1
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Bardin E, Pastor A, Semeraro M, Golec A, Hayes K, Chevalier B, Berhal F, Prestat G, Hinzpeter A, Gravier-Pelletier C, Pranke I, Sermet-Gaudelus I. Modulators of CFTR. Updates on clinical development and future directions. Eur J Med Chem 2021; 213:113195. [PMID: 33524685 DOI: 10.1016/j.ejmech.2021.113195] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 12/19/2022]
Abstract
Cystic fibrosis (CF) is the most frequent life-limiting autosomal recessive disorder in the Caucasian population. It is due to mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. Current symptomatic CF therapies, which treat the downstream consequences of CFTR mutations, have increased survival. Better knowledge of the CFTR protein has enabled pharmacologic therapy aiming to restore mutated CFTR expression and function. These CFTR "modulators" have revolutionised the CF therapeutic landscape, with the potential to transform prognosis for a considerable number of patients. This review provides a brief summary of their mechanism of action and presents a thorough review of the results obtained from clinical trials of CFTR modulators.
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Affiliation(s)
| | - Alexandra Pastor
- LCBPT, UMR CNRS 8601, Paris, France; Université de Paris, Paris, France
| | - Michaela Semeraro
- Centre d'Investigation Clinique, Unité de Recherche Clinique-CIC P1419, Hôpital Necker Enfants Malades, Université de Paris, Paris, France
| | - Anita Golec
- Institut Necker Enfants Malades. INSERM U1151, Paris, France
| | - Kate Hayes
- Clinical Trial Network, European Cystic Fibrosis Society, Belfast, Ireland
| | | | - Farouk Berhal
- LCBPT, UMR CNRS 8601, Paris, France; Université de Paris, Paris, France
| | - Guillaume Prestat
- LCBPT, UMR CNRS 8601, Paris, France; Université de Paris, Paris, France
| | | | | | - Iwona Pranke
- Institut Necker Enfants Malades. INSERM U1151, Paris, France
| | - Isabelle Sermet-Gaudelus
- Institut Necker Enfants Malades. INSERM U1151, Paris, France; Université de Paris, Paris, France; Clinical Trial Network, European Cystic Fibrosis Society, Belfast, Ireland; Centre de Référence Maladies Rares, Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Paris, France; European Respiratory Network Lung, Paris, France.
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2
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Hu J. Toward unzipping the ZIP metal transporters: structure, evolution, and implications on drug discovery against cancer. FEBS J 2020; 288:5805-5825. [PMID: 33296542 DOI: 10.1111/febs.15658] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 11/30/2020] [Accepted: 12/07/2020] [Indexed: 12/13/2022]
Abstract
The Zrt-/Irt-like protein (ZIP) family consists of divalent metal transporters, ubiquitous in all kingdoms of life. Since the discovery of the first ZIPs in the 1990s, the ZIP family has been expanding to contain tens of thousands of members playing key roles in uptake and homeostasis of life-essential trace elements, primarily zinc, iron and manganese. Some family members are also responsible for toxic metal (particularly cadmium) absorption and distribution. Their central roles in trace element biology, and implications in many human diseases, including cancers, have elicited interest across multiple disciplines for potential applications in biomedicine, agriculture and environmental protection. In this review and perspective, selected areas under rapid progress in the last several years, including structural biology, evolution, and drug discovery against cancers, are summarised and commented. Future research to address the most prominent issues associated with transport and regulation mechanisms are also discussed.
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Affiliation(s)
- Jian Hu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA.,Department of Chemistry, Michigan State University, East Lansing, MI, USA
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3
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Cui G, Hong J, Chung-Davidson YW, Infield D, Xu X, Li J, Simhaev L, Khazanov N, Stauffer B, Imhoff B, Cottrill K, Blalock JE, Li W, Senderowitz H, Sorscher E, McCarty NA, Gaggar A. An Ancient CFTR Ortholog Informs Molecular Evolution in ABC Transporters. Dev Cell 2019; 51:421-430.e3. [PMID: 31679858 DOI: 10.1016/j.devcel.2019.09.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 07/30/2019] [Accepted: 09/24/2019] [Indexed: 01/13/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel central to the development of secretory diarrhea and cystic fibrosis. The oldest CFTR ortholog identified is from dogfish shark, which retains similar structural and functional characteristics to the mammalian protein, thereby highlighting CFTR's critical role in regulating epithelial ion transport in vertebrates. However, the identification of an early CFTR ortholog with altered structure or function would provide critical insight into the evolution of epithelial anion transport. Here, we describe the earliest known CFTR, expressed in sea lamprey (Petromyzon marinus), with unique structural features, altered kinetics of activation and sensitivity to inhibition, and altered single-channel conductance compared to human CFTR. Our data provide the earliest evolutionary evidence of CFTR, offering insight regarding changes in gene and protein structure that underpin evolution from transporter to anion channel. Importantly, these data provide a unique platform to enhance our understanding of vertebrate phylogeny over a critical period of evolutionary expansion.
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Affiliation(s)
- Guiying Cui
- Department of Pediatrics and Children's Healthcare of Atlanta, Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA 30322, USA
| | - Jeong Hong
- Department of Pediatrics and Children's Healthcare of Atlanta, Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA 30322, USA; Department of Medicine, Gregory Fleming James Cystic Fibrosis Research Center, and Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Yu-Wen Chung-Davidson
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48823, USA
| | - Daniel Infield
- Department of Pediatrics and Children's Healthcare of Atlanta, Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA 30322, USA; Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA
| | - Xin Xu
- Department of Medicine, Gregory Fleming James Cystic Fibrosis Research Center, and Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; Birmingham Veterans Administration Medical Center, Birmingham, AL 35233, USA
| | - Jindong Li
- Department of Medicine, Gregory Fleming James Cystic Fibrosis Research Center, and Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; Birmingham Veterans Administration Medical Center, Birmingham, AL 35233, USA
| | - Luba Simhaev
- Department of Chemistry, Bar-Ilan University, Ramat Gan, Israel
| | - Netaly Khazanov
- Department of Chemistry, Bar-Ilan University, Ramat Gan, Israel
| | - Brandon Stauffer
- Department of Pediatrics and Children's Healthcare of Atlanta, Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA 30322, USA
| | - Barry Imhoff
- Department of Pediatrics and Children's Healthcare of Atlanta, Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA 30322, USA
| | - Kirsten Cottrill
- Department of Pediatrics and Children's Healthcare of Atlanta, Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA 30322, USA
| | - J Edwin Blalock
- Department of Medicine, Gregory Fleming James Cystic Fibrosis Research Center, and Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Weiming Li
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48823, USA
| | | | - Eric Sorscher
- Department of Pediatrics and Children's Healthcare of Atlanta, Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA 30322, USA; Department of Medicine, Gregory Fleming James Cystic Fibrosis Research Center, and Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Nael A McCarty
- Department of Pediatrics and Children's Healthcare of Atlanta, Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, GA 30322, USA
| | - Amit Gaggar
- Department of Medicine, Gregory Fleming James Cystic Fibrosis Research Center, and Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; Birmingham Veterans Administration Medical Center, Birmingham, AL 35233, USA.
