1
|
Tanjala AC, Jiang JX, Eckford PDW, Ramjeesingh M, Li C, Huan LJ, Langeveld G, Townsend C, Paone DV, Busch-Petersen J, Pekhletski R, Tang L, Raju V, Rowe SM, Bear CE. Comparison of a novel potentiator of CFTR channel activity to ivacaftor in ameliorating mucostasis caused by cigarette smoke in primary human bronchial airway epithelial cells. bioRxiv 2024:2024.03.01.582742. [PMID: 38496440 PMCID: PMC10942391 DOI: 10.1101/2024.03.01.582742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Background Cystic Fibrosis causing mutations in the gene CFTR , reduce the activity of the CFTR channel protein, and leads to mucus aggregation, airway obstruction and poor lung function. A role for CFTR in the pathogenesis of other muco-obstructive airway diseases such as Chronic Obstructive Pulmonary Disease (COPD) has been well established. The CFTR modulatory compound, Ivacaftor (VX-770), potentiates channel activity of CFTR and certain CF-causing mutations and has been shown to ameliorate mucus obstruction and improve lung function in people harbouring these CF-causing mutations. A pilot trial of Ivacaftor supported its potential efficacy for the treatment of mucus obstruction in COPD. These findings prompted the search for CFTR potentiators that are more effective in ameliorating cigarette-smoke (CS) induced mucostasis. Methods A novel small molecule potentiator (SK-POT1), previously identified in CFTR binding studies, was tested for its activity in augmenting CFTR channel activity using patch clamp electrophysiology in HEK-293 cells, a fluorescence-based assay of membrane potential in Calu-3 cells and in Ussing chamber studies of primary bronchial epithelial cultures. Addition of cigarette smoke extract (CSE) to the solutions bathing the apical surface of Calu-3 cells and primary bronchial airway cultures was used to model COPD. Confocal studies of the velocity of fluorescent microsphere movement on the apical surface of CSE exposed airway epithelial cultures, were used to assess the effect of potentiators on CFTR-mediated mucociliary movement. Results We showed that SK-POT1, like VX-770, was effective in augmenting the cyclic AMP-dependent channel activity of CFTR. SK-POT-1 enhanced CFTR channel activity in airway epithelial cells previously exposed to CSE and ameliorated mucostasis on the surface of primary airway cultures. Conclusion Together, this evidence supports the further development of SK-POT1 as an intervention in the treatment of COPD.
Collapse
|
2
|
Sadras I, Kerem E, Livnat G, Sarouk I, Breuer O, Reiter J, Gileles-Hillel A, Inbar O, Cohen M, Gamliel A, Stanleigh N, Gunawardena T, Bartlett C, Gonska T, Moraes T, Eckford PDW, Bear CE, Ratjen F, Kerem B, Wilschanski M, Shteinberg M, Cohen-Cymberknoh M. Clinical and functional efficacy of elexacaftor/tezacaftor/ivacaftor in people with cystic fibrosis carrying the N1303K mutation. J Cyst Fibros 2023; 22:1062-1069. [PMID: 37331863 DOI: 10.1016/j.jcf.2023.06.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 05/30/2023] [Accepted: 06/02/2023] [Indexed: 06/20/2023]
Abstract
BACKGROUND Elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) significantly improves health outcomes in people with cystic fibrosis (pwCF) carrying one or two F508del mutations. According to in vitro assays performed in FRT cells, 178 additional mutations respond to ELX/TEZ/IVA. The N1303K mutation is not included in this list of mutations. Recent in vitro data suggested that ELX/TEZ/IVA increases N1303K-CFTR activity. Based on the in vitro response, eight patients commenced treatment with ELX/TEZ/IVA. METHODS Two homozygotes; and six compound heterozygotes N1303K/nonsense or frameshift mutation pwCF were treated off label with ELX/TEZ/IVA. Clinical data before and 8 weeks after starting treatment were prospectively collected. The response to ELX/TEZ/IVA was assessed in intestinal organoids derived from 5 study patients and an additional patient carrying N1303K that is not receiving treatment. RESULTS Compared to the values before commencing treatment, mean forced expiratory volume in 1 second increased by 18.4 percentage points and 26.5% relative to baseline, mean BMI increased by 0.79 Kg/m2, and mean lung clearance index decreased by 3.6 points and 22.2%. There was no significant change in sweat chloride. Nasal potential difference normalized in four patients and remained abnormal in three. Results in 3D intestinal organoids and 2D nasal epithelial cultures showed a response in CFTR channel activity. CONCLUSIONS This report supports the previously reported in vitro data, performed in human nasal and bronchial epithelial cells and intestinal organoids, that pwCF who carry the N1303K mutation have a significant clinical benefit by ELX/TEZ/IVA treatment.
