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Hosseini Nami A, Kabiri M, Zafarghandi Motlagh F, Shirzadeh T, Bagherian H, Zeinali R, Karimi A, Zeinali S. Identification and in silico structural analysis for the first de novo mutation in the cystic fibrosis transmembrane conductance regulator protein in Iran: case report and developmental insight using microsatellite markers. Ther Adv Respir Dis 2024; 18:17534666241253990. [PMID: 38904297 PMCID: PMC11193346 DOI: 10.1177/17534666241253990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 04/19/2024] [Indexed: 06/22/2024] Open
Abstract
Cystic fibrosis (CF) is an autosomal recessive disease caused by the inheritance of two mutant cystic fibrosis transmembrane conductance regulator (CFTR) alleles, one from each parent. Autosomal recessive disorders are rarely associated with germline mutations or mosaicism. Here, we propose a case of paternal germline mutation causing CF. The subject also had an identifiable maternal mutant allele. We identified the compound heterozygous variants in the proband through Sanger sequencing, and in silico studies predicted functional effects on the protein. Also, short tandem repeat markers revealed the de novo nature of the mutation. The maternal mutation in the CFTR gene was c.1000C > T. The de novo mutation was c.178G > A, p.Glu60Lys. This mutation is located in the lasso motif of the CFTR protein and, according to in silico structural analysis, disrupts the interaction of the lasso motif and R-domain, thus influencing protein function. This first reported case of de novo mutation in Asia has notable implications for molecular diagnostics, genetic counseling, and understanding the genetic etiology of recessive disorders in the Iranian population.
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Affiliation(s)
- Amin Hosseini Nami
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
- Dr. Zeinali’s Medical Genetics Lab, Kawsar Human Genetics Research Center (KHGRC), Tehran, Iran
| | - Mahboubeh Kabiri
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
| | | | - Tina Shirzadeh
- Dr. Zeinali’s Medical Genetics Lab, Kawsar Human Genetics Research Center (KHGRC), Tehran, Iran
| | - Hamideh Bagherian
- Dr. Zeinali’s Medical Genetics Lab, Kawsar Human Genetics Research Center (KHGRC), Tehran, Iran
| | - Razie Zeinali
- Dr. Zeinali’s Medical Genetics Lab, Kawsar Human Genetics Research Center (KHGRC), Tehran, Iran
- Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran
| | - Ali Karimi
- Max Planck Institute for Brain Research, Frankfurt am Main, Germany
| | - Sirous Zeinali
- Dr. Zeinali’s Medical Genetics Lab, Kawsar Human Genetics Research Center (KHGRC), No. 41, Irna St., Valiasr St., Tehran, Iran
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2
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Kondratyeva E, Melyanovskaya Y, Bulatenko N, Davydenko K, Filatova A, Efremova A, Skoblov M, Bukharova T, Sherman V, Voronkova A, Zhekaite E, Krasovskiy S, Amelina E, Petrova N, Polyakov A, Adyan T, Starinova M, Krasnova M, Vasilyev A, Makhnach O, Zinchenko R, Kutsev S, Gokdemir Y, Karadag B, Goldshtein D. Clinical and Functional Characteristics of the E92K CFTR Gene Variant in the Russian and Turkish Population of People with Cystic Fibrosis. Int J Mol Sci 2023; 24:ijms24076351. [PMID: 37047318 PMCID: PMC10093870 DOI: 10.3390/ijms24076351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 03/19/2023] [Accepted: 03/23/2023] [Indexed: 03/30/2023] Open
Abstract
The pathogenic variant E92K (c.274G > A) of the CFTR gene is rare in America and Europe, but it is common for people with cystic fibrosis from Russia and Turkey. We studied the effect of the E92K genetic variant on the CFTR function. The function of the CFTR channel was studied using the intestinal current measurements (ICM) method. The effects of CFTR modulators on the restoration of the CFTR function were studied in the model of intestinal organoids. To assess the effect of E92K on pre-mRNA splicing, the RT-PCR products obtained from patients’ intestinal organoid cultures were analyzed. Patients with the genetic variant E92K are characterized by an older age of diagnosis compared to homozygotes F508del and a high frequency of pancreatic sufficiency. The results of the sweat test and the ICM method showed partial preservation of the function of the CFTR channel. Functional analysis of CFTR gene expression revealed a weak effect of the E92K variant on mRNA-CFTR splicing. Lumacaftor (VX-809) has been shown to restore CFTR function in an intestinal organoid model, which allows us to consider the E92K variant as a promising target for therapy with CFTR correctors.
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3
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Fiedorczuk K, Chen J. Molecular structures reveal synergistic rescue of Δ508 CFTR by Trikafta modulators. Science 2022; 378:284-290. [PMID: 36264792 PMCID: PMC9912939 DOI: 10.1126/science.ade2216] [Citation(s) in RCA: 59] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The predominant mutation causing cystic fibrosis, a deletion of phenylalanine 508 (Δ508) in the cystic fibrosis transmembrane conductance regulator (CFTR), leads to severe defects in CFTR biogenesis and function. The advanced therapy Trikafta combines the folding corrector tezacaftor (VX-661), the channel potentiator ivacaftor (VX-770), and the dual-function modulator elexacaftor (VX-445). However, it is unclear how elexacaftor exerts its effects, in part because the structure of Δ508 CFTR is unknown. Here, we present cryo-electron microscopy structures of Δ508 CFTR in the absence and presence of CFTR modulators. When used alone, elexacaftor partially rectified interdomain assembly defects in Δ508 CFTR, but when combined with a type I corrector, did so fully. These data illustrate how the different modulators in Trikafta synergistically rescue Δ508 CFTR structure and function.
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Affiliation(s)
- Karol Fiedorczuk
- Laboratory of Membrane Biology and Biophysics, The Rockefeller University, New York, NY 10065, USA
| | - Jue Chen
- Laboratory of Membrane Biology and Biophysics, The Rockefeller University, New York, NY 10065, USA,Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA,Corresponding author.
