1
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Kleinsasser B, Garreis F, Musialik M, Zahn I, Kral B, Kutlu Z, Sahin A, Paulsen F, Schicht M. Molecular detection of lacrimal apparatus and ocular surface - related ABC transporter genes. Ann Anat 2024; 255:152272. [PMID: 38697581 DOI: 10.1016/j.aanat.2024.152272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 04/25/2024] [Accepted: 04/28/2024] [Indexed: 05/05/2024]
Abstract
The ocular system is in constant interaction with the environment and with numerous pathogens. The ATP-binding cassette (ABC) transporters represent one of the largest groups among the transmembrane proteins. Their relevance has been demonstrated for their defense function against biotic and abiotic stress factors, for metabolic processes in tumors and for their importance in the development of resistance to drugs. The aim of this study was to analyze which ABC transporters are expressed at the ocular surface and in the human lacrimal apparatus. Using RT-PCR, all ABC transporters known to date in humans were examined in tissue samples from human cornea, conjunctiva, meibomian glands and lacrimal glands. The RT-PCR analyses revealed the presence of all ABC transporters in the samples examined, although the results for some of the 48 transporters known in human and analyzed were different in the various tissues. The present results provide information on the expression of ABC transporters at the mRNA level on the ocular surface and in the lacrimal system. Their detection forms the basis for follow-up studies at the protein level, which will provide more information about their physiological significance at the ocular surface and in the lacrimal system and which may explain pathological effects such as drug resistance.
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Affiliation(s)
- Benedikt Kleinsasser
- Department of Functional and Clinical Anatomy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Fabian Garreis
- Department of Functional and Clinical Anatomy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Maximilian Musialik
- Department of Functional and Clinical Anatomy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Ingrid Zahn
- Department of Functional and Clinical Anatomy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Barbara Kral
- Department of Functional and Clinical Anatomy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Zeynep Kutlu
- Koc University School of Medicine, Rumelifeneri Yolu, Istanbul 34450, Turkey
| | - Afsun Sahin
- Department of Ophthalmology, Koc University Medical School, Istanbul, Turkey
| | - Friedrich Paulsen
- Department of Functional and Clinical Anatomy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Martin Schicht
- Department of Functional and Clinical Anatomy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
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2
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Infield DT, Strickland KM, Gaggar A, McCarty NA. The molecular evolution of function in the CFTR chloride channel. J Gen Physiol 2021; 153:212705. [PMID: 34647973 PMCID: PMC8640958 DOI: 10.1085/jgp.202012625] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 08/11/2021] [Accepted: 09/09/2021] [Indexed: 12/13/2022] Open
Abstract
The ATP-binding cassette (ABC) transporter superfamily includes many proteins of clinical relevance, with genes expressed in all domains of life. Although most members use the energy of ATP binding and hydrolysis to accomplish the active import or export of various substrates across membranes, the cystic fibrosis transmembrane conductance regulator (CFTR) is the only known animal ABC transporter that functions primarily as an ion channel. Defects in CFTR, which is closely related to ABCC subfamily members that bear function as bona fide transporters, underlie the lethal genetic disease cystic fibrosis. This article seeks to integrate structural, functional, and genomic data to begin to answer the critical question of how the function of CFTR evolved to exhibit regulated channel activity. We highlight several examples wherein preexisting features in ABCC transporters were functionally leveraged as is, or altered by molecular evolution, to ultimately support channel function. This includes features that may underlie (1) construction of an anionic channel pore from an anionic substrate transport pathway, (2) establishment and tuning of phosphoregulation, and (3) optimization of channel function by specialized ligand–channel interactions. We also discuss how divergence and conservation may help elucidate the pharmacology of important CFTR modulators.
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Affiliation(s)
- Daniel T Infield
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
| | | | - Amit Gaggar
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL.,Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL.,Birmingham Veterans Administration Medical Center, Birmingham, AL
| | - Nael A McCarty
- Department of Pediatrics, Emory University, Atlanta, GA.,Children's Healthcare of Atlanta Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA
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3
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Poothong J, Jang I, Kaufman RJ. Defects in Protein Folding and/or Quality Control Cause Protein Aggregation in the Endoplasmic Reticulum. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 59:115-143. [PMID: 34050864 DOI: 10.1007/978-3-030-67696-4_6] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Protein aggregation is now a common hallmark of numerous human diseases, most of which involve cytosolic aggregates including Aβ (AD) and ⍺-synuclein (PD) in Alzheimer's disease and Parkinson's disease. However, it is also evident that protein aggregation can also occur in the lumen of the endoplasmic reticulum (ER) that leads to specific diseases due to loss of protein function or detrimental effects on the host cell, the former is inherited in a recessive manner where the latter are dominantly inherited. However, the mechanisms of protein aggregation, disaggregation and degradation in the ER are not well understood. Here we provide an overview of factors that cause protein aggregation in the ER and how the ER handles aggregated proteins. Protein aggregation in the ER can result from intrinsic properties of the protein (hydrophobic residues in the ER), oxidative stress or nutrient depletion. The ER has quality control mechanisms [chaperone functions, ER-associated protein degradation (ERAD) and autophagy] to ensure only correctly folded proteins exit the ER and enter the cis-Golgi compartment. Perturbation of protein folding in the ER activates the unfolded protein response (UPR) that evolved to increase ER protein folding capacity and efficiency and degrade misfolded proteins. Accumulation of misfolded proteins in the ER to a level that exceeds the ER-chaperone folding capacity is a major factor that exacerbates protein aggregation. The most significant ER resident protein that prevents protein aggregation in the ER is the heat shock protein 70 (HSP70) homologue, BiP/GRP78, which is a peptide-dependent ATPase that binds unfolded/misfolded proteins and releases them upon ATP binding. Since exogenous factors can also reduce protein misfolding and aggregation in the ER, such as chemical chaperones and antioxidants, these treatments have potential therapeutic benefit for ER protein aggregation-associated diseases.
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Affiliation(s)
- Juthakorn Poothong
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Insook Jang
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
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4
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Abstract
Cystic fibrosis (CF) is an autosomal recessive genetic disorder whose responsible gene - the CFTR gene - was discovered 30 years ago by a positional cloning strategy. This gene, which encodes a chloride channel, contains more than 2,000 mutations including a major one (p.Phe508del). This discovery has led to considerable progress in the understanding of the pathophysiology of CF as well as in the management of patients and their families. It has also paved the way for the development of specific therapies for the disease. From an epidemiological point of view, the incidence of CF, which shows loco-regional variations, is now estimated at 1/4,700 live births in France. The face of CF has dramatically changed over the past decades: CF has gradually become a disease of the adult with, today, more than 50% of the patients being 18 years old or more and a median predicted survival age that exceeds 45 years. © 2020 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.
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Affiliation(s)
- C Férec
- Inserm, Univ Brest, EFS, UMR 1078, GGB, F-29200 Brest, France; CHU Brest, Hôpital Morvan, Laboratoire de génétique moléculaire et d'histocompatibilité, F-29200 Brest, France.
| | - V Scotet
- Inserm, Univ Brest, EFS, UMR 1078, GGB, F-29200 Brest, France
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5
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Discovery of novel VX-809 hybrid derivatives as F508del-CFTR correctors by molecular modeling, chemical synthesis and biological assays. Eur J Med Chem 2020; 208:112833. [DOI: 10.1016/j.ejmech.2020.112833] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 09/04/2020] [Accepted: 09/05/2020] [Indexed: 11/21/2022]
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6
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Al‐Majdoub ZM, Achour B, Couto N, Howard M, Elmorsi Y, Scotcher D, Alrubia S, El‐Khateeb E, Vasilogianni A, Alohali N, Neuhoff S, Schmitt L, Rostami‐Hodjegan A, Barber J. Mass spectrometry-based abundance atlas of ABC transporters in human liver, gut, kidney, brain and skin. FEBS Lett 2020; 594:4134-4150. [PMID: 33128234 PMCID: PMC7756589 DOI: 10.1002/1873-3468.13982] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/24/2020] [Accepted: 10/15/2020] [Indexed: 12/31/2022]
Abstract
ABC transporters (ATP-binding cassette transporter) traffic drugs and their metabolites across membranes, making ABC transporter expression levels a key factor regulating local drug concentrations in different tissues and individuals. Yet, quantification of ABC transporters remains challenging because they are large and low-abundance transmembrane proteins. Here, we analysed 200 samples of crude and membrane-enriched fractions from human liver, kidney, intestine, brain microvessels and skin, by label-free quantitative mass spectrometry. We identified 32 (out of 48) ABC transporters: ABCD3 was the most abundant in liver, whereas ABCA8, ABCB2/TAP1 and ABCE1 were detected in all tissues. Interestingly, this atlas unveiled that ABCB2/TAP1 may have TAP2-independent functions in the brain and that biliary atresia (BA) and control livers have quite different ABC transporter profiles. We propose that meaningful biological information can be derived from a direct comparison of these data sets.