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4
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Pranke I, Golec A, Hinzpeter A, Edelman A, Sermet-Gaudelus I. Emerging Therapeutic Approaches for Cystic Fibrosis. From Gene Editing to Personalized Medicine. Front Pharmacol 2019; 10:121. [PMID: 30873022 PMCID: PMC6400831 DOI: 10.3389/fphar.2019.00121] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 01/31/2019] [Indexed: 12/13/2022] Open
Abstract
An improved understanding of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein structure and the consequences of CFTR gene mutations have allowed the development of novel therapies targeting specific defects underlying CF. Some strategies are mutation specific and have already reached clinical development; some strategies include a read-through of the specific premature termination codons (read-through therapies, nonsense mediated decay pathway inhibitors for Class I mutations); correction of CFTR folding and trafficking to the apical plasma membrane (correctors for Class II mutations); and an increase in the function of CFTR channel (potentiators therapy for Class III mutations and any mutant with a residual function located at the membrane). Other therapies that are in preclinical development are not mutation specific and include gene therapy to edit the genome and stem cell therapy to repair the airway tissue. These strategies that are directed at the basic CF defects are now revolutionizing the treatment for patients and should positively impact their survival rates.
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Affiliation(s)
- Iwona Pranke
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Descartes, Paris, France
| | - Anita Golec
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Descartes, Paris, France
| | - Alexandre Hinzpeter
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Descartes, Paris, France
| | - Aleksander Edelman
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Descartes, Paris, France
| | - Isabelle Sermet-Gaudelus
- INSERM U 1151, Institut Necker Enfants Malades, Université Paris Descartes, Paris, France.,Centre de Référence Maladie Rare, Mucoviscidose et Maladies de CFTR, Paris, France.,Faculté de Médecine, Université Paris Descartes, Paris, France
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5
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Molecular dynamics of the cryo-EM CFTR structure. Biochem Biophys Res Commun 2017; 491:986-993. [DOI: 10.1016/j.bbrc.2017.07.165] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 07/30/2017] [Indexed: 12/11/2022]
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6
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Zhang Z, Liu F, Chen J. Conformational Changes of CFTR upon Phosphorylation and ATP Binding. Cell 2017; 170:483-491.e8. [PMID: 28735752 DOI: 10.1016/j.cell.2017.06.041] [Citation(s) in RCA: 171] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 06/21/2017] [Accepted: 06/26/2017] [Indexed: 02/01/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel evolved from an ATP-binding cassette transporter. CFTR channel gating is strictly coupled to phosphorylation and ATP hydrolysis. Previously, we reported essentially identical structures of zebrafish and human CFTR in the dephosphorylated, ATP-free form. Here, we present the structure of zebrafish CFTR in the phosphorylated, ATP-bound conformation, determined by cryoelectron microscopy to 3.4 Å resolution. Comparison of the two conformations shows major structural rearrangements leading to channel opening. The phosphorylated regulatory domain is disengaged from its inhibitory position; the nucleotide-binding domains (NBDs) form a "head-to-tail" dimer upon binding ATP; and the cytoplasmic pathway, found closed off in other ATP-binding cassette transporters, is cracked open, consistent with CFTR's unique channel function. Unexpectedly, the extracellular mouth of the ion pore remains closed, indicating that local movements of the transmembrane helices can control ion access to the pore even in the NBD-dimerized conformation.
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Affiliation(s)
- Zhe Zhang
- Laboratory of Membrane Biophysics and Biology, The Rockefeller University, New York, NY, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Fangyu Liu
- Laboratory of Membrane Biophysics and Biology, The Rockefeller University, New York, NY, USA; Tri-Institutional Training Program in Chemical Biology, The Rockefeller University, New York, NY, USA
| | - Jue Chen
- Laboratory of Membrane Biophysics and Biology, The Rockefeller University, New York, NY, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
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7
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Musgaard M, Paramo T, Domicevica L, Andersen OJ, Biggin PC. Insights into channel dysfunction from modelling and molecular dynamics simulations. Neuropharmacology 2017; 132:20-30. [PMID: 28669899 DOI: 10.1016/j.neuropharm.2017.06.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 06/06/2017] [Accepted: 06/28/2017] [Indexed: 11/20/2022]
Abstract
Developments in structural biology mean that the number of different ion channel structures has increased significantly in recent years. Structures of ion channels enable us to rationalize how mutations may lead to channelopathies. However, determining the structures of ion channels is still not trivial, especially as they necessarily exist in many distinct functional states. Therefore, the use of computational modelling can provide complementary information that can refine working hypotheses of both wild type and mutant ion channels. The simplest but still powerful tool is homology modelling. Many structures are available now that can provide suitable templates for many different types of ion channels, allowing a full three-dimensional interpretation of mutational effects. These structural models, and indeed the structures themselves obtained by X-ray crystallography, and more recently cryo-electron microscopy, can be subjected to molecular dynamics simulations, either as a tool to help explore the conformational dynamics in detail or simply as a means to refine the models further. Here we review how these approaches have been used to improve our understanding of how diseases might be linked to specific mutations in ion channel proteins. This article is part of the Special Issue entitled 'Channelopathies.'
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Affiliation(s)
- Maria Musgaard
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
| | - Teresa Paramo
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
| | - Laura Domicevica
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
| | - Ole Juul Andersen
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
| | - Philip C Biggin
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom.
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8
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Locher KP. Mechanistic diversity in ATP-binding cassette (ABC) transporters. Nat Struct Mol Biol 2017; 23:487-93. [PMID: 27273632 DOI: 10.1038/nsmb.3216] [Citation(s) in RCA: 505] [Impact Index Per Article: 72.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 03/30/2016] [Indexed: 12/18/2022]
Abstract
ABC transporters catalyze transport reactions, such as the high-affinity uptake of micronutrients into bacteria and the export of cytotoxic compounds from mammalian cells. Crystal structures of ABC domains and full transporters have provided a framework for formulating reaction mechanisms of ATP-driven substrate transport, but recent studies have suggested remarkable mechanistic diversity within this protein family. This review evaluates the differing mechanistic proposals and outlines future directions for the exploration of ABC-transporter-catalyzed reactions.
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Affiliation(s)
- Kaspar P Locher
- Institute of Molecular Biology and Biophysics, Department of Biology, ETH Zurich, Zurich, Switzerland
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9
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Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel expressed in the apical membrane of epithelia. Mutations in the CFTR gene are the cause of cystsic fibrosis. CFTR is the only ABC-protein that constitutes an ion channel pore forming subunit. CFTR gating is regulated in complex manner as phosphorylation is mandatory for channel activity and gating is directly regulated by binding of ATP to specific intracellular sites on the CFTR protein. This review covers our current understanding on the gating mechanism in CFTR and illustrates the relevance of alteration of these mechanisms in the onset of cystic fibrosis.
