1
|
Kumar M, Aaron R, Varkki SD, Danda S, Ranganathan S, Paul GR. A rare variant c.1802T>C (p. Ile601Thr) associated with severe phenotype among people with cystic fibrosis from south India, and potential genetic admixture in Réunion, France. Pediatr Pulmonol 2024; 59:1820-1825. [PMID: 38501349 DOI: 10.1002/ppul.26965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 03/04/2024] [Accepted: 03/06/2024] [Indexed: 03/20/2024]
Affiliation(s)
- Madhan Kumar
- Department of Pediatrics, Christian Medical College, Vellore, India
| | - Rekha Aaron
- Department of Medical Genetics, Christian Medical College, Vellore, India
| | - Sneha D Varkki
- Department of Pediatrics, Christian Medical College, Vellore, India
| | - Sumita Danda
- Department of Medical Genetics, Christian Medical College, Vellore, India
| | - Sarath Ranganathan
- Murdoch Children's Research Institute, University of Melbourne, Australia
| | - Grace R Paul
- Division of Pulmonary and Sleep Medicine, Nationwide Children's Hospital, Columbus, Ohio, USA
| |
Collapse
|
2
|
Reporting Two Novel Mutations in Two Iranian Families with Cystic Fibrosis, Molecular and Bioinformatic Analysis. IRANIAN BIOMEDICAL JOURNAL 2022; 26:398-405. [PMID: 35468710 PMCID: PMC9763878 DOI: 10.52547/ibj.3713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Background Cystic fibrosis (CF) is the most common heredity disease among the Caucasian population. More than 350 known pathogenic variations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene (NM_000492.4) cause CF. Herein, we report the outcome of our investigation in two unrelated Iranian families with CF patients. Methods We conducted phenotypic examination, segregation, linkage analysis, and CFTR gene sequencing to define causative mutations. Results We found two novel mutations in the present study. The first one was a deletion causing frameshift, c.299delT p.(Leu100Profs*7), and the second one was a missense mutation, c.1857G>T, at nucleotide binding domain 1 of the CFTR protein. Haplotype segregation data supported our new mutation findings. Conclusion Findings of this study expand the spectrum of CFTR pathogenic variations and can improve prenatal diagnosis and genetic counseling for CF.
Collapse
|
3
|
Lin C, Woolfson JP. CFTR:F508d/A613T Mutation Is Associated With Recurrent Episodes of Pancreatitis. JPGN REPORTS 2022; 3:e142. [PMID: 37168745 PMCID: PMC10158408 DOI: 10.1097/pg9.0000000000000142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 10/10/2021] [Indexed: 05/13/2023]
Abstract
Pancreatic insufficiency (PI) is found in 85% of individuals with cystic fibrosis (CF). Of the remaining who are pancreatic sufficient (PS), there is potential for developing pancreatitis, and is described in ~20% of PS individuals. We report a case of a 17.5-year-old female presenting with acute recurrent pancreatitis (ARP) and PS, later diagnosed with CF. This is the first reported case of ARP in an individual with a F508d/A613T genotype. To date, there are only 6 other individuals with this genotype, and the mechanisms of it causing ARP and no overt respiratory symptoms of CF are unclear. Her diagnosis occurred 10 years after her initial presentation of pancreatitis, highlighting the importance of screening for CFTR mutations in the workup for ARP with no clear etiology.
Collapse
Affiliation(s)
- Cindy Lin
- From The University of Western Ontario, Schulich School of Medicine and Dentistry, London, ON, Canada
| | - Jessica P. Woolfson
- From The University of Western Ontario, Schulich School of Medicine and Dentistry, London, ON, Canada
- Division of Pediatric Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, The Children’s Hospital at London Health Sciences Centre, London, ON, Canada
| |
Collapse
|
4
|
Banjar H, Qeretli R, Ramadan A, Al-Ibraheem A, Bnatig F. The first report on CFTR mutations of meconium ileus in cystic fibrosis population in Saudi Arabia: A single center review. INTERNATIONAL JOURNAL OF PEDIATRICS AND ADOLESCENT MEDICINE 2021; 9:32-35. [PMID: 35573065 PMCID: PMC9072234 DOI: 10.1016/j.ijpam.2021.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 03/16/2021] [Indexed: 11/26/2022] Open
Abstract
Introduction Meconium ileus (MI) is one of the most common causes of intestinal obstruction in newborns. It is the earliest clinical manifestation of cystic fibrosis (CF). MI is suspected if a baby fails to pass meconium shortly after birth and develops symptoms of bowel obstruction, such as distention of the abdomen or vomiting. MI can lead to bowel perforation, a twisting of the bowel, or inflammation and infection of the abdominal cavity. Objectives To find the incidence and prevalence of meconium ileus in cystic fibrosis patients and to report on the most common gene mutation of MI in CF patients. Methodology Retrospective review of the medical documentations of all MI patients during the period of 1989–2018. Results A total of 40 CF confirmed patients were presented with MI. Twenty-nine patients (71%) are alive and 11 patients (29%) died or lost to follow-up. The following CFTR mutations were found: Eight patients (20%) with c.2988+1G>A; Intron 18. Seven patients (17.5%) with c.1418delG; Exon 11. Five patients (12.5%) with c.579+1G>T; Intron 5. Four patients (10%) with c.1911delG; Exon 14. Four patients (10%) with c.1521_1523delCTT; Exon 11. Four patients (10%) with c.416A>T; Exon 13. Three patients (7.5%) with c.2421A>G; Exon 14. Two patients (5%) with c.3908A>C; Exon 21. One patient (2.5%) with c.3889dupT; Exon 24. One patient (2.5%) with c.1657C>T; Exon 12. One patient (2.5%) with c.2547C>A; Exon 14a. Eighteen patients (45%) were presented with vomiting, 38 patients (95%) had postnatal radiological findings, 7 patients (17.5%) had electrolytes imbalance. Five patients (12.5%) had cholestasis and 4 patients (10%) developed chronic liver disease. Thirty-five patients (79.5%) underwent surgical repair and 9 patients (20.5%) were treated medically. Mean age of operation was 2.25 (2) days. Of 9 patients, 6 (66.6%) were treated with gastrograffin enema, 2 patients (22.2%) with oral N-acetylcysteine and 1 patient (11.1%) with saline rectal wash. Thirteen patients (31.5%) required TPN. Five patients had recurrent operation. Conclusion CF and meconium ileus are commonly present in CF patients in Saudi Arabia. Prognosis is similar to other CFs without MI, if treated early. Thirty percent of our CF/MI patients have intronic mutations.
Collapse
|
5
|
Haq IJ, Althaus M, Gardner AI, Yeoh HY, Joshi U, Saint-Criq V, Verdon B, Townshend J, O'Brien C, Ben-Hamida M, Thomas M, Bourke S, van der Sluijs P, Braakman I, Ward C, Gray MA, Brodlie M. Clinical and molecular characterization of the R751L-CFTR mutation. Am J Physiol Lung Cell Mol Physiol 2020; 320:L288-L300. [PMID: 33296276 PMCID: PMC8476205 DOI: 10.1152/ajplung.00137.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cystic fibrosis (CF) arises from mutations in the CF transmembrane conductance regulator (CFTR) gene, resulting in progressive and life-limiting respiratory disease. R751L is a rare CFTR mutation that is poorly characterized. Our aims were to describe the clinical and molecular phenotypes associated with R751L. Relevant clinical data were collected from three heterozygote individuals harboring R751L (2 patients with G551D/R751L and 1 with F508del/R751L). Assessment of R751L-CFTR function was made in primary human bronchial epithelial cultures (HBEs) and Xenopus oocytes. Molecular properties of R751L-CFTR were investigated in the presence of known CFTR modulators. Although sweat chloride was elevated in all three patients, the clinical phenotype associated with R751L was mild. Chloride secretion in F508del/R751L HBEs was reduced compared with non-CF HBEs and associated with a reduction in sodium absorption by the epithelial sodium channel (ENaC). However, R751L-CFTR function in Xenopus oocytes, together with folding and cell surface transport of R751L-CFTR, was not different from wild-type CFTR. Overall, R751L-CFTR was associated with reduced sodium chloride absorption but had functional properties similar to wild-type CFTR. This is the first report of R751L-CFTR that combines clinical phenotype with characterization of functional and biological properties of the mutant channel. Our work will build upon existing knowledge of mutations within this region of CFTR and, importantly, inform approaches for clinical management. Elevated sweat chloride and reduced chloride secretion in HBEs may be due to alternative non-CFTR factors, which require further investigation.
Collapse
Affiliation(s)
- Iram J Haq
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.,Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Mike Althaus
- Institute for Functional Gene Analytics, Department of Natural Sciences, Bonn-Rhein-Sieg University of Applied Sciences, Rheinbach, Germany
| | - Aaron Ions Gardner
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Hui Ying Yeoh
- Cellular Protein Chemistry, Science4Life, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Urjita Joshi
- Cellular Protein Chemistry, Science4Life, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Vinciane Saint-Criq
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Bernard Verdon
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Jennifer Townshend
- Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Christopher O'Brien
- Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Mahfud Ben-Hamida
- Department of Paediatrics, West Cumberland Hospital, Whitehaven, United Kingdom
| | - Matthew Thomas
- Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Stephen Bourke
- Respiratory Medicine, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Peter van der Sluijs
- Cellular Protein Chemistry, Science4Life, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Ineke Braakman
- Cellular Protein Chemistry, Science4Life, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Chris Ward
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Michael A Gray
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Malcolm Brodlie
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.,Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| |
Collapse
|
6
|
Billet A, Elbahnsi A, Jollivet-Souchet M, Hoffmann B, Mornon JP, Callebaut I, Becq F. Functional and Pharmacological Characterization of the Rare CFTR Mutation W361R. Front Pharmacol 2020; 11:295. [PMID: 32256364 PMCID: PMC7092619 DOI: 10.3389/fphar.2020.00295] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 02/27/2020] [Indexed: 11/15/2022] Open
Abstract
Understanding the functional consequence of rare cystic fibrosis (CF) mutations is mandatory for the adoption of precision therapeutic approaches for CF. Here we studied the effect of the very rare CF mutation, W361R, on CFTR processing and function. We applied western blot, patch clamp and pharmacological modulators of CFTR to study the maturation and ion transport properties of pEGFP-WT and mutant CFTR constructs, W361R, F508del and L69H-CFTR, expressed in HEK293 cells. Structural analyses were also performed to study the molecular environment of the W361 residue. Western blot showed that W361R-CFTR was not efficiently processed to a mature band C, similar to F508del CFTR, but unlike F508del CFTR, it did exhibit significant transport activity at the cell surface in response to cAMP agonists. Importantly, W361R-CFTR also responded well to CFTR modulators: its maturation defect was efficiently corrected by VX-809 treatment and its channel activity further potentiated by VX-770. Based on these results, we postulate that W361R is a novel class-2 CF mutation that causes abnormal protein maturation which can be corrected by VX-809, and additionally potentiated by VX-770, two FDA-approved small molecules. At the structural level, W361 is located within a class-2 CF mutation hotspot that includes other mutations that induce variable disease severity. Analysis of the 3D structure of CFTR within a lipid environment indicated that W361, together with other mutations located in this hotspot, is at the edge of a groove which stably accommodates lipid acyl chains. We suggest this lipid environment impacts CFTR folding, maturation and response to CFTR modulators.
