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Biochimica Et Biophysica Acta.... Jan 2020P-glycoprotein (Pgp) is a biomedically important member of the ABC transporter superfamily that mediates multidrug resistance in various cancer types. Substrate binding...
P-glycoprotein (Pgp) is a biomedically important member of the ABC transporter superfamily that mediates multidrug resistance in various cancer types. Substrate binding and transport in Pgp are modulated by the presence of cholesterol in the membrane. Structural information on cholesterol binding sites and mechanistic details of its redistribution are, however, largely unknown. In this study, a set of 40 independent molecular dynamics (MD) simulations of Pgp embedded in cholesterol-rich lipid bilayers are reported, totaling 8 μs, enabling extensive sampling of cholesterol-protein interactions in Pgp. Clustering analyses of the ensemble of cholesterol molecules (∼5740) sampled around Pgp in these simulations reveal specific and asymmetric cholesterol-binding regions formed by the transmembrane (TM) helices TM1-6 and TM8. Notably, not all the putative cholesterol binding sites identified by MD can be predicted by the primary sequence based cholesterol-recognition amino acid consensus (CRAC) or inverted CRAC (CARC) motifs, an observation that we attribute to inadequacy of these motifs to account for binding sites formed by remote amino acids in the sequence that can still be spatially adjacent to each other. Binding of cholesterol to Pgp occurs more frequently through its rough β-face formed by the two protruding methyl groups, whereas the opposite smooth α-face prefers packing alongside the membrane lipids. One full and two partial cholesterol flipping events between the two leaflets of the bilayer mediated by the surface of Pgp are also captured in these simulations. All flipping events are observed in a region formed by helices TM1, TM2, and TM11, featuring two full and two partial CRAC/CARC motifs, with Tyr49 and Tyr126 identified as key residues interacting with cholesterol during this event. Our study is the first to report direct observation of unconventional cholesterol translocation on the surface of Pgp, providing a secondary transport model for the known flippase activity of ABC exporters of cholesterol. This article is part of a Special Issue entitled: Molecular biophysics of membranes and membrane proteins.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Amino Acid Sequence; Binding Sites; Biological Transport; Cholesterol; Lipid Bilayers; Molecular Dynamics Simulation; Tyrosine
PubMed: 31676371
DOI: 10.1016/j.bbamem.2019.183090 -
Molecules (Basel, Switzerland) Feb 2018Multidrug resistance (MDR) is a phenotype of cancer cells with reduced sensitivity to a wide range of unrelated drugs. P-glycoprotein (P-gp)-a drug efflux pump (ABCB1... (Review)
Review
Multidrug resistance (MDR) is a phenotype of cancer cells with reduced sensitivity to a wide range of unrelated drugs. P-glycoprotein (P-gp)-a drug efflux pump (ABCB1 member of the ABC transporter gene family)-is frequently observed to be a molecular cause of MDR. The drug-efflux activity of P-gp is considered as the underlying mechanism of drug resistance against P-gp substrates and results in failure of cancer chemotherapy. Several pathological impulses such as shortages of oxygen and glucose supply, alterations of calcium storage mechanisms and/or processes of protein -glycosylation in the endoplasmic reticulum (ER) leads to ER stress (ERS), characterized by elevation of unfolded protein cell content and activation of the unfolded protein response (UPR). UPR is responsible for modification of protein folding pathways, removal of misfolded proteins by ER associated protein degradation (ERAD) and inhibition of proteosynthesis. However, sustained ERS may result in UPR-mediated cell death. Neoplastic cells could escape from the death pathway induced by ERS by switching UPR into pro survival mechanisms instead of apoptosis. Here, we aimed to present state of the art information about consequences of P-gp expression on mechanisms associated with ERS development and regulation of the ERAD system, particularly focused on advances in ERS-associated therapy of drug resistant malignancies.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Animals; Drug Resistance, Multiple; Endoplasmic Reticulum; Endoplasmic Reticulum Stress; Endoplasmic Reticulum-Associated Degradation; Glycosylation; Humans; Neoplasms; Signal Transduction; Unfolded Protein Response
PubMed: 29415493
DOI: 10.3390/molecules23020337 -
Journal of Veterinary Science Sep 2021Hepatocellular carcinoma is the most common primary hepatic malignancy in humans and dogs. Several differentially expressed molecules have been studied and reported in...