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4
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Molecular mechanisms of Cystic Fibrosis - how mutations lead to misfunction and guide therapy. Biosci Rep 2022; 42:231430. [PMID: 35707985 PMCID: PMC9251585 DOI: 10.1042/bsr20212006] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 06/03/2022] [Accepted: 06/13/2022] [Indexed: 11/17/2022] Open
Abstract
Cystic fibrosis, the most common autosomal recessive disorder in Caucasians, is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a cAMP-activated chloride and bicarbonate channel that regulates ion and water transport in secretory epithelia. Although all mutations lead to the lack or reduction in channel function, the mechanisms through which this occurs are diverse – ranging from lack of full-length mRNA, reduced mRNA levels, impaired folding and trafficking, targeting to degradation, decreased gating or conductance, and reduced protein levels to decreased half-life at the plasma membrane. Here, we review the different molecular mechanisms that cause cystic fibrosis and detail how these differences identify theratypes that can inform the use of directed therapies aiming at correcting the basic defect. In summary, we travel through CFTR life cycle from the gene to function, identifying what can go wrong and what can be targeted in terms of the different types of therapeutic approaches.
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5
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Ensinck MM, Carlon MS. One Size Does Not Fit All: The Past, Present and Future of Cystic Fibrosis Causal Therapies. Cells 2022; 11:cells11121868. [PMID: 35740997 PMCID: PMC9220995 DOI: 10.3390/cells11121868] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 05/25/2022] [Accepted: 05/28/2022] [Indexed: 02/04/2023] Open
Abstract
Cystic fibrosis (CF) is the most common monogenic disorder, caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. Over the last 30 years, tremendous progress has been made in understanding the molecular basis of CF and the development of treatments that target the underlying defects in CF. Currently, a highly effective CFTR modulator treatment (Kalydeco™/Trikafta™) is available for 90% of people with CF. In this review, we will give an extensive overview of past and ongoing efforts in the development of therapies targeting the molecular defects in CF. We will discuss strategies targeting the CFTR protein (i.e., CFTR modulators such as correctors and potentiators), its cellular environment (i.e., proteostasis modulation, stabilization at the plasma membrane), the CFTR mRNA (i.e., amplifiers, nonsense mediated mRNA decay suppressors, translational readthrough inducing drugs) or the CFTR gene (gene therapies). Finally, we will focus on how these efforts can be applied to the 15% of people with CF for whom no causal therapy is available yet.
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Affiliation(s)
- Marjolein M. Ensinck
- Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Flanders, Belgium;
| | - Marianne S. Carlon
- Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Flanders, Belgium;
- Laboratory of Respiratory Diseases and Thoracic Surgery (BREATHE), Department of Chronic Diseases and Metabolism, KU Leuven, 3000 Leuven, Flanders, Belgium
- Correspondence:
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6
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Wong SL, Awatade NT, Astore MA, Allan KM, Carnell MJ, Slapetova I, Chen PC, Capraro A, Fawcett LK, Whan RM, Griffith R, Ooi CY, Kuyucak S, Jaffe A, Waters SA. Molecular dynamics and functional characterization of I37R-CFTR lasso mutation provide insights into channel gating activity. iScience 2022; 25:103710. [PMID: 35072004 PMCID: PMC8761696 DOI: 10.1016/j.isci.2021.103710] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 11/27/2021] [Accepted: 12/28/2021] [Indexed: 12/30/2022] Open
Abstract
Characterization of I37R, a mutation located in the lasso motif of the CFTR chloride channel, was conducted by theratyping several CFTR modulators from both potentiator and corrector classes. Intestinal current measurements in rectal biopsies, forskolin-induced swelling (FIS) in intestinal organoids, and short circuit current measurements in organoid-derived monolayers from an individual with I37R/F508del CFTR genotype demonstrated that the I37R-CFTR results in a residual function defect amenable to treatment with potentiators and type III, but not type I, correctors. Molecular dynamics of I37R using an extended model of the phosphorylated, ATP-bound human CFTR identified an altered lasso motif conformation which results in an unfavorable strengthening of the interactions between the lasso motif, the regulatory (R) domain, and the transmembrane domain 2 (TMD2). Structural and functional characterization of the I37R-CFTR mutation increases understanding of CFTR channel regulation and provides a potential pathway to expand drug access to CF patients with ultra-rare genotypes.