Collapse
Affiliation(s)
- Arnaud Billet
- Laboratoire Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS, Poitiers, France
| | - Ahmad Elbahnsi
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, Paris, France
| | - Mathilde Jollivet-Souchet
- Laboratoire Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS, Poitiers, France
| | - Brice Hoffmann
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, Paris, France
| | - Jean-Paul Mornon
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, Paris, France
| | - Isabelle Callebaut
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, Paris, France
| | - Frédéric Becq
- Laboratoire Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS, Poitiers, France
| |
Collapse
|
7
|
Banjar HH, Tuleimat L, El Seoudi AAA, Mogarri I, Alhaider S, Nizami IY, AlMaghamsi T, Alkaf SA, Moghrabi N. Genotype patterns for mutations of the cystic fibrosis transmembrane conductance regulator gene: a retrospective descriptive study from Saudi Arabia. Ann Saudi Med 2020; 40:15-24. [PMID: 32026723 PMCID: PMC7012030 DOI: 10.5144/0256-4947.2020.15] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 07/20/2019] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Cystic fibrosis (CF) occurs in populations in Saudi Arabia and the Gulf area. Approximately 2000 known variants have been identified for the CF transmembrane conductance regulator (CTFR) gene. Screening for ten of the most common variants can detect 80% of alleles. OBJECTIVE Determine the pattern of CFTR variants in the CF population of Saudi Arabia. DESIGN A retrospective, descriptive. SETTING Tertiary care center. PATIENTS AND METHODS We examined the medical records of 396 confirmed CF patients of all age groups that were positive for a CFTR variant from the period of 1 January 1998 to 1 December 2017. MAIN OUTCOME MEASURES Zygosity, morbidity and mortality patterns of different types of CFTR variants. SAMPLE SIZE 312 families that included 396 patients. RESULTS Of 48 variants identified, 6 were novel, having not been described in the medical literature. A homozygous state was found in 283 families (90.7%) and compound heterozygosity in 23 (7.4%). Six families were heterozygous (1.9%). Median age (interquartile range) was 10.2 months (4.4 months to 5.7 years) at diagnosis and 9.7 (5.4-16.5) years at follow up. Of 396 patients, 378 patients (95.5%) survived and 18 (4.5%) died. The ten most common variants identified in descending frequency were: p.Gly473GlufsX54 in 98 alleles (16%), p.Ile1234Val in 66 alleles (11%), F508del in 64 alleles (11%), 711+1G>T in 62 alleles (10%), 3120+1G>A in 62 alleles (11%), p.His139Leuin 38 alleles (6.4%), p.Gln637Hisfs in 30 alleles (5.2%), p.Ser549Arg in 27 alleles (4.5%), p.Asn1303Lys in 14 alleles (2.3%), delExon19-21in 10 alleles (1.6%). This analysis identified 79.2% of our CFTR variants. CONCLUSION CFTR mutational patterns in our CF population are characterized by a high allelic heterogeneity. The high prevalence of homozygous variants reflects the high level of consanguinity between parents. LIMITATIONS Our CFTR screening reflected only about 80% of CF patients in Saudi Arabia. CONFLICT OF INTEREST None.
Collapse
Affiliation(s)
- Hanaa Hasan Banjar
- From the Department of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Lin Tuleimat
- From the Department of Medicine, Al Faisal University, Riyadh, Saudi Arabia
| | | | - Ibrahim Mogarri
- From the Department of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Sami Alhaider
- From the Department of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Imran Yaqoob Nizami
- From the Organ Transplant Center, King Faisal Specialist and Research Center, Riyadh, Saudi Arabia
| | - Talal AlMaghamsi
- From the Department of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Sara Andulrahman Alkaf
- From the Biostatistic Epidemiology and Scientific Computing Department, King Faisal Center for Research and Islamic Studies, Riyadh, Saudi Arabia
| | - Nabil Moghrabi
- From the Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| |
Collapse
|
8
|
Grangeia A, Alves S, Gonçalves L, Gregório I, Santos AC, Barros H, Barros A, Carvalho F, Moura C. Spectrum of CFTR gene sequence variants in a northern Portugal population. Pulmonology 2018; 24:3-9. [PMID: 29589582 DOI: 10.1016/j.pulmoe.2017.12.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 10/25/2017] [Accepted: 12/03/2017] [Indexed: 11/15/2022] Open
Abstract
In Portugal, the spectrum of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene variants is not known. The main objective of this work was to determine the type and frequency of CFTR variants in a sample from northern Portugal by the complete analysis of the CFTR coding sequencing performed in 512 Portuguese children. A total of 30 different CFTR sequence variants, already reported as cystic fibrosis (CF) or CFTR related disorders variants, were detected. Ninety-two children (18.0%; 95%CI: 14.7-21.6) were found to be carriers of one sequence variant and 8 (1.6%; 95%CI: 0.7-3.1) had two sequence variants. Taking into consideration only variants that may cause CF when combined with a pathogenic CF variant, the CF pathogenic variant carrier frequency was 3.3% (95%CI: 1.9-5.3). One (0.2%; 95%CI: 0.01-0.7) child presented two CF pathogenic variants. CONCLUSIONS The majority of CFTR variants detected have been associated with a less severe CF phenotype. A wide spectrum of CFTR variants was identified, confirming the highest CFTR allelic heterogeneity previously reported in Mediterranean country. Additionally, better knowledge about the CFTR sequence variation spectrum may contribute to more efficient genetic testing in the Portuguese population.
Collapse
Affiliation(s)
- A Grangeia
- Genetics Service, Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal.
| | - S Alves
- Genetics Service, Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal
| | - L Gonçalves
- Genetics Service, Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal
| | - I Gregório
- Genetics Service, Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal
| | - A C Santos
- Public Health and Forensic Sciences and Medical Education Department, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal; EPIUnit - Instituto de Saúde Pública, Universidade do Porto, Porto, Portugal
| | - H Barros
- Public Health and Forensic Sciences and Medical Education Department, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal; EPIUnit - Instituto de Saúde Pública, Universidade do Porto, Porto, Portugal
| | - A Barros
- Genetics Service, Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal
| | - F Carvalho
- Genetics Service, Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal
| | - C Moura
- Genetics Service, Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; São João Hospital Centre, 4200-319 Porto, Portugal
| |
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|
10
|
Exophiala dermatitidis Revealing Cystic Fibrosis in Adult Patients with Chronic Pulmonary Disease. Mycopathologia 2017; 183:71-79. [PMID: 29094263 DOI: 10.1007/s11046-017-0218-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 10/20/2017] [Indexed: 12/20/2022]
Abstract
Cystic fibrosis (CF) is a genetic inherited disease due to mutations in the gene cystic fibrosis transmembrane conductance regulator (CFTR). Because of the huge diversity of CFTR mutations, the CF phenotypes are highly heterogeneous, varying from typical to mild form of CF, also called atypical CF. These atypical features are more frequently diagnosed at adolescence or adulthood, and among clinical signs and symptoms leading to suspect a mild form of CF, colonization or infection of the respiratory tract due to well-known CF pathogens should be a warning signal. Exophiala dermatitidis is a melanized dimorphic fungus commonly detected in respiratory specimens from CF patients, but only very rarely from respiratory specimens from non-CF patients. We described here two cases of chronic colonization of the airways by E. dermatitidis, with recurrent pneumonia and hemoptysis in one patient, which led clinicians to diagnose mild forms of CF in these elderly patients who were 68- and 87-year-old. These cases of late CF diagnosis suggest that airway colonization or respiratory infections due to E. dermatitidis in patients with bronchiectasis should led to search for a mild form of CF, regardless of the age and associated symptoms. On a broader level, in patients with chronic respiratory disease and recurrent pulmonary infections, an allergic bronchopulmonary mycosis or an airway colonization by CF-related fungi like E. dermatitidis or some Aspergillus, Scedosporium or Rasamsonia species, should be considered as potential markers of atypical CF and should led clinicians to conduct investigations for CF diagnosis.
Collapse
|
11
|
Zak SM, Clancy JP, Brewington JJ. CFTR functional assays in drug development. Expert Opin Orphan Drugs 2017. [DOI: 10.1080/21678707.2017.1393413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Sara M. Zak
- Department of Pediatrics, Division of Pulmonary Medicine, Cincinnati Children’s Hospital Medical Center, Cincinnati, USA
| | - John P. Clancy
- Department of Pediatrics, Division of Pulmonary Medicine, Cincinnati Children’s Hospital Medical Center, Cincinnati, USA
| | - John J. Brewington
- Department of Pediatrics, Division of Pulmonary Medicine, Cincinnati Children’s Hospital Medical Center, Cincinnati, USA
| |
Collapse
|
12
|
Behar DM, Inbar O, Shteinberg M, Gur M, Mussaffi H, Shoseyov D, Ashkenazi M, Alkrinawi S, Bormans C, Hakim F, Mei-Zahav M, Cohen-Cymberknoh M, Dagan A, Prais D, Sarouk I, Stafler P, Bar Aluma BE, Akler G, Picard E, Aviram M, Efrati O, Livnat G, Rivlin J, Bentur L, Blau H, Kerem E, Singer A. Nationwide genetic analysis for molecularly unresolved cystic fibrosis patients in a multiethnic society: implications for preconception carrier screening. Mol Genet Genomic Med 2017; 5:223-236. [PMID: 28546993 PMCID: PMC5441412 DOI: 10.1002/mgg3.278] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 01/07/2017] [Accepted: 01/13/2017] [Indexed: 12/18/2022] Open
Abstract
Background Preconception carrier screening for cystic fibrosis (CF) is usually performed using ethnically targeted panels of selected mutations. This has been recently challenged by the use of expanded, ethnically indifferent, pan‐population panels. Israel is characterized by genetically heterogeneous populations carrying a wide range of CFTR mutations. To assess the potential of expanding the current Israeli preconception screening program, we sought the subset of molecularly unresolved CF patients listed in the Israeli CF data registry comprising ~650 patients. Methods An Israeli nationwide genotyping of 152 CF cases, representing 176 patients lacking molecular diagnosis, was conducted. Molecular analysis included Sanger sequencing for all exons and splice sites, multiplex ligation probe amplification (MLPA), and next‐generation sequencing of the poly‐T/TG tracts. Results We identified 54 different mutations, of which only 16 overlapped the 22 mutations included in the Israeli preconception screening program. A total of 29/54 (53.7%) mutations were already listed as CF causing by the CFTR2 database, and only 4/54 (7.4%) were novel. Molecular diagnosis was reached in 78/152 (51.3%) cases. Prenatal diagnosis of 24/78 (30.8%) cases could have been achieved by including all CFTR2‐causing mutations in the Israeli panel. Conclusions Our data reveal an overwhelming hidden abundance of CFTR gene mutations suggesting that expanded preconception carrier screening might achieve higher preconception detection rates.
