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McCarty NA. Tweaking the catalytic efficiency of the CFTR ion channel. J Gen Physiol 2023; 155:e202313343. [PMID: 37014352 PMCID: PMC10075223 DOI: 10.1085/jgp.202313343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
Abstract
CFTR, unique among ABC transporters, evolved to function as an ion channel in part by optimizing the stability of the open state.
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2
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Simon MA, Csanády L. Optimization of CFTR gating through the evolution of its extracellular loops. J Gen Physiol 2023; 155:e202213264. [PMID: 36723516 PMCID: PMC9929929 DOI: 10.1085/jgp.202213264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 12/02/2022] [Accepted: 01/17/2023] [Indexed: 02/02/2023] Open
Abstract
CFTR chloride channel mutations cause the lethal and incurable disease cystic fibrosis (CF). CFTR is activated by phosphorylation, and phosphorylated channels exhibit "bursting" behavior-"bursts" of openings separated by short "flickery" closures and flanked by long "interburst" closures-driven by ATP binding/hydrolysis at two nucleotide-binding domains. The human channel (hCFTR) and the distant zebrafish ortholog (zCFTR) display differences both in their gating properties and structures. In phosphorylated ATP-bound hCFTR, the hR117 side chain, conserved across evolution, forms an H-bond that stabilizes the open state. Lack of that bond in the hR117H mutant causes CF. In the phosphorylated ATP-bound zCFTR structure that H-bond is not observable. Here, we show that the zR118H mutation does not affect the function of zCFTR. Instead, we identify an H-bond between the zS109 and zS120 side chains of phosphorylated ATP-bound, but not of unphosphorylated apo-, zCFTR. We investigate the role of that interaction using thermodynamic mutant cycles built on gating parameters determined in inside-out patch clamp recordings. We find that zS109 indeed forms an H-bond with zN120 in the flickery closed state, but not in the open or interburst closed states. Although in hCFTR an isoleucine (hI119) replaces the asparagine, mutation hS108A produces a strong hR117H-like phenotype. Since the effects of the latter two mutations are not additive, we conclude that in hCFTR these two positions interact, and the hS108-hR117 and hR117-hE1124 H-bonds cooperate to stabilize the open state. These findings highlight an example of how the gating mechanism was optimized during CFTR molecular evolution.
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Affiliation(s)
- Márton A. Simon
- Department of Biochemistry, Semmelweis University, Budapest, Hungary
- HCEMM-SE Molecular Channelopathies Research Group, Budapest, Hungary
- ELKH-SE Ion Channel Research Group, Budapest, Hungary
| | - László Csanády
- Department of Biochemistry, Semmelweis University, Budapest, Hungary
- HCEMM-SE Molecular Channelopathies Research Group, Budapest, Hungary
- ELKH-SE Ion Channel Research Group, Budapest, Hungary
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3
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Barton TE, Frost F, Fothergill JL, Neill DR. Challenges and opportunities in the development of novel antimicrobial therapeutics for cystic fibrosis. J Med Microbiol 2022; 71. [PMID: 36748497 DOI: 10.1099/jmm.0.001643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Chronic respiratory infection is the primary driver of mortality in individuals with cystic fibrosis (CF). Existing drug screening models utilised in preclinical antimicrobial development are unable to mimic the complex CF respiratory environment. Consequently, antimicrobials showing promising activity in preclinical models often fail to translate through to clinical efficacy in people with CF. Model systems used in CF anti-infective drug discovery and development range from antimicrobial susceptibility testing in nutrient broth, through to 2D and 3D in vitro tissue culture systems and in vivo models. No single model fully recapitulates every key aspect of the CF lung. To improve the outcomes of people with CF (PwCF) it is necessary to develop a set of preclinical models that collectively recapitulate the CF respiratory environment to a high degree of accuracy. Models must be validated for their ability to mimic aspects of the CF lung and associated lung infection, through evaluation of biomarkers that can also be assessed following treatment in the clinic. This will give preclinical models greater predictive power for identification of antimicrobials with clinical efficacy. The landscape of CF is changing, with the advent of modulator therapies that correct the function of the CFTR protein, while antivirulence drugs and phage therapy are emerging alternative treatments to chronic infection. This review discusses the challenges faced in current antimicrobial development pipelines, including the advantages and disadvantages of current preclinical models and the impact of emerging treatments.