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Affiliation(s)
- Oscar Moran
- Istituto di Biofisica, CNR. Via De Marini, 6, 16149, Genoa, Italy.
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10
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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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11
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Ong T, Ramsey BW. New Therapeutic Approaches to Modulate and Correct Cystic Fibrosis Transmembrane Conductance Regulator. Pediatr Clin North Am 2016; 63:751-64. [PMID: 27469186 PMCID: PMC5478192 DOI: 10.1016/j.pcl.2016.04.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) modulators are clinically available personalized medicines approved for some individuals with cystic fibrosis (CF) to target the underlying defect of disease. This review summarizes strategies used to develop CFTR modulators as therapies that improve function and availability of CFTR protein. Lessons learned from dissemination of ivacaftor across the CF population responsive to this therapy and future approaches to predict and monitor treatment response of CFTR modulators are discussed. The goal remains to expand patient-centered and personalized therapy to all patients with CF, ultimately improving life expectancy and quality of life for this disease.
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Affiliation(s)
- Thida Ong
- University of Washington, Department of Pediatrics,Seattle Children’s Hospital, Division of Pulmonary and Sleep Medicine
| | - Bonnie W. Ramsey
- University of Washington, Department of Pediatrics,Seattle Children’s Research Institute, Center for Clinical and Translational Research,Corresponding Author: Bonnie Ramsey, MD, Seattle Children’s Research Institute, 2001 8th Avenue, Suite 400, M/S CW8-5B, Seattle, WA 98121, Tel: 206-987-5725, Fax: 206-987-7505,
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12
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Zwick M, Esposito C, Hellstern M, Seelig A. How Phosphorylation and ATPase Activity Regulate Anion Flux though the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). J Biol Chem 2016; 291:14483-98. [PMID: 27226582 DOI: 10.1074/jbc.m116.721415] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Indexed: 01/25/2023] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR, ABCC7), mutations of which cause cystic fibrosis, belongs to the ATP-binding cassette (ABC) transporter family and works as a channel for small anions, such as chloride and bicarbonate. Anion channel activity is known to depend on phosphorylation by cAMP-dependent protein kinase A (PKA) and CFTR-ATPase activity. Whereas anion channel activity has been extensively investigated, phosphorylation and CFTR-ATPase activity are still poorly understood. Here, we show that the two processes can be measured in a label-free and non-invasive manner in real time in live cells, stably transfected with CFTR. This study reveals three key findings. (i) The major contribution (≥90%) to the total CFTR-related ATP hydrolysis rate is due to phosphorylation by PKA and the minor contribution (≤10%) to CFTR-ATPase activity. (ii) The mutant CFTR-E1371S that is still conductive, but defective in ATP hydrolysis, is not phosphorylated, suggesting that phosphorylation requires a functional nucleotide binding domain and occurs in the post-hydrolysis transition state. (iii) CFTR-ATPase activity is inversely related to CFTR anion flux. The present data are consistent with a model in which CFTR is in a closed conformation with two ATPs bound. The open conformation is induced by ATP hydrolysis and corresponds to the post-hydrolysis transition state that is stabilized by phosphorylation and binding of chloride channel potentiators.
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Affiliation(s)
- Matthias Zwick
- From the Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Cinzia Esposito
- From the Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Manuel Hellstern
- From the Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Anna Seelig
- From the Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
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13
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Structural model of FeoB, the iron transporter from Pseudomonas aeruginosa, predicts a cysteine lined, GTP-gated pore. Biosci Rep 2016; 36:BSR20160046. [PMID: 26934982 PMCID: PMC4847171 DOI: 10.1042/bsr20160046] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/29/2016] [Indexed: 01/23/2023] Open
Abstract
The bacterial ferrous iron acquisition protein FeoB assembles as a homotrimer that is predicted to form a central pore lined by conserved cysteine residues. Structure-function analysis of FeoB indicates a putative mechanism more akin to a GTP-gated channel than a transporter. Iron is essential for the survival and virulence of pathogenic bacteria. The FeoB transporter allows the bacterial cell to acquire ferrous iron from its environment, making it an excellent drug target in intractable pathogens. The protein consists of an N-terminal GTP-binding domain and a C-terminal membrane domain. Despite the availability of X-ray crystal structures of the N-terminal domain, many aspects of the structure and function of FeoB remain unclear, such as the structure of the membrane domain, the oligomeric state of the protein, the molecular mechanism of iron transport, and how this is coupled to GTP hydrolysis at the N-terminal domain. In the present study, we describe the first homology model of FeoB. Due to the lack of sequence homology between FeoB and other transporters, the structures of four different proteins were used as templates to generate the homology model of full-length FeoB, which predicts a trimeric structure. We confirmed this trimeric structure by both blue-native-PAGE (BN-PAGE) and AFM. According to our model, the membrane domain of the trimeric protein forms a central pore lined by highly conserved cysteine residues. This pore aligns with a central pore in the N-terminal GTPase domain (G-domain) lined by aspartate residues. Biochemical analysis of FeoB from Pseudomonas aeruginosa further reveals a putative iron sensor domain that could connect GTP binding/hydrolysis to the opening of the pore. These results indicate that FeoB might not act as a transporter, but rather as a GTP-gated channel.
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14
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El Hiani Y, Linsdell P. Conformational changes opening and closing the CFTR chloride channel: insights from cysteine scanning mutagenesis. Biochem Cell Biol 2014; 92:481-8. [PMID: 25367045 DOI: 10.1139/bcb-2014-0038] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cystic fibrosis, the most common lethal genetic disease affecting young people in North America, is caused by failure of the chloride ion channel known as CFTR (cystic fibrosis transmembrane conductance regulator). CFTR belongs to the large family of ATP-binding cassette (ABC) membrane transporters. In CFTR, ATP-driven events at the nucleotide-binding domains (NBDs) open and close a gate that controls chloride permeation. However, the conformational changes concomitant with opening and closing of the CFTR gate are unknown. Diverse techniques including substituted cysteine accessibility method, disulfide cross-linking, and patch-clamp recording have been used to explore CFTR channel structure. Here, we consider the architecture of both the open and the closed CFTR channel. We review how CFTR channel structure changes between the closed and the open channel conformations and portray the relative function of both cytoplasmic and vestigial gates during the gating cycle. Understanding how the CFTR channel gates chloride permeation is central for understanding how CFTR defects lead to CF. Such knowledge opens the door for novel ways to maximize CFTR channel activity in a CF setting.
