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Tran NNB, Bui ATA, Jaramillo-Martinez V, Weber J, Zhang Q, Urbatsch IL. Lipid environment determines the drug-stimulated ATPase activity of P-glycoprotein. Front Mol Biosci 2023; 10:1141081. [PMID: 36911528 PMCID: PMC9995911 DOI: 10.3389/fmolb.2023.1141081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 02/06/2023] [Indexed: 02/25/2023] Open
Abstract
P-glycoprotein (Pgp) is a multidrug transporter that uses the energy from ATP binding and hydrolysis to export from cells a wide variety of hydrophobic compounds including anticancer drugs, and mediates the bioavailability and pharmacokinetics of many drugs. Lipids and cholesterol have been shown to modulate the substrate-stimulated ATPase activity of purified Pgp in detergent solution and the substrate transport activity after reconstitution into proteoliposomes. While lipid extracts from E. coli, liver or brain tissues generally support well Pgp's functionality, their ill-defined composition and high UV absorbance make them less suitable for optical biophysical assays. On the other hand, studies with defined synthetic lipids, usually the bilayer-forming phosphatidylcholine with or without cholesterol, are often plagued by low ATPase activity and low binding affinity of Pgp for drugs. Drawing from the lipid composition of mammalian plasma membranes, we here investigate how different head groups modulate the verapamil-stimulated ATPase activity of purified Pgp in detergent-lipid micelles and compare them with components of E. coli lipids. Our general approach was to assay modulation of verapamil-stimulation of ATPase activity by artificial lipid mixtures starting with the bilayer-forming palmitoyloyl-phosphatidylcholine (POPC) and -phosphatidylethanolamine (POPE). We show that POPC/POPE supplemented with sphingomyelin (SM), cardiolipin, or phosphatidic acid enhanced the verapamil-stimulated activity (Vmax) and decreased the concentration required for half-maximal activity (EC50). Cholesterol (Chol) and more so its soluble hemisuccinate derivative cholesteryl hemisuccinate substantially decreased EC50, perhaps by supporting the functional integrity of the drug binding sites. High concentrations of CHS (>15%) resulted in a significantly increased basal activity which could be due to binding of CHS to the drug binding site as transport substrate or as activator, maybe acting cooperatively with verapamil. Lastly, Pgp reconstituted into liposomes or nanodiscs displayed higher basal activity and sustained high levels of verapamil stimulated activity. The findings establish a stable source of artificial lipid mixtures containing either SM and cholesterol or CHS that restore Pgp functionality with activities and affinities similar to those in the natural plasma membrane environment and will pave the way for future functional and biophysical studies.
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Affiliation(s)
- Nghi N. B. Tran
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - A. T. A. Bui
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Valeria Jaramillo-Martinez
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Joachim Weber
- Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, United States
| | - Qinghai Zhang
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, United States
| | - Ina L. Urbatsch
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States
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2
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Interaction of a Homologous Series of Amphiphiles with P-glycoprotein in a Membrane Environment-Contributions of Polar and Non-Polar Interactions. Pharmaceutics 2023; 15:pharmaceutics15010174. [PMID: 36678803 PMCID: PMC9862096 DOI: 10.3390/pharmaceutics15010174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/06/2022] [Accepted: 12/26/2022] [Indexed: 01/05/2023] Open
Abstract
The transport of drugs by efflux transporters in biomembranes limits their bioavailability and is a major determinant of drug resistance development by cancer cells and pathogens. A large number of chemically dissimilar drugs are transported, and despite extensive studies, the molecular determinants of substrate specificity are still not well understood. In this work, we explore the role of polar and non-polar interactions on the interaction of a homologous series of fluorescent amphiphiles with the efflux transporter P-glycoprotein. The interaction of the amphiphiles with P-glycoprotein is evaluated through effects on ATPase activity, efficiency in inhibition of [125I]-IAAP binding, and partition to the whole native membranes containing the transporter. The results were complemented with partition to model membranes with a representative lipid composition, and details on the interactions established were obtained from MD simulations. We show that when the total concentration of amphiphile is considered, the binding parameters obtained are apparent and do not reflect the affinity for P-gp. A new formalism is proposed that includes sequestration of the amphiphiles in the lipid bilayer and the possible binding of several molecules in P-gp's substrate-binding pocket. The intrinsic binding affinity thus obtained is essentially independent of amphiphile hydrophobicity, highlighting the importance of polar interactions. An increase in the lipophilicity and amphiphilicity led to a more efficient association with the lipid bilayer, which maintains the non-polar groups of the amphiphiles in the bilayer, while the polar groups interact with P-gp's binding pocket. The presence of several amphiphiles in this orientation is proposed as a mechanism for inhibition of P-pg function.