Collapse
Affiliation(s)
- Doron M Behar
- Clalit National Personalized Medicine ProgramDepartment of Community Medicine and EpidemiologyCarmel Medical CenterHaifaIsrael.,Bruce Rappaport Faculty of MedicineTechnion-Israel Institute of TechnologyHaifaIsrael.,Gene by GeneGenomic Research CenterHoustonTexas
| | - Ori Inbar
- The Cystic Fibrosis Foundation of IsraelRamat GanIsrael
| | - Michal Shteinberg
- Bruce Rappaport Faculty of MedicineTechnion-Israel Institute of TechnologyHaifaIsrael.,Pulmonology Institute and CF CenterCarmel Medical CenterHaifaIsrael
| | - Michal Gur
- Bruce Rappaport Faculty of MedicineTechnion-Israel Institute of TechnologyHaifaIsrael.,Pediatric Pulmonary Institute and CF CenterRappaport Children's HospitalRambam Health Care CampusHaifaIsrael
| | - Huda Mussaffi
- Kathy and Lee Graub Cystic Fibrosis CenterSchneider Children's Medical Center of IsraelPetach TikvaIsrael.,Sackler Faculty of MedicineTel Aviv UniversityRamat AvivIsrael
| | - David Shoseyov
- Cystic Fibrosis CenterHadassah-Hebrew University Medical CenterJerusalemIsrael
| | | | | | | | - Fahed Hakim
- Bruce Rappaport Faculty of MedicineTechnion-Israel Institute of TechnologyHaifaIsrael.,Pediatric Pulmonary Institute and CF CenterRappaport Children's HospitalRambam Health Care CampusHaifaIsrael
| | - Meir Mei-Zahav
- Kathy and Lee Graub Cystic Fibrosis CenterSchneider Children's Medical Center of IsraelPetach TikvaIsrael.,Sackler Faculty of MedicineTel Aviv UniversityRamat AvivIsrael
| | | | - Adi Dagan
- Cystic Fibrosis CenterSheba Medical CenterRamat GanIsrael
| | - Dario Prais
- Kathy and Lee Graub Cystic Fibrosis CenterSchneider Children's Medical Center of IsraelPetach TikvaIsrael.,Sackler Faculty of MedicineTel Aviv UniversityRamat AvivIsrael
| | - Ifat Sarouk
- Cystic Fibrosis CenterSheba Medical CenterRamat GanIsrael
| | - Patrick Stafler
- Kathy and Lee Graub Cystic Fibrosis CenterSchneider Children's Medical Center of IsraelPetach TikvaIsrael.,Sackler Faculty of MedicineTel Aviv UniversityRamat AvivIsrael
| | | | - Gidon Akler
- Gene by GeneGenomic Research CenterHoustonTexas
| | - Elie Picard
- Cystic Fibrosis CenterShaare Zedek Medical CenterHebrew University Medical CenterJerusalemIsrael
| | - Micha Aviram
- Cystic Fibrosis CenterSoroka Medical CenterBeershevaIsrael
| | - Ori Efrati
- Cystic Fibrosis CenterSheba Medical CenterRamat GanIsrael
| | - Galit Livnat
- Bruce Rappaport Faculty of MedicineTechnion-Israel Institute of TechnologyHaifaIsrael.,Pulmonology Institute and CF CenterCarmel Medical CenterHaifaIsrael
| | - Joseph Rivlin
- Bruce Rappaport Faculty of MedicineTechnion-Israel Institute of TechnologyHaifaIsrael.,Pulmonology Institute and CF CenterCarmel Medical CenterHaifaIsrael
| | - Lea Bentur
- Bruce Rappaport Faculty of MedicineTechnion-Israel Institute of TechnologyHaifaIsrael.,Pediatric Pulmonary Institute and CF CenterRappaport Children's HospitalRambam Health Care CampusHaifaIsrael
| | - Hannah Blau
- Kathy and Lee Graub Cystic Fibrosis CenterSchneider Children's Medical Center of IsraelPetach TikvaIsrael.,Sackler Faculty of MedicineTel Aviv UniversityRamat AvivIsrael
| | - Eitan Kerem
- Cystic Fibrosis CenterHadassah-Hebrew University Medical CenterJerusalemIsrael
| | | |
Collapse
|
13
|
Billet A, Jia Y, Jensen TJ, Hou YX, Chang XB, Riordan JR, Hanrahan JW. Potential sites of CFTR activation by tyrosine kinases. Channels (Austin) 2015; 10:247-51. [PMID: 26645934 DOI: 10.1080/19336950.2015.1126010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The CFTR chloride channel is tightly regulated by phosphorylation at multiple serine residues. Recently it has been proposed that its activity is also regulated by tyrosine kinases, however the tyrosine phosphorylation sites remain to be identified. In this study we examined 2 candidate tyrosine residues near the boundary between the first nucleotide binding domain and the R domain, a region which is important for channel function but devoid of PKA consensus sequences. Mutating tyrosines at positions 625 and 627 dramatically reduced responses to Src or Pyk2 without altering the activation by PKA, suggesting they may contribute to CFTR regulation.
Collapse
Affiliation(s)
- Arnaud Billet
- a Department of Physiology , McGill University , Montreal , Quebec , Canada.,b CF Translational Research Center, McGill University , Montreal , Quebec , Canada
| | - Yanlin Jia
- a Department of Physiology , McGill University , Montreal , Quebec , Canada.,b CF Translational Research Center, McGill University , Montreal , Quebec , Canada
| | - Timothy J Jensen
- c Department of Biochemistry and Biophysics & CF Research Center , UNC Chapel Hill, Chapel Hill , NC , USA
| | - Yue-Xian Hou
- c Department of Biochemistry and Biophysics & CF Research Center , UNC Chapel Hill, Chapel Hill , NC , USA
| | - Xiu-Bao Chang
- c Department of Biochemistry and Biophysics & CF Research Center , UNC Chapel Hill, Chapel Hill , NC , USA
| | - John R Riordan
- c Department of Biochemistry and Biophysics & CF Research Center , UNC Chapel Hill, Chapel Hill , NC , USA
| | - John W Hanrahan
- a Department of Physiology , McGill University , Montreal , Quebec , Canada.,b CF Translational Research Center, McGill University , Montreal , Quebec , Canada.,d Research Institute of the McGill University Hospital Center , Montréal , Quebec , Canada
| |
Collapse
|
14
|
Marion H, Natacha G, Brigitte M, François C, Michel R, Corinne T, Emmanuelle G, Thierry B. The p.Gly622Asp (G622D) mutation, frequently found in Reunion Island and in black populations, is associated with a wide spectrum of CF and CFTR-RD phenotypes. J Cyst Fibros 2014; 14:305-9. [PMID: 25443471 DOI: 10.1016/j.jcf.2014.11.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 10/14/2014] [Accepted: 11/02/2014] [Indexed: 11/26/2022]
Abstract
Examination of genotype-phenotype correlations along with functional evaluation of CFTR mutations may not be straightforward. The c.1865G>A, p.Gly622Asp (G622D), located at the NBD1 C terminus of the CFTR protein, was initially reported in patients with male infertility. However, the substitution of Gly622 by an aspartic acid in vitro would perturb the local structure or even affect the CFTR folding itself. In order to determine whether p.Gly622Asp affects the risk of developing a CFTR-Related disorder (CFTR-RD) or cystic fibrosis (CF), we analyzed the phenotype of subjects bearing the p.Gly622Asp mutation. We report molecular and clinical analyses in eleven unrelated patients with CF or CFTR-RD with compound heterozygosity for the p.Gly622Asp mutation. On the basis of the clinical features presented by the eleven patients, we postulate that the p.Gly622Asp might be associated with a wide spectrum of phenotypes including classical cystic fibrosis.
Collapse
Affiliation(s)
- Heller Marion
- AP-HP, Laboratoire de Biochimie et Génétique Moléculaire, GH Cochin-Broca-Hôtel Dieu, Paris, France
| | - Gaitch Natacha
- AP-HP, Laboratoire de Biochimie et Génétique Moléculaire, GH Cochin-Broca-Hôtel Dieu, Paris, France
| | - Martinez Brigitte
- AP-HP, Laboratoire de Biochimie et Génétique Moléculaire, GH Cochin-Broca-Hôtel Dieu, Paris, France
| | - Cartault François
- Service de Génétique, Centre Hospitalier Saint Denis, Saint Denis, La Réunion, France
| | - Renouil Michel
- Service de Génétique, Centre Hospitalier Saint Denis, Saint Denis, La Réunion, France
| | - Theze Corinne
- Laboratoire de Génétique Moléculaire, IURC, Institut Universitaire de Recherche Clinique, 34093 Montpellier Cedex 5, France
| | - Girodon Emmanuelle
- AP-HP, Laboratoire de Biochimie et Génétique Moléculaire, GH Cochin-Broca-Hôtel Dieu, Paris, France
| | - Bienvenu Thierry
- AP-HP, Laboratoire de Biochimie et Génétique Moléculaire, GH Cochin-Broca-Hôtel Dieu, Paris, France; Université Paris Descartes Paris, Institut Cochin, INSERM U1016, Paris, France.
| |
Collapse
|
15
|
Pizzo L, Fariello MI, Lepanto P, Aguilar PS, Kierbel A. An image analysis method to quantify CFTR subcellular localization. Mol Cell Probes 2014; 28:175-80. [PMID: 24561544 DOI: 10.1016/j.mcp.2014.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 02/11/2014] [Accepted: 02/12/2014] [Indexed: 10/25/2022]
Abstract
Aberrant protein subcellular localization caused by mutation is a prominent feature of many human diseases. In Cystic Fibrosis (CF), a recessive lethal disorder that results from dysfunction of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR), the most common mutation is a deletion of phenylalanine-508 (pF508del). Such mutation produces a misfolded protein that fails to reach the cell surface. To date, over 1900 mutations have been identified in CFTR gene, but only a minority has been analyzed at the protein level. To establish if a particular CFTR variant alters its subcellular distribution, it is necessary to quantitatively determine protein localization in the appropriate cellular context. To date, most quantitative studies on CFTR localization have been based on immunoprecipitation and western blot. In this work, we developed and validated a confocal microscopy-image analysis method to quantitatively examine CFTR at the apical membrane of epithelial cells. Polarized MDCK cells transiently transfected with EGFP-CFTR constructs and stained for an apical marker were used. EGFP-CFTR fluorescence intensity in a region defined by the apical marker was normalized to EGFP-CFTR whole cell fluorescence intensity, rendering "apical CFTR ratio". We obtained an apical CFTR ratio of 0.67 ± 0.05 for wtCFTR and 0.11 ± 0.02 for pF508del. In addition, this image analysis method was able to discriminate intermediate phenotypes: partial rescue of the pF508del by incubation at 27 °C rendered an apical CFTR ratio value of 0.23 ± 0.01. We concluded the method has a good sensitivity and accurately detects milder phenotypes. Improving axial resolution through deconvolution further increased the sensitivity of the system as rendered an apical CFTR ratio of 0.76 ± 0.03 for wild type and 0.05 ± 0.02 for pF508del. The presented procedure is faster and simpler when compared with other available methods and it is therefore suitable as a screening method to identify mutations that completely or mildly affect CFTR processing. Moreover, it could be extended to other studies on the biology underlying protein subcellular localization in health and disease.