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Affiliation(s)
- Yassine El Hiani
- Department of Physiology & Biophysics, Dalhousie University, Halifax, NS B3H 4R2, Canada
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15
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Abstract
Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), a member of the ATP-binding cassette (ABC) family of membrane transport proteins. CFTR is unique among ABC proteins in that it functions not as an active transporter but as an ATP-gated Cl(-) channel. As an ion channel, the function of the CFTR transmembrane channel pore that mediates Cl(-) movement has been studied in great detail. On the other hand, only low resolution structural data is available on the transmembrane parts of the protein. The structure of the channel pore has, however, been modeled on the known structure of active transporter ABC proteins. Currently, significant barriers exist to building a unified view of CFTR pore structure and function. Reconciling functional data on the channel with indirect structural data based on other proteins with very different transport functions and substrates has proven problematic. This review summarizes current structural and functional models of the CFTR Cl(-) channel pore, including a comprehensive review of previous electrophysiological investigations of channel structure and function. In addition, functional data on the three-dimensional arrangement of pore-lining helices, as well as contemporary hypotheses concerning conformational changes in the pore that occur during channel opening and closing, are discussed. Important similarities and differences between different models of the pore highlight current gaps in our knowledge of CFTR structure and function. In order to fill these gaps, structural and functional models of the membrane-spanning pore need to become better integrated.
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Affiliation(s)
- Paul Linsdell
- Department of Physiology & Biophysics, Dalhousie University , Halifax, Nova Scotia , Canada
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16
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Catterall WA, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: ion channels. Br J Pharmacol 2013; 170:1607-51. [PMID: 24528239 PMCID: PMC3892289 DOI: 10.1111/bph.12447] [Citation(s) in RCA: 224] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Ion channels are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen PH Alexander
- School of Life Sciences, University of Nottingham Medical SchoolNottingham, NG7 2UH, UK
- *
Author for correspondence;
| | - Helen E Benson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Elena Faccenda
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Adam J Pawson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Joanna L Sharman
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - William A Catterall
- University of Washington, School of Medicine, Department of PharmacologyBox 357280, Seattle, WA 98195-7280, USA
| | | | - John A Peters
- Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of DundeeDundee, DD1 9SY, UK
| | - Anthony J Harmar
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
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Liao YJ, Shiang YC, Chen LY, Hsu CL, Huang CC, Chang HT. Detection of adenosine triphosphate through polymerization-induced aggregation of actin-conjugated gold/silver nanorods. NANOTECHNOLOGY 2013; 24:444003. [PMID: 24113811 DOI: 10.1088/0957-4484/24/44/444003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We have developed a simple and selective nanosensor for the optical detection of adenosine triphosphate (ATP) using globular actin-conjugated gold/silver nanorods (G-actin-Au/Ag NRs). By simply mixing G-actin and Au/Ag NRs (length ~56 nm and diameter ~12 nm), G-actin-Au/Ag NRs were prepared which were stable in physiological solutions (25 mM Tris-HCl, 150 mM NaCl, 5.0 mM KCl, 3.0 mM MgCl2 and 1.0 mM CaCl2; pH 7.4). Introduction of ATP into the G-actin-Au/Ag NR solutions in the presence of excess G-actin induced the formation of filamentous actin-conjugated Au/Ag NR aggregates through ATP-induced polymerization of G-actin. When compared to G-actin-modified spherical Au nanoparticles having a size of 13 nm or 56 nm, G-actin-Au/Ag NRs provided better sensitivity for ATP, mainly because the longitudinal surface plasmon absorbance of the Au/Ag NR has a more sensitive response to aggregation. This G-actin-Au/Ag NR probe provided high sensitivity (limit of detection 25 nM) for ATP with remarkable selectivity (>10-fold) over other adenine nucleotides (adenosine, adenosine monophosphate and adenosine diphosphate) and nucleoside triphosphates (guanosine triphosphate, cytidine triphosphate and uridine triphosphate). It also allowed the determination of ATP concentrations in plasma samples without conducting tedious sample pretreatments; the only necessary step was simple dilution. Our experimental results are in good agreement with those obtained from a commercial luciferin-luciferase bioluminescence assay. Our simple, sensitive and selective approach appears to have a practical potential for the clinical diagnosis of diseases (e.g. cystic fibrosis) associated with changes in ATP concentrations.
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Affiliation(s)
- Yu-Ju Liao
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
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18
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Nagant C, Pitts B, Stewart PS, Feng Y, Savage PB, Dehaye JP. Study of the effect of antimicrobial peptide mimic, CSA-13, on an established biofilm formed by Pseudomonas aeruginosa. Microbiologyopen 2013; 2:318-25. [PMID: 23436807 PMCID: PMC3633355 DOI: 10.1002/mbo3.77] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 01/24/2013] [Accepted: 01/29/2013] [Indexed: 12/11/2022] Open
Abstract
The formation of a Pseudomonas aeruginosa biofilm, a complex structure enclosing bacterial cells in an extracellular polymeric matrix, is responsible for persistent infections in cystic fibrosis patients leading to a high rate of morbidity and mortality. The protective environment created by the tridimensional structure reduces the susceptibility of the bacteria to conventional antibiotherapy. Cationic steroid antibiotics (CSA)-13, a nonpeptide mimic of antimicrobial peptides with antibacterial activity on planktonic cultures, was evaluated for its ability to interact with sessile cells. Using confocal laser scanning microscopy, we demonstrated that the drug damaged bacteria within an established biofilm showing that penetration did not limit the activity of this antimicrobial agent against a biofilm. When biofilms were grown during exposure to shear forces and to a continuous medium flow allowing the development of robust structures with a complex architecture, CSA-13 reached the bacteria entrapped in the biofilm within 30 min. The permeabilizing effect of CSA-13 could be associated with the death of the bacteria. In static conditions, the compound did not perturb the architecture of the biofilm. This study confirms the potential of CSA-13 as a new strategy to combat persistent infections involving biofilms formed by P. aeruginosa.
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Affiliation(s)
- Carole Nagant
- Laboratoire de Chimie biologique et Médicale et de Microbiologie Pharmaceutique, Faculté de Pharmacie, Université libre de Bruxelles, Brussels, Belgium
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19
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Abstract
Cystic fibrosis is a lethal genetic disease caused by lack of functional cystic fibrosis transmembrane conductance regulator (CFTR) proteins at the apical surface of secretory epithelia. CFTR is a multidomain protein, containing five domains, and its functional structure is attained in a hierarchical folding process. Most CF-causing mutations in CFTR, including the most common mutation, a deletion of phenylalanine at position 508 (ΔF508), are unable to properly fold into this functional native three dimensional structure. Currently, no high-resolution structural information about full length CFTR exists. However, insight has been gained through examining homologous ABC transporter structures, molecular modeling, and high-resolution structures of individual, isolated CFTR domains. Taken together, these studies indicate that the prevalent ΔF508 mutation disrupts two essential steps during the development of the native structure: folding of the first nucleotide binding domain (NBD1) and its later association with the fourth intracellular loop (ICL4) in the second transmembrane domain (TMD2). Therapeutics to rescue ΔF508 and other mutants in CFTR can be targeted to correct defects that occur during the complex folding process. This article reviews the structural relationships between CFTR and ABC transporters and current knowledge about how CFTR attains its structure–with a focus on how this process is altered by CF-causing mutations in a manner targetable by therapeutics.