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3
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Structural insights into the catalytic cycle of a bacterial multidrug ABC efflux pump. J Mol Biol 2022; 434:167541. [DOI: 10.1016/j.jmb.2022.167541] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/02/2022] [Accepted: 03/09/2022] [Indexed: 12/19/2022]
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4
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Yang Z, Muccio DD, Melo N, Atigadda VR, Renfrow MB. Stability of the Retinoid X Receptor-α Homodimer in the Presence and Absence of Rexinoid and Coactivator Peptide. Biochemistry 2021; 60:1165-1177. [PMID: 33792309 PMCID: PMC9949482 DOI: 10.1021/acs.biochem.0c00865] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Differential scanning calorimetry and differential scanning fluorimetry were used to measure the thermal stability of human retinoid X receptor-α ligand binding domain (RXRα LBD) homodimer in the absence or presence of rexinoid and coactivator peptide, GRIP-1. The apo-RXRα LBD homodimer displayed a single thermal unfolding transition with a Tm of 58.7 °C and an unfolding enthalpy (ΔH) of 673 kJ/mol (12.5 J/g), much lower than average value (35 J/g) of small globular proteins. Using a heat capacity change (ΔCp) of 15 kJ/(mol K) determined by measurements at different pH values, the free energy of unfolding (ΔG) of the native state was 33 kJ/mol at 37 °C. Rexinoid binding to the apo-homodimer increased Tm by 5 to 9 °C and increased the ΔG of the native homodimer by 12 to 20 kJ/mol at 37 °C, consistent with the nanomolar dissociation constant (Kd) of the rexinoids. GRIP-1 binding to holo-homodimers containing rexinoid resulted in additional increases in ΔG of 14 kJ/mol, a value that was the same for all three rexinoids. Binding of rexinoid and GRIP-1 resulted in a combined 50% increase in unfolding enthalpy, consistent with reduced structural fluidity and more compact folding observed in other published structural studies. The complexes of UAB110 and UAB111 are each more stable than the UAB30 complex by 8 kJ/mol due to enhanced hydrophobic interactions in the binding pocket because of their larger end groups. This increase in thermodynamic stability positively correlates with their improved RXR activation potency. Thermodynamic measurements are thus valuable in predicting agonist potency.
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Affiliation(s)
- Zhengrong Yang
- Department of Biochemistry & Molecular Genetics, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Donald D. Muccio
- Department of Biochemistry & Molecular Genetics, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Nathalia Melo
- Department of Biochemistry & Molecular Genetics, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Venkatram R. Atigadda
- Department of Dermatology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Matthew B. Renfrow
- Department of Biochemistry & Molecular Genetics, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
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5
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Kang P, Xie C, Fall O, Randrianalisoa J, Qin Z. Computational Investigation of Protein Photoinactivation by Molecular Hyperthermia. J Biomech Eng 2021; 143:031004. [PMID: 33156335 PMCID: PMC7871998 DOI: 10.1115/1.4049017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 10/08/2020] [Indexed: 12/30/2022]
Abstract
To precisely control protein activity in a living system is a challenging yet long-pursued objective in biomedical sciences. Recently, we have developed a new approach named molecular hyperthermia (MH) to photoinactivate protein activity of interest without genetic modification. MH utilizes nanosecond laser pulse to create nanoscale heating around plasmonic nanoparticles to inactivate adjacent protein in live cells. Here we use a numerical model to study important parameters and conditions for MH to efficiently inactivate proteins in nanoscale. To quantify the protein inactivation process, the impact zone is defined as the range where proteins are inactivated by the nanoparticle localized heating. Factors that reduce the MH impact zone include the laser pulse duration, temperature-dependent thermal conductivity (versus constant properties), and nonspherical nanoparticle geometry. In contrast, the impact zone is insensitive to temperature-dependent material density and specific heat, as well as thermal interface resistance based on reported data in the literature. The low thermal conductivity of cytoplasm increases the impact zone. Different proteins with various Arrhenius kinetic parameters have significantly different impact zones. This study provides guidelines to design the protein inactivation process by MH.