Collapse
Affiliation(s)
- Lucilla Pizzo
- Institut Pasteur de Montevideo, Montevideo 11400, Uruguay
| | - María Inés Fariello
- Institut Pasteur de Montevideo, Montevideo 11400, Uruguay; IMERL, Facultad de Ingeniería, Universidad de la República, Montevideo, Uruguay
| | - Paola Lepanto
- Institut Pasteur de Montevideo, Montevideo 11400, Uruguay
| | | | - Arlinet Kierbel
- Institut Pasteur de Montevideo, Montevideo 11400, Uruguay; Instituto de Investigaciones Biotecnológicas Dr. Rodolfo A. Ugalde (IIB-INTECH), Universidad Nacional de San Martín, Consejo Nacional de Investigaciones Científicas y Técnicas (UNSAM-CONICET), San Martín, Buenos Aires, Argentina.
| |
Collapse
|
16
|
Rauh R, Soell D, Haerteis S, Diakov A, Nesterov V, Krueger B, Sticht H, Korbmacher C. A mutation in the β-subunit of ENaC identified in a patient with cystic fibrosis-like symptoms has a gain-of-function effect. Am J Physiol Lung Cell Mol Physiol 2012; 304:L43-55. [PMID: 23087020 DOI: 10.1152/ajplung.00093.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In some patients with atypical cystic fibrosis (CF), only one allele of the CF transmembrane conductance regulator (CFTR) gene is affected. Mutations of the epithelial sodium channel (ENaC) may contribute to the pathophysiology of the disease in these patients. To functionally characterize a mutation in the β-subunit of ENaC (βV348M) recently identified in a patient with severe CF-like symptoms (Mutesa et al. 2009), we expressed wild-type (wt) αβγENaC or mutant αβV348MγENaC in Xenopus laevis oocytes. The βV348M mutation stimulated amiloride-sensitive whole-cell current (ΔI(ami)) by ∼40% but had no effect on surface expression or single-channel conductance of ENaC. Instead the mutation increased channel open probability (P(o)). Proteolytic activation of mutant ENaC by chymotrypsin was reduced compared with that of wt ENaC (∼3.0-fold vs. ∼4.2-fold), which is consistent with the increased baseline P(o) of mutant ENaC. Similarly, the ENaC activator S3969 stimulated mutant ENaC currents to a lesser degree (by ∼2.6-fold) than wt ENaC currents (by ∼3.5-fold). The gain-of-function effect of the βV348M mutation was confirmed by whole-cell current measurements in HEK293 cells transiently transfected with wt or mutant ENaC. Computational channel modeling in combination with functional expression of different βV348 mutants in oocytes suggests that the βV348M mutation increases channel P(o) by destabilizing the closed channel state. Our findings indicate that the gain-of-function effect of the βV348M mutation may contribute to CF pathophysiology by inappropriately increasing sodium and fluid absorption in the respiratory tract.
Collapse
Affiliation(s)
- Robert Rauh
- Institut für Zelluläre und Molekulare Physiologie, Erlangen, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Masica DL, Sosnay PR, Cutting GR, Karchin R. Phenotype-optimized sequence ensembles substantially improve prediction of disease-causing mutation in cystic fibrosis. Hum Mutat 2012; 33:1267-74. [PMID: 22573477 DOI: 10.1002/humu.22110] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 04/12/2012] [Indexed: 12/20/2022]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) mutation is associated with a phenotypic spectrum that includes cystic fibrosis (CF). The disease liability of some common CFTR mutations is known, but rare mutations are seen in too few patients to categorize unequivocally, making genetic diagnosis difficult. Computational methods can predict the impact of mutation, but prediction specificity is often below that required for clinical utility. Here, we present a novel supervised learning approach for predicting CF from CFTR missense mutation. The algorithm begins by constructing custom multiple sequence alignments called phenotype-optimized sequence ensembles (POSEs). POSEs are constructed iteratively, by selecting sequences that optimize predictive performance on a training set of CFTR mutations of known clinical significance. Next, we predict CF disease liability from a different set of CFTR mutations (test-set mutations). This approach achieves improved prediction performance relative to popular methods recently assessed using the same test-set mutations. Of clinical significance, our method achieves 94% prediction specificity. Because databases such as HGMD and locus-specific mutation databases are growing rapidly, methods that automatically tailor their predictions for a specific phenotype may be of immediate utility. If the performance achieved here generalizes to other systems, the approach could be an excellent tool to help establish genetic diagnoses.
Collapse
Affiliation(s)
- David L Masica
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland, USA
| | | | | | | |
Collapse
|
18
|
Saxena A, Banasavadi-Siddegowda YK, Fan Y, Bhattacharya S, Roy G, Giovannucci DR, Frizzell RA, Wang X. Human heat shock protein 105/110 kDa (Hsp105/110) regulates biogenesis and quality control of misfolded cystic fibrosis transmembrane conductance regulator at multiple levels. J Biol Chem 2012; 287:19158-70. [PMID: 22505710 DOI: 10.1074/jbc.m111.297580] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Heat shock protein 105/110-kDa (Hsp105/110), a member of the Hsp70 super family of molecular chaperones, serves as a nucleotide exchange factor for Hsc70, independently prevents the aggregation of misfolded proteins, and functionally relates to Hsp90. We investigated the roles of human Hsp105α, the constitutively expressed isoform, in the biogenesis and quality control of the cystic fibrosis transmembrane conductance regulator (CFTR). In the endoplasmic reticulum (ER), Hsp105 facilitates CFTR quality control at an early stage in its biosynthesis but promotes CFTR post-translational folding. Deletion of Phe-508 (ΔF508), the most prevalent mutation causing cystic fibrosis, interferes with de novo folding of CFTR, impairing its export from the ER and accelerating its clearance in the ER and post-Golgi compartments. We show that Hsp105 preferentially associates with and stabilizes ΔF508 CFTR at both levels. Introduction of the Hsp105 substrate binding domain potently increases the steady state level of ΔF508 CFTR by reducing its early-stage degradation. This in turn dramatically enhances ΔF508 CFTR cell surface functional expression in cystic fibrosis airway epithelial cells. Although other Hsc70 nucleotide exchange factors such as HspBP1 and BAG-2 inhibit CFTR post-translational degradation in the ER through cochaperone CHIP, Hsp105 has a primary role promoting CFTR quality control at an earlier stage. The Hsp105-mediated multilevel regulation of ΔF508 CFTR folding and quality control provides new opportunities to understand how chaperone machinery regulates the homeostasis and functional expression of misfolded proteins in the cell. Future studies in this direction will inform therapeutics development for cystic fibrosis and other protein misfolding diseases.
Collapse
Affiliation(s)
- Anita Saxena
- Department of Physiology and Pharmacology, University of Toledo College of Medicine, Toledo, Ohio 43614, USA
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Fresquet F, Clement R, Norez C, Sterlin A, Melin P, Becq F, Kitzis A, Thoreau V, Bilan F. Orphan missense mutations in the cystic fibrosis transmembrane conductance regulator: A three-step biological approach to establishing a correlation between genotype and phenotype. J Mol Diagn 2011; 13:520-7. [PMID: 21708286 DOI: 10.1016/j.jmoldx.2011.05.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 04/28/2011] [Accepted: 05/04/2011] [Indexed: 01/14/2023] Open
Abstract
More than 1860 mutations have been found within the human cystic fibrosis transmembrane conductance regulator (CFTR) gene sequence. These mutations can be classified according to their degree of severity in CF disease. Although the most common mutations are well characterized, few data are available for rare mutations. Thus, genetic counseling is particularly difficult when fetuses or patients with CF present these orphan variations. We describe a three-step in vitro assay that can evaluate rare missense CFTR mutation consequences to establish a correlation between genotype and phenotype. By using a green fluorescent protein-tagged CFTR construct, we expressed mutated proteins in COS-7 cells. CFTR trafficking was visualized by confocal microscopy, and the cellular localization of CFTR was determined using intracellular markers. We studied the CFTR maturation process using Western blot analysis and evaluated CFTR channel activity by automated iodide efflux assays. Of six rare mutations that we studied, five have been isolated in our laboratory. The cellular and functional impact that we observed in each case was compared with the clinical data concerning the patients in whom we encountered these mutations. In conclusion, we propose that performing this type of analysis for orphan CFTR missense mutations can improve CF genetic counseling.
Collapse
Affiliation(s)
- Fleur Fresquet
- Institute of Physiology and Cell Biology (IPCB), National Centre for Scientific Research (NCSR), Université de Poitiers, Poitiers, France
| | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Billet A, Melin P, Jollivet M, Mornon JP, Callebaut I, Becq F. C terminus of nucleotide binding domain 1 contains critical features for cystic fibrosis transmembrane conductance regulator trafficking and activation. J Biol Chem 2010; 285:22132-40. [PMID: 20435887 DOI: 10.1074/jbc.m110.120683] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl(-) channel physiologically important in fluid-transporting epithelia and pathologically relevant in several human diseases. Here, we show that mutations in the C terminus of the first nucleotide binding domain comprising the latest beta strands (beta(c)5 and beta(c)6) influence the trafficking, channel activity, and pharmacology of CFTR. We mutated CFTR amino acids located in the beta(c)5-beta(c)6 hairpin, within the beta(c)5 strand (H620Q), within the beta-turn linking the two beta strands (E621G, G622D), as well as within (S623A, S624A) and at the extremity (G628R) of the beta(c)6 strand. Functional analysis reveals that the current density was largely reduced for G622D and G628R channels compared with wt CFTR, similar for E621G and S624A, but increased for H620Q and S623A. For G622D and G628R, the abnormal activity is likely due to a defective maturation process, as assessed by the augmented activity and mature C-band observed in the presence of the trafficking corrector miglustat. In addition, in presence of the CFTR activator benzo[c]quinolizinium, the CFTR current density compared with that of wt CFTR was abolished for G622D and G628R channels, but similar for H620Q, S623A, and S624A or slightly increased for E621G. Finally, G622D and G628R were activated by the CFTR agonists genistein, RP-107, and isobutylmethylxanthine. Our results identify the C terminus of the CFTR first nucleotide binding domain as an important molecular site for the trafficking of CFTR protein, for the control of CFTR channel gating, and for the pharmacological effect of a dual activity agent.