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Affiliation(s)
- Anna E Patrick
- Department of Physiology, University of Texas Southwestern Medical Center Dallas, TX, USA
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20
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Wang W, Linsdell P. Relative movements of transmembrane regions at the outer mouth of the cystic fibrosis transmembrane conductance regulator channel pore during channel gating. J Biol Chem 2012; 287:32136-46. [PMID: 22843683 DOI: 10.1074/jbc.m112.385096] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Multiple transmembrane (TM) segments line the pore of the cystic fibrosis transmembrane conductance regulator Cl(-) channel; however, the relative alignment of these TMs and their relative movements during channel gating are unknown. To gain three-dimensional structural information on the outer pore, we have used patch clamp recording to study the proximity of pairs of cysteine side chains introduced into TMs 6 and 11, using both disulfide cross-linking and Cd(2+) coordination. Following channel activation, disulfide bonds could apparently be formed between three cysteine pairs (of 15 studied): R334C/T1122C, R334C/G1127C, and T338C/S1118C. To examine the state dependence of cross-linking, we combined these cysteine mutations with a nucleotide-binding domain mutation (E1371Q) that stabilizes the channel open state. Investigation of the effects of the E1371Q mutation on disulfide bond formation and Cd(2+) coordination suggests that although R334C/T1122C and T338C/S1118C are closer together in the channel open state, R334C/G1127C are close together and can form disulfide bonds only when the channel is closed. These results provide important new information on the three-dimensional structure of the outer mouth of the cystic fibrosis transmembrane conductance regulator channel pore: TMs 6 and 11 are close enough together to form disulfide bonds in both open and closed channels. Moreover, the altered relative locations of residues in open and in closed channels that we infer allow us to propose that channel opening and closing may be associated with a relative translational movement of TMs 6 and 11, with TM6 moving "down" (toward the cytoplasm) during channel opening.
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Affiliation(s)
- Wuyang Wang
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
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21
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El Hiani Y, Linsdell P. Role of the juxtamembrane region of cytoplasmic loop 3 in the gating and conductance of the cystic fibrosis transmembrane conductance regulator chloride channel. Biochemistry 2012; 51:3971-81. [PMID: 22545782 PMCID: PMC3381012 DOI: 10.1021/bi300065z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Opening and closing of the cystic fibrosis transmembrane conductance regulator chloride channel are controlled by interactions of ATP with its cytoplasmic nucleotide binding domains (NBDs). The NBDs are connected to the transmembrane pore via four cytoplasmic loops. These loops have been suggested to play roles both in channel gating and in forming a cytoplasmic extension of the channel pore. To investigate the structure and function of one of these cytoplasmic loops, we have used patch clamp recording to investigate the accessibility of cytoplasmically applied cysteine-reactive reagents to cysteines introduced into loop 3. We find that methanethiosulfonate (MTS) reagents modify cysteines introduced at 14 of 16 sites studied in the juxtamembrane region of loop 3, in all cases leading to inhibition of channel function. In most cases, both the functional effects of modification and the rate of modification were similar for negatively and positively charged MTS reagents. Single-channel recordings indicated that, at all sites, inhibition was the result of an MTS reagent-induced decrease in channel open probability; in no case was the Cl(-) conductance of open channels altered by modification. These results indicate that loop 3 is readily accessible to the cytoplasm and support the involvement of this region in the control of channel gating. However, our results do not support the hypothesis that this region is close enough to the Cl(-) permeation pathway to exert any influence on permeating Cl(-) ions. We propose that either the cytoplasmic pore is very wide or cytoplasmic Cl(-) ions use other routes to access the transmembrane pore.
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Affiliation(s)
- Yassine El Hiani
- Department of Physiology and Biophysics, Dalhousie University , Halifax, Nova Scotia B3H 4R2, Canada
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22
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Insights into the mechanisms underlying CFTR channel activity, the molecular basis for cystic fibrosis and strategies for therapy. Essays Biochem 2012; 50:233-48. [PMID: 21967060 DOI: 10.1042/bse0500233] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) cause CF (cystic fibrosis), a fatal genetic disease commonly leading to airway obstruction with recurrent airway inflammation and infection. Pulmonary obstruction in CF has been linked to the loss of CFTR function as a regulated Cl- channel on the lumen-facing membrane of the epithelium lining the airways. We have learned much about the molecular basis for nucleotide- and phosphorylation-dependent regulation of channel activity of the normal (wild-type) version of the CFTR protein through electrophysiological studies. The major CF-causing mutation, F508del-CFTR, causes the protein to misfold and be retained in the ER (endoplasmic reticulum). Importantly, recent studies in cell culture have shown that retention in the ER can be 'corrected' through the application of certain small-molecule modulators and, once at the surface, the altered channel function of the major mutant can be 'potentiated', pharmacologically. Importantly, two such small molecules, a 'corrector' (VX-809) and a 'potentiator' (VX-770) compound are undergoing clinical trial for the treatment of CF. In this chapter, we describe recent discoveries regarding the wild-type CFTR and F508del-CFTR protein, in the context of molecular models based on X-ray structures of prokaryotic ABC (ATP-binding cassette) proteins. Finally, we discuss the promise of small-molecule modulators to probe the relationship between structure and function in the wild-type protein, the molecular defects caused by the most common mutation and the structural changes required to correct these defects.
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23
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Sala-Rabanal M, Wang S, Nichols CG. On potential interactions between non-selective cation channel TRPM4 and sulfonylurea receptor SUR1. J Biol Chem 2012; 287:8746-56. [PMID: 22291026 DOI: 10.1074/jbc.m111.336131] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The sulfonylurea receptor SUR1 associates with Kir6.2 or Kir6.1 to form K(ATP) channels, which link metabolism to excitability in multiple cell types. The strong physical coupling of SUR1 with Kir6 subunits appears exclusive, but recent studies argue that SUR1 also modulates TRPM4, a member of the transient receptor potential family of non-selective cation channels. It has been reported that, following stroke, brain, or spinal cord injury, SUR1 is increased in neurovascular cells at the site of injury. This is accompanied by up-regulation of a non-selective cation conductance with TRPM4-like properties and apparently sensitive to sulfonylureas, leading to the postulation that post-traumatic non-selective cation currents are determined by TRPM4/SUR1 channels. To investigate the mechanistic hypothesis for the coupling between TRPM4 and SUR1, we performed electrophysiological and FRET studies in COSm6 cells expressing TRPM4 channels with or without SUR1. TRPM4-mediated currents were Ca(2+)-activated, voltage-dependent, underwent desensitization, and were inhibited by ATP but were insensitive to glibenclamide and tolbutamide. These properties were not affected by cotransfection with SUR1. When the same SUR1 was cotransfected with Kir6.2, functional K(ATP) channels were formed. In cells cotransfected with Kir6.2, SUR1, and TRPM4, we measured K(ATP)-mediated K(+) currents and Ca(2+)-activated, sulfonylurea-insensitive Na(+) currents in the same patch, further showing that SUR1 controls K(ATP) channel activity but not TRPM4 channels. FRET signal between fluorophore-tagged TRPM4 subunits was similar to that between Kir6.2 and SUR1, whereas there was no detectable FRET efficiency between TRPM4 and SUR1. Our data suggest that functional or structural association of TRPM4 and SUR1 is unlikely.