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Affiliation(s)
- Zubida M. Al‐Majdoub
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
| | - Brahim Achour
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
| | - Narciso Couto
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
| | - Martyn Howard
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
| | - Yasmine Elmorsi
- Clinical Pharmacy DepartmentFaculty of PharmacyTanta UniversityEgypt
| | - Daniel Scotcher
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
| | - Sarah Alrubia
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
- Pharmaceutical Chemistry DepartmentCollege of PharmacyKing Saud UniversityRiyadhSaudi Arabia
| | - Eman El‐Khateeb
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
- Clinical Pharmacy DepartmentFaculty of PharmacyTanta UniversityEgypt
| | | | - Noura Alohali
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
- Pharmaceutical Practice DepartmentCollege of PharmacyPrincess Noura Bint Abdul Rahman UniversityRiyadhSaudi Arabia
| | | | - Lutz Schmitt
- Institute of BiochemistryHeinrich Heine University DüsseldorfGermany
| | - Amin Rostami‐Hodjegan
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
- Simcyp DivisionCertara UK LtdSheffieldUK
| | - Jill Barber
- Centre for Applied Pharmacokinetic ResearchSchool of Health SciencesUniversity of ManchesterUK
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7
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Zappe K, Cichna-Markl M. Aberrant DNA Methylation of ABC Transporters in Cancer. Cells 2020; 9:cells9102281. [PMID: 33066132 PMCID: PMC7601986 DOI: 10.3390/cells9102281] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/18/2020] [Accepted: 09/21/2020] [Indexed: 12/21/2022] Open
Abstract
ATP-binding cassette (ABC) transporters play a crucial role in multidrug resistance (MDR) of cancers. They function as efflux pumps, resulting in limited effectiveness or even failure of therapy. Increasing evidence suggests that ABC transporters are also involved in tumor initiation, progression, and metastasis. Tumors frequently show multiple genetic and epigenetic abnormalities, including changes in histone modification and DNA methylation. Alterations in the DNA methylation status of ABC transporters have been reported for a variety of cancer types. In this review, we outline the current knowledge of DNA methylation of ABC transporters in cancer. We give a brief introduction to structure, function, and gene regulation of ABC transporters that have already been investigated for their DNA methylation status in cancer. After giving an overview of the applied methodologies and the CpGs analyzed, we summarize and discuss the findings on aberrant DNA methylation of ABC transporters by cancer types. We conclude our review with the discussion of the potential to target aberrant DNA methylation of ABC transporters for cancer therapy.
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8
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Abreu B, Lopes EF, Oliveira ASF, Soares CM. F508del disturbs the dynamics of the nucleotide binding domains of CFTR before and after ATP hydrolysis. Proteins 2019; 88:113-126. [PMID: 31298435 DOI: 10.1002/prot.25776] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 06/17/2019] [Accepted: 07/06/2019] [Indexed: 12/20/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) channel is an ion channel responsible for chloride transport in epithelia and it belongs to the class of ABC transporters. The deletion of phenylalanine 508 (F508del) in CFTR is the most common mutation responsible for cystic fibrosis. Little is known about the effect of the mutation in the isolated nucleotide binding domains (NBDs), on dimer dynamics, ATP hydrolysis and even on nucleotide binding. Using molecular dynamics simulations of the human CFTR NBD dimer, we showed that F508del increases, in the prehydrolysis state, the inter-motif distance in both ATP binding sites (ABP) when ATP is bound. Additionally, a decrease in the number of catalytically competent conformations was observed in the presence of F508del. We used the subtraction technique to study the first 300 ps after ATP hydrolysis in the catalytic competent site and found that the F508del dimer evidences lower conformational changes than the wild type. Using longer simulation times, the magnitude of the conformational changes in both forms increases. Nonetheless, the F508del dimer shows lower C-α RMS values in comparison to the wild-type, on the F508del loop, on the residues surrounding the catalytic site and the portion of NBD2 adjacent to ABP1. These results provide evidence that F508del interferes with the NBD dynamics before and after ATP hydrolysis. These findings shed a new light on the effect of F508del on NBD dynamics and reveal a novel mechanism for the influence of F508del on CFTR.
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Affiliation(s)
- Bárbara Abreu
- Protein Modelling Lab, ITQB-NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Emanuel F Lopes
- Protein Modelling Lab, ITQB-NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
| | - A S F Oliveira
- Protein Modelling Lab, ITQB-NOVA, Universidade Nova de Lisboa, Oeiras, Portugal.,School of Biochemistry & Center for Computational Chemistry, University of Bristol, Bristol, UK
| | - Cláudio M Soares
- Protein Modelling Lab, ITQB-NOVA, Universidade Nova de Lisboa, Oeiras, Portugal
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9
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Wang C, Aleksandrov AA, Yang Z, Forouhar F, Proctor EA, Kota P, An J, Kaplan A, Khazanov N, Boël G, Stockwell BR, Senderowitz H, Dokholyan NV, Riordan JR, Brouillette CG, Hunt JF. Ligand binding to a remote site thermodynamically corrects the F508del mutation in the human cystic fibrosis transmembrane conductance regulator. J Biol Chem 2018; 293:17685-17704. [PMID: 29903914 PMCID: PMC6240863 DOI: 10.1074/jbc.ra117.000819] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 05/31/2018] [Indexed: 01/07/2023] Open
Abstract
Many disease-causing mutations impair protein stability. Here, we explore a thermodynamic strategy to correct the disease-causing F508del mutation in the human cystic fibrosis transmembrane conductance regulator (hCFTR). F508del destabilizes nucleotide-binding domain 1 (hNBD1) in hCFTR relative to an aggregation-prone intermediate. We developed a fluorescence self-quenching assay for compounds that prevent aggregation of hNBD1 by stabilizing its native conformation. Unexpectedly, we found that dTTP and nucleotide analogs with exocyclic methyl groups bind to hNBD1 more strongly than ATP and preserve electrophysiological function of full-length F508del-hCFTR channels at temperatures up to 37 °C. Furthermore, nucleotides that increase open-channel probability, which reflects stabilization of an interdomain interface to hNBD1, thermally protect full-length F508del-hCFTR even when they do not stabilize isolated hNBD1. Therefore, stabilization of hNBD1 itself or of one of its interdomain interfaces by a small molecule indirectly offsets the destabilizing effect of the F508del mutation on full-length hCFTR. These results indicate that high-affinity binding of a small molecule to a remote site can correct a disease-causing mutation. We propose that the strategies described here should be applicable to identifying small molecules to help manage other human diseases caused by mutations that destabilize native protein conformation.