Collapse
Affiliation(s)
- Ido Sadras
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Eitan Kerem
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel.
| | - Galit Livnat
- Cystic Fibrosis Center, Carmel Medical center, The Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Israel
| | - Ifat Sarouk
- Pediatric Pulmonology Unit, The National Center for Cystic Fibrosis, Sheba Medical Center, Tel Hashomer and the Sackler Faculty of Medicine, Safra Children's Hospital, Tel Aviv University, Israel
| | - Oded Breuer
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Joel Reiter
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Alex Gileles-Hillel
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Ori Inbar
- The Cystic Fibrosis Foundation of Israel, Israel
| | - Michael Cohen
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Ayelet Gamliel
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Noemie Stanleigh
- Department of Genetics, The Life Sciences Institute, Hebrew University, Jerusalem Israel
| | - Tarini Gunawardena
- Molecular Medicine, Hospital for Sick Children, Toronto, ON, Canada; Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada
| | - Claire Bartlett
- Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada
| | - Tanja Gonska
- Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada; Division of Gastroenterology, Hepatology & Nutrition, Division of Respiratory Medicine, SickKids Hospital, Toronto, ON, Canada; Department of Physiology and Pediatrics, University of Toronto, Toronto, ON, Canada
| | - Theo Moraes
- Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada; Division of Gastroenterology, Hepatology & Nutrition, Division of Respiratory Medicine, SickKids Hospital, Toronto, ON, Canada; Department of Physiology and Pediatrics, University of Toronto, Toronto, ON, Canada
| | - Paul D W Eckford
- Molecular Medicine, Hospital for Sick Children, Toronto, ON, Canada
| | - Christine E Bear
- Molecular Medicine, Hospital for Sick Children, Toronto, ON, Canada; Department of Physiology and Pediatrics, University of Toronto, Toronto, ON, Canada
| | - Felix Ratjen
- Translational Medicine, Hospital for Sick Children, Toronto, ON, Canada; Division of Gastroenterology, Hepatology & Nutrition, Division of Respiratory Medicine, SickKids Hospital, Toronto, ON, Canada; Department of Physiology and Pediatrics, University of Toronto, Toronto, ON, Canada
| | - Batsheva Kerem
- Department of Genetics, The Life Sciences Institute, Hebrew University, Jerusalem Israel
| | - Michael Wilschanski
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Michal Shteinberg
- Cystic Fibrosis Center, Carmel Medical center, The Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Israel
| | - Malena Cohen-Cymberknoh
- Cystic Fibrosis Center, Hadassah Hebrew Medical Center and Faculty of Medicine, Hadassah-Hebrew University Medical Center, Hebrew University of Jerusalem, Jerusalem 91120, Israel
| |
Collapse
|
3
|
Sahakyan Y, Abrahamyan L, Ratjen F, Bear C, Strug L, Eckford PDW, Peel JK, Krahn M, Sander B. Cost-effectiveness analysis of genetic tools to predict treatment response in patients with cystic fibrosis. J Cyst Fibros 2023; 22:933-940. [PMID: 37100704 DOI: 10.1016/j.jcf.2023.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 04/17/2023] [Accepted: 04/19/2023] [Indexed: 04/28/2023]
Abstract
BACKGROUND Cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulator therapies show variable efficacy for patients with CF. Patient-derived predictive tools may identify individuals likely to respond to CFTRs, but are not in routine use. We aimed to determine the cost-utility of predictive tool-guided treatment with CFTRs as add-on to standard of care (SoC) for individuals with CF. METHODS This economic evaluation compared two strategies using an individual level simulation: (i) Treat All, where all patients received CFTRs plus SoC and (ii) Test→Treat, where patients who tested positive on predictive tools received CFTRs plus SoC and those who tested negative received SoC only. We simulated 50,000 individuals over their lifetime, and estimated costs (2020 CAD) per quality-adjusted life year (QALY) from the healthcare payer's perspective, discounted at 1.5% annually. The model was populated using Canadian CF registry data and published literature. Probabilistic and deterministic sensitivity were conducted. RESULTS The Treat All and Test→Treat and strategies yielded 22.41 and 21.36 QALYs, and cost $4.21 M and $3.15 M respectively. Results of probabilistic sensitivity analysis showed that Test→Treat was highly cost-effective compared to Treat All in 100% of simulations at cost-effectiveness thresholds as high as $500,000 per QALY. Test→Treat may save between $931 K to $1.1 M per QALY lost, depending on sensitivity and specificity of predictive tools. CONCLUSION The use of predictive tools could optimize the health benefits of CFTR modulators while reducing costs. Our findings support the use of pre-treatment predictive testing and may help inform coverage and reimbursement policies for individuals with CF.