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Affiliation(s)
- Thomas E Barton
- Department of Clinical Infection, Microbiology and Immunology, University of Liverpool, Ronald Ross Building, 8 West Derby Street, Liverpool, L69 7BE, UK
| | - Frederick Frost
- Adult Cystic Fibrosis Centre, Liverpool Heart & Chest Hospital NHS Foundation Trust, Liverpool, UK.,Liverpool Centre for Cardiovascular Sciences, University of Liverpool, Liverpool, UK
| | - Joanne L Fothergill
- Department of Clinical Infection, Microbiology and Immunology, University of Liverpool, Ronald Ross Building, 8 West Derby Street, Liverpool, L69 7BE, UK
| | - Daniel R Neill
- Department of Clinical Infection, Microbiology and Immunology, University of Liverpool, Ronald Ross Building, 8 West Derby Street, Liverpool, L69 7BE, UK
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4
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Aleksandrov LA, Aleksandrov AA, Jensen TJ, Strauss JD, Fay JF. Conformational Variability in Ground-State CFTR Lipoprotein Particle Cryo-EM Ensembles. Int J Mol Sci 2022; 23:9248. [PMID: 36012518 PMCID: PMC9409475 DOI: 10.3390/ijms23169248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 06/21/2022] [Accepted: 08/12/2022] [Indexed: 11/17/2022] Open
Abstract
Cystic fibrosis transmembrane regulator (CFTR) is a dynamic membrane protein belonging to the ABC transporter family. It is unusual within this family as it is an ion channel, as opposed to a transporter. Activation of CFTR requires ATP and phosphorylation by PKA, and dysregulation of CFTR mediated salt and water homeostasis can lead to cystic fibrosis. Recent advancements in structural biological methods have led to more than 10 published CFTR structures, and, so far, all of these structures of CFTR, determined by cryo-EM, have been limited to detergent-purified protein preparations. To visualize CFTR in an environment that more closely represents its native membranous environment, we utilized two different lipoprotein particle encapsulation techniques: one in which the ion channel is first purified and then reconstituted using the membrane scaffolding protein Saposin A and another that uses the solubilizing polymer Sokalan CP9 (DIBMA) to extract CFTR directly from membranes. Structures derived from these types of preparations may better correlate to their function, for instance, the single-channel measurements from membrane vesicles.
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Affiliation(s)
| | | | | | | | - Jonathan F. Fay
- Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 6107 Thurston Bowles Building, Chapel Hill, NC 27599, USA
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5
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Simon MA, Csanády L. Molecular pathology of the R117H cystic fibrosis mutation is explained by loss of a hydrogen bond. eLife 2021; 10:74693. [PMID: 34870594 PMCID: PMC8673840 DOI: 10.7554/elife.74693] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 12/03/2021] [Indexed: 11/21/2022] Open
Abstract
The phosphorylation-activated anion channel cystic fibrosis transmembrane conductance regulator (CFTR) is gated by an ATP hydrolysis cycle at its two cytosolic nucleotide-binding domains, and is essential for epithelial salt-water transport. A large number of CFTR mutations cause cystic fibrosis. Since recent breakthrough in targeted pharmacotherapy, CFTR mutants with impaired gating are candidates for stimulation by potentiator drugs. Thus, understanding the molecular pathology of individual mutations has become important. The relatively common R117H mutation affects an extracellular loop, but nevertheless causes a strong gating defect. Here, we identify a hydrogen bond between the side chain of arginine 117 and the backbone carbonyl group of glutamate 1124 in the cryo-electronmicroscopic structure of phosphorylated, ATP-bound CFTR. We address the functional relevance of that interaction for CFTR gating using macroscopic and microscopic inside-out patch-clamp recordings. Employing thermodynamic double-mutant cycles, we systematically track gating-state-dependent changes in the strength of the R117-E1124 interaction. We find that the H-bond is formed only in the open state, but neither in the short-lived ‘flickery’ nor in the long-lived ‘interburst’ closed state. Loss of this H-bond explains the strong gating phenotype of the R117H mutant, including robustly shortened burst durations and strongly reduced intraburst open probability. The findings may help targeted potentiator design.