Collapse
Affiliation(s)
- Arnaud Billet
- Institut de Physiologie et Biologie Cellulaires, Université de Poitiers, CNRS, 86022 Poitiers, France
| | | | | | | | | | | |
Collapse
|
21
|
Roy G, Chalfin EM, Saxena A, Wang X. Interplay between ER exit code and domain conformation in CFTR misprocessing and rescue. Mol Biol Cell 2009; 21:597-609. [PMID: 20032308 PMCID: PMC2820424 DOI: 10.1091/mbc.e09-05-0427] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Multiple mutations in cystic fibrosis transmembrane conductance regulator (CFTR) impair its exit from the endoplasmic reticulum (ER). We compared two processing mutants: DeltaF508 and the ER exit code mutant DAA. Although both have severe kinetic processing defect, DAA but not DeltaF508 has substantial accumulation in its mature form, leading to higher level of processing at the steady state. DAA has much less profound conformational abnormalities. It has lower Hsp70 association and higher post-ER stability than DeltaF508. The ER exit code is necessary for DeltaF508 residual export and rescue. R555K, a mutation that rescues DeltaF508 misprocessing, improves Sec24 association and enhances its post-ER stability. Using in situ limited proteolysis, we demonstrated a clear change in trypsin sensitivity in DeltaF508 NBD1, which is reversed, together with that of other domains, by low temperature, R555K or both. We observed a conversion of the proteolytic pattern of DAA from the one resembling DeltaF508 to the one similar to wild-type CFTR during its maturation. Low temperature and R555K are additive in improving DeltaF508 conformational maturation and processing. Our data reveal a dual contribution of ER exit code and domain conformation to CFTR misprocessing and underscore the importance of conformational repair in effective rescue of DeltaF508.
Collapse
Affiliation(s)
- Gargi Roy
- Department of Physiology and Pharmacology, University of Toledo College of Medicine, Toledo, OH 43614, USA
| | | | | | | |
Collapse
|
22
|
Oca F, Dreux S, Gérard B, Simon-Bouy B, de Becdelièvre A, Ferec C, Girodon E, Muller F. Amniotic fluid digestive enzyme analysis is useful for identifying CFTR gene mutations of unclear significance. Clin Chem 2009; 55:2214-7. [PMID: 19833837 DOI: 10.1373/clinchem.2009.133298] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The large number of CFTR [cystic fibrosis transmembrane conductance regulator (ATP-binding cassette sub-family C, member 7)] mutations and the existence of variants of unclear significance complicate the prenatal diagnosis of cystic fibrosis (CF). The aim of this study was to determine whether the pattern of amniotic fluid digestive enzymes (AF-DEs) could be correlated with the severity of CFTR mutations. METHODS The AF-DE pattern (gamma-glutamyltranspeptidase, aminopeptidase M, and the intestinal isoform of alkaline phosphatase) was retrospectively analyzed in 43 AF samples. All fetuses presented 2 CFTR mutations, which were classified according to the severity of the disease: CF/CF (n = 38); CF/CFTR-related disorders (n = 1); and CF/unknown variant (n = 4). The relationships between clinical CF status, CFTR mutations, and AF-DE pattern were studied. RESULTS Of 38 severely affected CF fetuses, an "obstructive" AF-DE pattern was observed in 15 of 15 samples collected before 22 weeks, irrespective of the CFTR mutation (diagnostic sensitivity, 100%; diagnostic specificity, 99.8%). In the 23 fetuses evaluated after 22 weeks, the AF-DE pattern was abnormal in 7 cases and noncontributive in 16 (diagnostic sensitivity, 30.4%; diagnostic specificity, 99.8%). Of the 5 questionable cases (F508del/N1224K, F508del/L73F, 3849+10kbC>T/G1127E, F508del/S1235R, F508del/G622D), all were CF symptom free at 2-4 years of follow-up. The AF-DE pattern (<22 weeks) was typical in 3 cases but abnormal in the last 2 cases. CONCLUSIONS AF-DE analysis is of value for prenatal CF diagnosis in classic forms of CF and could be helpful in nonclassic CF.
Collapse
Affiliation(s)
- Florine Oca
- Biochimie-Hormonologie, Hôpital Robert Debré, AP-HP, Paris, France
| | | | | | | | | | | | | | | |
Collapse
|
23
|
Norez C, Bilan F, Kitzis A, Mettey Y, Becq F. Proteasome-Dependent Pharmacological Rescue of Cystic Fibrosis Transmembrane Conductance Regulator Revealed by Mutation of Glycine 622. J Pharmacol Exp Ther 2008; 325:89-99. [DOI: 10.1124/jpet.107.134502] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
|
24
|
Riveira-Munoz E, Chang Q, Godefroid N, Hoenderop JG, Bindels RJ, Dahan K, Devuyst O. Transcriptional and functional analyses of SLC12A3 mutations: new clues for the pathogenesis of Gitelman syndrome. J Am Soc Nephrol 2007; 18:1271-83. [PMID: 17329572 DOI: 10.1681/asn.2006101095] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Gitelman syndrome (GS) is a recessive salt-losing tubulopathy that is caused by mutations in the SLC12A3 gene that encodes the sodium-chloride co-transporter (NCC). GS is characterized by significant inter- and intrafamilial phenotype variability, with early onset and/or severe clinical manifestations in some patients. No correlations between the disease variability and the position/nature of SLC12A3 mutations have been investigated thus far. In this study, extensive mutational analyses of SLC12A3 were performed in 27 patients with GS, including genomic DNA sequencing, multiplex ligation-dependent probe amplification, cDNA analysis, and quantification of allele-specific transcripts, in parallel with functional analyses in Xenopus laevis oocytes and detailed phenotyping. Twenty-six SLC12A3 mutations were identified in 25 patients with GS, including eight novel (detection rate 80%). Transcript analysis demonstrated that splicing mutations of SLC12A3 lead to frameshifted mRNA subject to degradation by nonsense-mediated decay. Heterologous expression documented a novel class of NCC mutants with defective intrinsic transport activity. A subgroup of patients presented with early onset, growth retardation, and/or detrimental manifestations, confirming the potential severity of GS. The mutations that were associated with a severe presentation were the combination at least for one allele of a missplicing resulting in a truncated transcript that was downregulated by nonsense-mediated decay or a nonfunctional, cell surface-absent mutant. The most recurrent mutation on the second allele was a newly described NCC mutant that affected the functional properties of the co-transporter. These data suggest that the nature/position of SLC12A3 mutation, combined with male gender, is a determinant factor in the severity of GS and provide new insights in the underlying pathogenic mechanisms of the disease.
Collapse
Affiliation(s)
- Eva Riveira-Munoz
- Division of Nephrology, Université Catholique de Louvain Medical School, Brussels, Belgium
| | | | | | | | | | | | | |
Collapse
|
25
|
Matsumura Y, Ban N, Ueda K, Inagaki N. Characterization and classification of ATP-binding cassette transporter ABCA3 mutants in fatal surfactant deficiency. J Biol Chem 2006; 281:34503-14. [PMID: 16959783 DOI: 10.1074/jbc.m600071200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ATP-binding cassette transporter ABCA3 is expressed predominantly at the limiting membrane of the lamellar bodies in lung alveolar type II cells. Recent study has shown that mutation of the ABCA3 gene causes fatal surfactant deficiency in newborns. In this study, we investigated in HEK293 cells the intracellular localization and N-glycosylation of the ABCA3 mutants so far identified in fatal surfactant deficiency patients. Green fluorescent protein-tagged L101P, L982P, L1553P, Q1591P, and Ins1518fs/ter1519 mutant proteins remained localized in the endoplasmic reticulum, and processing of oligosaccharide was impaired, whereas wild-type and N568D, G1221S, and L1580P mutant ABCA3 proteins trafficked to the LAMP3-positive intracellular vesicle, accompanied by processing of oligosaccharide from high mannose type to complex type. Vanadate-induced nucleotide trapping and ATP-binding analyses showed that ATP hydrolysis activity was dramatically decreased in the N568D, G1221S, and L1580P mutants, accompanied by a moderate decrease in ATP binding in N568D and L1580P mutants but not in the G1221S mutant, compared with the wild-type ABCA3 protein. In addition, mutational analyses of the Gly-1221 residue in the 11th transmembrane segment and the Leu-1580 residue in the cytoplasmic tail, and homology modeling of nucleotide binding domain 2 demonstrate the significance of these residues for ATP hydrolysis and suggest a mechanism for impaired ATP hydrolysis in G1221S and L1580P mutants. Thus, surfactant deficiency because of ABCA3 gene mutation may be classified into two categories as follows: abnormal intracellular localization (type I) and normal intracellular localization with decreased ATP binding and/or ATP hydrolysis of the ABCA3 protein (type II). These distinct pathophysiologies may reflect both the severity and effective therapy for surfactant deficiency.
Collapse
Affiliation(s)
- Yoshihiro Matsumura
- Department of Physiology, Akita University School of Medicine, Akita 010-8543, Japan
| | | | | | | |
Collapse
|
26
|
Phenotypic discordance in three siblings affected by atypical cystic fibrosis with the F508del/D614G genotype. J Cyst Fibros 2006; 5:193-5. [DOI: 10.1016/j.jcf.2005.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 11/30/2005] [Accepted: 12/01/2005] [Indexed: 11/20/2022]
|
27
|
Frelet A, Klein M. Insight in eukaryotic ABC transporter function by mutation analysis. FEBS Lett 2006; 580:1064-84. [PMID: 16442101 DOI: 10.1016/j.febslet.2006.01.024] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/21/2022]
Abstract
With regard to structure-function relations of ATP-binding cassette (ABC) transporters several intriguing questions are in the spotlight of active research: Why do functional ABC transporters possess two ATP binding and hydrolysis domains together with two ABC signatures and to what extent are the individual nucleotide-binding domains independent or interacting? Where is the substrate-binding site and how is ATP hydrolysis functionally coupled to the transport process itself? Although much progress has been made in the elucidation of the three-dimensional structures of ABC transporters in the last years by several crystallographic studies including novel models for the nucleotide hydrolysis and translocation catalysis, site-directed mutagenesis as well as the identification of natural mutations is still a major tool to evaluate effects of individual amino acids on the overall function of ABC transporters. Apart from alterations in characteristic sequence such as Walker A, Walker B and the ABC signature other parts of ABC proteins were subject to detailed mutagenesis studies including the substrate-binding site or the regulatory domain of CFTR. In this review, we will give a detailed overview of the mutation analysis reported for selected ABC transporters of the ABCB and ABCC subfamilies, namely HsCFTR/ABCC7, HsSUR/ABCC8,9, HsMRP1/ABCC1, HsMRP2/ABCC2, ScYCF1 and P-glycoprotein (Pgp)/MDR1/ABCB1 and their effects on the function of each protein.