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Affiliation(s)
- Sharon L. Wong
- School of Women's and Children's Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre (miCF_RC), UNSW Sydney, Sydney, Australia
| | - Nikhil T. Awatade
- School of Women's and Children's Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre (miCF_RC), UNSW Sydney, Sydney, Australia
| | - Miro A. Astore
- School of Physics, University of Sydney, Sydney, Australia
| | - Katelin M. Allan
- School of Women's and Children's Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre (miCF_RC), UNSW Sydney, Sydney, Australia
| | - Michael J. Carnell
- Katharina Gaus Light Microscopy Facility, Mark Wainwright Analytical Centre, UNSW Sydney, Sydney, Australia
| | - Iveta Slapetova
- Katharina Gaus Light Microscopy Facility, Mark Wainwright Analytical Centre, UNSW Sydney, Sydney, Australia
| | - Po-chia Chen
- School of Physics, University of Sydney, Sydney, Australia
| | - Alexander Capraro
- School of Women's and Children's Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre (miCF_RC), UNSW Sydney, Sydney, Australia
| | - Laura K. Fawcett
- School of Women's and Children's Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre (miCF_RC), UNSW Sydney, Sydney, Australia
- Department of Respiratory Medicine, Sydney Children's Hospital, Randwick, Australia
| | - Renee M. Whan
- Katharina Gaus Light Microscopy Facility, Mark Wainwright Analytical Centre, UNSW Sydney, Sydney, Australia
| | | | - Chee Y. Ooi
- School of Women's and Children's Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre (miCF_RC), UNSW Sydney, Sydney, Australia
- Department of Gastroenterology, Sydney Children's Hospital, Randwick, Australia
| | - Serdar Kuyucak
- School of Physics, University of Sydney, Sydney, Australia
| | - Adam Jaffe
- School of Women's and Children's Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre (miCF_RC), UNSW Sydney, Sydney, Australia
- Department of Respiratory Medicine, Sydney Children's Hospital, Randwick, Australia
| | - Shafagh A. Waters
- School of Women's and Children's Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre (miCF_RC), UNSW Sydney, Sydney, Australia
- Department of Respiratory Medicine, Sydney Children's Hospital, Randwick, Australia
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7
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Sabusap CM, Joshi D, Simhaev L, Oliver KE, Senderowitz H, van Willigen M, Braakman I, Rab A, Sorscher EJ, Hong JS. The CFTR P67L variant reveals a key role for N-terminal lasso helices in channel folding, maturation, and pharmacologic rescue. J Biol Chem 2021; 296:100598. [PMID: 33781744 PMCID: PMC8102917 DOI: 10.1016/j.jbc.2021.100598] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/15/2021] [Accepted: 03/25/2021] [Indexed: 12/14/2022] Open
Abstract
Patients with cystic fibrosis (CF) harboring the P67L variant in the cystic fibrosis transmembrane conductance regulator (CFTR) often exhibit a typical CF phenotype, including severe respiratory compromise. This rare mutation (reported in <300 patients worldwide) responds robustly to CFTR correctors, such as lumacaftor and tezacaftor, with rescue in model systems that far exceed what can be achieved for the archetypical CFTR mutant F508del. However, the specific molecular consequences of the P67L mutation are poorly characterized. In this study, we conducted biochemical measurements following low-temperature growth and/or intragenic suppression, which suggest a mechanism underlying P67L that (1) shares key pathogenic features with F508del, including off-pathway (non-native) folding intermediates, (2) is linked to folding stability of nucleotide-binding domains 1 and 2, and (3) demonstrates pharmacologic rescue that requires domains in the carboxyl half of the protein. We also investigated the "lasso" helices 1 and 2, which occur immediately upstream of P67. Based on limited proteolysis, pulse chase, and molecular dynamics analysis of full-length CFTR and a series of deletion constructs, we argue that P67L and other maturational processing (class 2) defects impair the integrity of the lasso motif and confer misfolding of downstream domains. Thus, amino-terminal missense variants elicit a conformational change throughout CFTR that abrogates maturation while providing a robust substrate for pharmacologic repair.
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Affiliation(s)
- Carleen Mae Sabusap
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Disha Joshi
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Luba Simhaev
- Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel
| | - Kathryn E Oliver
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
| | | | - Marcel van Willigen
- Department of Cellular Protein Chemistry, Utrecht University, Utrecht, Netherlands
| | - Ineke Braakman
- Department of Cellular Protein Chemistry, Utrecht University, Utrecht, Netherlands
| | - Andras Rab
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Eric J Sorscher
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA.
| | - Jeong S Hong
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
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8
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Next-Generation Sequencing for Molecular Diagnosis of Cystic Fibrosis in a Brazilian Cohort. DISEASE MARKERS 2021; 2021:9812074. [PMID: 33613790 PMCID: PMC7878085 DOI: 10.1155/2021/9812074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 12/23/2020] [Accepted: 01/27/2021] [Indexed: 12/05/2022]
Abstract
Cystic fibrosis (CF), an autosomal recessive genetic disease, is recognized as one of the most prevalent diseases in Caucasian populations. Epidemiological data show that the incidence of CF varies between countries and ethnic groups in the same region. CF occurs due to pathogenic variants in the gene encoding cystic fibrosis transmembrane conductance regulator (CFTR), located on chromosome 7q31.2. To date, more than 2,000 variants have been registered in the CFTR database. The study of these variants leads to the diagnosis and the possibility of a specific treatment for each patient through precision medicine. In this study, complete screening of CFTR was performed through next-generation sequencing (NGS) to gain insight into the variants circulating in the population of Rio de Janeiro and to provide patient access to treatment through genotype-specific therapies. Samples from 93 patients with an inconclusive molecular diagnosis were subjected to full-length screening of CFTR using an Illumina NGS HiSeq platform. Among these patients, 46 had two pathogenic variants, whereas 12 had only one CFTR variant. Twenty-four variants were not part of our routine screening. Of these 24 variants, V938Gfs∗37 had not been described in the CF databases previously. This research achieved a molecular diagnosis of the patients with CF and identification of possible molecular candidates for genotype-specific treatments.
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9
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Carriers of cystic fibrosis among sperm donors: complete CFTR gene analysis versus CFTR genotyping. Fertil Steril 2020; 114:524-534. [PMID: 32773111 DOI: 10.1016/j.fertnstert.2020.04.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 04/08/2020] [Accepted: 04/09/2020] [Indexed: 02/06/2023]
Abstract
OBJECTIVE To determine the frequency of cystic fibrosis (CF) carriers among sperm donors in Spain studied through a complete analysis of the CFTR gene and to compare the results with those that would have been obtained by the 4 genotyping panels of the CFTR gene most commonly used as a carrier test in the context of assisted reproduction in our country. DESIGN Descriptive observational study. SETTING Private center. PATIENTS Nine hundred thirty-five sperm donors, from January 2014 to June 2019. INTERVENTION None. MAIN OUTCOME MEASURE Presence of pathogenic variants in the CFTR gene. RESULTS 17% of the donors were carriers of at least 1 pathogenic variant in CFTR, with 39 different pathogenic variants detected. Only 4 of these 39 variants (10.27%) would have been detected by the 4 genotyping tests considered, and 22 variants (56.41%) would not have been detected by any of the genotyping tests. The pathogenic variants of the CFTR gene included in the different genotyping tests analyzed vary widely, and <50% are common to all of them. CONCLUSIONS Although the was not based in the general population, these results show that the use of genotyping tests is associated with a high reproductive risk, because the rate of detection of CF carriers was lower when these panels were applied, in comparison with the complete study of the CFTR gene. We recommend that complete sequencing of the CFTR gene by next-generation sequencing be performed as a screening method for CF in sperm donors.