Collapse
Affiliation(s)
- Yeva Sahakyan
- Toronto Health Economics and Technology Assessment Collaborative (THETA), University Health Network, Toronto, ON, Canada.
| | - Lusine Abrahamyan
- Toronto Health Economics and Technology Assessment Collaborative (THETA), University Health Network, Toronto, ON, Canada; Toronto General Hospital Research Institute, University Health Network, Toronto, ON, Canada; Institute of Health Policy, Management, and Evaluation, University of Toronto, Toronto, ON, Canada
| | - Felix Ratjen
- Division of Respiratory Medicine, Department of Pediatrics, Translational Medicine, Research Institute, Hospital for Sick Children, Toronto, ON, Canada; Department of Pediatrics, University of Toronto, Toronto, ON, Canada
| | - Christine Bear
- Molecular Medicine Programme, Hospital for Sick Children, Toronto, ON, Canada; Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Lisa Strug
- Program in Genetics and Genome Biology, Hospital for Sick Children, Toronto, ON, Canada; Departments of Statistical Sciences and Computer Science, University of Toronto, Toronto, ON, Canada
| | - Paul D W Eckford
- Molecular Medicine Programme, Hospital for Sick Children, Toronto, ON, Canada
| | - John K Peel
- Institute of Health Policy, Management, and Evaluation, University of Toronto, Toronto, ON, Canada
| | - Murray Krahn
- Toronto Health Economics and Technology Assessment Collaborative (THETA), University Health Network, Toronto, ON, Canada; Toronto General Hospital Research Institute, University Health Network, Toronto, ON, Canada; Institute of Health Policy, Management, and Evaluation, University of Toronto, Toronto, ON, Canada
| | - Beate Sander
- Toronto Health Economics and Technology Assessment Collaborative (THETA), University Health Network, Toronto, ON, Canada; Toronto General Hospital Research Institute, University Health Network, Toronto, ON, Canada; Institute of Health Policy, Management, and Evaluation, University of Toronto, Toronto, ON, Canada; Public Health Ontario, Toronto, ON, Canada; ICES, Toronto, ON, Canada
| |
Collapse
|
4
|
Gunawardena TNA, Bozóky Z, Bartlett C, Ouyang H, Eckford PDW, Moraes TJ, Ratjen F, Gonska T, Bear CE. Correlation of Electrophysiological and Fluorescence-Based Measurements of Modulator Efficacy in Nasal Epithelial Cultures Derived from People with Cystic Fibrosis. Cells 2023; 12:cells12081174. [PMID: 37190083 DOI: 10.3390/cells12081174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/05/2023] [Accepted: 04/12/2023] [Indexed: 05/17/2023] Open
Abstract
It has been suggested that in vitro studies of the rescue effect of CFTR modulator drugs in nasal epithelial cultures derived from people with cystic fibrosis have the potential to predict clinical responses to the same drugs. Hence, there is an interest in evaluating different methods for measuring in vitro modulator responses in patient-derived nasal cultures. Commonly, the functional response to CFTR modulator combinations in these cultures is assessed by bioelectric measurements, using the Ussing chamber. While this method is highly informative, it is time-consuming. A fluorescence-based, multi-transwell method for assaying regulated apical chloride conductance (Fl-ACC) promises to provide a complementary approach to theratyping in patient-derived nasal cultures. In the present work, we compared Ussing chamber measurements and fluorescence-based measurements of CFTR-mediated apical conductance in matching, fully differentiated nasal cultures derived from CF patients, homozygous for F508del (n = 31) or W1282X (n = 3), or heterozygous for Class III mutations G551D or G178R (n = 5). These cultures were obtained through a bioresource called the Cystic Fibrosis Canada-Sick Kids Program in Individual CF Therapy (CFIT). We found that the Fl-ACC method was effective in detecting positive responses to interventions for all genotypes. There was a correlation between patient-specific drug responses measured in cultures harbouring F508del, as measured using the Ussing chamber technique and the fluorescence-based assay (Fl-ACC). Finally, the fluorescence-based assay has the potential for greater sensitivity for detecting responses to pharmacological rescue strategies targeting W1282X.