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Affiliation(s)
- Monica Sala-Rabanal
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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24
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Chávez JC, Hernández-González EO, Wertheimer E, Visconti PE, Darszon A, Treviño CL. Participation of the Cl-/HCO(3)- exchangers SLC26A3 and SLC26A6, the Cl- channel CFTR, and the regulatory factor SLC9A3R1 in mouse sperm capacitation. Biol Reprod 2012; 86:1-14. [PMID: 21976599 DOI: 10.1095/biolreprod.111.094037] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Sperm capacitation is required for fertilization and involves several ion permeability changes. Although Cl(-) and HCO(3)(-) are essential for capacitation, the molecular entities responsible for their transport are not fully known. During mouse sperm capacitation, the intracellular concentration of Cl(-) ([Cl(-)](i)) increases and membrane potential (Em) hyperpolarizes. As in noncapacitated sperm, the Cl(-) equilibrium potential appears to be close to the cell resting Em, opening of Cl(-) channels could not support the [Cl(-)](i) increase observed during capacitation. Alternatively, the [Cl(-)](i) increase might be mediated by anion exchangers. Among them, SLC26A3 and SLC26A6 are good candidates, since, in several cell types, they increase [Cl(-)](i) and interact with cystic fibrosis transmembrane conductance regulator (CFTR), a Cl(-) channel present in mouse and human sperm. This interaction is known to be mediated and probably regulated by the Na(+)/H(+) regulatory factor-1 (official symbol, SLC9A3R1). Our RT-PCR, immunocytochemistry, Western blot, and immunoprecipitation data indicate that SLC26A3, SLC26A6, and SLC9A3R1 are expressed in mouse sperm, localize to the midpiece, and interact between each other and with CFTR. Moreover, we present evidence indicating that CFTR and SLC26A3 are involved in the [Cl(-)](i) increase induced by db-cAMP in noncapacitated sperm. Furthermore, we found that inhibitors of SLC26A3 (Tenidap and 5099) interfere with the Em changes that accompany capacitation. Together, these findings indicate that a CFTR/SLC26A3 functional interaction is important for mouse sperm capacitation.
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Affiliation(s)
- Julio C Chávez
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología-Universidad Nacional Autónoma de México, Cuernavaca, México
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25
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Wang W, Linsdell P. Conformational change opening the CFTR chloride channel pore coupled to ATP-dependent gating. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:851-60. [PMID: 22234285 DOI: 10.1016/j.bbamem.2011.12.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 12/21/2011] [Accepted: 12/23/2011] [Indexed: 12/13/2022]
Abstract
Opening and closing of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel are controlled by ATP binding and hydrolysis by its nucleotide binding domains (NBDs). This is presumed to control opening of a single "gate" within the permeation pathway, however, the location of such a gate has not been described. We used patch clamp recording to monitor access of cytosolic cysteine reactive reagents to cysteines introduced into different transmembrane (TM) regions in a cysteine-less form of CFTR. The rate of modification of Q98C (TM1) and I344C (TM6) by both [2-sulfonatoethyl] methanethiosulfonate (MTSES) and permeant Au(CN)(2)(-) ions was reduced when ATP concentration was reduced from 1mM to 10μM, and modification by MTSES was accelerated when 2mM pyrophosphate was applied to prevent channel closure. Modification of K95C (TM1) and V345C (TM6) was not affected by these manoeuvres. We also manipulated gating by introducing the mutations K464A (in NBD1) and E1371Q (in NBD2). The rate of modification of Q98C and I344C by both MTSES and Au(CN)(2)(-) was decreased by K464A and increased by E1371Q, whereas modification of K95C and V345C was not affected. These results suggest that access from the cytoplasm to K95 and V345 is similar in open and closed channels. In contrast, modifying ATP-dependent channel gating alters access to Q98 and I344, located further into the pore. We propose that ATP-dependent gating of CFTR is associated with the opening and closing of a gate within the permeation pathway at the level of these pore-lining amino acids.
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Affiliation(s)
- Wuyang Wang
- Department of Physiology and Biophysics, Dalhousie University, Nova Scotia, Canada
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Krasilnikov OV, Sabirov RZ, Okada Y. ATP hydrolysis-dependent asymmetry of the conformation of CFTR channel pore. J Physiol Sci 2011; 61:267-78. [PMID: 21461971 PMCID: PMC10717511 DOI: 10.1007/s12576-011-0144-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 03/20/2011] [Indexed: 01/13/2023]
Abstract
Despite substantial efforts, the entire cystic fibrosis transmembrane conductance regulator (CFTR) protein proved to be difficult for structural analysis at high resolution, and little is still known about the actual dimensions of the anion-transporting pathway of CFTR channel. In the present study, we therefore gauged geometrical features of the CFTR Cl(-) channel pore by a nonelectrolyte exclusion technique. Polyethylene glycols with a hydrodynamic radius (R (h)) smaller than 0.95 nm (PEG 300-1,000) added from the intracellular side greatly suppressed the inward unitary anionic conductance, whereas only molecules with R (h) ≤ 0.62 nm (PEG 200-400) applied extracellularly were able to affect the outward unitary anionic currents. Larger molecules with R (h) = 1.16-1.84 nm (PEG 1,540-3,400) added from either side were completely excluded from the pore and had no significant effect on the single-channel conductance. The cut-off radius of the inner entrance of CFTR channel pore was assessed to be 1.19 ± 0.02 nm. The outer entrance was narrower with its cut-off radius of 0.70 ± 0.16 nm and was dilated to 0.93 ± 0.23 nm when a non-hydrolyzable ATP analog, 5'-adenylylimidodiphosphate (AMP-PNP), was added to the intracellular solution. Thus, it is concluded that the structure of CFTR channel pore is highly asymmetric with a narrower extracellular entrance and that a dilating conformational change of the extracellular entrance is associated with the channel transition to a non-hydrolytic, locked-open state.