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Affiliation(s)
- Peiyuan Kang
- Department of Mechanical Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080
| | - Chen Xie
- Department of Mechanical Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080
| | - Oumar Fall
- Department of Mechanical Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080;Ecole nationale Supérieure d'Ingénieur de Reims (ESIReims), University of Reims Champagne-Ardenne, 3 Esplanade Roland Garros, Reims 51100, France
| | - Jaona Randrianalisoa
- Institut de Thermique, Mécanique, Matériaux (ITheMM), EA 7548, Université de Reims Champagne-Ardenne, Campus du Moulin de la Housse, F-51687, Reims, France
| | - Zhenpeng Qin
- Department of Mechanical Engineering, Department of Bioengineering, Center for Advanced Pain Studies, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080;Department of Surgery, University of Texas at Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390
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6
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Lusvarghi S, Durell SR, Ambudkar SV. Does the ATP-bound EQ mutant reflect the pre- or post-ATP hydrolysis state in the catalytic cycle of human P-glycoprotein (ABCB1)? FEBS Lett 2021; 595:750-762. [PMID: 33547668 DOI: 10.1002/1873-3468.14054] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 01/14/2021] [Accepted: 01/28/2021] [Indexed: 12/15/2022]
Abstract
P-glycoprotein (P-gp, ABCB1) is an ABC transporter associated with the development of multidrug resistance to chemotherapy. During its catalytic cycle, P-gp undergoes significant conformational changes. Recently, atomic structures of some of these conformations have been resolved using cryo-electron microscopy. The ATP hydrolysis-defective mutant of the catalytic glutamate residue of the Walker B motif (E556Q/E1201Q) has been used to determine the structure of the ATP-bound inward-closed conformation of P-gp. Here, we show that this mutant does not appear to undergo the same steps as wild-type P-gp. We discuss conformational differences in the EQ mutant that may lead to a better understanding of the catalytic cycle of P-gp and propose that additional structural studies with wild-type P-gp are required.
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Affiliation(s)
- Sabrina Lusvarghi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Stewart R Durell
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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7
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Clouser AF, Alam YH, Atkins WM. Cholesterol Asymmetrically Modulates the Conformational Ensemble of the Nucleotide-Binding Domains of P-Glycoprotein in Lipid Nanodiscs. Biochemistry 2020; 60:85-94. [PMID: 33350827 DOI: 10.1021/acs.biochem.0c00824] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
P-Glycoprotein (P-gp) is an ATP-dependent efflux pump that clears a wide variety of drugs and toxins from cells. P-gp undergoes large-scale structural changes and demonstrates conformational heterogeneity even within a single catalytic or drug-bound state, although the role of heterogeneity remains unclear. P-gp is found in a variety of cell types that vary in lipid composition, which modulates its activity. An understanding of structural or dynamic changes due to the lipid environment is lacking. We aimed to determine the effects of cholesterol in a membrane on the conformational behavior of P-gp in lipid nanodiscs. The presence of cholesterol stimulates ATP hydrolysis and alters lipid order and fluidity. Hydrogen/deuterium exchange mass spectrometry demonstrates that cholesterol in the membrane induces asymmetric, long-range changes in the distributions and exchange kinetics of conformations of the nucleotide-binding domains, correlating the effects of lipid composition on activity with specific changes in the P-gp conformational landscape.
