scholarly journals Synthetic hydrophobic peptides are substrates for P-glycoprotein and stimulate drug transport

1996 ◽  
Vol 320 (2) ◽  
pp. 421-428 ◽  
Author(s):  
Frances J. SHAROM ◽  
Xiaohong YU ◽  
Giulio DiDIODATO ◽  
Joseph W. K. CHU
Keyword(s):  
Drug Transport ◽  
Efflux Pump ◽  
Membrane Vesicles ◽  
Multidrug Resistant ◽  
Drug Uptake ◽  
Peptide Transport ◽  
Active Efflux ◽  
Hydrophobic Peptides ◽  
P Glycoprotein ◽  
Drug Studies

P-Glycoprotein functions as an ATP-driven active efflux pump for many natural products and chemotherapeutic drugs. Hydrophobic peptides have been shown to block drug uptake by P-glycoprotein, indicating that they might be transport substrates. The present study examines the interaction of the synthetic peptide series NAc-LnY-amide with the multidrug transporter. Several peptides in this series caused up to 3.5-fold enhancement of colchicine accumulation in membrane vesicles from multidrug resistant (MDR) cells, which suggests the existence of novel interactions between the binding sites for peptides and drug. Peptides did not stimulate vinblastine transport, which was inhibited as expected for competing substrates. These peptides displayed modest stimulatory effects on the ATPase activity of P-glycoprotein. None blocked azidopine photoaffinity labelling, showing that they probably occupy a binding site separate from that for the drug. Studies with 125I-labelled NAc-LLY-amide showed that it was transported by P-glycoprotein in both membrane vesicles and reconstituted proteoliposomes. Uptake of the peptide was rapid, saturable, osmotically sensitive and occurred against a concentration gradient. The enhancing effect of NAc-LLY-amide on colchicine transport was reciprocated, i.e. colchicine greatly increased the transport of labelled peptide by P-glycoprotein. Peptide transport was also modulated, both positively and negatively, by other MDR spectrum drugs. It is concluded that linear hydrophobic peptides are indeed transported by P-glycoprotein, and some have interactions with drug substrates that result in mutual stimulation of transport.

scholarly journals Linear and cyclic peptides as substrates and modulators of P-glycoprotein: peptide binding and effects on drug transport and accumulation

1998 ◽  
Vol 333 (3) ◽  
pp. 621-630 ◽  
Author(s):  
Frances J. SHAROM ◽  
Peihua LU ◽  
Ronghua LIU ◽  
Xiaohong YU
Keyword(s):  
Cyclic Peptides ◽  
Drug Transport ◽  
Membrane Vesicles ◽  
Drug Uptake ◽  
Multidrug Transporter ◽  
Chemotherapeutic Drugs ◽  
Plasma Membrane Vesicles ◽  
Hydrophobic Peptides ◽  
P Glycoprotein ◽  
Highly Correlated

One cause of multidrug resistance (MDR) in human cancers is the overexpression of the P-glycoprotein multidrug transporter, a member of the ABC superfamily of membrane proteins. Natural products and chemotherapeutic drugs are pumped out of the cell by P-glycoprotein in an ATP-dependent fashion. There is growing evidence that many hydrophobic peptides are also P-glycoprotein substrates. With the use of a fluorescence-quenching assay, we have shown that some linear and cyclic hydrophobic peptides interact with P-glycoprotein, whereas others do not. The measured values of the quenching constant, Kq, for interaction of peptides with P-glycoprotein ranged from 200 nM for cyclosporine A to 138 µM for the tripeptide N-acetyl-leucyl-leucyl-norleucinal. Peptides that interacted with P-glycoprotein in the fluorescence assay also blocked colchicine transport into plasma membrane vesicles from MDR cells. The values of Dm, the peptide concentration causing 50% inhibition of drug uptake, were highly correlated with the values of Kq, over three orders of magnitude. The P-glycoprotein ATPase stimulation/inhibition profile of the peptides was not helpful in making a quantitative assessment of the ability of a peptide to interact with P-glycoprotein or to block drug transport. Some hydrophobic peptides were able to restore accumulation in MDR cells of the chemotherapeutic drug daunorubicin and the fluorescent dye rhodamine 123 to the levels observed in the drug-sensitive parent. Peptides that interacted with P-glycoprotein also displayed a relatively low overall toxicity to intact MDR cells, and inhibited drug transport at concentrations below the toxic range. Hydrophobic peptides should be given serious consideration for development as clinical chemosensitizing agents.