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10
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Ubiquitination of disease-causing CFTR variants in a microsome-based assay. Anal Biochem 2020; 604:113829. [PMID: 32621804 DOI: 10.1016/j.ab.2020.113829] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 06/10/2020] [Accepted: 06/11/2020] [Indexed: 12/14/2022]
Abstract
Soluble secreted proteins and membrane proteins are subjected to protein quality control pathways during their synthesis in the endoplasmic reticulum (ER) and delivery to other destinations. Foremost among these quality control pathways is the selection of misfolded proteins for ER-associated degradation (ERAD). A growing number of diseases, including Cystic Fibrosis, are linked to the ERAD pathway. In most cases, a membrane protein known as the Cystic Fibrosis Transmembrane Conductance Regulator, or CFTR, is prematurely degraded by ERAD. Cell-based assays and in vitro studies have elucidated factors required for the recognition and degradation of CFTR, yet mechanistic details on how these factors target specific disease-causing variants is limited. Given the possibility that variants might exhibit unique susceptibilities to ubiquitin modification, which is required for proteasome-mediated degradation, we devised an assay that recapitulates this event. Here, we demonstrate that ER-enriched membranes from transfected human cells support CFTR ubiquitination when combined with radiolabeled ubiquitin and isolated enzymes in the ubiquitination cascade. We also show that select disease-causing variants are ubiquitinated more extensively than wild-type channels and to varying degrees. Our system provides a platform to examine how other purified factors impact CFTR ubiquitination and the ubiquitination of additional disease-associated membrane proteins.
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11
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Baaklini I, Gonçalves CDC, Lukacs GL, Young JC. Selective Binding of HSC70 and its Co-Chaperones to Structural Hotspots on CFTR. Sci Rep 2020; 10:4176. [PMID: 32144307 PMCID: PMC7060200 DOI: 10.1038/s41598-020-61107-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 02/07/2020] [Indexed: 12/17/2022] Open
Abstract
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) channel cause cystic fibrosis. Chaperones, including HSC70, DNAJA1 and DNAJA2, play key roles in both the folding and degradation of wild-type and mutant CFTR at multiple cellular locations. DNAJA1 and HSC70 promote the folding of newly synthesized CFTR at the endoplasmic reticulum (ER), but are required for the rapid turnover of misfolded channel at the plasma membrane (PM). DNAJA2 and HSC70 are also involved in the ER-associated degradation (ERAD) of misfolded CFTR, while they assist the refolding of destabilized channel at the PM. These outcomes may depend on the binding of chaperones to specific sites within CFTR, which would be exposed in non-native states. A CFTR peptide library was used to identify binding sites for HSC70, DNAJA1 and DNAJA2, validated by competition and functional assays. Each chaperone had a distinct binding pattern, and sites were distributed between the surfaces of the CFTR cytosolic domains, and domain interfaces known to be important for channel assembly. The accessibility of sites to chaperones will depend on the degree of CFTR folding or unfolding. Different folded states may be recognized by unique combinations of HSC70, DNAJA1 and DNAJA2, leading to divergent biological effects.
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Affiliation(s)
- Imad Baaklini
- McGill University, Department of Biochemistry, Montreal, H3G 1Y6, Canada
| | | | - Gergely L Lukacs
- McGill University, Department of Biochemistry, Montreal, H3G 1Y6, Canada.,McGill University, Department of Physiology, Montreal, H3G 1Y6, Canada
| | - Jason C Young
- McGill University, Department of Biochemistry, Montreal, H3G 1Y6, Canada.
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12
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Hwang TC, Yeh JT, Zhang J, Yu YC, Yeh HI, Destefano S. Structural mechanisms of CFTR function and dysfunction. J Gen Physiol 2018; 150:539-570. [PMID: 29581173 PMCID: PMC5881446 DOI: 10.1085/jgp.201711946] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 03/05/2018] [Indexed: 12/18/2022] Open
Abstract
Hwang et al. integrate new structural insights with prior functional studies to reveal the functional anatomy of CFTR chloride channels. Cystic fibrosis (CF) transmembrane conductance regulator (CFTR) chloride channel plays a critical role in regulating transepithelial movement of water and electrolyte in exocrine tissues. Malfunction of the channel because of mutations of the cftr gene results in CF, the most prevalent lethal genetic disease among Caucasians. Recently, the publication of atomic structures of CFTR in two distinct conformations provides, for the first time, a clear overview of the protein. However, given the highly dynamic nature of the interactions among CFTR’s various domains, better understanding of the functional significance of these structures requires an integration of these new structural insights with previously established biochemical/biophysical studies, which is the goal of this review.