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Affiliation(s)
- Amanda F Clouser
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195-7610, United States
| | - Yasmine H Alam
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195-7610, United States.,Department of Biological Sciences, MARC Program, California State University, Fullerton, California 92834-6850, United States
| | - William M Atkins
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195-7610, United States
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8
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ATP-dependent thermostabilization of human P-glycoprotein (ABCB1) is blocked by modulators. Biochem J 2020; 476:3737-3750. [PMID: 31774117 DOI: 10.1042/bcj20190736] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 11/13/2019] [Accepted: 11/27/2019] [Indexed: 11/17/2022]
Abstract
P-glycoprotein (P-gp), an ATP-binding cassette transporter associated with multidrug resistance in cancer cells, is capable of effluxing a number of xenobiotics as well as anticancer drugs. The transport of molecules through the transmembrane (TM) region of P-gp involves orchestrated conformational changes between inward-open and inward-closed forms, the details of which are still being worked out. Here, we assessed how the binding of transport substrates or modulators in the TM region and the binding of ATP to the nucleotide-binding domains (NBDs) affect the thermostability of P-gp in a membrane environment. P-gp stability after exposure at high temperatures (37-80°C) was assessed by measuring ATPase activity and loss of monomeric P-gp. Our results show that P-gp is significantly thermostabilized (>22°C higher IT50) by the binding of ATP under non-hydrolyzing conditions (in the absence of Mg2+). By using an ATP-binding-deficient mutant (Y401A) and a hydrolysis-deficient mutant (E556Q/E1201Q), we show that thermostabilization of P-gp requires binding of ATP to both NBDs and their dimerization. Additionally, we found that transport substrates do not affect the thermal stability of P-gp either in the absence or presence of ATP; in contrast, inhibitors of P-gp including tariquidar and zosuquidar prevent ATP-dependent thermostabilization in a concentration-dependent manner, by stabilizing the inward-open conformation. Altogether, our data suggest that modulators, which bind in the TM regions, inhibit ATP hydrolysis and drug transport by preventing the ATP-dependent dimerization of the NBDs of P-gp.
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9
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Guyot L, Hartmann L, Mohammed-Bouteben S, Caro L, Wagner R. Preparation of Recombinant Membrane Proteins from Pichia pastoris for Molecular Investigations. ACTA ACUST UNITED AC 2020; 100:e104. [PMID: 32289210 DOI: 10.1002/cpps.104] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pichia pastoris is a eukaryotic microorganism reputed for its ability to mass-produce recombinant proteins, including integral membrane proteins, for various applications. This article details a series of protocols that progress towards the production of integral membrane proteins, their extraction and purification in the presence of detergents, and their eventual reconstitution in lipid nanoparticles. These basic procedures can be further optimized to provide integral membrane protein samples that are compatible with a number of structural and/or functional investigations at the molecular level. Each protocol provides general guidelines, technical hints, and specific recommendations, and is illustrated with case studies corresponding to several representative mammalian proteins. © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Production of membrane proteins in a P. pastoris recombinant clone using methanol induction Basic Protocol 2: Preparation of whole-membrane fractions Alternate Protocol 1: Preparation of yeast protoplasts Basic Protocol 3: Extraction of membrane proteins from whole-membrane fractions Basic Protocol 4: Purification of membrane proteins Alternate Protocol 2: Purification of membrane proteins from yeast protoplasts Alternate Protocol 3: Simultaneous protoplast preparation and membrane solubilization for purification of membrane proteins Basic Protocol 5: Reconstitution of detergent-purified membrane proteins in lipid nanoparticles.