Collapse
Affiliation(s)
- Tarini N A Gunawardena
- Program of Molecular Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
- Program of Translational Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Zoltán Bozóky
- Providence Health Care, Vancouver, BC V6Z 1Y6, Canada
| | - Claire Bartlett
- Program of Translational Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Hong Ouyang
- Program of Translational Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Paul D W Eckford
- Program of Molecular Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Theo J Moraes
- Program of Translational Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
- Department of Paediatrics, Division of Respiratory Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Felix Ratjen
- Program of Translational Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
- Department of Paediatrics, Division of Respiratory Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Tanja Gonska
- Program of Translational Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
- Department of Paediatrics, Division of Gastroenterology, Hepatology and Nutrition, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Christine E Bear
- Program of Molecular Medicine, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
- Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| |
Collapse
|
5
|
Laselva O, Bartlett C, Gunawardena TNA, Ouyang H, Eckford PDW, Moraes TJ, Bear CE, Gonska T. Rescue of multiple class II CFTR mutations by elexacaftor+tezacaftor+ivacaftor mediated in part by the dual activities of elexacaftor as both corrector and potentiator. Eur Respir J 2021; 57:13993003.02774-2020. [PMID: 33303536 PMCID: PMC8209484 DOI: 10.1183/13993003.02774-2020] [Citation(s) in RCA: 83] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 11/20/2020] [Indexed: 12/20/2022]
Abstract
Positive results in pre-clinical studies of the triple combination of elexacaftor, tezacaftor and ivacaftor, performed in airway epithelial cell cultures obtained from patients harbouring the class II cystic fibrosis transmembrane conductance regulator (CFTR) mutation F508del-CFTR, translated to impressive clinical outcomes for subjects carrying this mutation in clinical trials and approval of Trikafta.Encouraged by this correlation, we were prompted to evaluate the effect of the elexacaftor, tezacaftor and ivacaftor triple combination on primary nasal epithelial cultures obtained from individuals with rare class II CF-causing mutations (G85E, M1101K and N1303K) for which Trikafta is not approved.Cultures from individuals homozygous for M1101K responded better than cultures harbouring G85E and N1303K after treatment with the triple combination with respect to improvement in regulated channel function and protein processing. A similar genotype-specific effect of the triple combination was observed when the different mutations were expressed in HEK293 cells, supporting the hypothesis that these modulators may act directly on the mutant proteins. Detailed studies in nasal cultures and HEK293 cells showed that the corrector, elexacaftor, exhibited dual activity as both corrector and potentiator, and suggested that the potentiator activity contributes to its pharmacological activity.These pre-clinical studies using nasal epithelial cultures identified mutation genotypes for which elexacaftor, tezacaftor and ivacaftor may produce clinical responses that are comparable to, or inferior to, those observed for F508del-CFTR.