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Affiliation(s)
- Oleg V. Krasilnikov
- Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8585 Japan
- Department of Biophysics and Radiobiology, Federal University of Pernambuco, Recife, PE 50670-901 Brazil
| | - Ravshan Z. Sabirov
- Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8585 Japan
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Academy of Science RUz, Niyazova 1, 100095 Tashkent, Uzbekistan
- Department of Biophysics, National University, Niyazova 1, 100095 Tashkent, Uzbekistan
| | - Yasunobu Okada
- Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8585 Japan
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Szollosi A, Muallem DR, Csanády L, Vergani P. Mutant cycles at CFTR's non-canonical ATP-binding site support little interface separation during gating. ACTA ACUST UNITED AC 2011; 137:549-62. [PMID: 21576373 PMCID: PMC3105517 DOI: 10.1085/jgp.201110608] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel belonging to the adenosine triphosphate (ATP)-binding cassette (ABC) superfamily. ABC proteins share a common molecular mechanism that couples ATP binding and hydrolysis at two nucleotide-binding domains (NBDs) to diverse functions. This involves formation of NBD dimers, with ATP bound at two composite interfacial sites. In CFTR, intramolecular NBD dimerization is coupled to channel opening. Channel closing is triggered by hydrolysis of the ATP molecule bound at composite site 2. Site 1, which is non-canonical, binds nucleotide tightly but is not hydrolytic. Recently, based on kinetic arguments, it was suggested that this site remains closed for several gating cycles. To investigate movements at site 1 by an independent technique, we studied changes in thermodynamic coupling between pairs of residues on opposite sides of this site. The chosen targets are likely to interact based on both phylogenetic analysis and closeness on structural models. First, we mutated T460 in NBD1 and L1353 in NBD2 (the corresponding site-2 residues become energetically coupled as channels open). Mutation T460S accelerated closure in hydrolytic conditions and in the nonhydrolytic K1250R background; mutation L1353M did not affect these rates. Analysis of the double mutant showed additive effects of mutations, suggesting that energetic coupling between the two residues remains unchanged during the gating cycle. We next investigated pairs 460–1348 and 460–1375. Although both mutations H1348A and H1375A produced dramatic changes in hydrolytic and nonhydrolytic channel closing rates, in the corresponding double mutants these changes proved mostly additive with those caused by mutation T460S, suggesting little change in energetic coupling between either positions 460–1348 or positions 460–1375 during gating. These results provide independent support for a gating model in which ATP-bound composite site 1 remains closed throughout the gating cycle.
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Affiliation(s)
- Andras Szollosi
- Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary
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Csanády L, Vergani P, Gulyás-Kovács A, Gadsby DC. Electrophysiological, biochemical, and bioinformatic methods for studying CFTR channel gating and its regulation. Methods Mol Biol 2011; 741:443-469. [PMID: 21594801 DOI: 10.1007/978-1-61779-117-8_28] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
CFTR is the only member of the ABC (ATP-binding cassette) protein superfamily known to function as an ion channel. Most other ABC proteins are ATP-driven transporters, in which a cycle of ATP binding and hydrolysis, at intracellular nucleotide binding domains (NBDs), powers uphill substrate translocation across the membrane. In CFTR, this same ATP-driven cycle opens and closes a transmembrane pore through which chloride ions flow rapidly down their electrochemical gradient. Detailed analysis of the pattern of gating of CFTR channels thus offers the opportunity to learn about mechanisms of function not only of CFTR channels but also of their ABC transporter ancestors. In addition, CFTR channel gating is subject to complex regulation by kinase-mediated phosphorylation at multiple consensus sites in a cytoplasmic regulatory domain that is unique to CFTR. Here we offer a practical guide to extract useful information about the mechanisms that control opening and closing of CFTR channels: on how to plan (including information obtained from analysis of multiple sequence alignments), carry out, and analyze electrophysiological and biochemical experiments, as well as on how to circumvent potential pitfalls.
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Affiliation(s)
- László Csanády
- Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary.
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29
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El Hiani Y, Linsdell P. Changes in accessibility of cytoplasmic substances to the pore associated with activation of the cystic fibrosis transmembrane conductance regulator chloride channel. J Biol Chem 2010; 285:32126-40. [PMID: 20675380 DOI: 10.1074/jbc.m110.113332] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Opening of the cystic fibrosis transmembrane conductance regulator Cl(-) channel is dependent both on phosphorylation and on ATP binding and hydrolysis. However, the mechanisms by which these cytoplasmic regulatory factors open the Cl(-) channel pore are not known. We have used patch clamp recording to investigate the accessibility of cytoplasmically applied cysteine-reactive reagents to cysteines introduced along the length of the pore-lining sixth transmembrane region (TM6) of a cysteine-less variant of cystic fibrosis transmembrane conductance regulator. We find that methanethiosulfonate (MTS) reagents modify irreversibly cysteines substituted for TM6 residues Phe-337, Thr-338, Ser-341, Ile-344, Val-345, Met-348, Ala-349, Arg-352, and Gln-353 when applied to the cytoplasmic side of open channels. However, the apparent rate of modification by internal [2-sulfonatoethyl] methanethiosulfonate (MTSES), a negatively charged MTS reagent, is dependent on the activation state of the channels. In particular, cysteines introduced far along the axis of TM6 from the inside (T338C, S341C, I344C) showed no evidence of significant modification even after prolonged pretreatment of non-activated channels with internal MTSES. In contrast, cysteines introduced closer to the inside of TM6 (V345C, M348C) were readily modified in both activated and non-activated channels. Access of a permeant anion, Au(CN)(2)(-), to T338C was similarly dependent upon channel activation state. The pattern of MTS modification we observe allows us to designate different pore-lining amino acid side chains to distinct functional regions of the channel pore. One logical interpretation of these findings is that cytoplasmic access to residues at the narrowest region of the pore changes concomitant with activation.