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Affiliation(s)
- Tzyh-Chang Hwang
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO .,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO.,Department of Biological Engineering, University of Missouri, Columbia, MO
| | - Jiunn-Tyng Yeh
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO
| | - Jingyao Zhang
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO.,Department of Biological Engineering, University of Missouri, Columbia, MO
| | - Ying-Chun Yu
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO.,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
| | - Han-I Yeh
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO.,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
| | - Samantha Destefano
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO.,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
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13
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Zhang Z, Chen J. Atomic Structure of the Cystic Fibrosis Transmembrane Conductance Regulator. Cell 2017; 167:1586-1597.e9. [PMID: 27912062 DOI: 10.1016/j.cell.2016.11.014] [Citation(s) in RCA: 224] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 10/28/2016] [Accepted: 11/04/2016] [Indexed: 02/07/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel evolved from the ATP-binding cassette (ABC) transporter family. In this study, we determined the structure of zebrafish CFTR in the absence of ATP by electron cryo-microscopy to 3.7 Å resolution. Human and zebrafish CFTR share 55% sequence identity, and 42 of the 46 cystic-fibrosis-causing missense mutational sites are identical. In CFTR, we observe a large anion conduction pathway lined by numerous positively charged residues. A single gate near the extracellular surface closes the channel. The regulatory domain, dephosphorylated, is located in the intracellular opening between the two nucleotide-binding domains (NBDs), preventing NBD dimerization and channel opening. The structure also reveals why many cystic-fibrosis-causing mutations would lead to defects either in folding, ion conduction, or gating and suggests new avenues for therapeutic intervention.
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Affiliation(s)
- Zhe Zhang
- The Rockefeller University and Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA
| | - Jue Chen
- The Rockefeller University and Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA.
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14
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Johnson ZL, Chen J. Structural Basis of Substrate Recognition by the Multidrug Resistance Protein MRP1. Cell 2017; 168:1075-1085.e9. [PMID: 28238471 DOI: 10.1016/j.cell.2017.01.041] [Citation(s) in RCA: 250] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/23/2017] [Accepted: 01/30/2017] [Indexed: 12/30/2022]
Abstract
The multidrug resistance protein MRP1 is an ATP-binding cassette (ABC) transporter that confers resistance to many anticancer drugs and plays a role in the disposition and efficacy of several opiates, antidepressants, statins, and antibiotics. In addition, MRP1 regulates redox homeostasis, inflammation, and hormone secretion. Using electron cryomicroscopy, we determined the molecular structures of bovine MRP1 in two conformations: an apo form at 3.5 Å without any added substrate and a complex form at 3.3 Å with one of its physiological substrates, leukotriene C4. These structures show that by forming a single bipartite binding site, MRP1 can recognize a spectrum of substrates with different chemical structures. We also observed large conformational changes induced by leukotriene C4, explaining how substrate binding primes the transporter for ATP hydrolysis. Structural comparison of MRP1 and P-glycoprotein advances our understanding of the common and unique properties of these two important molecules in multidrug resistance to chemotherapy.
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Affiliation(s)
- Zachary Lee Johnson
- Laboratory of Membrane Biology and Biophysics, The Rockefeller University and the Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA
| | - Jue Chen
- Laboratory of Membrane Biology and Biophysics, The Rockefeller University and the Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA.
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Xu Z, Pissarra LS, Farinha CM, Liu J, Cai Z, Thibodeau PH, Amaral MD, Sheppard DN. Revertant mutants modify, but do not rescue, the gating defect of the cystic fibrosis mutant G551D-CFTR. J Physiol 2014; 592:1931-47. [PMID: 24591578 DOI: 10.1113/jphysiol.2014.271817] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cystic fibrosis (CF) is caused by dysfunction of the epithelial anion channel cystic fibrosis transmembrane conductance regulator (CFTR). One strategy to restore function to CF mutants is to suppress defects in CFTR processing and function using revertant mutations. Here, we investigate the effects of the revertant mutations G550E and 4RK (the simultaneous disruption of four arginine-framed tripeptides (AFTs): R29K, R516K, R555K and R766K) on the CF mutant G551D, which impairs severely channel gating without altering protein processing and which affects a residue in the same α-helix as G550 and R555. Both G550E and 4RK augmented strongly CFTR-mediated iodide efflux from BHK cells expressing G551D-CFTR. To learn how revertant mutations influence G551D-CFTR function, we studied protein processing and single-channel behaviour. Neither G550E nor 4RK altered the expression and maturation of G551D-CFTR protein. By contrast, both revertants had marked effects on G551D-CFTR channel gating, increasing strongly opening frequency, while 4RK also diminished noticeably the duration of channel openings. Because G551D-CFTR channel gating is ATP independent, we investigated whether revertant mutations restore ATP dependence to G551D-CFTR. Like wild-type CFTR, the activity of 4RK-G551D-CFTR varied with ATP concentration, suggesting that 4RK confers some ATP dependence on the G551D-CFTR channel. Thus, the revertant mutations G550E and 4RK alter the gating pattern and ATP dependence of G551D-CFTR without restoring single-channel activity to wild-type levels. Based on their impact on the CF mutants F508del and G551D, we conclude that G550E and 4RK have direct effects on CFTR structure, but that their action on CFTR processing and channel function is CF mutation specific.
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Affiliation(s)
- Zhe Xu
- University of Bristol, School of Physiology and Pharmacology, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.
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Martinez B, Heller M, Gaitch N, Hubert D, Burgel PR, Levy P, Girodon E, Bienvenu T. p.Arg75Gln, a CFTR variant involved in the risk of CFTR-related disorders? J Hum Genet 2014; 59:206-10. [DOI: 10.1038/jhg.2014.2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/02/2013] [Accepted: 12/05/2013] [Indexed: 01/08/2023]
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Milosevic K, Nikolic A, Divac Rankov A, Ljujic M, Nestorovic B, Radojkovic D. Analysis of CFTR Gene Variants in Idiopathic Bronchiectasis in Serbian Children. PEDIATRIC ALLERGY IMMUNOLOGY AND PULMONOLOGY 2013; 26:93-98. [PMID: 23781395 DOI: 10.1089/ped.2013.0238] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 03/06/2013] [Indexed: 02/06/2023]
Abstract
This study has investigated a potential role of common Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene variants in the etiology of noncystic fibrosis bronchiectasis in Serbian children. The study has encompassed 48 patients (19 male and 29 female, aged between 5 and 18 years, median age 10.6±3.3), diagnosed with idiopathic bronchiectasis based on high-resolution computed tomography of thorax and pathologic examination of lobectomy materials. The CFTR gene analysis was performed on genomic DNA extracted from peripheral blood samples of patients by polymerase chain reaction (PCR)-Mediated Site-Directed Mutagenesis method, Denaturing Gradient Gel Electrophoresis method, and DNA sequencing. Mutation c.1521_1523delCTT (F508del) was detected with an allelic frequency of 1.0%, and c.224G>A (R75Q) variant. Carriers of c.1210-12T[5] (IVS8-5T) allele were significantly more common than in the general population (10.4% vs. 5.0%, P=0.0302). The frequency of homozygotes for Met 470 allele was higher in patients than in the general population (33% vs. 20%), while heterozygotes for p.Met470Val were less frequent (31% vs. 50%), and this difference was statistically significant (P=0.0222). The results obtained in this study indicate involvement of 2 common CFTR variants, c.1210-12T[5] and c.1408A, in idiopathic bronchiectasis in children, but this observation should be further confirmed by more extensive analysis of the CFTR gene in a larger group of patients.