Collapse
Affiliation(s)
- Annie Frelet
- Zurich Basel Plant Science Center, University of Zurich, Plant Biology, Zollikerstrasse 107, CH-8008 Zurich, Switzerland
| | | |
Collapse
|
28
|
Monaghan KG, Bluhm D, Phillips M, Feldman GL. Preconception and prenatal cystic fibrosis carrier screening of African Americans reveals unanticipated frequencies for specific mutations. Genet Med 2005; 6:141-4. [PMID: 15354332 DOI: 10.1097/01.gim.0000127269.42279.83] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE It is recommended that cystic fibrosis (CF) carrier screening be made available to African Americans who are either pregnant or planning a pregnancy. We analyzed the carrier and mutant allele frequencies for African Americans undergoing CF carrier screening in our laboratories. METHODS Between December 2001 and September 2003, we performed carrier screening for 2189 African Americans, testing for at least the 25 recommended mutations. RESULTS A total of 33 CF carriers were identified. The most common mutations detected were deltaF508, G622D, R117H/7T, and G551D. The G622D allele frequency among African Americans was 0.18%. We did not detect any 3120 + 1G --> A carriers, although 4 were expected (P < 0.05). CONCLUSIONS When considering only the 25 recommended CF mutations, 1 in 75 African Americans screened in our laboratories were carriers (within the expected range, given a 69% mutation detection rate). The addition of 2 mutations, G622D and Q98R (incidentally identified while screening for ACOG/ACMG mutations), increased the observed carrier frequency to 1 in 66, which is not significantly different from the known African American carrier frequency of 1 in 65. The frequencies of several specific mutations detected were unanticipated, as was the absence of 3120 + 1G --> A carriers. Further studies on African American patients with classic CF are needed to examine the incidence of CF mutations that are not part of the current panel, such as G622D.
Collapse
Affiliation(s)
- Kristin G Monaghan
- Department of Medical Genetics, Henry Ford Hospital, 2799 West Grand Boulevard, CFP 466, Detroit, MI 48202, USA
| | | | | | | |
Collapse
|
29
|
Vankeerberghen A, Cuppens H, Cassiman JJ. The cystic fibrosis transmembrane conductance regulator: an intriguing protein with pleiotropic functions. J Cyst Fibros 2004; 1:13-29. [PMID: 15463806 DOI: 10.1016/s1569-1993(01)00003-0] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2001] [Indexed: 12/19/2022]
Abstract
Cystic fibrosis is a frequent autosomal recessive disorder that is caused by the malfunctioning of a small chloride channel, the cystic fibrosis transmembrane conductance regulator. The protein is found in the apical membrane of epithelial cells lining exocrine glands. Absence of this channel results in imbalance of ion concentrations across the cell membrane. As a result, fluids secreted through these glands become more viscous and, in the end, ducts become plugged and atrophic. Little is known about the pathways that link the malfunctioning of the CFTR protein with the observed clinical phenotype. Moreover, there is no strict correlation between specific CFTR mutations and the CF phenotype. This might be explained by the fact that environmental and additional genetic factors may influence the phenotype. The CFTR protein itself is regulated at the maturational level by chaperones and SNARE proteins and at the functional level by several protein kinases. Moreover, CFTR functions also as a regulator of other ion channels and of intracellular membrane transport processes. In order to be able to function as a protein with pleiotropic actions, CFTR seems to be linked with other proteins and with the cytoskeleton through interaction with PDZ-domain-containing proteins at the apical pole of the cell. Progress in cystic fibrosis research is substantial, but still leaves many questions unanswered.
Collapse
|
30
|
Abstract
Cystic fibrosis is a common autosomal recessive disorder that primarily affects the epithelial cells in the intestine, respiratory system, pancreas, gall bladder and sweat glands. Over one thousand mutations have currently been identified in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene that are associated with CF disease. There have been many studies on the correlation of the CFTR genotype and CF disease phenotype; however, this relationship is still not well understood. A connection between CFTR genotype and disease manifested in the pancreas has been well described, but pulmonary disease appears to be highly variable even between individuals with the same genotype. This review describes the current classification of CFTR mutation classes and resulting CF disease phenotypes. Complex disease alleles and modifier genes are discussed along with alternative disorders, such as disseminated bronchiectasis and pancreatitis, which are also thought to result from CFTR mutations.
Collapse
Affiliation(s)
- Rebecca K Rowntree
- Paediatric Molecular Genetics, Institute of Molecular Medicine, Oxford University, John Radcliffe Hospital, Oxford, OX3 9DS, UK
| | | |
Collapse
|
31
|
Huber KR, Mirkovic B, Nersesian R, Myers A, Saiki R, Bauer K. Survey of CF mutations in the clinical laboratory. BMC Clin Pathol 2002; 2:4. [PMID: 12437773 PMCID: PMC138794 DOI: 10.1186/1472-6890-2-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2002] [Accepted: 11/19/2002] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND: Since it is impossible to sequence the complete CFTR gene routinely, clinical laboratories must rely on test systems that screen for a panel of the most frequent mutations causing disease in a high percentage of patients. Thus, in a cohort of 257 persons that were referred to our laboratory for analysis of CF gene mutations, reverse line probe assays for the most common CF mutations were performed. These techniques were evaluated as routine first-line analyses of the CFTR gene status. METHODS: DNA from whole blood specimens was extracted and subjected to PCR amplification of 9 exons and 6 introns of the CFTR gene. The resulting amplicons were hybridised to probes for CF mutations and polymorphisms, immobilised on membranes supplied by Roche Molecular Systems, Inc. and Innogenetics, Inc. Denaturing gradient gel electrophoresis and sequencing of suspicious fragments indicating mutations were done with CF exon and intron specific primers. RESULTS: Of the 257 persons tested over the last three years (referrals based on 1) clinical symptoms typical for/indicative of CF, 2) indication for in vitro fertilisation, and 3) gene status determination because of anticipated parenthood and partners or relatives affected by CF), the reverse line blots detected heterozygote or homozygote mutations in the CFTR gene in 68 persons (26%). Eighty-three percent of those affected were heterozygous (47 persons) or homozygous (10 persons) for the DeltaF508 allele. The only other CF-alleles that we found with these tests were the G542X allele (3 persons), the G551D allele (3 persons), the 3849+10kb C-T allele (2 persons) the R117H allele (2 persons) and the 621+1G-T allele (1 person).Of the fifteen IVS8-5T-polymorphisms detected in intron 8, seven (47%) were found in males referred to us from IVF clinics. These seven 5T-alleles were all coupled with a heterozygous DeltaF508 allele, they make up 35% of the males with fertility problems (20 men) referred to us. CONCLUSIONS: In summary, the frequency of CF chromosomes in the cohort examined with these tests was 26%, with the DeltaF508 allele affecting 83% of the CF chromosomes. It is a substantial improvement for routine CF diagnostics to have available a test system for 30 mutations plus the polypyrimidine length variants in intron 8. Our results show that this test system allows a routine first-line analyses of the CFTR gene status.
Collapse
Affiliation(s)
- Klaus Roland Huber
- Ludwig Boltzmann Institute for moleculargenetic laboratory diagnostics, Donauspital, Vienna, Austria
| | - Borka Mirkovic
- Ludwig Boltzmann Institute for moleculargenetic laboratory diagnostics, Donauspital, Vienna, Austria
| | | | | | | | - Kurt Bauer
- Ludwig Boltzmann Institute for moleculargenetic laboratory diagnostics, Donauspital, Vienna, Austria
| |
Collapse
|
32
|
Chen EY, Clarke DM. The PEST sequence does not contribute to the stability of the cystic fibrosis transmembrane conductance regulator. BMC BIOCHEMISTRY 2002; 3:29. [PMID: 12361483 PMCID: PMC130031 DOI: 10.1186/1471-2091-3-29] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2002] [Accepted: 10/02/2002] [Indexed: 11/13/2022]
Abstract
BACKGROUND Endoplasmic reticulum retention of misfolded cystic fibrosis transmembrane conductance regulator (CFTR) mutants and their rapid degradation is the major cause of cystic fibrosis (CF). An important goal is to understand the mechanism of how the misfolded proteins are recognized, retained, and targeted for degradation. RESULTS Using a web-based algorithm, PESTFind, we found a PEST sequence in the regulatory (R) domain of CFTR. The PEST sequence is found in many short-lived eukaryotic proteins and plays a role in their degradation. To determine its role in the stability and degradation of misprocessed CFTR, we introduced a number of site-directed mutations into the PEST sequence in the cDNA of DeltaF508 CFTR, the most prevalent misprocessed mutation found in CF patients. Analysis of these mutants showed that the disruption of the PEST sequence plays a minor role in the degradation of the CFTR mutants. Multiple mutations to the PEST sequence within the R domain of CFTR inhibit maturation of CFTR and prevent the formation of a 100 kDa degradation product. The mutations, however, do not improve the stability of the mutant DeltaF508 CFTR. CONCLUSION These observations show that disruption of the structure of the R domain of CFTR can inhibit maturation of the protein and that the predicted PEST sequence plays no significant role in the degradation of CFTR.
Collapse
Affiliation(s)
- Eva Y Chen
- Canadian Institutes for Health Research Group in Membrane Biology, Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| | - David M Clarke
- Canadian Institutes for Health Research Group in Membrane Biology, Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| |
Collapse
|
33
|
Gentzsch M, Aleksandrov A, Aleksandrov L, Riordan JR. Functional analysis of the C-terminal boundary of the second nucleotide binding domain of the cystic fibrosis transmembrane conductance regulator and structural implications. Biochem J 2002; 366:541-8. [PMID: 12020354 PMCID: PMC1222794 DOI: 10.1042/bj20020511] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2002] [Revised: 05/16/2002] [Accepted: 05/20/2002] [Indexed: 12/22/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) contains two nucleotide-binding domains (NBDs) or ATP-binding cassettes (ABCs) that characterize a large family of membrane transporters. Although the three-dimensional structures of these domains from several ABC proteins have been determined, this is not the case for CFTR, and hence the domains are defined simply on the basis of sequence alignment. The functional C-terminal boundary of NBD1 of CFTR was located by analysis of chloride channel function [Chan, Csanady, Seto-Young, Nairn and Gadsby (2000) J. Gen. Physiol. 116, 163-180]. However, the boundary between the C-terminal end of NBD2 and sequences further downstream in the whole protein, that are important for its cellular localization and endocytotic turnover, has not been defined. We have now done this by assaying the influence of progressive C-terminal truncations on photolabelling of NBD2 by 8-azido-ATP, which reflects hydrolysis, as well as binding, at that domain, and on NBD2-dependent channel gating itself. The boundary defined in this way is between residues 1420 and 1424, which corresponds to the final beta-strand in aligned NBDs whose structures have been determined. Utilization of this information should facilitate the generation of monodisperse NBD2 polypeptides for structural analysis, which until now has not been possible. The established boundary includes within NBD2 a hydrophobic patch of four residues (1413-1416) previously shown to be essential for CFTR maturation and stability [Gentzsch and Riordan (2001) J. Biol. Chem. 276, 1291-1298]. This hydrophobic cluster is conserved in most ABC proteins, and on alignment with ones of known structure constitutes the penultimate beta-strand of the domain which is likely to participate in essential structure-stabilizing beta-sheet formation.