BACKGROUND
Hepatocellular carcinoma is the most common primary hepatic malignancy in humans and dogs. Several differentially expressed molecules have been studied and reported in human hepatocellular carcinoma and non-neoplastic liver lesions. However, studies on the features of canine hepatocellular carcinoma are limited, especially related to the differential characteristics of neoplastic and non-neoplastic lesions.
OBJECTIVES
The study's objective was 1) to examine and evaluate the expression of arginase-1, P-glycoprotein, and cytokeratin 19 in canine liver tissues and 2) to investigate the differential features of hepatocellular carcinomas, liver tissue with non-neoplastic lesions, and paracancerous liver tissues in dogs.
METHODS
The expression levels of three markers underwent immunohistochemical analysis in 40 non-neoplastic liver tissues, 32 hepatocellular carcinoma tissues, and 11 paracancerous liver tissues. Scoring of each marker was performed semi-quantitatively.
RESULTS
Arginase-1 and P-glycoprotein were significantly downregulated in hepatocellular carcinoma, compared with hepatic tissues with non-neoplastic diseases ( < 0.001). Expression levels of arginase-1 and P-glycoprotein were also significantly lower in hepatocellular carcinoma than in paracancerous liver tissues (arginase-1, 0.0195; P-glycoprotein, 0.047). Few cytokeratin 19-positive hepatocytes were detected and only in one hepatocellular carcinoma and one cirrhotic liver sample.
CONCLUSIONS
The results of this study suggest that downregulation of arginase-1 and P-glycoprotein is a feature of canine hepatocellular carcinoma; thus, those markers are potential candidates for use in differentiating hepatocellular carcinomas from non-neoplastic liver lesions in dogs.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Animals; Arginase; Carcinoma, Hepatocellular; Dog Diseases; Dogs; Down-Regulation
PubMed: 34423599
DOI: 10.4142/jvs.2021.22.e61 -
International Journal of Molecular... Feb 2023Acute myeloid leukemia (AML) remains an insidious neoplasm due to the percentage of patients who develop resistance to both classic chemotherapy and emerging drugs.... (Review)
Review
Acute myeloid leukemia (AML) remains an insidious neoplasm due to the percentage of patients who develop resistance to both classic chemotherapy and emerging drugs. Multidrug resistance (MDR) is a complex process determined by multiple mechanisms, and it is often caused by the overexpression of efflux pumps, the most important of which is P-glycoprotein (P-gp). This mini-review aims to examine the advantages of using natural substances as P-gp inhibitors, focusing on four molecules: phytol, curcumin, lupeol, and heptacosane, and their mechanism of action in AML.
Topics: Humans; ATP Binding Cassette Transporter, Subfamily B, Member 1; Curcumin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Leukemia, Myeloid, Acute
PubMed: 36835550
DOI: 10.3390/ijms24044140 -
Journal of Veterinary Internal Medicine Jan 2015Drug-drug interactions can cause unanticipated patient morbidity and mortality. The consequences of drug-drug interactions can be especially severe when anticancer drugs... (Review)
Review
Drug-drug interactions can cause unanticipated patient morbidity and mortality. The consequences of drug-drug interactions can be especially severe when anticancer drugs are involved because of their narrow therapeutic index. Veterinary clinicians have traditionally been taught that drug-drug interactions result from alterations in drug metabolism, renal excretion or protein binding. More recently, drug-drug interactions resulting from inhibition of P-glycoprotein-mediated drug transport have been identified in both human and veterinary patients. Many drugs commonly used in veterinary patients are capable of inhibiting P-glycoprotein function and thereby causing an interaction that results in severe chemotherapeutic drug toxicity. The intent of this review is to describe the mechanism and clinical implications of drug-drug interactions involving P-glycoprotein and anticancer drugs. Equipped with this information, veterinarians can prevent serious drug-drug interactions by selecting alternate drugs or adjusting the dose of interacting drugs.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Animals; Antineoplastic Agents; Drug Interactions; Humans; Neoplasms
PubMed: 25619511
DOI: 10.1111/jvim.12525 -
Journal of Medicinal Chemistry Jun 2018Multidrug resistance (MDR) is a major cause of failure in cancer chemotherapy. P-glycoprotein (P-gp), a promiscuous drug efflux pump, has been extensively studied for... (Review)
Review
Multidrug resistance (MDR) is a major cause of failure in cancer chemotherapy. P-glycoprotein (P-gp), a promiscuous drug efflux pump, has been extensively studied for its association with MDR due to overexpression in cancer cells. Several P-gp inhibitors or modulators have been investigated in clinical trials in hope of circumventing MDR, with only limited success. Alternative strategies are actively pursued, such as the modification of existing drugs, development of new drugs, or combination of novel drug delivery agents to evade P-gp-dependent efflux. Despite the importance and numerous studies, these efforts have mostly been undertaken without a priori knowledge of how drugs interact with P-gp at the molecular level. This review highlights and discusses progress toward and challenges impeding drug development for inhibiting or evading P-gp in the context of our improved understanding of the structural basis and mechanism of P-gp-mediated MDR.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Antineoplastic Agents; Drug Resistance, Neoplasm; Humans; Protein Conformation
PubMed: 29251920
DOI: 10.1021/acs.jmedchem.7b01457 -
British Journal of Pharmacology Nov 2021P-glycoprotein (P-gp) exhibits a broad substrate specificity and affects pharmacokinetics, especially intestinal absorption. However, prediction, in vivo, of...