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Affiliation(s)
- Chi Wang
- From the Departments of Biological Sciences and
| | - Andrei A. Aleksandrov
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Zhengrong Yang
- the Department of Chemistry, University of Alabama, Birmingham, Alabama 35294, and
| | | | - Elizabeth A. Proctor
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Pradeep Kota
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Jianli An
- the Department of Chemistry, University of Alabama, Birmingham, Alabama 35294, and
| | - Anna Kaplan
- From the Departments of Biological Sciences and
| | - Netaly Khazanov
- the Department of Chemistry, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | | | - Brent R. Stockwell
- From the Departments of Biological Sciences and ,Chemistry, Columbia University, New York, New York 10027
| | - Hanoch Senderowitz
- the Department of Chemistry, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Nikolay V. Dokholyan
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - John R. Riordan
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | | | - John F. Hunt
- From the Departments of Biological Sciences and , To whom correspondence should be addressed. Tel.:
212-854-5443; Fax:
212-865-8246; E-mail:
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10
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Veit G, Xu H, Dreano E, Avramescu RG, Bagdany M, Beitel LK, Roldan A, Hancock MA, Lay C, Li W, Morin K, Gao S, Mak PA, Ainscow E, Orth AP, McNamara P, Edelman A, Frenkiel S, Matouk E, Sermet-Gaudelus I, Barnes WG, Lukacs GL. Structure-guided combination therapy to potently improve the function of mutant CFTRs. Nat Med 2018; 24:1732-1742. [PMID: 30297908 PMCID: PMC6301090 DOI: 10.1038/s41591-018-0200-x] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 08/08/2018] [Indexed: 12/17/2022]
Abstract
Available corrector drugs are unable to effectively rescue the folding defects of CFTR-ΔF508 (or CFTR-F508del), the most common disease-causing mutation of the cystic fibrosis transmembrane conductance regulator, a plasma membrane (PM) anion channel, and thus to substantially ameliorate clinical phenotypes of cystic fibrosis (CF). To overcome the corrector efficacy ceiling, here we show that compounds targeting distinct structural defects of CFTR can synergistically rescue mutant expression and function at the PM. High-throughput cell-based screens and mechanistic analysis identified three small-molecule series that target defects at nucleotide-binding domain (NBD1), NBD2 and their membrane-spanning domain (MSD) interfaces. Although individually these compounds marginally improve ΔF508-CFTR folding efficiency, function and stability, their combinations lead to ~50-100% of wild-type-level correction in immortalized and primary human airway epithelia and in mouse nasal epithelia. Likewise, corrector combinations were effective against rare missense mutations in various CFTR domains, probably acting via structural allostery, suggesting a mechanistic framework for their broad application.
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Affiliation(s)
- Guido Veit
- Department of Physiology, McGill University, Montréal, Quebec, Canada.
| | - Haijin Xu
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | - Elise Dreano
- Institut Necker-Enfants Malades (INEM)-INSERM U1151, Paris, France
| | - Radu G Avramescu
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | - Miklos Bagdany
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | - Lenore K Beitel
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | - Ariel Roldan
- Department of Physiology, McGill University, Montréal, Quebec, Canada
| | - Mark A Hancock
- SPR-MS Facility, McGill University, Montréal, Quebec, Canada
| | - Cecilia Lay
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Wei Li
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Katelin Morin
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Sandra Gao
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Puiying A Mak
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Edward Ainscow
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Anthony P Orth
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Peter McNamara
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | | | - Saul Frenkiel
- Department of Otolaryngology - Head and Neck Surgery, McGill University, Montréal, Quebec, Canada
| | - Elias Matouk
- Adult Cystic Fibrosis Clinic, Montreal Chest Institute, McGill University, Montréal, Quebec, Canada
| | | | - William G Barnes
- Genomic Institute of the Novartis Research Foundation, San Diego, CA, USA
| | - Gergely L Lukacs
- Department of Physiology, McGill University, Montréal, Quebec, Canada. .,Department of Biochemistry, McGill University, Montréal, Quebec, Canada. .,Groupe de Recherche Axé sur la Structure des Protéines (GRASP), McGill University, Montréal, Quebec, Canada.
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11
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Callebaut I, Hoffmann B, Mornon JP. The implications of CFTR structural studies for cystic fibrosis drug development. Curr Opin Pharmacol 2017; 34:112-118. [PMID: 29096277 DOI: 10.1016/j.coph.2017.09.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 09/12/2017] [Accepted: 09/14/2017] [Indexed: 02/08/2023]
Abstract
Development of Cystic Fibrosis Transmembrane conductance Regulator (CFTR) modulators, targeting the root cause of cystic fibrosis (CF), represents a challenge in the era of personalized medicine, as CFTR mutations lead to a variety of phenotypes, which likely require different, specific treatments. CF drug development is also complicated by the need to preserve the right balance between stability and flexibility, required for optimal function of the CFTR protein. In this review, we highlight how structural data can be exploited in this context to understand the molecular mechanisms of disease-associated mutations, to characterize the mechanisms of action of known modulators and to rationalize the search for novel, specific compounds.
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Affiliation(s)
- Isabelle Callebaut
- CNRS UMR7590, Sorbonne Universités, Université Pierre et Marie Curie - Paris 6 - MNHN - IRD - IUC, Paris, France.
| | - Brice Hoffmann
- CNRS UMR7590, Sorbonne Universités, Université Pierre et Marie Curie - Paris 6 - MNHN - IRD - IUC, Paris, France
| | - Jean-Paul Mornon
- CNRS UMR7590, Sorbonne Universités, Université Pierre et Marie Curie - Paris 6 - MNHN - IRD - IUC, Paris, France
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12
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Xavier BM, Hildebrandt E, Jiang F, Ding H, Kappes JC, Urbatsch IL. Substitution of Yor1p NBD1 residues improves the thermal stability of Human Cystic Fibrosis Transmembrane Conductance Regulator. Protein Eng Des Sel 2017; 30:729-741. [PMID: 29053845 PMCID: PMC5914393 DOI: 10.1093/protein/gzx054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 09/08/2017] [Accepted: 09/15/2017] [Indexed: 01/05/2023] Open
Abstract
The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a plasma membrane chloride channel protein that regulates vertebrate fluid homeostasis. The inefficiency of wild type human CFTR protein folding/trafficking is exacerbated by genetic mutations that can cause protein misfolding in the endoplasmic reticulum (ER) and subsequent degradation. This project investigates small changes in protein sequence that can alter the thermal stability of the large multi-domain CFTR protein. We target a conserved 70-residue α-subdomain located in the first nucleotide-binding domain that hosts the common misfolding mutation ∆F508. To investigate substitutions that can stabilize this domain, we constructed chimeras between human CFTR and its closest yeast homolog Yor1p. The α-subdomain of Yor1p was replaced with that of CFTR in Saccharomyces cerevisiae. Cellular localization of green fluorescence protein-tagged Yor1p-CFTR chimeras was analyzed by fluorescence microscopy and quantitative multispectral imaging flow cytometry, steady-state protein levels were compared by SDS-PAGE and protein function probed by a phenotypic oligomycin resistance assay. The chimeras exhibited ER retention in yeast characteristic of defective protein folding/processing. Substitution of seven CFTR α-subdomain residues that are highly conserved in Yor1p and other transporters but differ in CFTR (S495P/R516K/F533L/A534P/K536G/I539T/R553K) improved Yor1p-CFTR chimera localization to the yeast plasma membrane. When introduced into human CFTR expressed in mammalian cells, the same substitutions improve the purified protein thermal stability. This stabilized human CFTR protein will be directly useful for structural and biophysical studies that have been limited by the thermal sensitivity of wild type CFTR. The insights into critical structural residues within CFTR could facilitate development of effective therapeutics for CF-causing mutations.
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Affiliation(s)
- B M Xavier
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - E Hildebrandt
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - F Jiang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - H Ding
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - J C Kappes
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
- Veterans Affairs Medical Center, Research Service, Birmingham, AL 35294, USA
| | - I L Urbatsch
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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13
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Callebaut I, Chong PA, Forman-Kay JD. CFTR structure. J Cyst Fibros 2017; 17:S5-S8. [PMID: 28866450 DOI: 10.1016/j.jcf.2017.08.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 08/06/2017] [Accepted: 08/16/2017] [Indexed: 02/08/2023]
Abstract
Structural studies of the cystic fibrosis transmembrane conductance regulator (CFTR) protein are critical to understand molecular mechanisms involved in gating of the apical anion channel as well as the way in which the gating is regulated, especially by the regulatory region (R region). They are also instrumental for understanding the root cause of cystic fibrosis (CF) and supporting the development of therapeutic strategies. In this short review, we summarize recent progress in the knowledge of the CFTR 3D structure and briefly discuss implications for CF drug development.