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Affiliation(s)
- Lucile Guyot
- IMPReSs Facility, Biotechnology and Cell Signaling UMR 7242, CNRS-University of Strasbourg, Illkirch, Cedex, France.,NovAliX, Illkirch, France
| | - Lucie Hartmann
- IMPReSs Facility, Biotechnology and Cell Signaling UMR 7242, CNRS-University of Strasbourg, Illkirch, Cedex, France
| | - Sarah Mohammed-Bouteben
- IMPReSs Facility, Biotechnology and Cell Signaling UMR 7242, CNRS-University of Strasbourg, Illkirch, Cedex, France
| | - Lydia Caro
- IMPReSs Facility, Biotechnology and Cell Signaling UMR 7242, CNRS-University of Strasbourg, Illkirch, Cedex, France
| | - Renaud Wagner
- IMPReSs Facility, Biotechnology and Cell Signaling UMR 7242, CNRS-University of Strasbourg, Illkirch, Cedex, France
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10
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Replacing the eleven native tryptophans by directed evolution produces an active P-glycoprotein with site-specific, non-conservative substitutions. Sci Rep 2020; 10:3224. [PMID: 32081894 PMCID: PMC7035247 DOI: 10.1038/s41598-020-59802-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 01/28/2020] [Indexed: 11/09/2022] Open
Abstract
P-glycoprotein (Pgp) pumps an array of hydrophobic compounds out of cells, and has major roles in drug pharmacokinetics and cancer multidrug resistance. Yet, polyspecific drug binding and ATP hydrolysis-driven drug export in Pgp are poorly understood. Fluorescence spectroscopy using tryptophans (Trp) inserted at strategic positions is an important tool to study ligand binding. In Pgp, this method will require removal of 11 endogenous Trps, including highly conserved Trps that may be important for function, protein-lipid interactions, and/or protein stability. Here, we developed a directed evolutionary approach to first replace all eight transmembrane Trps and select for transport-active mutants in Saccharomyces cerevisiae. Surprisingly, many Trp positions contained non-conservative substitutions that supported in vivo activity, and were preferred over aromatic amino acids. The most active construct, W(3Cyto), served for directed evolution of the three cytoplasmic Trps, where two positions revealed strong functional bias towards tyrosine. W(3Cyto) and Trp-less Pgp retained wild-type-like protein expression, localization and transport function, and purified proteins retained drug stimulation of ATP hydrolysis and drug binding affinities. The data indicate preferred Trp substitutions specific to the local context, often dictated by protein structural requirements and/or membrane lipid interactions, and these new insights will offer guidance for membrane protein engineering.
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11
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Li MJ, Guttman M, Atkins WM. Conformational dynamics of P-glycoprotein in lipid nanodiscs and detergent micelles reveal complex motions on a wide time scale. J Biol Chem 2018; 293:6297-6307. [PMID: 29511086 DOI: 10.1074/jbc.ra118.002190] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 02/26/2018] [Indexed: 11/06/2022] Open
Abstract
P-glycoprotein (P-gp) is a highly substrate-promiscuous efflux transporter that plays a critical role in drug disposition. P-gp utilizes ATP hydrolysis by nucleotide-binding domains (NBDs) to drive transitions between inward-facing (IF) conformations that bind drugs and outward-facing (OF) conformations that release them to the extracellular solution. However, the details of the protein dynamics within either macroscopic IF or OF conformation remain uncharacterized, and the functional role of local dynamics has not been determined. In this work we measured the local dynamics of the IF state of P-gp in lipid nanodiscs and in detergent solution by hydrogen-deuterium (H/D) exchange MS. We observed "EX1 exchange kinetics," or bimodal kinetics, for several peptides distributed in both NBDs, particularly for P-gp in the lipid nanodiscs. Remarkably, the EX1 kinetics occurred on several time scales, ranging from seconds to hours, suggesting highly complex, and correlated, motions. The results indicate at least three distinct conformational states in the ligand-free P-gp and suggest a rough conformational landscape. Addition of excess ATP and vanadate, to favor the OF conformations, caused a generalized, but modest, decrease in H/D exchange throughout the NBDs and slowed the EX1 kinetic transitions of several peptides. The functional implications of the results are consistent with the possibility that conformational selection provides a source of substrate promiscuity.