Collapse
Affiliation(s)
- Onofrio Laselva
- Programme in Molecular Medicine, The Hospital for Sick Children, Toronto, ON, Canada.,Dept of Physiology, University of Toronto, Toronto, ON, Canada
| | - Claire Bartlett
- Programme in Translational Medicine, The Hospital for Sick Children, Toronto, ON, Canada
| | - Tarini N A Gunawardena
- Programme in Molecular Medicine, The Hospital for Sick Children, Toronto, ON, Canada.,Programme in Translational Medicine, The Hospital for Sick Children, Toronto, ON, Canada
| | - Hong Ouyang
- Programme in Translational Medicine, The Hospital for Sick Children, Toronto, ON, Canada
| | - Paul D W Eckford
- Programme in Molecular Medicine, The Hospital for Sick Children, Toronto, ON, Canada
| | - Theo J Moraes
- Programme in Translational Medicine, The Hospital for Sick Children, Toronto, ON, Canada.,Dept of Paediatrics, University of Toronto, Toronto, ON, Canada
| | - Christine E Bear
- Programme in Molecular Medicine, The Hospital for Sick Children, Toronto, ON, Canada.,Dept of Physiology, University of Toronto, Toronto, ON, Canada.,Dept of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Tanja Gonska
- Programme in Translational Medicine, The Hospital for Sick Children, Toronto, ON, Canada .,Dept of Paediatrics, University of Toronto, Toronto, ON, Canada
| |
Collapse
|
6
|
Laselva O, McCormack J, Bartlett C, Ip W, Gunawardena TNA, Ouyang H, Eckford PDW, Gonska T, Moraes TJ, Bear CE. Preclinical Studies of a Rare CF-Causing Mutation in the Second Nucleotide Binding Domain (c.3700A>G) Show Robust Functional Rescue in Primary Nasal Cultures by Novel CFTR Modulators. J Pers Med 2020; 10:jpm10040209. [PMID: 33167369 PMCID: PMC7712331 DOI: 10.3390/jpm10040209] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/01/2020] [Accepted: 11/03/2020] [Indexed: 12/12/2022] Open
Abstract
The combination therapies ORKAMBITM and TRIKAFTATM are approved for people who have the F508del mutation on at least one allele. In this study we examine the effects of potentiator and corrector combinations on the rare mutation c.3700A>G. This mutation produces a cryptic splice site that deletes six amino acids in NBD2 (I1234-R1239del). Like F508del it causes protein misprocessing and reduced chloride channel function. We show that a novel cystic fibrosis transmembrane conductance regulator CFTR modulator triple combination (AC1, corrector, AC2-2, co-potentiator and AP2, potentiator), rescued I1234-R1239del-CFTR activity to WT-CFTR level in HEK293 cells. Moreover, we show that although the response to ORKAMBI was modest in nasal epithelial cells from two individuals homozygous for I1234-R1239del-CFTR, a substantial functional rescue was achieved with the novel triple combination. Interestingly, while both the novel CFTR triple combination and TRIKAFTATM treatment showed functional rescue in gene-edited I1234-R1239del-CFTR-expressing HBE cells and in nasal cells from two CF patients heterozygous for I1234-R1239del/W1282X, nasal cells homozygous for I1234-R1239del-CFTR showed no significant response to the TRIKAFTATM combination. These data suggest a potential benefit of CFTR modulators on the functional rescue of I1234-R1239del -CFTR, which arises from the rare CF-causing mutation c.3700A>G, and highlight that patient tissues are crucial to our full understanding of functional rescue in rare CFTR mutations.
Collapse
Affiliation(s)
- Onofrio Laselva
- Programme in Molecular Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (O.L.); (J.M.); (T.N.A.G.); (P.D.W.E.)
- Department of Physiology, University of Toronto, Toronto, ON M5G 8X4, Canada
| | - Jacqueline McCormack
- Programme in Molecular Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (O.L.); (J.M.); (T.N.A.G.); (P.D.W.E.)
| | - Claire Bartlett
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (C.B.); (W.I.); (H.O.); (T.G.); (T.J.M.)
| | - Wan Ip
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (C.B.); (W.I.); (H.O.); (T.G.); (T.J.M.)
| | - Tarini N. A. Gunawardena
- Programme in Molecular Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (O.L.); (J.M.); (T.N.A.G.); (P.D.W.E.)
| | - Hong Ouyang
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (C.B.); (W.I.); (H.O.); (T.G.); (T.J.M.)
| | - Paul D. W. Eckford
- Programme in Molecular Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (O.L.); (J.M.); (T.N.A.G.); (P.D.W.E.)
| | - Tanja Gonska
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (C.B.); (W.I.); (H.O.); (T.G.); (T.J.M.)
- Department of Paediatrics, University of Toronto, Toronto, ON M5G 8X4, Canada
| | - Theo J. Moraes
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (C.B.); (W.I.); (H.O.); (T.G.); (T.J.M.)