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Affiliation(s)
- Isabelle Callebaut
- IMPMC, Sorbonne Universités - UPMC Université Paris 06, UMR CNRS 7590, Muséum National d'Histoire Naturelle, IRD UMR 206, 4 Place Jussieu, Paris, France.
| | - P Andrew Chong
- Molecular Medicine, The Hospital for Sick Children, Toronto M5G 0A4, Canada
| | - Julie D Forman-Kay
- Molecular Medicine, The Hospital for Sick Children, Toronto M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto M5G 1X8, Canada
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14
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15
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Meng X, Wang Y, Wang X, Wrennall JA, Rimington TL, Li H, Cai Z, Ford RC, Sheppard DN. Two Small Molecules Restore Stability to a Subpopulation of the Cystic Fibrosis Transmembrane Conductance Regulator with the Predominant Disease-causing Mutation. J Biol Chem 2017; 292:3706-3719. [PMID: 28087700 PMCID: PMC5339754 DOI: 10.1074/jbc.m116.751537] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 01/12/2017] [Indexed: 12/17/2022] Open
Abstract
Cystic fibrosis (CF) is caused by mutations that disrupt the plasma membrane expression, stability, and function of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel. Two small molecules, the CFTR corrector lumacaftor and the potentiator ivacaftor, are now used clinically to treat CF, although some studies suggest that they have counteracting effects on CFTR stability. Here, we investigated the impact of these compounds on the instability of F508del-CFTR, the most common CF mutation. To study individual CFTR Cl- channels, we performed single-channel recording, whereas to assess entire CFTR populations, we used purified CFTR proteins and macroscopic CFTR Cl- currents. At 37 °C, low temperature-rescued F508del-CFTR more rapidly lost function in cell-free membrane patches and showed altered channel gating and current flow through open channels. Compared with purified wild-type CFTR, the full-length F508del-CFTR was about 10 °C less thermostable. Lumacaftor partially stabilized purified full-length F508del-CFTR and slightly delayed deactivation of individual F508del-CFTR Cl- channels. By contrast, ivacaftor further destabilized full-length F508del-CFTR and accelerated channel deactivation. Chronic (prolonged) co-incubation of F508del-CFTR-expressing cells with lumacaftor and ivacaftor deactivated macroscopic F508del-CFTR Cl- currents. However, at the single-channel level, chronic co-incubation greatly increased F508del-CFTR channel activity and temporal stability in most, but not all, cell-free membrane patches. We conclude that chronic lumacaftor and ivacaftor co-treatment restores stability in a small subpopulation of F508del-CFTR Cl- channels but that the majority remain destabilized. A fuller understanding of these effects and the characterization of the small F508del-CFTR subpopulation might be crucial for CF therapy development.
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Affiliation(s)
- Xin Meng
- From the Faculty of Biology, Medicine and Health, School of Biological Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PL, United Kingdom and
| | - Yiting Wang
- the School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom
| | - Xiaomeng Wang
- From the Faculty of Biology, Medicine and Health, School of Biological Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PL, United Kingdom and
| | - Joe A Wrennall
- the School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom
| | - Tracy L Rimington
- From the Faculty of Biology, Medicine and Health, School of Biological Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PL, United Kingdom and
| | - Hongyu Li
- the School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom
| | - Zhiwei Cai
- the School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom
| | - Robert C Ford
- From the Faculty of Biology, Medicine and Health, School of Biological Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PL, United Kingdom and
| | - David N Sheppard
- the School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom
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16
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Callebaut I, Hoffmann B, Lehn P, Mornon JP. Molecular modelling and molecular dynamics of CFTR. Cell Mol Life Sci 2017; 74:3-22. [PMID: 27717958 PMCID: PMC11107702 DOI: 10.1007/s00018-016-2385-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 12/11/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) protein is a member of the ATP-binding cassette (ABC) transporter superfamily that functions as an ATP-gated channel. Considerable progress has been made over the last years in the understanding of the molecular basis of the CFTR functions, as well as dysfunctions causing the common genetic disease cystic fibrosis (CF). This review provides a global overview of the theoretical studies that have been performed so far, especially molecular modelling and molecular dynamics (MD) simulations. A special emphasis is placed on the CFTR-specific evolution of an ABC transporter framework towards a channel function, as well as on the understanding of the effects of disease-causing mutations and their specific modulation. This in silico work should help structure-based drug discovery and design, with a view to develop CFTR-specific pharmacotherapeutic approaches for the treatment of CF in the context of precision medicine.
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Affiliation(s)
- Isabelle Callebaut
- UMR CNRS 7590, Museum National d'Histoire Naturelle, IRD UMR 206, IUC, Case 115, IMPMC, Sorbonne Universités, UPMC Univ Paris 06, 4 Place Jussieu, 75005, Paris Cedex 05, France.
| | - Brice Hoffmann
- UMR CNRS 7590, Museum National d'Histoire Naturelle, IRD UMR 206, IUC, Case 115, IMPMC, Sorbonne Universités, UPMC Univ Paris 06, 4 Place Jussieu, 75005, Paris Cedex 05, France
| | - Pierre Lehn
- INSERM U1078, SFR ScInBioS, Université de Bretagne Occidentale, Brest, France
| | - Jean-Paul Mornon
- UMR CNRS 7590, Museum National d'Histoire Naturelle, IRD UMR 206, IUC, Case 115, IMPMC, Sorbonne Universités, UPMC Univ Paris 06, 4 Place Jussieu, 75005, Paris Cedex 05, France
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17
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Linsdell P. Architecture and functional properties of the CFTR channel pore. Cell Mol Life Sci 2017; 74:67-83. [PMID: 27699452 PMCID: PMC11107662 DOI: 10.1007/s00018-016-2389-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 12/12/2022]
Abstract
The main function of the cystic fibrosis transmembrane conductance regulator (CFTR) is as an ion channel for the movement of small anions across epithelial cell membranes. As an ion channel, CFTR must form a continuous pathway across the cell membrane-referred to as the channel pore-for the rapid electrodiffusional movement of ions. This review summarizes our current understanding of the architecture of the channel pore, as defined by electrophysiological analysis and molecular modeling studies. This includes consideration of the characteristic functional properties of the pore, definition of the overall shape of the entire extent of the pore, and discussion of how the molecular structure of distinct regions of the pore might control different facets of pore function. Comparisons are drawn with closely related proteins that are not ion channels, and also with structurally unrelated proteins with anion channel function. A simple model of pore function is also described.
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Affiliation(s)
- Paul Linsdell
- Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS, B3H 4R2, Canada.
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18
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Hildebrandt E, Khazanov N, Kappes JC, Dai Q, Senderowitz H, Urbatsch IL. Specific stabilization of CFTR by phosphatidylserine. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:289-293. [PMID: 27913277 DOI: 10.1016/j.bbamem.2016.11.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 11/08/2016] [Accepted: 11/28/2016] [Indexed: 10/20/2022]
Abstract
The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR, ABCC7) is a plasma membrane chloride ion channel in the ABC transporter superfamily. CFTR is a key target for cystic fibrosis drug development, and its structural elucidation would advance those efforts. However, the limited in vivo and in vitro stability of the protein, particularly its nucleotide binding domains, has made structural studies challenging. Here we demonstrate that phosphatidylserine uniquely stimulates and thermally stabilizes the ATP hydrolysis function of purified human CFTR. Among several lipids tested, the greatest stabilization was observed with brain phosphatidylserine, which shifted the Tm for ATPase activity from 22.7±0.8°C to 35.0±0.2°C in wild-type CFTR, and from 26.6±0.7°C to 42.1±0.2°C in a more stable mutant CFTR having deleted regulatory insertion and S492P/A534P/I539T mutations. When ATPase activity was measured at 37°C in the presence of brain phosphatidylserine, Vmax for wild-type CFTR was 240±60nmol/min/mg, a rate higher than previously reported and consistent with rates for other purified ABC transporters. The significant thermal stabilization of CFTR by phosphatidylserine may be advantageous in future structural and biophysical studies of CFTR.
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Affiliation(s)
- Ellen Hildebrandt
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA.
| | - Netaly Khazanov
- 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 Medical Center, Research Service, Birmingham, AL 35233, USA.
| | - Qun Dai
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA.
| | - Hanoch Senderowitz
- Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel.
| | - Ina L Urbatsch
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA.