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Affiliation(s)
- Katarina Milosevic
- Department of Pulmonology and Allergology, University Children's Hospital , Belgrade, Serbia
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Masvidal L, Alvarez A, Ruano L, de Gracia J, Larriba S, Casals T. GUSB and ATP2B4 are suitable reference genes for CFTR gene expression data normalization in nasal epithelium cells. J Cyst Fibros 2012; 11:398-404. [PMID: 22525089 DOI: 10.1016/j.jcf.2012.03.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 02/14/2012] [Accepted: 03/21/2012] [Indexed: 11/17/2022]
Abstract
BACKGROUND CFTR expression studies contribute in understanding the relationship between CFTR transcripts and clinical outcomes. Normalization of qPCR data is an essential step to determine target gene expression. Consequently, appropriate reference genes must be selected for each gene/tissue. In this work, we have assessed the suitability of four potential reference genes for CFTR expression analysis in nasal epithelium. METHODS B2M, GUSB, HPRT1 and ATP2B4 expression was evaluated in nasal epithelium samples (CFTR-wt controls, n=21; CFTR-splicing group, n=18) by RT-qPCR. Calibration curves were built and different analyses (geNorm, NormFinder, Mann-Whitney) were performed to evaluate gene expression stability between samples as well as between groups. RESULTS AND CONCLUSIONS We have applied an accurate approach to select reference genes for CFTR expression analysis in nasal epithelium. From the four genes assessed, GUSB and ATP2B4 have been validated as a reliable gene combination for CFTR gene qPCR data normalization.
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Affiliation(s)
- Laia Masvidal
- Human Molecular Genetics Group, IDIBELL, 08908 Barcelona, Spain
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Hao DC, Feng Y, Xiao R, Xiao PG. Non-neutral nonsynonymous single nucleotide polymorphisms in human ABC transporters: the first comparison of six prediction methods. Pharmacol Rep 2012; 63:924-34. [PMID: 22001980 DOI: 10.1016/s1734-1140(11)70608-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 02/07/2011] [Indexed: 11/28/2022]
Abstract
Nonsynonymous single nucleotide polymorphisms (nsSNPs) in coding regions that can lead to amino acid changes may cause alteration of protein function and account for susceptibility to disease and altered drug/xenobiotic response. Abundant nsSNPs have been found in genes coding for human ATP-binding cassette (ABC) transporters, but there is little known about the relationship between the genotype and phenotype of nsSNPs in these membrane proteins. In addition, it is unknown which prediction method is better suited for the prediction of non-neutral nsSNPs of ABC transporters. We have identified 2,172 validated nsSNPs in 49 human ABC transporter genes from the Ensembl genome database and the NCBI SNP database. Using six different algorithms, 41 to 52% of nsSNPs in ABC transporter genes were predicted to have functional impacts on protein function. Predictions largely agreed with the available experimental annotations. Overall, 78.5% of non-neutral nsSNPs were predicted correctly as damaging by SNAP, which together with SIFT and PolyPhen, was superior to the prediction methods Pmut, PhD-SNP, and Panther. This study also identified any amino acids that were likely to be functionally critical but have not yet been studied experimentally. There was significant concordance between the predicted results of SIFT and PolyPhen. Evolutionarily non-neutral (destabilizing) amino acid substitutions are predicted to be the basis for the pathogenic alteration of ABC transporter activity that is associated with disease susceptibility and altered drug/xenobiotic response.
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Affiliation(s)
- Da Cheng Hao
- Laboratory of Biotechnology, College of Environment, Dalian Jiaotong University, Dalian 116028, China.
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Spicuzza L, Sciuto C, Di Dio L, Mattina T, Leonardi S, del Giudice MM, La Rosa M. Mild cystic fibrosis in patients with the rare P5L CFTR mutation. J Cyst Fibros 2011; 11:30-3. [PMID: 21983161 DOI: 10.1016/j.jcf.2011.08.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 08/26/2011] [Accepted: 08/29/2011] [Indexed: 11/27/2022]
Abstract
Over 1800 Cystic Fibrosis Transmembrane Conductance Regulator gene (CFTR) mutations have been identified so far, determining different degrees of CFTR dysfunction and a range of different cystic fibrosis phenotypes. The P5L CFTR mutation is a recently described N-terminus missense variant which may cause defect of protein folding and processing/trafficking, but the functional classification is still unclear. Given the rarity of the mutation, the associated clinical phenotype is still unknown. The aim of our study was to describe the clinical phenotypes in a group of 7 patients with the P5L mutation including 2 adults, 2 adolescents and 3 children. The P5L variant was associated with ΔF508 in 5 patients and with W1282X in two patients. All patients had positive or borderline sweat test values. All had pancreatic sufficiency, no hepatobiliary disease, no or mild respiratory symptoms and normal lung function. The two adult males were fertile. Most of the patients presented recurrent episodes of dehydration and hypochloronatremia. We conclude that, although it has been speculated that the N-terminus CFTR missense variants may severely affect the behaviour of the CFTR chloride channel, patients with the P5L CFTR mutation, in association with a severe class II mutation, may be asymptomatic or may be affected by mild disease.
