scholarly journals A complex suite of loci and elements in eukaryotic type II topoisomerases determine selective sensitivity to distinct poisoning agents

2019 ◽  
Vol 47 (15) ◽  
pp. 8163-8179 ◽  
Author(s):  
Tim R Blower ◽  
Afif Bandak ◽  
Amy S Y Lee ◽  
Caroline A Austin ◽  
John L Nitiss ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Amino Acid ◽  
Drug Targets ◽  
Topoisomerase Ii ◽  
Point Mutations ◽  
Amino Acid Position ◽  
Drug Binding ◽  
Type Ii ◽  
Resistance Mutations ◽  
Selective Sensitivity

AbstractType II topoisomerases catalyze essential DNA transactions and are proven drug targets. Drug discrimination by prokaryotic and eukaryotic topoisomerases is vital to therapeutic utility, but is poorly understood. We developed a next-generation sequencing (NGS) approach to identify drug-resistance mutations in eukaryotic topoisomerases. We show that alterations conferring resistance to poisons of human and yeast topoisomerase II derive from a rich mutational ‘landscape’ of amino acid substitutions broadly distributed throughout the entire enzyme. Both general and discriminatory drug-resistant behaviors are found to arise from different point mutations found at the same amino acid position and to occur far outside known drug-binding sites. Studies of selected resistant enzymes confirm the NGS data and further show that the anti-cancer quinolone vosaroxin acts solely as an intercalating poison, and that the antibacterial ciprofloxacin can poison yeast topoisomerase II. The innate drug-sensitivity of the DNA binding and cleavage region of human and yeast topoisomerases (particularly hTOP2β) is additionally revealed to be significantly regulated by the enzymes’ adenosine triphosphatase regions. Collectively, these studies highlight the utility of using NGS-based methods to rapidly map drug resistance landscapes and reveal that the nucleotide turnover elements of type II topoisomerases impact drug specificity.

scholarly journals Active Participation of Membrane Lipids in Inhibition of Multidrug Transporter P-Glycoprotein

2020 ◽  
Author(s):  
Karan Kapoor ◽  
Shashank Pant ◽  
Emad Tajkhorshid
Keyword(s):  
Conformational Changes ◽  
Bound States ◽  
Transmembrane Domain ◽  
Membrane Lipids ◽  
Conformational Dynamics ◽  
Drug Binding ◽  
Multi Drug Resistance ◽  
Third Generation ◽  
P Glycoprotein ◽  
Lipid Environment

AbstractP-glycoprotein (Pgp) is a major efflux pump in humans, overexpressed in a variety of cancers and associated with the development of multi-drug resistance. Allosteric modulation induced by binding of various ligands (e.g., transport substrates, inhibitors, and ATP) has been bio-chemically shown to directly influence the function of Pgp. However, the molecular details of such effects are not well established. In particular, the role and involvement of the surrounding lipid environment on ligand-induced modulation of the conformational dynamics of the transporter have not been investigated at any level. Here, we employ all-atom molecular dynamics (MD) simulations to study the conformational landscape of Pgp in the presence of a high-affinity, third-generation inhibitor, tariquidar, in comparison to the nucleotide-free (APO) and the ATP-bound states, in order to shed light on and to characterize how the inhibitor blocks the function of the transporter. Simulations in a multi-component lipid bilayer show a dynamic equilibrium between open and closed inward-facing (IF) conformations in the APO-state, with binding of ATP shifting the equilibrium towards conformations feasible for ATP hydrolysis and subsequent completion of the transport cycle. In the presence of the inhibitor bound to the drug-binding pocket in the transmembrane domain (TMD), the transporter samples more open IF conformations, and the nucleotide binding domains (NBDs) are observed to become highly dynamic. Interestingly, and reproduced in multiple independent simulations, the inhibitor is observed to recruit lipid molecules into the Pgp lumen through the two proposed drug-entry portals, where the lipid head groups from the lower leaflet translocate inside the TMD, while the lipids tails remain extended into the bulk lipid environment. These “wedge-lipid” molecules likely enhance the inhibitor-induced conformational changes in the TMD leading to the differential modulation of coupling pathways observed with the NBDs downstream. We suggest a novel inhibitory mechanism for tariquidar, and for related third-generation Pgp inhibitors, where lipids are seen to enhance the inhibitory role in the catalytic cycle of membrane transporters.

scholarly journals Structural insight into substrate and inhibitor discrimination by human P-glycoprotein

Science ◽  
2019 ◽  
Vol 363 (6428) ◽  
pp. 753-756 ◽  
Author(s):  
Amer Alam ◽  
Julia Kowal ◽  
Eugenia Broude ◽  
Igor Roninson ◽  
Kaspar P. Locher
Keyword(s):  
Single Molecule ◽  
Conformational Changes ◽  
Binding Pocket ◽  
Drug Binding ◽  
Therapeutic Drug ◽  
Binding Domains ◽  
Drug Binding Site ◽  
Cryo Electron Microscopy ◽  
P Glycoprotein ◽  
Insight Into

ABCB1, also known as P-glycoprotein, actively extrudes xenobiotic compounds across the plasma membrane of diverse cells, which contributes to cellular drug resistance and interferes with therapeutic drug delivery. We determined the 3.5-angstrom cryo–electron microscopy structure of substrate-bound human ABCB1 reconstituted in lipidic nanodiscs, revealing a single molecule of the chemotherapeutic compound paclitaxel (Taxol) bound in a central, occluded pocket. A second structure of inhibited, human-mouse chimeric ABCB1 revealed two molecules of zosuquidar occupying the same drug-binding pocket. Minor structural differences between substrate- and inhibitor-bound ABCB1 sites are amplified toward the nucleotide-binding domains (NBDs), revealing how the plasticity of the drug-binding site controls the dynamics of the adenosine triphosphate–hydrolyzing NBDs. Ordered cholesterol and phospholipid molecules suggest how the membrane modulates the conformational changes associated with drug binding and transport.

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