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19
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El Hiani Y, Negoda A, Linsdell P. Cytoplasmic pathway followed by chloride ions to enter the CFTR channel pore. Cell Mol Life Sci 2016; 73:1917-25. [PMID: 26659082 PMCID: PMC11108287 DOI: 10.1007/s00018-015-2113-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 11/18/2015] [Accepted: 12/07/2015] [Indexed: 12/19/2022]
Abstract
Most ATP-binding cassette (ABC) proteins function as ATP-dependent membrane pumps. One exception is the cystic fibrosis transmembrane conductance regulator (CFTR), an ABC protein that functions as a Cl(-) ion channel. As such, the CFTR protein must form a continuous pathway for the movement of Cl(-) ions from the cytoplasm to the extracellular solution when in its open channel state. Extensive functional investigations have characterized most parts of this Cl(-) permeation pathway. However, one region remains unexplored-the pathway connecting the cytoplasm to the membrane-spanning pore. We used patch clamp recording and extensive substituted cysteine accessibility mutagenesis to identify amino acid side-chains in cytoplasmic regions of CFTR that lie close to the pathway taken by Cl(-) ions as they pass from the cytoplasm through this pathway. Our results suggest that Cl(-) ions enter the permeation pathway via a single lateral tunnel formed by the cytoplasmic parts of the protein, and then follow a fairly direct central pathway towards the membrane-spanning parts of the protein. However, this pathway is not lined continuously by any particular part of the protein; instead, the contributions of different cytoplasmic regions of the protein appear to change as the permeation pathway approaches the membrane, which appears to reflect the ways in which different cytoplasmic regions of the protein are oriented towards its central axis. Our results allow us to define for the first time the complete Cl(-) permeation pathway in CFTR, from the cytoplasm to the extracellular solution.
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Affiliation(s)
- Yassine El Hiani
- Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS, B3H 4R2, Canada
| | - Alexander Negoda
- Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS, B3H 4R2, Canada
| | - Paul Linsdell
- Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS, B3H 4R2, Canada.
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20
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Hall JD, Wang H, Byrnes LJ, Shanker S, Wang K, Efremov IV, Chong PA, Forman-Kay JD, Aulabaugh AE. Binding screen for cystic fibrosis transmembrane conductance regulator correctors finds new chemical matter and yields insights into cystic fibrosis therapeutic strategy. Protein Sci 2016; 25:360-73. [PMID: 26444971 DOI: 10.1002/pro.2821] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 10/01/2015] [Indexed: 11/08/2022]
Abstract
The most common mutation in cystic fibrosis (CF) patients is deletion of F508 (ΔF508) in the first nucleotide binding domain (NBD1) of the CF transmembrane conductance regulator (CFTR). ΔF508 causes a decrease in the trafficking of CFTR to the cell surface and reduces the thermal stability of isolated NBD1; it is well established that both of these effects can be rescued by additional revertant mutations in NBD1. The current paradigm in CF small molecule drug discovery is that, like revertant mutations, a path may exist to ΔF508 CFTR correction through a small molecule chaperone binding to NBD1. We, therefore, set out to find small molecule binders of NBD1 and test whether it is possible to develop these molecules into potent binders that increase CFTR trafficking in CF-patient-derived human bronchial epithelial cells. Several fragments were identified that bind NBD1 at either the CFFT-001 site or the BIA site. However, repeated attempts to improve the affinity of these fragments resulted in only modest gains. Although these results cannot prove that there is no possibility of finding a high-affinity small molecule binder of NBD1, they are discouraging and lead us to hypothesize that the nature of these two binding sites, and isolated NBD1 itself, may not contain the features needed to build high-affinity interactions. Future work in this area may, therefore, require constructs including other domains of CFTR in addition to NBD1, if high-affinity small molecule binding is to be achieved.
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Affiliation(s)
- Justin D Hall
- Structural Biology and Biophysics Group, Pfizer, Groton, Connecticut, 06340
| | - Hong Wang
- Structural Biology and Biophysics Group, Pfizer, Groton, Connecticut, 06340
| | - Laura J Byrnes
- Structural Biology and Biophysics Group, Pfizer, Groton, Connecticut, 06340
| | - Suman Shanker
- Structural Biology and Biophysics Group, Pfizer, Groton, Connecticut, 06340
| | - Kelong Wang
- Structural Biology and Biophysics Group, Pfizer, Groton, Connecticut, 06340
| | - Ivan V Efremov
- Worldwide Medicinal Chemistry, , Pfizer, Cambridge, Massachusetts, 02140
| | - P Andrew Chong
- Molecular Structure and Function Program, Hospital for Sick Kids, Toronto, Ontario, M5G 0A4, Canada.,Department of Biochemistry, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| | - Julie D Forman-Kay
- Molecular Structure and Function Program, Hospital for Sick Kids, Toronto, Ontario, M5G 0A4, Canada.,Department of Biochemistry, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| | - Ann E Aulabaugh
- Structural Biology and Biophysics Group, Pfizer, Groton, Connecticut, 06340
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21
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Infield DT, Cui G, Kuang C, McCarty NA. Positioning of extracellular loop 1 affects pore gating of the cystic fibrosis transmembrane conductance regulator. Am J Physiol Lung Cell Mol Physiol 2015; 310:L403-14. [PMID: 26684250 DOI: 10.1152/ajplung.00259.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 12/16/2015] [Indexed: 02/06/2023] Open
Abstract
The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) is a chloride ion channel, the dysfunction of which directly leads to the life-shortening disease CF. Extracellular loop 1 (ECL1) of CFTR contains several residues involved in stabilizing the open state of the channel; some, including D110, are sites of disease-associated gating mutations. Structures from related proteins suggest that the position of CFTR's extracellular loops may change considerably during gating. To better understand the roles of ECL1 in CFTR function, we utilized functional cysteine cross-linking to determine the effects of modulation of D110C-CFTR and of a double mutant of D110C with K892C in extracellular loop 4 (ECL4). The reducing agent DTT elicited a large potentiation of the macroscopic conductance of D110C/K892C-CFTR, likely due to breakage of a spontaneous disulfide bond between C110 and C892. DTT-reduced D110C/K892C-CFTR was rapidly inhibited by binding cadmium ions with high affinity, suggesting that these residues frequently come in close proximity in actively gating channels. Effects of DTT and cadmium on modulation of pore gating were demonstrated at the single-channel level. Finally, disulfided D110C/K892C-CFTR channels were found to be less sensitive than wild-type or DTT-treated D110C/K892C-CFTR channels to stimulation by IBMX, suggesting an impact of this conformational restriction on channel activation by phosphorylation. The results are best explained in the context of a model of CFTR gating wherein stable channel opening requires correct positioning of functional elements structurally influenced by ECL1.
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Affiliation(s)
- Daniel T Infield
- Division of Pulmonology, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, Georgia; and Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, Georgia
| | - Guiying Cui
- Division of Pulmonology, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, Georgia; and
| | - Christopher Kuang
- Division of Pulmonology, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, Georgia; and
| | - Nael A McCarty
- Division of Pulmonology, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, Georgia; and
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22
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Thermal stability of purified and reconstituted CFTR in a locked open channel conformation. Protein Expr Purif 2015; 116:159-66. [PMID: 26384709 DOI: 10.1016/j.pep.2015.09.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 09/11/2015] [Accepted: 09/14/2015] [Indexed: 11/20/2022]
Abstract
CFTR is unique among ABC transporters as the only one functioning as an ion channel and from a human health perspective because mutations in its gene cause cystic fibrosis. Although considerable advances have been made towards understanding CFTR's mechanism of action and the impact of mutations, the lack of a high-resolution 3D structure has hindered progress. The large multi-domain membrane glycoprotein is normally present at low copy number and when over expressed at high levels it aggregates strongly, limiting the production of stable mono-disperse preparations. While the reasons for the strong self-association are not fully understood, its relatively low thermal stability seems likely to be one. The major CF causing mutation, ΔF508, renders the protein very thermally unstable and therefore a great deal of attention has been paid to this property of CFTR. Multiple second site mutations of CFTR in NBD1 where F508 normally resides and small molecule binders of the domain increase the thermal stability of the mutant. These manipulations also stabilize the wild-type protein. Here we have applied ΔF508-stabilizing changes and other modifications to generate wild-type constructs that express at much higher levels in scaled-up suspension cultures of mammalian cells. After purification and reconstitution into liposomes these proteins are active in a locked-open conformation at temperatures as high as 50 °C and remain monodisperse at 4 °C in detergent or lipid for at least a week. The availability of adequate amounts of these and related stable active preparations of homogeneous CFTR will enable stalled structural and ligand binding studies to proceed.
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Abstract
PURPOSE OF REVIEW The field of cystic fibrosis (CF) continues to evolve at a fast pace thanks to novel observations that have enabled deeper understanding of the disease pathophysiology. Parallel groundbreaking developments in innovative therapies permit, for the first time, distinct disease modification. RECENT FINDINGS This review highlights important discoveries in fluid homeostasis and mucus secretion in CF that further informs the pathophysiology of the airway disease that characterizes CF. In addition, current concepts and novel paradigms, such as 'theratypes' and 'CF transmembrane conductance regulator chaperome', which will be important for the continued development of disease modifying therapies, are reviewed. SUMMARY The rate of progress in the field continues to accelerate with new knowledge informing the development of innovative therapies. This has already led to tangible substantial and unprecedented clinical benefit for selected subsets of the CF patient population. In the years ahead, further knowledge acquisition may motivate the extension of these benefits to the larger population of people with CF.