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Affiliation(s)
- Márton A Simon
- Department of Biochemistry, Semmelweis University, Budapest, Hungary.,HCEMM-SE Molecular Channelopathies Research Group, Budapest, Hungary
| | - László Csanády
- Department of Biochemistry, Semmelweis University, Budapest, Hungary.,HCEMM-SE Molecular Channelopathies Research Group, Budapest, Hungary.,MTA-SE Ion Channel Research Group, Semmelweis University, Budapest, Hungary
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6
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Liang T, Xu Q, Zhang H, Wang S, Diekwisch TGH, Qin C, Lu Y. Enamel Defects Associated With Dentin Sialophosphoprotein Mutation in Mice. Front Physiol 2021; 12:724098. [PMID: 34630144 PMCID: PMC8497714 DOI: 10.3389/fphys.2021.724098] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Accepted: 08/31/2021] [Indexed: 12/04/2022] Open
Abstract
Dentin sialophosphoprotein (DSPP) is an extracellular matrix protein that is highly expressed in odontoblasts, but only transiently expressed in presecretory ameloblasts during tooth development. We previously generated a knockin mouse model expressing a mouse equivalent (DSPP, p.P19L) of human mutant DSPP (p.P17L; referred to as “DsppP19L/+”), and reported that DsppP19L/+ and DsppP19L/P19L mice manifested a dentin phenotype resembling human dentinogenesis imperfecta (DGI). In this study, we analyzed pathogenic effects of mutant P19L-DSPP on enamel development in DsppP19L/+ and DsppP19L/P19L mice. Micro-Computed Tomography (μCT) analyses of 7-week-old mouse mandibular incisors showed that DsppP19L/P19L mice had significantly decreased enamel volume and/or enamel density at different stages of amelogenesis examined. Acid-etched scanning electron microscopy (SEM) analyses of mouse incisors demonstrated that, at the mid-late maturation stage of amelogenesis, the enamel of wild-type mice already had apparent decussating pattern of enamel rods, whereas only minute particulates were found in DsppP19L/+ mice, and no discernible structures in DsppP19L/P19L mouse enamel. However, by the time that incisor enamel was about to erupt into oral cavity, distinct decussating enamel rods were evident in DsppP19L/+ mice, but only poorly-defined enamel rods were revealed in DsppP19L/P19L mice. Moreover, μCT analyses of the mandibular first molars showed that DsppP19L/+ and DsppP19L/P19L mice had a significant reduction in enamel volume and enamel density at the ages of 2, 3, and 24weeks after birth. Backscattered and acid-etched SEM analyses revealed that while 3-week-old DsppP19L/+ mice had similar pattern of enamel rods in the mandibular first molars as age-matched wild-type mice, no distinct enamel rods were observed in DsppP19L/P19L mice. Yet neither DsppP19L/+ nor DsppP19L/P19L mice showed well-defined enamel rods in the mandibular first molars by the age of 24weeks, as judged by backscattered and acid-etched SEM. In situ hybridization showed that DSPP mRNA level was markedly reduced in the presecretory ameloblasts, but immunohistochemistry revealed that DSP/DSPP immunostaining signals were much stronger within the presecretory ameloblasts in Dspp mutant mice than in wild-type mice. These results suggest that mutant P19L-DSPP protein caused developmental enamel defects in mice, which may be associated with intracellular retention of mutant DSPP in the presecretory ameloblasts.