BACKGROUND AND PURPOSE
P-glycoprotein (P-gp) exhibits a broad substrate specificity and affects pharmacokinetics, especially intestinal absorption. However, prediction, in vivo, of P-gp-mediated drug-drug interaction (DDI) and non-linear absorption at the preclinical stage, is challenging. Here we evaluate the use of human MDR1 mouse artificial chromosome (hMDR1-MAC) mice carrying human P-gp and lacking their own murine P-gp to quantitatively predict human P-gp-mediated DDI and non-linear absorption.
EXPERIMENTAL APPROACH
The P-gp substrates (aliskiren, betrixaban, celiprolol, digoxin, fexofenadine and talinolol) were administered orally to wild-type, Mdr1a/b-knockout (KO) and hMDR1-MAC mice, and their plasma concentrations were measured. We calculated the ratio of area under the curve (AUCR) in mice (AUC /AUC or AUC /AUC ) estimated as attributable to complete P-gp inhibition and the human AUCR with and without P-gp inhibitor administration. The correlations of AUCR with AUCR and AUCR were investigated. For aliskiren, betrixaban and celiprolol, the K and V values for P-gp in hMDR1-MAC mice and humans were optimized from different dosing studies using GastroPlus. The correlations of K and V for P-gp between human and hMDR1-MAC mice were investigated.
KEY RESULTS
A better correlation between AUCR and AUCR (R = 0.88) was observed. Moreover, good relationships of K (R = 1.00) and V (R = 0.98) for P-gp between humans and hMDR1-MAC mice were observed.
CONCLUSIONS AND IMPLICATIONS
These results suggest that P-gp-mediated DDI and non-linear absorption can be predicted using hMDR1-MAC mice. These mice are a useful in vivo tool for quantitatively predicting P-gp-mediated disposition in drug discovery and development.
Topics: ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1; Animals; Drug Interactions; Intestinal Absorption; Mice; Pharmaceutical Preparations
PubMed: 34232502
DOI: 10.1111/bph.15612 -
Expert Opinion on Drug Metabolism &... Aug 2018P-glycoprotein (P-gp)/ABCB1 and breast cancer resistance protein (BCRP)/ABCG2 are highly expressed in the placenta and fetus throughout gestation and can modulate... (Review)
Review
P-glycoprotein (P-gp)/ABCB1 and breast cancer resistance protein (BCRP)/ABCG2 are highly expressed in the placenta and fetus throughout gestation and can modulate exposure and toxicity of drugs and xenobiotics to the vulnerable fetus during the sensitive times of growth and development. We aim to provide an update on current knowledge on placental and fetal expressions of the two transporters in different species, and to provide insight on interpreting transporter expression and fetal exposure relative to the concept of fraction of drug transported. Areas covered: Comprehensive literature review through PubMed (primarily from July 2010 to February 2018) on P-gp and BCRP expression and function in the placenta and fetus of primarily human, mouse, rat, and guinea pig. Expert opinion: While there are many commonalities in the expression and function of P-gp and BCRP in the placenta and fetal tissues across species, there are distinct differences in expression levels and temporal changes. Further studies are needed to quantify protein abundance of these transporters and functionally assess their activities at various gestational stages. Combining the knowledge of interspecies differences and the concept of fraction of drug transported, we may better predict the magnitude of impact these transporters have on fetal drug exposure.