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24
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Hildebrandt E, Mulky A, Ding H, Dai Q, Aleksandrov AA, Bajrami B, Diego PA, Wu X, Ray M, Naren AP, Riordan JR, Yao X, DeLucas LJ, Urbatsch IL, Kappes JC. A stable human-cell system overexpressing cystic fibrosis transmembrane conductance regulator recombinant protein at the cell surface. Mol Biotechnol 2015; 57:391-405. [PMID: 25577540 PMCID: PMC4405497 DOI: 10.1007/s12033-014-9830-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Recent human clinical trials results demonstrated successful treatment for certain genetic forms of cystic fibrosis (CF). To extend treatment opportunities to those afflicted with other genetic forms of CF disease, structural and biophysical characterization of CF transmembrane conductance regulator (CFTR) is urgently needed. In this study, CFTR was modified with various tags, including a His10 purification tag, the SUMOstar (SUMO*) domain, an extracellular FLAG epitope, and an enhanced green fluorescent protein (EGFP), each alone or in various combinations. Expressed in HEK293 cells, recombinant CFTR proteins underwent complex glycosylation, compartmentalized with the plasma membrane, and exhibited regulated chloride-channel activity with only modest alterations in channel conductance and gating kinetics. Surface CFTR expression level was enhanced by the presence of SUMO* on the N-terminus. Quantitative mass-spectrometric analysis indicated approximately 10% of the total recombinant CFTR (SUMO*-CFTR(FLAG)-EGFP) localized to the plasma membrane. Trial purification using dodecylmaltoside for membrane protein extraction reproducibly recovered 178 ± 56 μg SUMO*-CFTR(FLAG)-EGFP per billion cells at 80% purity. Fluorescence size-exclusion chromatography indicated purified CFTR was monodisperse. These findings demonstrate a stable mammalian cell expression system capable of producing human CFTR of sufficient quality and quantity to augment future CF drug discovery efforts, including biophysical and structural studies.
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Affiliation(s)
- Ellen Hildebrandt
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430
| | - Alok Mulky
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Haitao Ding
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Qun Dai
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Andrei A. Aleksandrov
- Department of Biochemistry & Biophysics, University of North Carolina, Chapel Hill, NC 27599
| | - Bekim Bajrami
- Department of Chemistry, University of Connecticut, Storrs, CT 06269
| | - Pamela Ann Diego
- Department of Chemistry, University of Connecticut, Storrs, CT 06269
| | - Xing Wu
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Marjorie Ray
- Department of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294
| | | | - John R. Riordan
- Department of Biochemistry & Biophysics, University of North Carolina, Chapel Hill, NC 27599
| | - Xudong Yao
- Department of Chemistry, University of Connecticut, Storrs, CT 06269
| | - Lawrence J. DeLucas
- Department of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Ina L. Urbatsch
- Department of Cell Biology and Biochemistry, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430
| | - John C. Kappes
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
- Birmingham Veterans Affairs Medical Center, Research Service, Birmingham, AL 35233
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25
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Shah K, Cheng Y, Hahn B, Bridges R, Bradbury NA, Mueller DM. Synonymous codon usage affects the expression of wild type and F508del CFTR. J Mol Biol 2015; 427:1464-1479. [PMID: 25676312 DOI: 10.1016/j.jmb.2015.02.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 02/03/2015] [Accepted: 02/04/2015] [Indexed: 10/24/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel composed of 1480 amino acids. The major mutation responsible for cystic fibrosis results in loss of amino acid residue, F508 (F508del). Loss of F508 in CFTR alters the folding pathway resulting in endoplasmic-reticulum-associated degradation. This study investigates the role of synonymous codon in the expression of CFTR and CFTR F508del in human HEK293 cells. DNA encoding the open reading frame (ORF) for CFTR containing synonymous codon replacements was expressed using a heterologous vector integrated into the genome. The results indicate that the codon usage greatly affects the expression of CFTR. While the promoter strength driving expression of the ORFs was largely unchanged and the mRNA half-lives were unchanged, the steady-state levels of the mRNA varied by as much as 30-fold. Experiments support that this apparent inconsistency is attributed to nonsense mediated decay independent of exon junction complex. The ratio of CFTR/mRNA indicates that mRNA containing native codons was more efficient in expressing mature CFTR as compared to mRNA containing synonymous high-expression codons. However, when F508del CFTR was expressed after codon optimization, a greater percentage of the protein escaped endoplasmic-reticulum-associated degradation resulting in considerable levels of mature F508del CFTR on the plasma membrane, which showed channel activity. These results indicate that codon usage has an effect on mRNA levels and protein expression, for CFTR, and likely on chaperone-assisted folding pathway, for F508del CFTR.
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Affiliation(s)
- Kalpit Shah
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University, The Chicago Medical School, North Chicago, IL 60064, USA; Department of Physiology and Biophysics, Rosalind Franklin University, The Chicago Medical School, North Chicago, IL 60064, USA
| | - Yi Cheng
- Department of Physiology and Biophysics, Rosalind Franklin University, The Chicago Medical School, North Chicago, IL 60064, USA
| | - Brian Hahn
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University, The Chicago Medical School, North Chicago, IL 60064, USA
| | - Robert Bridges
- Department of Physiology and Biophysics, Rosalind Franklin University, The Chicago Medical School, North Chicago, IL 60064, USA
| | - Neil A Bradbury
- Department of Physiology and Biophysics, Rosalind Franklin University, The Chicago Medical School, North Chicago, IL 60064, USA
| | - David M Mueller
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University, The Chicago Medical School, North Chicago, IL 60064, USA.
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Broadbent SD, Wang W, Linsdell P. Interaction between 2 extracellular loops influences the activity of the cystic fibrosis transmembrane conductance regulator chloride channel. Biochem Cell Biol 2014; 92:390-6. [PMID: 25253636 DOI: 10.1139/bcb-2014-0066] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Activity of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel is thought to be controlled by cytoplasmic factors. However, recent evidence has shown that overall channel activity is also influenced by extracellular anions that interact directly with the extracellular loops (ECLs) of the CFTR protein. Very little is known about the structure of the ECLs or how substances interacting with these ECLs might affect CFTR function. We used patch-clamp recording to investigate the accessibility of cysteine-reactive reagents to cysteines introduced throughout ECL1 and 2 key sites in ECL4. Furthermore, interactions between ECL1 and ECL4 were investigated by the formation of disulfide crosslinks between cysteines introduced into these 2 regions. Crosslinks could be formed between R899C (in ECL4) and a number of sites in ECL1 in a manner that was dependent on channel activity, suggesting that the relative orientation of these 2 loops changes on activation. Formation of these crosslinks inhibited channel function, suggesting that relative movement of these ECLs is important to normal channel function. Implications of these findings for the effects of mutations in the ECLs that are associated with cystic fibrosis and interactions with extracellular substances that influence channel activity are discussed.