scholarly journals Conformational changes of P-glycoprotein by nucleotide binding

1997 ◽  
Vol 328 (3) ◽  
pp. 897-904 ◽  
Author(s):  
Guichun WANG ◽  
Roxana PINCHEIRA ◽  
Mei ZHANG ◽  
Jian-Ting ZHANG
Keyword(s):  
Conformational Changes ◽  
Drug Transport ◽  
Atp Hydrolysis ◽  
Human Cancer ◽  
Limited Proteolysis ◽  
Membrane Vesicles ◽  
Multidrug Resistant ◽  
Conformational States ◽  
Human Cancer Cells ◽  
P Glycoprotein

P-glycoprotein (Pgp) is a membrane protein that transports chemotherapeutic drugs, causing multidrug resistance in human cancer cells. Pgp is a member of the ATP-binding cassette superfamily and functions as a transport ATPase. It has been suggested that the conformation of Pgp changes in the catalytic cycle. In this study, we tested this hypothesis by using limited proteolysis as a tool to detect different conformational states trapped by binding of nucleotide ligands and inhibitors. Pgp has high basal ATPase activity; that is, ATP hydrolysis by Pgp is not rigidly associated with drug transport. This activity provides a convenient method for studying the conformational change of Pgp induced by nucleotide ligands, in the absence of drug substrates which may generate complications due to their own binding. Inside-out membrane vesicles containing human Pgp were isolated from multidrug-resistant SKOV/VLB cells and treated with trypsin in the absence or presence of MgATP, Mg-adenosine 5ʹ-[β,γ-imido]triphosphate (Mg-p[NH]ppA) and MgADP. Changes in the proteolysis profile of Pgp owing to binding of nucleotides were used to indicate the conformational changes in Pgp. We found that generation of tryptic fragments, including the loop linking transmembrane (TM) regions TM8 and TM9 of Pgp, were stimulated by the binding of Mg-p[NH]ppA, MgATP and MgADP, indicating that the Pgp conformation was changed by the binding of these nucleotides. The effects of nucleotides on Pgp conformation are directly associated with the binding and/or hydrolysis of these ligands. Four conformational states of Pgp were stabilized under different conditions with various ligands and inhibitors. We propose that cycling through these four states couples the Pgp-mediated MgATP hydrolysis to drug transport.

scholarly journals The Fluorescent Probe Bodipy-FL-Verapamil Is a Substrate for Both P-glycoprotein and Multidrug Resistance-related Protein (MRP)-1

2002 ◽  
Vol 50 (5) ◽  
pp. 731-734 ◽  
Author(s):  
Enrico Crivellato ◽  
Luigi Candussio ◽  
Anna M. Rosati ◽  
Fiora Bartoli-Klugmann ◽  
Franco Mallardi ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Drug Transport ◽  
Mrna Level ◽  
Fluorescent Microscopy ◽  
Flow Cytometric Analysis ◽  
Cell Types ◽  
Multidrug Resistant ◽  
Related Protein ◽  
P Glycoprotein ◽  
Multidrug Resistance Related Protein