Topics: ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1; ATP Binding Cassette Transporter, Subfamily G, Member 2; Animals; Biological Transport; Female; Fetus; Gene Expression Regulation; Guinea Pigs; Humans; Mice; Neoplasm Proteins; Pharmaceutical Preparations; Placenta; Pregnancy; Rats; Species Specificity
PubMed: 30010462
DOI: 10.1080/17425255.2018.1499726 -
Molecular Oncology Jan 2023Chemotherapy resistance is a persistent clinical problem in relapsed high-risk neuroblastomas. We tested a panel of 15 drugs for sensitization of neuroblastoma cells to...
Chemotherapy resistance is a persistent clinical problem in relapsed high-risk neuroblastomas. We tested a panel of 15 drugs for sensitization of neuroblastoma cells to the conventional chemotherapeutic vincristine, identifying tariquidar, an inhibitor of the transmembrane pump P-glycoprotein (P-gp/ABCB1), and the ERBB family inhibitor afatinib as the top resistance breakers. Both compounds were efficient in sensitizing neuroblastoma cells to vincristine in trypan blue exclusion assays and in inducing apoptotic cell death. The evaluation of ERBB signaling revealed no functional inhibition, that is, dephosphorylation of the downstream pathways upon afatinib treatment but direct off-target interference with P-gp function. Depletion of ABCB1, but not ERRB4, sensitized cells to vincristine treatment. P-gp inhibition substantially broke vincristine resistance in vitro and in vivo (zebrafish embryo xenograft). The analysis of gene expression datasets of more than 50 different neuroblastoma cell lines (primary and relapsed) and more than 160 neuroblastoma patient samples from the pediatric precision medicine platform INFORM (Individualized Therapy For Relapsed Malignancies in Childhood) confirmed a pivotal role of P-gp specifically in neuroblastoma resistance at relapse, while the ERBB family appears to play a minor part.
Topics: Animals; Humans; ATP Binding Cassette Transporter, Subfamily B, Member 1; Vincristine; Afatinib; Zebrafish; Drug Resistance, Neoplasm; Neuroblastoma; ATP Binding Cassette Transporter, Subfamily B; ErbB Receptors; Recurrence; Cell Line, Tumor
PubMed: 36181342
DOI: 10.1002/1878-0261.13318 -
International Journal of Molecular... Nov 2022ABC transporters play a critical role in both drug bioavailability and toxicity, and with the discovery of the P-glycoprotein (P-gp), this became even more evident, as... (Review)
Review
ABC transporters play a critical role in both drug bioavailability and toxicity, and with the discovery of the P-glycoprotein (P-gp), this became even more evident, as it plays an important role in preventing intracellular accumulation of toxic compounds. Over the past 30 years, intensive studies have been conducted to find new therapeutic molecules to reverse the phenomenon of multidrug resistance (MDR) ), that research has found is often associated with overexpression of P-gp, the most extensively studied drug efflux transporter; in MDR, therapeutic drugs are prevented from reaching their targets due to active efflux from the cell. The development of P-gp inhibitors is recognized as a good way to reverse this type of MDR, which has been the subject of extensive studies over the past few decades. Despite the progress made, no effective P-gp inhibitors to reverse multidrug resistance are yet on the market, mainly because of their toxic effects. Computational studies can accelerate this process, and in silico models such as QSAR models that predict the activity of compounds associated with P-gp (or analogous transporters) are of great value in the early stages of drug development, along with molecular modelling methods, which provide a way to explain how these molecules interact with the ABC transporter. This review highlights recent advances in computational P-gp research, spanning the last five years to 2022. Particular attention is given to the use of machine-learning approaches, drug-transporter interactions, and recent discoveries of potential P-gp inhibitors that could act as modulators of multidrug resistance.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Drug Resistance, Neoplasm; Drug Resistance, Multiple; ATP-Binding Cassette Transporters; Antineoplastic Agents
PubMed: 36499131
DOI: 10.3390/ijms232314804