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Affiliation(s)
- Mavis Jiarong Li
- From the Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195-7610
| | - Miklos Guttman
- From the Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195-7610
| | - William M Atkins
- From the Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195-7610
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12
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Yang Z, Hildebrandt E, Jiang F, Aleksandrov AA, Khazanov N, Zhou Q, An J, Mezzell AT, Xavier BM, Ding H, Riordan JR, Senderowitz H, Kappes JC, Brouillette CG, Urbatsch IL. Structural stability of purified human CFTR is systematically improved by mutations in nucleotide binding domain 1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1193-1204. [PMID: 29425673 DOI: 10.1016/j.bbamem.2018.02.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 01/19/2018] [Accepted: 02/05/2018] [Indexed: 12/17/2022]
Abstract
The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is an ABC transporter containing two transmembrane domains forming a chloride ion channel, and two nucleotide binding domains (NBD1 and NBD2). CFTR has presented a formidable challenge to obtain monodisperse, biophysically stable protein. Here we report a comprehensive study comparing effects of single and multiple NBD1 mutations on stability of both the NBD1 domain alone and on purified full length human CFTR. Single mutations S492P, A534P, I539T acted additively, and when combined with M470V, S495P, and R555K cumulatively yielded an NBD1 with highly improved structural stability. Strategic combinations of these mutations strongly stabilized the domain to attain a calorimetric Tm > 70 °C. Replica exchange molecular dynamics simulations on the most stable 6SS-NBD1 variant implicated fluctuations, electrostatic interactions and side chain packing as potential contributors to improved stability. Progressive stabilization of NBD1 directly correlated with enhanced structural stability of full-length CFTR protein. Thermal unfolding of the stabilized CFTR mutants, monitored by changes in intrinsic fluorescence, demonstrated that Tm could be shifted as high as 67.4 °C in 6SS-CFTR, more than 20 °C higher than wild-type. H1402S, an NBD2 mutation, conferred CFTR with additional thermal stability, possibly by stabilizing an NBD-dimerized conformation. CFTR variants with NBD1-stabilizing mutations were expressed at the cell surface in mammalian cells, exhibited ATPase and channel activity, and retained these functions to higher temperatures. The capability to produce enzymatically active CFTR with improved structural stability amenable to biophysical and structural studies will advance mechanistic investigations and future cystic fibrosis drug development.
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Affiliation(s)
- Zhengrong Yang
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Ellen Hildebrandt
- Department of Cell Biology and Biochemistry, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA
| | - Fan Jiang
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - Andrei A Aleksandrov
- Department of Biochemistry and Biophysics and Cystic Fibrosis Treatment and Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Netaly Khazanov
- Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel
| | - Qingxian Zhou
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jianli An
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Andrew T Mezzell
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - Bala M Xavier
- Department of Cell Biology and Biochemistry, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA
| | - Haitao Ding
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - John R Riordan
- Department of Biochemistry and Biophysics and Cystic Fibrosis Treatment and Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Hanoch Senderowitz
- Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel
| | - John C Kappes
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA; Birmingham Veterans Affairs Medical Center, Research Service, Birmingham, AL 35233, USA
| | | | - Ina L Urbatsch
- Department of Cell Biology and Biochemistry, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA.
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13
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Investigation of the effects of the CFTR potentiator ivacaftor on human P-glycoprotein (ABCB1). Sci Rep 2017; 7:17481. [PMID: 29235532 PMCID: PMC5727471 DOI: 10.1038/s41598-017-17773-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 11/29/2017] [Indexed: 11/08/2022] Open
Abstract
Ivacaftor is a potentiator of the CFTR chloride channel and is in worldwide clinical use for the chronic treatment of cystic fibrosis in patients. There is evidence that the bioavailability of ivacaftor in the body may be influenced by the multi-drug exporter P-glycoprotein. Here we have employed purified and reconstituted P-glycoprotein to study its interaction with ivacaftor as well as the ability of the drug to compete with a known transported substrate of the protein. We find that ivacaftor stimulates the ATPase activity of the purified protein and can compete with the transport of the fluorescent substrate Hoechst 33342. These findings lead us to conclude that ivacaftor is very likely an efficiently transported substrate of P-glycoprotein. Evidence for state-dependent binding of ivacaftor was obtained using a fluorescent, cysteine-reactive reporter dye. The quiescent, nucleotide-free state in the P-glycoprotein transport cycle appears to bind ivacaftor strongly.
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