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Affiliation(s)
- Steven D Broadbent
- Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, NS B3H 4R2, Canada
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27
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Hildebrandt E, Zhang Q, Cant N, Ding H, Dai Q, Peng L, Fu Y, DeLucas LJ, Ford R, Kappes JC, Urbatsch IL. A survey of detergents for the purification of stable, active human cystic fibrosis transmembrane conductance regulator (CFTR). BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2825-37. [PMID: 25065669 DOI: 10.1016/j.bbamem.2014.07.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 07/15/2014] [Accepted: 07/17/2014] [Indexed: 01/12/2023]
Abstract
Structural knowledge of the cystic fibrosis transmembrane conductance regulator (CFTR) requires developing methods to purify and stabilize this aggregation-prone membrane protein above 1mg/ml. Starting with green fluorescent protein- and epitope-tagged human CFTR produced in mammalian cells known to properly fold and process CFTR, we devised a rapid tandem affinity purification scheme to minimize CFTR exposure to detergent in order to preserve its ATPase function. We compared a panel of detergents, including widely used detergents (maltosides, neopentyl glycols (MNG), C12E8, lysolipids, Chaps) and innovative detergents (branched alkylmaltosides, facial amphiphiles) for CFTR purification, function, monodispersity and stability. ATPase activity after reconstitution into proteoliposomes was 2-3 times higher when CFTR was purified using facial amphiphiles. ATPase activity was also demonstrated in purified CFTR samples without detergent removal using a novel lipid supplementation assay. By electron microscopy, negatively stained CFTR samples were monodisperse at low concentration, and size exclusion chromatography showed a predominance of monomer even after CFTR concentration above 1mg/ml. Rates of CFTR aggregation quantified in an electrophoretic mobility shift assay showed that detergents which best preserved reconstituted ATPase activity also supported the greatest stability, with CFTR monomer half-lives of 6-9days in MNG or Chaps, and 12-17days in facial amphiphile. Cryoelectron microscopy of concentrated CFTR in MNG or facial amphiphile confirmed mostly monomeric protein, producing low resolution reconstructions in conformity with similar proteins. These protocols can be used to generate samples of pure, functional, stable CFTR at concentrations amenable to biophysical characterization.
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Affiliation(s)
- Ellen Hildebrandt
- Department of Cell Biology and Biochemistry and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA
| | - Qinghai Zhang
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Natasha Cant
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Haitao Ding
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - Qun Dai
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - Lingling Peng
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Yu Fu
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Lawrence J DeLucas
- Department of Optometry, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA
| | - Robert Ford
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - John C Kappes
- Department of Medicine, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA; Department of Microbiology, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA; Department of Pathology, University of Alabama at Birmingham, 701 19th Street South, Birmingham, AL 35294-0007, USA; Birmingham Veterans Medical Center, Research Service, Birmingham, AL 35233, USA
| | - Ina L Urbatsch
- Department of Cell Biology and Biochemistry and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, 3601 4th Street, Stop 6540, Lubbock, TX 79430, USA.
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Cui G, Rahman KS, Infield DT, Kuang C, Prince CZ, McCarty NA. Three charged amino acids in extracellular loop 1 are involved in maintaining the outer pore architecture of CFTR. ACTA ACUST UNITED AC 2014; 144:159-79. [PMID: 25024266 PMCID: PMC4113900 DOI: 10.1085/jgp.201311122] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Disease-associated mutation of charged amino acids in extracellular loop 1 of CFTR may reduce chloride flow by damaging the outer pore architecture. The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) bears six extracellular loops (ECL1–6); ECL1 is the site of several mutations associated with CF. Mutation R117H has been reported to reduce current amplitude, whereas D110H, E116K, and R117C/L/P may impair channel stability. We hypothesized that these amino acids might not be directly involved in ion conduction and permeation but may contribute to stabilizing the outer vestibule architecture in CFTR. We used cRNA injected oocytes combined with electrophysiological techniques to test this hypothesis. Mutants bearing cysteine at these sites were not functionally modified by extracellular MTS reagents and were blocked by GlyH-101 similarly to WT-CFTR. These results suggest that these three residues do not contribute directly to permeation in CFTR. In contrast, mutants D110R-, E116R-, and R117A-CFTR exhibited instability of the open state and significantly shortened burst duration compared with WT-CFTR and failed to be locked into the open state by AMP-PNP (adenosine 5′-(β,γ-imido) triphosphate); charge-retaining mutants showed mainly the full open state with comparably longer open burst duration. These interactions suggest that these ECL1 residues might be involved in maintaining the outer pore architecture of CFTR. A CFTR homology model suggested that E116 interacts with R104 in both the closed and open states, D110 interacts with K892 in the fully closed state, and R117 interacts with E1126 in the open state. These interactions were confirmed experimentally. The results suggest that D110, E116, and R117 may contribute to stabilizing the architecture of the outer pore of CFTR by interactions with other charged residues.
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Affiliation(s)
- Guiying Cui
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322
| | - Kazi S Rahman
- Parker H. Petit Institute for Bioengineering and Bioscience and School of Biology, Georgia Institute of Technology, Atlanta, GA 30332 Parker H. Petit Institute for Bioengineering and Bioscience and School of Biology, Georgia Institute of Technology, Atlanta, GA 30332
| | - Daniel T Infield
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322
| | - Christopher Kuang
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322
| | - Chengyu Z Prince
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322
| | - Nael A McCarty
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322 Parker H. Petit Institute for Bioengineering and Bioscience and School of Biology, Georgia Institute of Technology, Atlanta, GA 30332
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Molecular modelling approaches for cystic fibrosis transmembrane conductance regulator studies. Int J Biochem Cell Biol 2014; 52:39-46. [DOI: 10.1016/j.biocel.2014.04.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 04/01/2014] [Accepted: 04/04/2014] [Indexed: 12/30/2022]
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Pranke IM, Sermet-Gaudelus I. Biosynthesis of cystic fibrosis transmembrane conductance regulator. Int J Biochem Cell Biol 2014; 52:26-38. [DOI: 10.1016/j.biocel.2014.03.020] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 03/19/2014] [Accepted: 03/20/2014] [Indexed: 01/19/2023]
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Strauss AS, Wang D, Stock M, Gretscher RR, Groth M, Boland W, Burse A. Tissue-specific transcript profiling for ABC transporters in the sequestering larvae of the phytophagous leaf beetle Chrysomela populi. PLoS One 2014; 9:e98637. [PMID: 24887102 PMCID: PMC4041752 DOI: 10.1371/journal.pone.0098637] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 05/05/2014] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Insects evolved ingenious adaptations to use extraordinary food sources. Particularly, the diet of herbivores enriched with noxious plant secondary metabolites requires detoxification mechanisms. Sequestration, which involves the uptake, transfer, and concentration of occasionally modified phytochemicals into specialized tissues or hemolymph, is one of the most successful detoxification strategies found in most insect orders. Due to the ability of ATP-binding cassette (ABC) carriers to transport a wide range of molecules including phytochemicals and xenobiotics, it is highly likely that they play a role in this sequestration process. To shed light on the role of ABC proteins in sequestration, we describe an inventory of putative ABC transporters in various tissues in the sequestering juvenile poplar leaf beetle, Chrysomela populi. RESULTS In the transcriptome of C. populi, we predicted 65 ABC transporters. To link the proteins with a possible function, we performed comparative phylogenetic analyses with ABC transporters of other insects and of humans. While tissue-specific profiling of each ABC transporter subfamily suggests that ABCB, C and G influence the plant metabolite absorption in the gut, ABCC with 14 members is the preferred subfamily responsible for the excretion of these metabolites via Malpighian tubules. Moreover, salicin, which is sequestered from poplar plants, is translocated into the defensive glands for further deterrent production. In these glands and among all identified ABC transporters, an exceptionally high transcript level was observed only for Cpabc35 (Cpmrp). RNAi revealed the deficiency of other ABC pumps to compensate the function of CpABC35, demonstrating its key role during sequestration. CONCLUSION We provide the first comprehensive phylogenetic study of the ABC family in a phytophagous beetle species. RNA-seq data from different larval tissues propose the importance of ABC pumps to achieve a homeostasis of plant-derived compounds and offer a basis for future analyses of their physiological function in sequestration processes.
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Affiliation(s)
- Anja S. Strauss
- Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Str. 8, D-07745 Jena, Thuringia, Germany
| | - Ding Wang
- Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Str. 8, D-07745 Jena, Thuringia, Germany
| | - Magdalena Stock
- Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Str. 8, D-07745 Jena, Thuringia, Germany
| | - René R. Gretscher
- Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Str. 8, D-07745 Jena, Thuringia, Germany
| | - Marco Groth
- Leibniz Institute for Age Research – Fritz Lipmann Institute, Beutenbergstr. 11, D-07745 Jena, Thuringia, Germany
| | - Wilhelm Boland
- Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Str. 8, D-07745 Jena, Thuringia, Germany
| | - Antje Burse
- Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Str. 8, D-07745 Jena, Thuringia, Germany
- * E-mail:
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Wang Y, Wrennall JA, Cai Z, Li H, Sheppard DN. Understanding how cystic fibrosis mutations disrupt CFTR function: from single molecules to animal models. Int J Biochem Cell Biol 2014; 52:47-57. [PMID: 24727426 DOI: 10.1016/j.biocel.2014.04.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 04/01/2014] [Accepted: 04/02/2014] [Indexed: 12/21/2022]
Abstract
Defective epithelial ion transport is the hallmark of the life-limiting genetic disease cystic fibrosis (CF). This abnormality is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), the ATP-binding cassette transporter that functions as a ligand-gated anion channel. Since the identification of the CFTR gene, almost 2000 disease-causing mutations associated with a spectrum of clinical phenotypes have been reported, but the majority remain poorly characterised. Studies of a small number of mutations including the most common, F508del-CFTR, have identified six general mechanisms of CFTR dysfunction. Here, we review selectively progress to understand how CF mutations disrupt CFTR processing, stability and function. We explore CFTR structure and function to explain the molecular mechanisms of CFTR dysfunction and highlight new knowledge of disease pathophysiology emerging from large animal models of CF. Understanding CFTR dysfunction is crucial to the development of transformational therapies for CF patients.