Collapse
Affiliation(s)
- Martina Gentzsch
- Mayo Foundation and Mayo Clinic Scottsdale, S. C. Johnson Medical Research Center, 13400 E. Shea Blvd., Scottsdale, AZ 85259, USA
| | | | | | | |
Collapse
|
34
|
Xie J, Adams LM, Zhao J, Gerken TA, Davis PB, Ma J. A short segment of the R domain of cystic fibrosis transmembrane conductance regulator contains channel stimulatory and inhibitory activities that are separable by sequence modification. J Biol Chem 2002; 277:23019-27. [PMID: 11950844 DOI: 10.1074/jbc.m201661200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The regulatory (R) domain of the cystic fibrosis transmembrane conductance regulator (CFTR) contains consensus phosphorylation sites for cAMP-dependent protein kinase (PKA) that are the basis for physiological regulation of the CFTR chloride channel. A short peptide segment in the R domain with a net negative charge of B9 (amino acids 817-838, NEG2) and predicted helical tendency is shown to play a critical role in CFTR chloride channel function. Deletion of NEG2 from CFTR completely eliminates the PKA dependence of channel activity. Exogenous NEG2 peptide interacts with CFTR to exert both stimulatory and inhibitory effects on the channel function. The NEG2 peptide with sequence scrambled to remove helical tendencies also inhibits channel function, but does not stimulate. Similar results are found for a NEG2 peptide whose helical structure is disrupted by a proline residue. When six of the negatively charged carboxylic acid residues are replaced by their cognate amides, reducing net negative charge to B3, but increasing helical propensity as assessed by circular dichroism, the peptide stimulates CFTR channel function, but does not inhibit. We speculate that the NEG2 region interacts with other cytosolic domains of CFTR to control opening and closing transitions of the chloride channel.
Collapse
Affiliation(s)
- Junxia Xie
- Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
| | | | | | | | | | | |
Collapse
|
35
|
Tan ALC, Ong SAK, Venkatesh B. Biochemical implications of sequence comparisons of the cystic fibrosis transmembrane conductance regulator. Arch Biochem Biophys 2002; 401:215-22. [PMID: 12054472 DOI: 10.1016/s0003-9861(02)00057-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel that is both of medical significance in humans and of interest with regard to osmoregulation in aquatic organisms. CFTR is composed of five domains: two membrane-spanning domains, two nucleotide-binding domains, and a regulatory domain. Notwithstanding the plethora of information concerning the structure and function of CFTR, the biochemistry of many facets of CFTR are not completely understood. In this regard, we have performed a sequence alignment of representative vertebrate CFTR with the aim of generating hypotheses on the functional significance of conserved and variable residues. Postulates on function common to all organisms are: (i) Thr338 in the sixth transmembrane segment could have a function related to that of the pore-lining residue Lys335, and it is possible that Thr338 hydrogen bonds to Lys335, thus indirectly affecting anion permeability; (ii) the fragment (111)PDNKE could be an ion sensor; (iii) motifs in the two nucleotide-binding domains reflect differential ATP binding and hydrolysis; and (iv) an interaction in the R domain involving (765)RRQSVL and the C terminal end of the domain results in an inhibitory conformation. Major adaptations in fishes include variations in the postulated ion sensor (111)PDNKE, and the absence of a proline residue in the R domain with consequent higher chloride efflux.
Collapse
Affiliation(s)
- Agnes L C Tan
- Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609, Republic of Singapore.
| | | | | |
Collapse
|
36
|
Ostedgaard LS, Zabner J, Vermeer DW, Rokhlina T, Karp PH, Stecenko AA, Randak C, Welsh MJ. CFTR with a partially deleted R domain corrects the cystic fibrosis chloride transport defect in human airway epithelia in vitro and in mouse nasal mucosa in vivo. Proc Natl Acad Sci U S A 2002; 99:3093-8. [PMID: 11854474 PMCID: PMC122478 DOI: 10.1073/pnas.261714599] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In developing gene therapy for cystic fibrosis (CF) airways disease, a transgene encoding a partially deleted CF transmembrane conductance regulator (CFTR) Cl- channel could be of value for vectors such as adeno-associated virus that have a limited packaging capacity. Earlier studies in heterologous cells indicated that the CFTR R (regulatory) domain is predominantly random coil and that parts of the R domain can be deleted without abolishing channel function. Therefore, we designed a series of CFTR variants with shortened R domains (between residues 708 and 835) and expressed them in well-differentiated cultures of CF airway epithelia. All of the variants showed normal targeting to the apical membrane, and for the constructs we tested, biosynthesis was like wild type. Moreover, all constructs generated transepithelial Cl- current in CF epithelia. Comparison of the Cl- transport suggested that the length of the R domain, the presence of phosphorylation sites, and other factors contribute to channel activity. A variant deleting residues 708-759 complemented CF airway epithelia to the same extent as wild-type CFTR and showed no current in the absence of cAMP stimulation. In addition, expression in nasal mucosa of CF mice corrected the Cl- transport defect. These data provide insight into the structure and function of the R domain and identify regions that can be deleted with retention of function. Thus they suggest a strategy for shortening the transgene used in CF gene therapy.
Collapse
Affiliation(s)
- Lynda S Ostedgaard
- Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA 52242, USA
| | | | | | | | | | | | | | | |
Collapse
|
37
|
Webe WM, Segal A, Vankeerberghen A, Cassiman JJ, Van Driessche W. Different activation mechanisms of cystic fibrosis transmembrane conductance regulator expressed in Xenopus laevis oocytes. Comp Biochem Physiol A Mol Integr Physiol 2001; 130:521-31. [PMID: 11913463 DOI: 10.1016/s1095-6433(01)00427-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP sensitive Cl- channel that is defective in cystic fibrosis (CF). The most frequent mutation, namely deltaF508-CFTR, accounts for 66% of CF. Here we show that cAMP-activation of CFTR occurs via at least two distinct pathways: activation of CFTR molecules already present in the plasma membrane and protein kinase A (PKA)-mediated vesicular transport of new CFTR molecules to the plasma membrane and functional insertion into the membrane. We investigated the mechanisms that are responsible for these activation pathways using the Xenopus laevis oocytes expression system. We expressed CFTR and recorded continuously membrane current (Im), conductance (Gm) and capacitance (Cm), which is a direct measure of membrane surface area. Expression of CFTR alone did not change the plasma membrane surface area. However, activation of CFTR with cAMP increased Im, Gm and Cm while deltaF508-CFTR-expressing oocytes showed no response on cAMP. Inhibition of protein kinase A or buffering intracellular Ca2+ abolished the cAMP-induced increase in Cm while increases of Im and Gm were still present. ATP or the xanthine derivative 8-cyclopentyl-1,3-dipropylxanthine (CPX) did not further activate CFTR. Insertion of pre-formed CFTR into the plasma membrane could be prevented by compounds that interfere with intracellular transport mechanisms such as primaquine, brefeldin A, nocodazole. From these data we conclude that cAMP activates CFTR by at least two distinct pathways: activation of CFTR already present in the plasma membrane and exocytotic delivery of new CFTR molecules to the oocyte membrane and functional insertion into it.
Collapse
Affiliation(s)
- W M Webe
- Laboratory of Physiology, K U Leuven, Belgium.
| | | | | | | | | |
Collapse
|
38
|
Wang N, Silver DL, Thiele C, Tall AR. ATP-binding cassette transporter A1 (ABCA1) functions as a cholesterol efflux regulatory protein. J Biol Chem 2001; 276:23742-7. [PMID: 11309399 DOI: 10.1074/jbc.m102348200] [Citation(s) in RCA: 361] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
ABCA1, an ATP-binding cassette transporter mutated in Tangier disease, promotes cellular phospholipid and cholesterol efflux by loading free apoA-I with these lipids. This process involves binding of apoA-I to the cell surface and phospholipid translocation by ABCA1. The goals of this study were to examine the relationship between ABCA1-mediated lipid efflux and apolipoprotein binding and to determine whether phospholipid and cholesterol efflux are coupled. Inhibition of lipid efflux by glybenclamide treatment or by mutation of the ATP-binding cassette of ABCA1 showed a close correlation between lipid efflux, the binding of apoA-I to cells, and cross-linking of apoA-I to ABCA1. The data suggest that a functionally important apoA-I binding site exists on ABCA1 and that the binding site could also involve lipids. After using cyclodextrin preincubation to deplete cellular cholesterol, ABCA1-mediated cholesterol efflux was abolished but phospholipid efflux and the binding of apoA-I were unaffected. The conditioned media from cyclodextrin-pretreated, ABCA1-expressing cells readily promoted cholesterol efflux when added to fresh cells not expressing ABCA1, indicating that cholesterol efflux can be dissociated from phospholipid efflux. Further, using a photoactivatable cholesterol analog, we showed that ABCA1 did not bind cholesterol directly, even though several other cholesterol-binding proteins specifically bound the cholesterol analog. The data suggest that the binding of apoA-I to ABCA1 leads to the formation of phospholipid-apoA-I complexes, which subsequently promote cholesterol efflux in an autocrine or paracrine fashion.
Collapse
Affiliation(s)
- N Wang
- Division of Molecular Medicine, Department of Medicine, Columbia University, New York, New York 10032, USA.
| | | | | | | |
Collapse
|
39
|
Abstract
The specific effects of some mutations that cause cystic fibrosis suggest that reduced HCO(3)(-) transport is the key to understanding cystic fibrosis pathology. But there is a puzzling discrepancy between measures of CFTR-mediated chloride conductance in expression systems and the sweat chloride values of patients.
Collapse
Affiliation(s)
- J J Wine
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California 94305-2130, USA
| |
Collapse
|
40
|
Ahn W, Kim KH, Lee JA, Kim JY, Choi JY, Moe OW, Milgram SL, Muallem S, Lee MG. Regulatory interaction between the cystic fibrosis transmembrane conductance regulator and HCO3- salvage mechanisms in model systems and the mouse pancreatic duct. J Biol Chem 2001; 276:17236-43. [PMID: 11278980 DOI: 10.1074/jbc.m011763200] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The pancreatic duct expresses cystic fibrosis transmembrane conductance regulator (CFTR) and HCO3- secretory and salvage mechanisms in the luminal membrane. Although CFTR plays a prominent role in HCO3- secretion, the role of CFTR in HCO3- salvage is not known. In the present work, we used molecular, biochemical, and functional approaches to study the regulatory interaction between CFTR and the HCO3- salvage mechanism Na+/H+ exchanger isoform 3 (NHE3) in heterologous expression systems and in the native pancreatic duct. We found that CFTR regulates NHE3 activity by both acute and chronic mechanisms. In the pancreatic duct, CFTR increases expression of NHE3 in the luminal membrane. Thus, luminal expression of NHE3 was reduced by 53% in ducts of homozygote DeltaF508 mice. Accordingly, luminal Na+-dependent and HOE694- sensitive recovery from an acid load was reduced by 60% in ducts of DeltaF508 mice. CFTR and NHE3 were co-immunoprecipitated from PS120 cells expressing both proteins and the pancreatic duct of wild type mice but not from PS120 cells lacking CFTR or the pancreas of DeltaF508 mice. The interaction between CFTR and NHE3 required the COOH-terminal PDZ binding motif of CFTR, and mutant CFTR proteins lacking the C terminus were not co-immunoprecipitated with NHE3. Furthermore, when expressed in PS120 cells, wild type CFTR, but not CFTR mutants lacking the C-terminal PDZ binding motif, augmented cAMP-dependent inhibition of NHE3 activity by 31%. These findings reveal that CFTR controls overall HCO3- homeostasis by regulating both pancreatic ductal HCO3- secretory and salvage mechanisms.