- Department of Paediatrics, University of Toronto, Toronto, ON M5G 8X4, Canada
| | - Christine E. Bear
- Programme in Molecular Medicine, Hospital for Sick Children, Toronto, ON M5G 8X4, Canada; (O.L.); (J.M.); (T.N.A.G.); (P.D.W.E.)
- Department of Physiology, University of Toronto, Toronto, ON M5G 8X4, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 8X4, Canada
- Correspondence: ; Tel.: +1-416-816-5981
| |
Collapse
|
7
|
Chin S, Yang D, Miles AJ, Eckford PDW, Molinski S, Wallace BA, Bear CE. Attenuation of Phosphorylation-dependent Activation of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) by Disease-causing Mutations at the Transmission Interface. J Biol Chem 2016; 292:1988-1999. [PMID: 28003367 PMCID: PMC5290968 DOI: 10.1074/jbc.m116.762633] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/07/2016] [Indexed: 12/21/2022] Open
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is a multidomain membrane protein that functions as a phosphorylation-regulated anion channel. The interface between its two cytosolic nucleotide binding domains and coupling helices conferred by intracellular loops extending from the channel pore domains has been referred to as a transmission interface and is thought to be critical for the regulated channel activity of CFTR. Phosphorylation of the regulatory domain of CFTR by protein kinase A (PKA) is required for its channel activity. However, it was unclear if phosphorylation modifies the transmission interface. Here, we studied purified full-length CFTR protein using spectroscopic techniques to determine the consequences of PKA-mediated phosphorylation. Synchrotron radiation circular dichroism spectroscopy confirmed that purified full-length wild-type CFTR is folded and structurally responsive to phosphorylation. Intrinsic tryptophan fluorescence studies of CFTR showed that phosphorylation reduced iodide-mediated quenching, consistent with an effect of phosphorylation in burying tryptophans at the transmission interface. Importantly, the rate of phosphorylation-dependent channel activation was compromised by the introduction of disease-causing mutations in either of the two coupling helices predicted to interact with nucleotide binding domain 1 at the interface. Together, these results suggest that phosphorylation modifies the interface between the catalytic and pore domains of CFTR and that this modification facilitates CFTR channel activation.
Collapse
Affiliation(s)
- Stephanie Chin
- From the Programme of Molecular Structure and Function, Hospital for Sick Children, Toronto M5G 0A4, Canada; the Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Donghe Yang
- From the Programme of Molecular Structure and Function, Hospital for Sick Children, Toronto M5G 0A4, Canada
| | - Andrew J Miles
- the Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, United Kingdom
| | - Paul D W Eckford
- From the Programme of Molecular Structure and Function, Hospital for Sick Children, Toronto M5G 0A4, Canada
| | - Steven Molinski
- From the Programme of Molecular Structure and Function, Hospital for Sick Children, Toronto M5G 0A4, Canada; the Department of Biochemistry, University of Toronto, Toronto, Canada
| | - B A Wallace
- the Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, United Kingdom
| | - Christine E Bear
- From the Programme of Molecular Structure and Function, Hospital for Sick Children, Toronto M5G 0A4, Canada; the Department of Biochemistry, University of Toronto, Toronto, Canada; the Department of Physiology, University of Toronto, Toronto, Canada.
| |
Collapse
|
8
|
Eckford PDW, Li C, Bear CE. Functional reconstitution and channel activity measurements of purified wildtype and mutant CFTR protein. J Vis Exp 2015. [PMID: 25867140 DOI: 10.3791/52427] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a unique channel-forming member of the ATP Binding Cassette (ABC) superfamily of transporters. The phosphorylation and nucleotide dependent chloride channel activity of CFTR has been frequently studied in whole cell systems and as single channels in excised membrane patches. Many Cystic Fibrosis-causing mutations have been shown to alter this activity. While a small number of purification protocols have been published, a fast reconstitution method that retains channel activity and a suitable method for studying population channel activity in a purified system have been lacking. Here rapid methods are described for purification and functional reconstitution of the full-length CFTR protein into proteoliposomes of defined lipid composition that retains activity as a regulated halide channel. This reconstitution method together with a novel flux-based assay of channel activity is a suitable system for studying the population channel properties of wild type CFTR and the disease-causing mutants F508del- and G551D-CFTR. Specifically, the method has utility in studying the direct effects of phosphorylation, nucleotides and small molecules such as potentiators and inhibitors on CFTR channel activity. The methods are also amenable to the study of other membrane channels/transporters for anionic substrates.