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Affiliation(s)
- Tian Liang
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, Dallas, TX, United States
| | - Qian Xu
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, Dallas, TX, United States
| | - Hua Zhang
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, Dallas, TX, United States
| | - Suzhen Wang
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, Dallas, TX, United States
| | - Thomas G H Diekwisch
- Department of Periodontics and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, Dallas, TX, United States
| | - Chunlin Qin
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, Dallas, TX, United States
| | - Yongbo Lu
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, Dallas, TX, United States
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Li F, Egea PF, Vecchio AJ, Asial I, Gupta M, Paulino J, Bajaj R, Dickinson MS, Ferguson-Miller S, Monk BC, Stroud RM. Highlighting membrane protein structure and function: A celebration of the Protein Data Bank. J Biol Chem 2021; 296:100557. [PMID: 33744283 PMCID: PMC8102919 DOI: 10.1016/j.jbc.2021.100557] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 02/10/2021] [Accepted: 03/16/2021] [Indexed: 12/13/2022] Open
Abstract
Biological membranes define the boundaries of cells and compartmentalize the chemical and physical processes required for life. Many biological processes are carried out by proteins embedded in or associated with such membranes. Determination of membrane protein (MP) structures at atomic or near-atomic resolution plays a vital role in elucidating their structural and functional impact in biology. This endeavor has determined 1198 unique MP structures as of early 2021. The value of these structures is expanded greatly by deposition of their three-dimensional (3D) coordinates into the Protein Data Bank (PDB) after the first atomic MP structure was elucidated in 1985. Since then, free access to MP structures facilitates broader and deeper understanding of MPs, which provides crucial new insights into their biological functions. Here we highlight the structural and functional biology of representative MPs and landmarks in the evolution of new technologies, with insights into key developments influenced by the PDB in magnifying their impact.
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Affiliation(s)
- Fei Li
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA; Department of Neurology, University of California San Francisco, San Francisco, California, USA
| | - Pascal F Egea
- Department of Biological Chemistry, School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Alex J Vecchio
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | | | - Meghna Gupta
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Joana Paulino
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Ruchika Bajaj
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, California, USA
| | - Miles Sasha Dickinson
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
| | - Brian C Monk
- Sir John Walsh Research Institute and Department of Oral Sciences, University of Otago, North Dunedin, Dunedin, New Zealand
| | - Robert M Stroud
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA.
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8
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Banerjee A, Moreno A, Pata J, Falson P, Prasad R. ABCG: a new fold of ABC exporters and a whole new bag of riddles! ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2020; 123:163-191. [PMID: 33485482 DOI: 10.1016/bs.apcsb.2020.09.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
ATP-binding cassette (ABC) superfamily comprises membrane transporters that power the active transport of substrates across biological membranes. These proteins harness the energy of nucleotide binding and hydrolysis to fuel substrate translocation via an alternating-access mechanism. The primary structural blueprint is relatively conserved in all ABC transporters. A transport-competent ABC transporter is essentially made up of two nucleotide-binding domains (NBDs) and two transmembrane domains (TMDs). While the NBDs are conserved in their primary sequence and form at their interface two nucleotide-binding sites (NBSs) for ATP binding and hydrolysis, the TMDs are variable among different families and form the translocation channel. Transporters catalyzing the efflux of substrates from the cells are called exporters. In humans, they range from A to G subfamilies, with the B, C and G subfamilies being involved in chemoresistance. The recently elucidated structures of ABCG5/G8 followed by those of ABCG2 highlighted a novel structural fold that triggered extensive research. Notably, suppressor genetics in the orthologous yeast Pleiotropic Drug Resistance (PDR) subfamily proteins have pointed to a crosstalk between TMDs and NBDs modulating substrate export. Considering the structural information provided by their neighbors from the G subfamily, these studies provide mechanistic keys and posit a functional role for the non-hydrolytic NBS found in several ABC exporters. The present chapter provides an overview of structural and functional aspects of ABCG proteins with a special emphasis on the yeast PDR systems.