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Affiliation(s)
- Lucia Spicuzza
- Department of Pediatrics, Bronchopneumology Unit, University of Catania, Italy.
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Abstract
OBJECTIVES To assess specific etiologies of acute recurrent pancreatitis at a single Italian pediatric cystic fibrosis (CF) center. METHODS We studied, retrospectively, 78 young patients (39 female subjects; mean age at diagnosis, 8.8 ± 5.1 years) affected by acute recurrent episodes of pancreatitis, remained etiologically undiagnosed at first-level assessment. All patients were submitted to endoscopic retrograde cholangiopancreatography to exclude biliopancreatic malformations and tested for CF by a sweat chloride test. Most patients also were studied for the research of CFTR, PRSS1, and SPINK1 gene mutations. RESULTS A high percentage of family history for chronic pancreatitis was observed (20.5%). The sweat test identified 8 subjects (10.3%) with classic CF (2 patients) or at risk for CF (6 patients). Genetic analysis showed mutations in CFTR, SPINK1, and PRSS1 genes in 39.6%, 7.1%, and 4.5% of patients, respectively. A biliopancreatic malformation was diagnosed in 15 patients (19.2%). We also observed biliary lithiasis (5 patients [6.5%]), congenital pancreatic polycystosis (2 patients), a case of dyslipidemia, and 1 patient with a posttransplantation, drug-induced pancreatitis. CONCLUSIONS Recurrent pancreatitis in children has several etiologies. Genetic testing confirms the high frequency of CFTR mutations. This suggests that it is of some value to identify patients with late-onset CF and CFTR-related disorders.
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Schneider A, LaRusch J, Sun X, Aloe A, Lamb J, Hawes R, Cotton P, Brand RE, Anderson MA, Money ME, Banks PA, Lewis MD, Baillie J, Sherman S, DiSario J, Burton FR, Gardner TB, Amann ST, Gelrud A, George R, Kassabian S, Martinson J, Slivka A, Yadav D, Oruc N, Barmada MM, Frizzell R, Whitcomb DC, Whitcomb DC. Combined bicarbonate conductance-impairing variants in CFTR and SPINK1 variants are associated with chronic pancreatitis in patients without cystic fibrosis. Gastroenterology 2011; 140:162-71. [PMID: 20977904 PMCID: PMC3171690 DOI: 10.1053/j.gastro.2010.10.045] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 09/14/2010] [Accepted: 10/15/2010] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS Idiopathic chronic pancreatitis (ICP) is a complex inflammatory disorder associated with multiple genetic and environmental factors. In individuals without cystic fibrosis (CF), variants of CFTR that inhibit bicarbonate conductance but maintain chloride conductance might selectively impair secretion of pancreatic juice, leading to trypsin activation and pancreatitis. We investigated whether sequence variants in the gene encoding the pancreatic secretory trypsin inhibitor SPINK1 further increase the risk of pancreatitis in these patients. METHODS We screened patients and controls for variants in SPINK1 associated with risk of chronic pancreatitis and in all 27 exons of CFTR. The final study group included 53 patients with sporadic ICP, 27 probands with familial ICP, 150 unrelated controls, 375 additional controls for limited genotyping. CFTR wild-type and p.R75Q were cloned and expressed in HEK293 cells, and relative conductances of HCO(3)(-) and Cl(-) were measured. RESULTS SPINK1 variants were identified in 36% of subjects and 3% of controls (odds ratio [OR], 18.1). One variant of CFTR not associated with CF, p.R75Q, was found in 16% of subjects and 5.3% of controls (OR, 3.4). Coinheritance of CFTR p.R75Q and SPINK1 variants occurred in 8.75% of patients and 0.38% of controls (OR, 25.1). Patch-clamp recordings of cells that expressed CFTR p.R75Q showed normal chloride currents but significantly reduced bicarbonate currents (P = .0001). CONCLUSIONS The CFTR variant p.R75Q causes a selective defect in bicarbonate conductance and increases risk of pancreatitis. Coinheritance of p.R75Q or CF causing CFTR variants with SPINK1 variants significantly increases the risk of ICP.