Collapse
Affiliation(s)
- W Ahn
- Department of Pharmacology and Brain Korea 21 Project for Medical Sciences, Yonsei University College of Medicine, Seoul 120-752, Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Ostedgaard LS, Baldursson O, Welsh MJ. Regulation of the cystic fibrosis transmembrane conductance regulator Cl- channel by its R domain. J Biol Chem 2001; 276:7689-92. [PMID: 11244086 DOI: 10.1074/jbc.r100001200] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- L S Ostedgaard
- Howard Hughes Medical Institute, Departments of Internal Medicine and Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA
| | | | | |
Collapse
|
42
|
Choi JY, Muallem D, Kiselyov K, Lee MG, Thomas PJ, Muallem S. Aberrant CFTR-dependent HCO3- transport in mutations associated with cystic fibrosis. Nature 2001; 410:94-7. [PMID: 11242048 PMCID: PMC3943212 DOI: 10.1038/35065099] [Citation(s) in RCA: 294] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cystic fibrosis (CF) is a disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). Initially, Cl- conductance in the sweat duct was discovered to be impaired in CF, a finding that has been extended to all CFTR-expressing cells. Subsequent cloning of the gene showed that CFTR functions as a cyclic-AMP-regulated Cl- channel; and some CF-causing mutations inhibit CFTR Cl- channel activity. The identification of additional CF-causing mutants with normal Cl- channel activity indicates, however, that other CFTR-dependent processes contribute to the disease. Indeed, CFTR regulates other transporters, including Cl(-)-coupled HCO3- transport. Alkaline fluids are secreted by normal tissues, whereas acidic fluids are secreted by mutant CFTR-expressing tissues, indicating the importance of this activity. HCO3- and pH affect mucin viscosity and bacterial binding. We have examined Cl(-)-coupled HCO3- transport by CFTR mutants that retain substantial or normal Cl- channel activity. Here we show that mutants reported to be associated with CF with pancreatic insufficiency do not support HCO3- transport, and those associated with pancreatic sufficiency show reduced HCO3- transport. Our findings demonstrate the importance of HCO3- transport in the function of secretory epithelia and in CF.
Collapse
Affiliation(s)
- J Y Choi
- Department of Physiology, The University of Texas Southwestern Medical Center, Dallas 75390, USA
| | | | | | | | | | | |
Collapse
|
43
|
Chen JM, Scotet V, Ferec C. Definition of a "functional R domain" of the cystic fibrosis transmembrane conductance regulator. Mol Genet Metab 2000; 71:245-9. [PMID: 11001817 DOI: 10.1006/mgme.2000.3041] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The R domain of the cystic fibrosis transmembrane conductance regulator (CFTR) was originally defined as 241 amino acids, encoded by exon 13. Such exon/intron boundaries provide a convenient way to define the R domain, but do not necessarily reflect the corresponding functional domain within CFTR. A two-domain model was later proposed based on a comparison of the R-domain sequences from 10 species. While RD1, the N-terminal third of the R domain is highly conserved, RD2, the large central region of the R domain has less rigid structural requirements. Although this two-domain model was given strong support by recent functional analysis data, the simple observation that two of the four main phosphorylation sites are excluded from RD2 clearly indicates that RD2 still does not satisfy the requirements of a "functional R domain." Nevertheless, knowledge of the CFTR structure and function accumulated over the past decade and reevaluated in the context of a comprehensive sequence comparison of 15 CFTR homologues made it possible to define such a "functional R domain," i.e., amino acids C647 to D836. This definition is validated primarily because it contains all of the important potential consensus phosphorylation sequences. In addition, it includes the highly charged motif from E822 to D836. Finally, it includes all of the deletions/insertions in this region. This definition also aids in understanding the effects of missense mutations occurring within this domain.
Collapse
Affiliation(s)
- J M Chen
- Etablissement Français du Sang-Bretagne, Site de Brest, Brest, France
| | | | | |
Collapse
|
44
|
Van Oene M, Lukacs GL, Rommens JM. Cystic fibrosis mutations lead to carboxyl-terminal fragments that highlight an early biogenesis step of the cystic fibrosis transmembrane conductance regulator. J Biol Chem 2000; 275:19577-84. [PMID: 10764788 DOI: 10.1074/jbc.m002186200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inefficient delivery of the cystic fibrosis transmembrane conductance regulator (CFTR) to the surface of cells contributes to disease in the majority of cystic fibrosis patients. Analysis of cystic fibrosis-associated missense mutations in the first nucleotide binding domain (NBD1), including A455E, S549R, Y563N, and P574H, revealed reduced levels of mature CFTR with elevated levels of carboxyl-terminal polypeptide fragments of 105 and 90 kDa. These fragments appear early in biogenesis and degrade rapidly in four distinct cell types tested including the bronchial epithelial IB3-1 cell line. They were detected at highest levels with CFTRA455E where the 105-kDa fragment accounted for 40% of newly synthesized polypeptide but for only 20 and 7% of nascent wild type and mutant DeltaF508 proteins, respectively. The bands represent core- and unglycosylated forms of the same CFTR fragment supporting that precursor forms are correctly inserted into the membrane of the endoplasmic reticulum. Proteolytic cleavage would be predicted to occur on the cytosolic face of the endoplasmic reticulum within the NBD1-R domain segment, but pharmacological testing did not support involvement of the 26 S proteasome. The examined missense mutations in NBD1 manifest differently than the major mutant, DeltaF508, and highlight a critical conformational aspect of biogenesis of CFTR.
Collapse
Affiliation(s)
- M Van Oene
- Department of Molecular and Medical Genetics, Program in Genetics & Genomic Biology, University of Toronto, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
| | | | | |
Collapse
|
45
|
Wei L, Vankeerberghen A, Jaspers M, Cassiman J, Nilius B, Cuppens H. Suppressive interactions between mutations located in the two nucleotide binding domains of CFTR. FEBS Lett 2000; 473:149-53. [PMID: 10812063 DOI: 10.1016/s0014-5793(00)01519-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The S1235R locus in CFTR was studied in combination with alleles found at the M470V and G628R loci. While R628 caused a maturational defect, R1235 did not. The impact of R1235 was found to be influenced by the alleles present at the G628R and M470V loci. At the single channel level, R1235-V (R1235 on a V470 background) was characterized by an open probability significantly higher than V470-wildtype CFTR. M470, which on its own increases CFTR chloride transport activity when compared to V470-wildtype CFTR, suppressed the activity of R1235 in such a way that a protein with an open probability not significantly different from V470-wildtype CFTR was obtained. While R628-V CFTR had similar current densities as V470-wildtype CFTR in Xenopus laevis oocytes, R1235-V resulted in current densities that were more than twofold higher than those of V470-wildtype CFTR. However, the current densities generated by R1235/R628-V (R1235 and R628 on a V470 background) CFTR were significant lower than R1235-V or R628-V CFTR.
Collapse
Affiliation(s)
- L Wei
- Department of Physiology, University of Leuven, B-3000, Leuven, Belgium
| | | | | | | | | | | |
Collapse
|
46
|
Ostedgaard LS, Baldursson O, Vermeer DW, Welsh MJ, Robertson AD. A functional R domain from cystic fibrosis transmembrane conductance regulator is predominantly unstructured in solution. Proc Natl Acad Sci U S A 2000; 97:5657-62. [PMID: 10792060 PMCID: PMC25884 DOI: 10.1073/pnas.100588797] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2000] [Indexed: 11/18/2022] Open
Abstract
Phosphorylation of the regulatory (R) domain initiates cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel activity. To discover how the function of this domain is determined by its structure, we produced an R domain protein (R8) that spanned residues 708-831 of CFTR. Phosphorylated, but not unphosphorylated, R8 stimulated activity of CFTR channels lacking this domain, indicating that R8 is functional. Unexpectedly, this functional R8 was predominantly random coil, as revealed by CD and limited proteolysis. The CD spectra of both phosphorylated and nonphosphorylated R8 were similar in aqueous buffer. The folding agent trimethylamine N-oxide induced only a small increase in the helical content of nonphosphorylated R8 and even less change in the helical content of phosphorylated R8. These data, indicating that the R domain is predominantly random coil, may explain the seemingly complex way in which phosphorylation regulates CFTR channel activity.
Collapse
Affiliation(s)
- L S Ostedgaard
- Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA 52242, USA
| | | | | | | | | |
Collapse
|
47
|
Falcón-Pérez JM, Mazón MJ, Molano J, Eraso P. Functional domain analysis of the yeast ABC transporter Ycf1p by site-directed mutagenesis. J Biol Chem 1999; 274:23584-90. [PMID: 10438540 DOI: 10.1074/jbc.274.33.23584] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The yeast cadmium factor (Ycf1p) is a vacuolar protein involved in resistance to Cd(2+) and to exogenous glutathione S-conjugate precursors in yeast. It belongs to the superfamily of ATP binding cassette transporters, which includes the human cystic fibrosis transmembrane conductance regulator and the multidrug resistance-associated protein. To examine the functional significance of conserved amino acid residues in Ycf1p, we performed an extensive mutational analysis. Twenty-two single amino acid substitutions or deletions were generated by site-directed mutagenesis in the nucleotide binding domains, the proposed regulatory domain, and the fourth cytoplasmic loop. Mutants were analyzed phenotypically by measuring their ability to grow in the presence of Cd(2+). Expression and subcellular localization of the mutant proteins were examined by immunodetection in vacuolar membranes. For functional characterization of the Ycf1p variants, the kinetic parameters of glutathione S-conjugated leukotriene C(4) transport were measured. Our analysis shows that residues Ile(711), Leu(712), Phe(713), Glu(927), and Gly(1413) are essential for Ycf1p expression. Five other amino acids, Gly(663), Gly(756), Asp(777), Gly(1306), and Gly(1311), are critical for Ycf1p function, and two residues, Glu(709) and Asp(821), are unnecessary for Ycf1p biogenesis and function. We also identify several regulatory domain mutants in which Cd(2+) tolerance of the mutant strain and transport activity of the protein are dissociated.
Collapse
Affiliation(s)
- J M Falcón-Pérez
- Instituto de Investigaciones Biomédicas "Alberto Sols, " Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Arturo Duperier 4, 28029-Madrid, Spain
| | | | | | | |
Collapse
|