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Affiliation(s)
- Atanu Banerjee
- Amity Institute of Biotechnology, Amity University Haryana, Gurgaon, Haryana, India
| | - Alexis Moreno
- Drug Resistance & Membrane Proteins Team, Molecular Microbiology and Structural Biochemistry Laboratory, CNRS-Lyon 1 University UMR5086, Institut de Biologie et Chimie des Protéines, Lyon, France
| | - Jorgaq Pata
- Drug Resistance & Membrane Proteins Team, Molecular Microbiology and Structural Biochemistry Laboratory, CNRS-Lyon 1 University UMR5086, Institut de Biologie et Chimie des Protéines, Lyon, France
| | - Pierre Falson
- Drug Resistance & Membrane Proteins Team, Molecular Microbiology and Structural Biochemistry Laboratory, CNRS-Lyon 1 University UMR5086, Institut de Biologie et Chimie des Protéines, Lyon, France
| | - Rajendra Prasad
- Amity Institute of Biotechnology, Amity University Haryana, Gurgaon, Haryana, India; Amity Institute of Integrative Sciences and Health, Amity University Haryana, Gurgaon, Haryana, India
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9
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Carrageta DF, Bernardino RL, Alves MG, Oliveira PF. CFTR regulation of aquaporin-mediated water transport. VITAMINS AND HORMONES 2020; 112:163-177. [PMID: 32061340 DOI: 10.1016/bs.vh.2019.08.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel responsible for the direct transport of bicarbonate and chloride. CFTR-dependent ionic transport is crucial for pH regulation and fluid homeodynamics among epithelial surfaces. Particularly, CFTR performs an essential role in the male reproductive tract, which requires a tight regulation of water and electrolytes in order to produce healthy spermatozoa. The absence or malfunction of CFTR results in cystic fibrosis, the most common lethal disease among Caucasians, that is characterized by an impaired fluid and ionic homeostasis in the whole organism. Due to the wide expression and importance of CFTR, the male reproductive tract is highly affected by cystic fibrosis, resulting in male infertility. Although CFTR is not permeable to water, this protein acts as a regulator of other protein channels, such as aquaporins. In fact, CFTR acts as a molecular partner of aquaporins in epithelial cells, regulating fluid homeodynamics. Herein, up-to-date data concerning the regulation of aquaporin-mediated water transport by CFTR will be discussed, highlighting the role of both channels in the male reproductive tract.
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Affiliation(s)
- David F Carrageta
- Department of Microscopy, Laboratory of Cell Biology, Unit for Multidisciplinary Research in Biomedicine (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal
| | - Raquel L Bernardino
- Department of Microscopy, Laboratory of Cell Biology, Unit for Multidisciplinary Research in Biomedicine (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal
| | - Marco G Alves
- Department of Microscopy, Laboratory of Cell Biology, Unit for Multidisciplinary Research in Biomedicine (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal
| | - Pedro F Oliveira
- Department of Microscopy, Laboratory of Cell Biology, Unit for Multidisciplinary Research in Biomedicine (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal; Department of Genetics, Faculty of Medicine, University of Porto, Porto, Portugal; i3S-Instituto de Investigação e Inovação em Saúde, University of Porto, Porto, Portugal.
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10
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Farkas B, Tordai H, Padányi R, Tordai A, Gera J, Paragi G, Hegedűs T. Discovering the chloride pathway in the CFTR channel. Cell Mol Life Sci 2020; 77:765-778. [PMID: 31327045 PMCID: PMC7039865 DOI: 10.1007/s00018-019-03211-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 06/22/2019] [Accepted: 06/26/2019] [Indexed: 12/15/2022]
Abstract
Cystic fibrosis (CF), a lethal monogenic disease, is caused by pathogenic variants of the CFTR chloride channel. The majority of CF mutations affect protein folding and stability leading overall to diminished apical anion conductance of epithelial cells. The recently published cryo-EM structures of full-length human and zebrafish CFTR provide a good model to gain insight into structure-function relationships of CFTR variants. Although, some of the structures were determined in the phosphorylated and ATP-bound active state, none of the static structures showed an open pathway for chloride permeation. Therefore, we performed molecular dynamics simulations to generate a conformational ensemble of the protein and used channel detecting algorithms to identify conformations with an opened channel. Our simulations indicate a main intracellular entry at TM4/6, a secondary pore at TM10/12, and a bottleneck region involving numerous amino acids from TM1, TM6, and TM12 in accordance with experiments. Since chloride ions entered the pathway in our equilibrium simulations, but did not traverse the bottleneck region, we performed metadynamics simulations, which revealed two possible exits. One of the chloride ions exits includes hydrophobic lipid tails that may explain the lipid-dependency of CFTR function. In summary, our in silico study provides a detailed description of a potential chloride channel pathway based on a recent cryo-EM structure and may help to understand the gating of the CFTR chloride channel, thus contributing to novel strategies to rescue dysfunctional mutants.