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Affiliation(s)
| | - Jessica LaRusch
- Department of Medicine, University of Pittsburgh, Pittsburgh PA
| | - Xiumei Sun
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh PA
| | - Amy Aloe
- Department of Medicine, University of Pittsburgh, Pittsburgh PA
| | - Janette Lamb
- Department of Medicine, University of Pittsburgh, Pittsburgh PA
| | - Robert Hawes
- Digestive Disease Center, Medical University of South Carolina, Charleston, SC
| | - Peter Cotton
- Digestive Disease Center, Medical University of South Carolina, Charleston, SC
| | - Randall E. Brand
- Department of Medicine, Evanston Northwestern Healthcare, Chicago IL
| | | | | | - Peter A. Banks
- Division of Gastroenterology, Brigham and Women’s Hospital, Boston MD
| | - Michele D. Lewis
- Division of Gastroenterology and Hepatology, Mayo Clinic, Jacksonville, FL
| | - John Baillie
- Department of Medicine, Duke University Medical Center, Durham NC
| | - Stuart Sherman
- Department of Medicine, Indiana University Medical Center, Indianapolis, IN
| | - James DiSario
- Monterey Bay Gastroenterology Consultants, Monterey, CA
| | - Frank R. Burton
- Department of Internal Medicine, St. Louis University School of Medicine, St Louis, MO
| | | | | | - Andres Gelrud
- Department of Internal Medicine, University of Cincinnati, Cincinnati, OH
| | - Ryan George
- Department of Medicine, University of Pittsburgh, Pittsburgh PA
| | | | - Jeremy Martinson
- Department of Infectious Diseases and Microbiology, University of Pittsburgh, Pittsburgh PA
| | - Adam Slivka
- Department of Medicine, University of Pittsburgh, Pittsburgh PA
| | - Dhiraj Yadav
- Department of Medicine, University of Pittsburgh, Pittsburgh PA
| | - Nevin Oruc
- Department of Medicine, University of Pittsburgh, Pittsburgh PA
| | | | - Raymond Frizzell
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh PA
| | - David C. Whitcomb
- Department of Medicine, University of Pittsburgh, Pittsburgh PA, Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh PA, Department of Human Genetics, University of Pittsburgh, Pittsburgh PA
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Smith L, Page RC, Xu Z, Kohli E, Litman P, Nix JC, Ithychanda SS, Liu J, Qin J, Misra S, Liedtke CM. Biochemical basis of the interaction between cystic fibrosis transmembrane conductance regulator and immunoglobulin-like repeats of filamin. J Biol Chem 2010; 285:17166-76. [PMID: 20351101 DOI: 10.1074/jbc.m109.080911] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mutations in the chloride channel cystic fibrosis transmembrane regulator (CFTR) cause cystic fibrosis, a genetic disorder characterized by defects in CFTR biosynthesis, localization to the cell surface, or activation by regulatory factors. It was discovered recently that surface localization of CFTR is stabilized by an interaction between the CFTR N terminus and the multidomain cytoskeletal protein filamin. The details of the CFTR-filamin interaction, however, are unclear. Using x-ray crystallography, we show how the CFTR N terminus binds to immunoglobulin-like repeat 21 of filamin A (FlnA-Ig21). CFTR binds to beta-strands C and D of FlnA-Ig21 using backbone-backbone hydrogen bonds, a linchpin serine residue, and hydrophobic side-chain packing. We use NMR to determine that the CFTR N terminus also binds to several other immunoglobulin-like repeats from filamin A in vitro. Our structural data explain why the cystic fibrosis-causing S13F mutation disrupts CFTR-filamin interaction. We show that FlnA-Ig repeats transfected into cultured Calu-3 cells disrupt CFTR-filamin interaction and reduce surface levels of CFTR. Our findings suggest that filamin A stabilizes surface CFTR by anchoring it to the actin cytoskeleton through interactions with multiple filamin Ig repeats. Such an interaction mode may allow filamins to cluster multiple CFTR molecules and to promote colocalization of CFTR and other filamin-binding proteins in the apical plasma membrane of epithelial cells.
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Affiliation(s)
- Laura Smith
- Department of Pediatrics at Rainbow Babies and Children's Hospital and of Physiology and Biophysics, Case Western Reserve University, Willard Alan Bernbaum Center for Cystic Fibrosis Research, Cleveland, Ohio 44106, USA
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Ramalho AS, Lewandowska MA, Farinha CM, Mendes F, Gonçalves J, Barreto C, Harris A, Amaral MD. Deletion of CFTR translation start site reveals functional isoforms of the protein in CF patients. Cell Physiol Biochem 2009; 24:335-46. [PMID: 19910674 PMCID: PMC2793277 DOI: 10.1159/000257426] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2009] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND/AIMS Mutations in the CFTR gene cause Cystic Fibrosis (CF) the most common life-threatening autosomal recessive disease affecting Caucasians. We identified a CFTR mutation (c.120del23) abolishing the normal translation initiation codon, which occurs in two Portuguese CF patients. This study aims at functionally characterizing the effect of this novel mutation. METHODS RNA and protein techniques were applied to both native tissues from CF patients and recombinant cells expressing CFTR constructs to determine whether c.120del23 allows CFTR protein production through usage of alternative internal codons, and to characterize the putative truncated CFTR form(s). RESULTS Our data show that two shorter forms of CFTR protein are produced when the initiation translation codon is deleted indicating usage of internal initiation codons. The N-truncated CFTR generated by this mutation has decreased stability, very low processing efficiency, and drastically reduced function. Analysis of mutants of four methionine codons downstream to M1 (M82, M150, M152, M156) revealed that each of the codons M150/M152/M156 (exon 4) can mediate CFTR alternative translation. CONCLUSIONS The CFTR N-terminus has an important role in avoiding CFTR turnover and in rendering effective its plasma membrane traffic. These data correlate well with the severe clinical phenotype of CF patients bearing the c.120del23 mutation.
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Affiliation(s)
- Anabela S. Ramalho
- University of Lisboa, Faculty of Sciences, Centre for Biodiversity, Functional and Integrative Genomics (BioFIG), Lisboa, Portugal
- Department of Genetics, National Institute of Health, Lisboa, Portugal
| | - Marzena A. Lewandowska
- Human Molecular Genetics Program, Children's Memorial Research Center, Northwestern University, Chicago IL, USA
| | - Carlos M. Farinha
- University of Lisboa, Faculty of Sciences, Centre for Biodiversity, Functional and Integrative Genomics (BioFIG), Lisboa, Portugal
- Department of Genetics, National Institute of Health, Lisboa, Portugal
| | - Filipa Mendes
- University of Lisboa, Faculty of Sciences, Centre for Biodiversity, Functional and Integrative Genomics (BioFIG), Lisboa, Portugal
- Department of Genetics, National Institute of Health, Lisboa, Portugal
| | - Juan Gonçalves
- Hospital do Divino Espírito Santo, Ponta Delgada, Portugal
| | | | - Ann Harris
- Human Molecular Genetics Program, Children's Memorial Research Center, Northwestern University, Chicago IL, USA
| | - Margarida D. Amaral
- University of Lisboa, Faculty of Sciences, Centre for Biodiversity, Functional and Integrative Genomics (BioFIG), Lisboa, Portugal
- Department of Genetics, National Institute of Health, Lisboa, Portugal
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