Several fluorescent probes have been used in functional studies to analyze drug transport in multidrug-resistant cells by fluorescent microscopy. Because many of these molecules have some drawbacks, such as toxicity, nonspecific background, or accumulation in mitochondria, new fluorescent compounds have been proposed as more useful tools. Among these substances, Bodipy-FL-Verapamil, a fluorescent conjugate of the drug efflux blocker verapamil, has been used to study P-glycoprotein activity in different cell types. In this study we tested by fluorescent microscopy the accumulation of Bodipy-FL- Verapamil in cell lines that overexpress either P-glycoprotein (P-gp) or multidrug resistance-related protein 1 (MRP1). Expression of P-gp and MRP1 was evaluated at the mRNA level by RT-PCR technique and at the protein level by flow cytometric analysis using C219 and MRP-m6 monoclonal antibodies. Results indicate that Bodipy-FL-Verapamil is actually a substrate for both proteins. As a consequence, any conclusion about P-gp activity obtained by the use of Bodipy-FL-Verapamil as fluorescent tracer should be interpreted with caution.

scholarly journals P-glycoprotein expression in human plasma cell myeloma: correlation with prior chemotherapy

Blood ◽  
1993 ◽  
Vol 81 (2) ◽  
pp. 490-495 ◽  
Author(s):  
TM Grogan ◽  
CM Spier ◽  
SE Salmon ◽  
M Matzner ◽  
J Rybski ◽  
...  
Keyword(s):  
Drug Exposure ◽  
Plasma Cells ◽  
Efflux Pump ◽  
Multidrug Resistant ◽  
Significant Variable ◽  
Prior Chemotherapy ◽  
Prior Therapy ◽  
P Glycoprotein ◽  
Immunocytochemical Assay ◽  
Low Incidence

Abstract Multidrug-resistant (MDR) myeloma patients failing chemotherapy may express P-glycoprotein (PGP), which serves as an efflux pump protecting the neoplastic cells. Unknown is whether PGP expression might relate to prior cytotoxic drug exposure. To address this question, we studied 106 consecutive bone marrow samples from 104 myeloma patients with samples studied either before or after therapy and at the time of relapse. We performed an established immunocytochemical assay of PGP using an MDR-1- specific monoclonal antibody and correlated PGP status with prior chemotherapy dosage. Myeloma patients with no prior therapy had a low incidence of PGP expression (6%, 3/47), whereas those receiving chemotherapy had a significantly higher incidence (43%, 21/49) (P < .0001). A substantially higher incidence of PGP expression (50%, 83%, respectively) occurred when the total vincristine dose exceeded 20 mg and when doxorubicin exceeded 340 mg. In the 11 patients who received both high vincristine and doxorubicin dosages (> 20 mg, > 340 mg total dose) there was 100% incidence of PGP expression in the tumor cells. These data provided the basis for a predictive mathematical model from which dose-related PGP expression normograms were generated. Time with myeloma for PGP-negative patients (mean 33 months) had overlapping confidence limits with PGP-positive patients (mean 42 months), suggesting that disease duration was not a significant variable. PGP expression did not correlate with other clinical factors or immunophenotypic factors. Our findings indicate a strong correlation between PGP expression in myeloma and past chemotherapy in myeloma, in particular, related to prior exposure to the natural product agents vincristine and doxorubicin. Additionally, the proportion of PGP- positive plasma cells was significantly higher in the doxorubicin- treated patients than the nondoxorubicin-treated patients (87.7% v 65.17%; P = .013). Combined high vincristine and doxorubicin total dosage appear highly predictive of PGP expression.

scholarly journals Reversing the direction of drug transport mediated by the human multidrug transporter P-glycoprotein

2020 ◽  
Vol 117 (47) ◽  
pp. 29609-29617
Author(s):  
Andaleeb Sajid ◽  
Sabrina Lusvarghi ◽  
Megumi Murakami ◽  
Eduardo E. Chufan ◽  
Biebele Abel ◽  
...  
Keyword(s):  
Drug Transport ◽  
Atp Hydrolysis ◽  
Binding Pocket ◽  
Drug Binding ◽  
Drug Uptake ◽  
Cancer Drug ◽  
Binding Domains ◽  
Cancer Drug Resistance ◽  
P Glycoprotein ◽  
Cell Transforming