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Affiliation(s)
- Bianka Farkas
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
- Faculty of Information Technology, Pázmány Péter Catholic University, Budapest, Hungary
| | - Hedvig Tordai
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Rita Padányi
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
- MTA-SE Molecular Biophysics Research Group, Hungarian Academy of Sciences, Budapest, Hungary
| | - Attila Tordai
- Department of Pathophysiology, Semmelweis University, Budapest, Hungary
| | - János Gera
- Department of Medical Chemistry, University of Szeged, Szeged, Hungary
| | - Gábor Paragi
- MTA-SZTE Biomimetic System Research Group, Hungarian Academy of Sciences, Szeged, Hungary
- Institute of Physics, University of Pécs, Pecs, Hungary
| | - Tamás Hegedűs
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary.
- MTA-SE Molecular Biophysics Research Group, Hungarian Academy of Sciences, Budapest, Hungary.
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11
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Towards next generation therapies for cystic fibrosis: Folding, function and pharmacology of CFTR. J Cyst Fibros 2020; 19 Suppl 1:S25-S32. [PMID: 31902693 PMCID: PMC7052731 DOI: 10.1016/j.jcf.2019.12.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 12/16/2019] [Accepted: 12/18/2019] [Indexed: 12/19/2022]
Abstract
The treatment of cystic fibrosis (CF) has been transformed by orally-bioavailable small molecule modulators of the cystic fibrosis transmembrane conductance regulator (CFTR), which restore function to CF mutants. However, CFTR modulators are not available to all people with CF and better modulators are required to prevent disease progression. Here, we review selectively recent advances in CFTR folding, function and pharmacology. We highlight ensemble and single-molecule studies of CFTR folding, which provide new insight into CFTR assembly, its perturbation by CF mutations and rescue by CFTR modulators. We discuss species-dependent differences in the action of the F508del-CFTR mutation on CFTR expression, stability and function, which might influence pharmacological studies of CFTR modulators in CF animal models. Finally, we illuminate the identification of combinations of two CFTR potentiators (termed co-potentiators), which restore therapeutically-relevant levels of CFTR activity to rare CF mutations. Thus, mechanistic studies of CFTR folding, function and pharmacology inform the development of highly effective CFTR modulators.
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12
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Laselva O, Erwood S, Du K, Ivakine Z, Bear CE. Activity of lumacaftor is not conserved in zebrafish Cftr bearing the major cystic fibrosis-causing mutation. FASEB Bioadv 2019; 1:661-670. [PMID: 32123813 PMCID: PMC6996396 DOI: 10.1096/fba.2019-00039] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 05/02/2019] [Accepted: 08/30/2019] [Indexed: 12/11/2022] Open
Abstract
F508del-cystic fibrosis transmembrane conductance regulator (CFTR) is the major mutant responsible for cystic fibrosis (CF). ORKAMBI®, approved for patients bearing this mutant, contains lumacaftor (VX-809) that partially corrects F508del-CFTR's processing defect and ivacaftor (VX-770) that potentiates its defective channel activity. Unfortunately, the clinical efficacy of ORKAMBI® is modest, highlighting the need to understand how the small molecules work so that superior compounds can be developed. Because, human CFTR (hCFTR) and zebrafish Cftr (zCftr) are structurally conserved as determined in recent cryo-EM structural models, we hypothesized that the consequences of the major mutation and small molecule modulators would be similar for the two species of protein. As expected, like the F508del mutation in hCFTR, the homologous mutation in zCftr (F507del) is misprocessed, yet not as severely as the human mutant and this defect was restored by low-temperature (27°C) culture conditions. After rescue to the cell surface, F507del-zCftr exhibited regulated channel activity that was potentiated by ivacaftor. Surprisingly, lumacaftor failed to rescue misprocessing of the F507del-zCftr at either 37 or 27°C suggesting that future comparative studies with F508del-hCFTR would provide insight into its structure: function relationships. Interestingly, the robust rescue of F508del-zCftr at 27°C and availability of methods for in vivo screening in zebrafish present the opportunity to define the cellular pathways underlying rescue.