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Affiliation(s)
- Yiting Wang
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Joe A Wrennall
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Zhiwei Cai
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Hongyu Li
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - David N Sheppard
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.
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Linsdell P. Cystic fibrosis transmembrane conductance regulator chloride channel blockers: Pharmacological, biophysical and physiological relevance. World J Biol Chem 2014; 5:26-39. [PMID: 24600512 PMCID: PMC3942540 DOI: 10.4331/wjbc.v5.i1.26] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 11/15/2013] [Accepted: 12/11/2013] [Indexed: 02/05/2023] Open
Abstract
Dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel causes cystic fibrosis, while inappropriate activity of this channel occurs in secretory diarrhea and polycystic kidney disease. Drugs that interact directly with CFTR are therefore of interest in the treatment of a number of disease states. This review focuses on one class of small molecules that interacts directly with CFTR, namely inhibitors that act by directly blocking chloride movement through the open channel pore. In theory such compounds could be of use in the treatment of diarrhea and polycystic kidney disease, however in practice all known substances acting by this mechanism to inhibit CFTR function lack either the potency or specificity for in vivo use. Nevertheless, this theoretical pharmacological usefulness set the scene for the development of more potent, specific CFTR inhibitors. Biophysically, open channel blockers have proven most useful as experimental probes of the structure and function of the CFTR chloride channel pore. Most importantly, the use of these blockers has been fundamental in developing a functional model of the pore that includes a wide inner vestibule that uses positively charged amino acid side chains to attract both permeant and blocking anions from the cell cytoplasm. CFTR channels are also subject to this kind of blocking action by endogenous anions present in the cell cytoplasm, and recently this blocking effect has been suggested to play a role in the physiological control of CFTR channel function, in particular as a novel mechanism linking CFTR function dynamically to the composition of epithelial cell secretions. It has also been suggested that future drugs could target this same pathway as a way of pharmacologically increasing CFTR activity in cystic fibrosis. Studying open channel blockers and their mechanisms of action has resulted in significant advances in our understanding of CFTR as a pharmacological target in disease states, of CFTR channel structure and function, and of how CFTR activity is controlled by its local environment.
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Calcium signaling in pancreatic ductal epithelial cells: an old friend and a nasty enemy. Cell Calcium 2014; 55:337-45. [PMID: 24602604 DOI: 10.1016/j.ceca.2014.02.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 02/04/2014] [Accepted: 02/05/2014] [Indexed: 12/20/2022]
Abstract
Ductal epithelial cells of the exocrine pancreas secrete HCO3(-) rich, alkaline pancreatic juice, which maintains the intraluminal pH and washes the digestive enzymes out from the ductal system. Importantly, damage of this secretory process can lead to pancreatic diseases such as acute and chronic pancreatitis. Intracellular Ca(2+) signaling plays a central role in the physiological regulation of HCO3(-) secretion, however uncontrolled Ca(2+) release can lead to intracellular Ca(2+) overload and toxicity, including mitochondrial damage and impaired ATP production. Recent findings suggest that the most common pathogenic factors leading to acute pancreatitis, such as bile acids, or ethanol and ethanol metabolites can evoke different types of intracellular Ca(2+) signals, which can stimulate or inhibit ductal HCO3(-) secretion. Therefore, understanding the intracellular Ca(2+) pathways and the mechanisms which can switch a good signal to a bad signal in pancreatic ductal epithelial cells are crucially important. This review summarizes the variety of Ca(2+) signals both in physiological and pathophysiological aspects and highlight molecular targets which may strengthen our old friend or release our nasty enemy.
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35
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CFTR structure and cystic fibrosis. Int J Biochem Cell Biol 2014; 52:15-25. [PMID: 24534272 DOI: 10.1016/j.biocel.2014.02.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 02/04/2014] [Accepted: 02/06/2014] [Indexed: 12/31/2022]
Abstract
CFTR (cystic fibrosis transmembrane conductance regulator) is a member of the ATP-binding cassette family of membrane proteins. Although almost all members of this family are transporters, CFTR functions as a channel with specificity for anions, in particular chloride and bicarbonate. In this review we look at what is known about CFTR structure and function within the context of the ATP-binding cassette family. We also review current strategies aimed at obtaining the high resolution structure of the protein.
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Wang W, El Hiani Y, Rubaiy HN, Linsdell P. Relative contribution of different transmembrane segments to the CFTR chloride channel pore. Pflugers Arch 2013; 466:477-90. [PMID: 23955087 DOI: 10.1007/s00424-013-1317-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 06/18/2013] [Accepted: 06/18/2013] [Indexed: 12/16/2022]
Abstract
The membrane-spanning part of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel comprises 12 transmembrane (TM) α-helices, arranged in 2 symmetrical groups of 6. However, those TMs that line the channel pore are not completely defined. We used patch clamp recording to compare the accessibility of cysteine-reactive reagents to cysteines introduced into different TMs. Several residues in TM11 were accessible to extracellular and/or intracellular cysteine reactive reagents; however, no reactive cysteines were identified in TMs 5 or 11. Two accessible residues in TM11 (T1115C and S1118C) were found to be more readily modified from the extracellular solution in closed channels, but more readily modified from the intracellular solution in open channels, as previously reported for T338C in TM6. However, the effects of mutagenesis at S1118 (TM11) on a range of pore functional properties were relatively minor compared to the large effects of mutagenesis at T338 (TM6). Our results suggest that the CFTR pore is lined by TM11 but not by TM5 or TM7. Comparison with previous works therefore suggests that the pore is lined by TMs 1, 6, 11, and 12, suggesting that the structure of the open channel pore is asymmetric in terms of the contributions of different TMs. Although TMs 6 and 11 appear to undergo similar conformational changes during channel opening and closing, the influence of these two TMs on the functional properties of the narrowest region of the pore is clearly unequal.
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Affiliation(s)
- Wuyang Wang
- Department of Physiology and Biophysics, Dalhousie University, PO Box 15000 Halifax, Nova Scotia, B3H 4R2, Canada
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Correctors of the basic trafficking defect of the mutant F508del-CFTR that causes cystic fibrosis. Curr Opin Chem Biol 2013; 17:353-60. [DOI: 10.1016/j.cbpa.2013.04.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 04/16/2013] [Accepted: 04/18/2013] [Indexed: 01/01/2023]
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38
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Tsui LC, Dorfman R. The cystic fibrosis gene: a molecular genetic perspective. Cold Spring Harb Perspect Med 2013; 3:a009472. [PMID: 23378595 DOI: 10.1101/cshperspect.a009472] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The positional cloning of the gene responsible for cystic fibrosis (CF) was the important first step in understanding the basic defect and pathophysiology of the disease. This study aims to provide a historical account of key developments as well as factors that contributed to the cystic fibrosis transmembrane conductance regulator (CFTR) gene identification work. A redefined gene structure based on the full sequence of the gene derived from the Human Genome Project is presented, along with brief reviews of the transcription regulatory sequences for the CFTR gene, the role of mRNA splicing in gene regulation and CF disease, and, various related sequences in the human genome and other species. Because CF mutations and genotype-phenotype correlations are covered by our colleagues (Ferec C, Cutting GR. 2012. Assessing the disease-liability of mutations in CFTR. Cold Spring Harb Perspect Med doi: 10.1101/cshperspect.a009480), we only attempt to provide an introduction of the CF mutation database here for reference purposes.
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Affiliation(s)
- Lap-Chee Tsui
- The University of Hong Kong, Hong Kong, Special Administrative Region, China.
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