P-glycoprotein (P-gp), also known as ABCB1, is a cell membrane transporter that mediates the efflux of chemically dissimilar amphipathic drugs and confers resistance to chemotherapy in most cancers. Homologous transmembrane helices (TMHs) 6 and 12 of human P-gp connect the transmembrane domains with its nucleotide-binding domains, and several residues in these TMHs contribute to the drug-binding pocket. To investigate the role of these helices in the transport function of P-gp, we substituted a group of 14 conserved residues (seven in both TMHs 6 and 12) with alanine and generated a mutant termed 14A. Although the 14A mutant lost the ability to pump most of the substrates tested out of cancer cells, surprisingly, it acquired a new function. It was able to import four substrates, including rhodamine 123 (Rh123) and the taxol derivative flutax-1. Similar to the efflux function of wild-type P-gp, we found that uptake by the 14A mutant is ATP hydrolysis-, substrate concentration-, and time-dependent. Consistent with the uptake function, the mutant P-gp also hypersensitizes HeLa cells to Rh123 by 2- to 2.5-fold. Further mutagenesis identified residues from both TMHs 6 and 12 that synergistically form a switch in the central region of the two helices that governs whether a given substrate is pumped out of or into the cell. Transforming P-gp or an ABC drug exporter from an efflux transporter into a drug uptake pump would constitute a paradigm shift in efforts to overcome cancer drug resistance.

Identification of the synthetic surfactant nonylphenol ethoxylate: a P-glycoprotein substrate in human urine

1998 ◽  
Vol 274 (6) ◽  
pp. F1127-F1139 ◽  
Author(s):  
Jeffrey H. M. Charuk ◽  
Arthur A. Grey ◽  
Reinhart A. F. Reithmeier
Keyword(s):  
Cyclosporin A ◽  
Drug Transport ◽  
Mdck Cells ◽  
Chinese Hamster ◽  
Multidrug Resistant ◽  
The Body ◽  
Transepithelial Transport ◽  
Synthetic Surfactant ◽  
Nonylphenol Ethoxylate ◽  
P Glycoprotein

P-glycoprotein (Mdr1p) is an ATP-dependent drug efflux pump that is overexpressed in multidrug-resistant cells and some cancers. Mdr1p is also expressed in normal tissues like the kidney, where it can mediate transepithelial drug transport. A human urinary compound that reverses multidrug resistance and blocks [3H]azidopine photolabeling of P-glycoprotein was purified to homogeneity and identified by 1H-NMR and mass spectrometry as the synthetic surfactant nonylphenol ethoxylate (NPE). Multidrug-resistant Chinese hamster ovary (CHO) C5 cells accumulated less [3H]NPE than parental drug-sensitive Aux-B1 cells, and Mdr1p substrates, verapamil and cyclosporin A, increased this surfactant’s accumulation in C5 cells. NPE blocked the net transepithelial transport (basolateral to apical) of [3H]cyclosporin A in epithelia formed by Madin-Darby canine kidney (MDCK) cells. Net transepithelial transport (basal to apical) of [3H]NPE was demonstrated in MDCK cells and was inhibited by cyclosporin A. These findings show NPE is a Mdr1p substrate excreted into urine by kidney P-glycoprotein. NPE is a widely used surfactant and a known hormone disrupter that is readily absorbed orally or topically. The current findings indicate the function of kidney Mdr1p may be to eliminate exogenous compounds from the body.