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Affiliation(s)
- Onofrio Laselva
- Programme in Molecular MedicineHospital for Sick ChildrenTorontoCanada
- Department of PhysiologyUniversity of TorontoTorontoCanada
| | - Steven Erwood
- Programme in Genetics and Genome BiologyHospital for Sick ChildrenTorontoCanada
| | - Kai Du
- Programme in Molecular MedicineHospital for Sick ChildrenTorontoCanada
| | - Zhenya Ivakine
- Programme in Genetics and Genome BiologyHospital for Sick ChildrenTorontoCanada
| | - Christine E. Bear
- Programme in Molecular MedicineHospital for Sick ChildrenTorontoCanada
- Department of PhysiologyUniversity of TorontoTorontoCanada
- Department of BiochemistryUniversity of TorontoTorontoCanada
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13
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Yeh HI, Qiu L, Sohma Y, Conrath K, Zou X, Hwang TC. Identifying the molecular target sites for CFTR potentiators GLPG1837 and VX-770. J Gen Physiol 2019; 151:912-928. [PMID: 31164398 PMCID: PMC6605684 DOI: 10.1085/jgp.201912360] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/29/2019] [Accepted: 05/10/2019] [Indexed: 01/14/2023] Open
Abstract
Identification of the binding sites for small molecules that alleviate gating
defects in CFTR would assist rational drug design for the treatment of cystic
fibrosis. Yeh et al. identify two potential binding sites for prototypical CFTR
potentiators at the interface of CFTR’s two transmembrane domains. The past two decades have witnessed major breakthroughs in developing compounds
that target the chloride channel CFTR for the treatment of patients with cystic
fibrosis. However, further improvement in affinity and efficacy for these CFTR
modulators will require insights into the molecular interactions between CFTR
modulators and their binding targets. In this study, we use in silico molecular
docking to identify potential binding sites for GLPG1837, a CFTR potentiator
that may share a common mechanism and binding site with VX-770, the FDA-approved
drug for patients carrying mutations with gating defects. Among the five binding
sites predicted by docking, the two top-scoring sites are located at the
interface between CFTR’s two transmembrane domains: site I consists of
D924, N1138, and S1141, and site IIN includes F229, F236, Y304, F312,
and F931. Using mutagenesis to probe the importance of these sites for GLPG187
binding, we find that disruption of predicted hydrogen-bonding interactions by
mutation of D924 decreases apparent affinity, while hydrophobic amino acids
substitutions at N1138 and introduction of positively charged amino acids at
S1141 improve the apparent affinity for GLPG1837. Alanine substitutions at Y304,
F312, and F931 (site IIN) decrease the affinity for GLPG1837, whereas
alanine substitutions at F229 and F236 (also site IIN), or at
residues in the other three lower-scoring sites, have little effect. In
addition, current relaxation analysis to assess the apparent dissociation rate
of VX-770 yields results consistent with the dose–response experiments
for GLPG8137, with the dissociation rate of VX-770 accelerated by D924N, F236A,
Y304A, and F312A, but decelerated by N1138L and S1141K mutations. Collectively,
these data identify two potential binding sites for GLPG1837 and VX-770 in CFTR.
We discuss the pros and cons of evidence for these two loci and the implications
for future drug design.
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Affiliation(s)
- Han-I Yeh
- Dalton Cardiovascular Research Center and Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
| | - Liming Qiu
- Dalton Cardiovascular Research Center, Department of Physics and Astronomy, Department of Biochemistry, and Informatics Institute, University of Missouri, Columbia, MO
| | - Yoshiro Sohma
- Dalton Cardiovascular Research Center and Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO.,Department of Pharmaceutical Sciences, School of Pharmacy and Center for Medical Science, International University of Health and Welfare, Tochigi, Japan
| | | | - Xiaoqin Zou
- Dalton Cardiovascular Research Center, Department of Physics and Astronomy, Department of Biochemistry, and Informatics Institute, University of Missouri, Columbia, MO
| | - Tzyh-Chang Hwang
- Dalton Cardiovascular Research Center and Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
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