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Affiliation(s)
- Yassine El Hiani
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
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Aittoniemi J, de Wet H, Ashcroft FM, Sansom MSP. Asymmetric switching in a homodimeric ABC transporter: a simulation study. PLoS Comput Biol 2010; 6:e1000762. [PMID: 20454684 PMCID: PMC2861673 DOI: 10.1371/journal.pcbi.1000762] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Accepted: 03/24/2010] [Indexed: 12/02/2022] Open
Abstract
ABC transporters are a large family of membrane proteins involved in a variety of cellular processes, including multidrug and tumor resistance and ion channel regulation. Advances in the structural and functional understanding of ABC transporters have revealed that hydrolysis at the two canonical nucleotide-binding sites (NBSs) is co-operative and non-simultaneous. A conserved core architecture of bacterial and eukaryotic ABC exporters has been established, as exemplified by the crystal structure of the homodimeric multidrug exporter Sav1866. Currently, it is unclear how sequential ATP hydrolysis arises in a symmetric homodimeric transporter, since it implies at least transient asymmetry at the NBSs. We show by molecular dynamics simulation that the initially symmetric structure of Sav1866 readily undergoes asymmetric transitions at its NBSs in a pre-hydrolytic nucleotide configuration. MgATP-binding residues and a network of charged residues at the dimer interface are shown to form a sequence of putative molecular switches that allow ATP hydrolysis only at one NBS. We extend our findings to eukaryotic ABC exporters which often consist of two non-identical half-transporters, frequently with degeneracy substitutions at one of their two NBSs. Interestingly, many residues involved in asymmetric conformational switching in Sav1866 are substituted in degenerate eukaryotic NBS. This finding strengthens recent suggestions that the interplay of a consensus and a degenerate NBS in eukaroytic ABC proteins pre-determines the sequence of hydrolysis at the two NBSs. ABC transporters are a large family of membrane proteins present in all organisms. Typically, they utilize ATP hydrolysis, the most prominent biological energy source, to translocate substrates into cells (e.g., bacterial nutritient uptake) or out of cells (e.g., multidrug exporters that contribute to antimicrobial resistance in bacteria and resistance to chemotherapeutic drugs in cancer). Also clinically relevant non-transport roles have been identified among ABC proteins. ABC transporters bind two molecules of ATP but do not hydrolyze them simultaneously. Therefore, an ABC transporter that consists of two symmetric halves must temporarily adopt asymmetric conformations at the two ATP-binding sites. Such transient conformational changes are difficult to address biochemically, but may be amenable to study by simulation methods, leading to future experiments. We employ molecular dynamics simulations to study how asymmetric switching might occur in the homodimeric bacterial ABC multidrug exporter Sav1866. The simulations suggest a mechanism of conformational switching that encompasses the ATP-binding sites and their interface towards the substrate-binding site. We extend our findings to show how asymmetric residue substitutions may render the switching process non-stochastic in mammalian Sav1866-like ABC exporters. This contributes to ongoing discussions about the role of two dissimilar ATP-binding sites in clinically relevant ABC proteins.
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Affiliation(s)
- Jussi Aittoniemi
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, United Kingdom
| | - Heidi de Wet
- Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M. Ashcroft
- Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, United Kingdom
| | - Mark S. P. Sansom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- * E-mail:
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Zhou JJ, Li MS, Qi J, Linsdell P. Regulation of conductance by the number of fixed positive charges in the intracellular vestibule of the CFTR chloride channel pore. ACTA ACUST UNITED AC 2010; 135:229-45. [PMID: 20142516 PMCID: PMC2828907 DOI: 10.1085/jgp.200910327] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Rapid chloride permeation through the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel is dependent on the presence of fixed positive charges in the permeation pathway. Here, we use site-directed mutagenesis and patch clamp recording to show that the functional role played by one such positive charge (K95) in the inner vestibule of the pore can be "transplanted" to a residue in a different transmembrane (TM) region (S1141). Thus, the mutant channel K95S/S1141K showed Cl(-) conductance and open-channel blocker interactions similar to those of wild-type CFTR, thereby "rescuing" the effects of the charge-neutralizing K95S mutation. Furthermore, the function of K95C/S1141C, but not K95C or S1141C, was inhibited by the oxidizing agent copper(II)-o-phenanthroline, and this inhibition was reversed by the reducing agent dithiothreitol, suggesting disulfide bond formation between these two introduced cysteine side chains. These results suggest that the amino acid side chains of K95 (in TM1) and S1141 (in TM12) are functionally interchangeable and located closely together in the inner vestibule of the pore. This allowed us to investigate the functional effects of increasing the number of fixed positive charges in this vestibule from one (in wild type) to two (in the S1141K mutant). The S1141K mutant had similar Cl(-) conductance as wild type, but increased susceptibility to channel block by cytoplasmic anions including adenosine triphosphate, pyrophosphate, 5-nitro-2-(3-phenylpropylamino)benzoic acid, and Pt(NO(2))(4)(2-) in inside-out membrane patches. Furthermore, in cell-attached patch recordings, apparent voltage-dependent channel block by cytosolic anions was strengthened by the S1141K mutation. Thus, the Cl(-) channel function of CFTR is maximal with a single fixed positive charge in this part of the inner vestibule of the pore, and increasing the number of such charges to two causes a net decrease in overall Cl(-) transport through a combination of failure to increase Cl(-) conductance and increased susceptibility to channel block by cytosolic substances.
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Affiliation(s)
- Jing-Jun Zhou
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
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Gadsby DC. Ion channels versus ion pumps: the principal difference, in principle. Nat Rev Mol Cell Biol 2009; 10:344-52. [PMID: 19339978 DOI: 10.1038/nrm2668] [Citation(s) in RCA: 302] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The incessant traffic of ions across cell membranes is controlled by two kinds of border guards: ion channels and ion pumps. Open channels let selected ions diffuse rapidly down electrical and concentration gradients, whereas ion pumps labour tirelessly to maintain the gradients by consuming energy to slowly move ions thermodynamically uphill. Because of the diametrically opposed tasks and the divergent speeds of channels and pumps, they have traditionally been viewed as completely different entities, as alike as chalk and cheese. But new structural and mechanistic information about both of these classes of molecular machines challenges this comfortable separation and forces its re-evaluation.
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Affiliation(s)
- David C Gadsby
- Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, 1230 York Avenue, New York, New York 10065-6399, USA.
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Ashcroft F, Gadsby D, Miller C. Introduction. The blurred boundary between channels and transporters. Philos Trans R Soc Lond B Biol Sci 2009; 364:145-7. [PMID: 18957372 DOI: 10.1098/rstb.2008.0245] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Frances Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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Aittoniemi J, Fotinou C, Craig TJ, de Wet H, Proks P, Ashcroft FM. Review. SUR1: a unique ATP-binding cassette protein that functions as an ion channel regulator. Philos Trans R Soc Lond B Biol Sci 2009; 364:257-67. [PMID: 18990670 DOI: 10.1098/rstb.2008.0142] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
SUR1 is an ATP-binding cassette (ABC) transporter with a novel function. In contrast to other ABC proteins, it serves as the regulatory subunit of an ion channel. The ATP-sensitive (KATP) channel is an octameric complex of four pore-forming Kir6.2 subunits and four regulatory SUR1 subunits, and it links cell metabolism to electrical activity in many cell types. ATPase activity at the nucleotide-binding domains of SUR results in an increase in KATP channel open probability. Conversely, ATP binding to Kir6.2 closes the channel. Metabolic regulation is achieved by the balance between these two opposing effects. Precisely how SUR1 talks to Kir6.2 remains unclear, but recent studies have identified some residues and domains that are involved in both physical and functional interactions between the two proteins. The importance of these interactions is exemplified by the fact that impaired regulation of Kir6.2 by SUR1 results in human disease, with loss-of-function SUR1 mutations causing congenital hyperinsulinism and gain-of-function SUR1 mutations leading to neonatal diabetes. This paper reviews recent data on the regulation of Kir6.2 by SUR1 and considers the molecular mechanisms by which SUR1 mutations produce disease.
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Affiliation(s)
- Jussi Aittoniemi
- Department of Physiology, Henry Wellcome Centre for Gene Function, University of Oxford, Parks Road, Oxford, UK
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