Modeling of P-glycoprotein-involved epithelial drug transport in MDCK cells

1999 ◽  
Vol 277 (1) ◽  
pp. F84-F96 ◽  
Author(s):  
Shinya Ito ◽  
Cindy Woodland ◽  
Balázs Sarkadi ◽  
Guido Hockmann ◽  
Scott E. Walker ◽  
...  
Keyword(s):  
Drug Transport ◽  
Diffusion Processes ◽  
Efflux Pump ◽  
Mdck Cells ◽  
Basolateral Membrane ◽  
Drug Efflux ◽  
Drug Transfer ◽  
P Glycoprotein ◽  
Drug Efflux Pump ◽  
Apical Membranes

P-glycoprotein (P-gp) on the apical membranes of epithelial cells is known as a drug efflux pump. However, unclear is its integral quantitative role in the overall epithelial drug transfer, which also involves distinct diffusion processes in parallel and sequence. We used a simple three-compartment model to obtain kinetic parameters of each drug transfer mechanism, which can quantitatively describe the transport time courses of P-gp substrates, digoxin and vinblastine, across P-gp-expressing MDCK cell monolayers grown on permeable filters. Our results show that the model, which assumes a functionally single drug efflux pump in the apical membrane with diffusion across two membranes and intercellular junctions, is the least complex model with which to quantitatively reproduce the characteristics of the data. Interestingly, the model predicts that the MDCK apical membranes are less diffusion permeable than the basolateral membrane for both drugs and that the distribution volume of vinblastine is 10-fold higher than that of digoxin. Additional experiments verified these model predictions. The modeling approach is feasible to quantitatively describe overall kinetic picture of epithelial drug transport. Further model refinement is necessary to incorporate other modes of drug transport such as transcytosis. Also, whether P-gp solely accounts for the pump function in this model awaits more studies.

Drug transport to the brain: key roles for the efflux pump P-glycoprotein in the blood–brain barrier

2002 ◽  
Vol 38 (6) ◽  
pp. 339-348 ◽  
Author(s):  
Michel Demeule ◽  
Anthony Régina ◽  
Julie Jodoin ◽  
Alain Laplante ◽  
Claude Dagenais ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Drug Transport ◽  
Efflux Pump ◽  
Brain Barrier ◽  
P Glycoprotein ◽  
Blood Brain ◽  
The Brain

scholarly journals In Situ Biochemical Demonstration That P-Glycoprotein Is a Drug Efflux Pump with Broad Specificity

2000 ◽  
Vol 148 (5) ◽  
pp. 863-870 ◽  
Author(s):  
Yu Chen ◽  
Sanford M. Simon
Keyword(s):  
Fluorescent Protein ◽  
Efflux Pump ◽  
Multiple Drug Resistance ◽  
Living Cells ◽  
Drug Accumulation ◽  
Multiple Drug ◽  
Gfp Expression ◽  
Active Efflux ◽  
P Glycoprotein ◽  
Wide Range

While P-glycoprotein (Pgp) is the most studied protein involved in resistance to anti-cancer drugs, its mechanism of action is still under debate. Studies of Pgp have used cell lines selected with chemotherapeutics which may have developed many mechanisms of resistance. To eliminate the confounding effects of drug selection on understanding the action of Pgp, we studied cells transiently transfected with a Pgp-green fluorescent protein (GFP) fusion protein. This method generated a mixed population of unselected cells with a wide range of Pgp-GFP expression levels and allowed simultaneous measurements of Pgp level and drug accumulation in living cells. The results showed that Pgp-GFP expression was inversely related to the accumulation of chemotherapeutic drugs. The reduction in drug concentration was reversed by agents that block multiple drug resistance (MDR) and by the UIC2 anti-Pgp antibody. Quantitative analysis revealed an inverse linear relationship between the fluorescence of Pgp-GFP and MDR dyes. This suggests that Pgp levels alone limit drug accumulation by active efflux; cooperativity between enzyme, substrate, or inhibitor molecules is not required. Additionally, Pgp-GFP expression did not change cellular pH. Our study demonstrates the value of using GFP fusion proteins for quantitative biochemistry in living cells.

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