Collapse
Affiliation(s)
- Paul D W Eckford
- Programme in Molecular Structure and Function, Hospital for Sick Children
| | - Canhui Li
- Programme in Molecular Structure and Function, Hospital for Sick Children
| | - Christine E Bear
- Programme in Molecular Structure and Function, Hospital for Sick Children; Department of Biochemistry, University of Toronto; Department of Physiology, University of Toronto;
| |
Collapse
|
9
|
Molinski S, Eckford PDW, Pasyk S, Ahmadi S, Chin S, Bear CE. Functional Rescue of F508del-CFTR Using Small Molecule Correctors. Front Pharmacol 2012; 3:160. [PMID: 23055971 PMCID: PMC3458236 DOI: 10.3389/fphar.2012.00160] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 08/17/2012] [Indexed: 01/21/2023] Open
Abstract
High-throughput screens for small molecules that are effective in “correcting” the functional expression of F508del-CFTR have yielded several promising hits. Two such compounds are currently in clinical trial. Despite this success, it is clear that further advances will be required in order to restore 50% or greater of wild-type CFTR function to the airways of patients harboring the F508del-CFTR protein. Progress will be enhanced by our better understanding of the molecular and cellular defects caused by the F508del mutation, present in 90% of CF patients. The goal of this chapter is to review the current understanding of defects caused by F508del in the CFTR protein and in CFTR-mediated interactions important for its biosynthesis, trafficking, channel function, and stability at the cell surface. Finally, we will discuss the gaps in our knowledge regarding the mechanism of action of existing correctors, the unmet need to discover compounds which restore proper CFTR structure and function in CF affected tissues and new strategies for therapy development.
Collapse
Affiliation(s)
- Steven Molinski
- Programme in Molecular Structure and Function, Research Institute, Hospital for Sick Children Toronto, ON, Canada ; Department of Biochemistry, University of Toronto Toronto, ON, Canada
| | | | | | | | | | | |
Collapse
|
10
|
Eckford PDW, Li C, Ramjeesingh M, Bear CE. Cystic fibrosis transmembrane conductance regulator (CFTR) potentiator VX-770 (ivacaftor) opens the defective channel gate of mutant CFTR in a phosphorylation-dependent but ATP-independent manner. J Biol Chem 2012; 287:36639-49. [PMID: 22942289 DOI: 10.1074/jbc.m112.393637] [Citation(s) in RCA: 205] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) acts as a channel on the apical membrane of epithelia. Disease-causing mutations in the cystic fibrosis gene can lead to CFTR protein misfolding as in the case of the F508del mutation and/or channel dysfunction. Recently, a small molecule, VX-770 (ivacaftor), has shown efficacy in restoring lung function in patients bearing the G551D mutation, and this has been linked to repair of its channel gating defect. However, these studies did not reveal the mechanism of action of VX-770 in detail. Normally, CFTR channel activity is regulated by phosphorylation, ATP binding, and hydrolysis. Hence, it has been hypothesized that VX-770 modifies one or more of these metabolic events. In this study, we examined VX-770 activity using a reconstitution system for purified CFTR protein, a system that enables control of known regulatory factors. We studied the consequences of VX-770 interaction with CFTR incorporated in planar lipid bilayers and in proteoliposomes, using a novel flux-based assay. We found that purified and phosphorylated CFTR was potentiated in the presence of Mg-ATP, suggesting that VX-770 bound directly to the CFTR protein, rather than associated kinases or phosphatases. Interestingly, we also found that VX-770 enhanced the channel activity of purified and mutant CFTR in the nominal absence of Mg-ATP. These findings suggest that VX-770 can cause CFTR channel opening through a nonconventional ATP-independent mechanism. This work sets the stage for future studies of the structural properties that mediate CFTR gating using VX-770 as a probe.
Collapse
Affiliation(s)
- Paul D W Eckford
- Programme of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto M5G 1X8, Canada
| | | | | | | |
Collapse
|
11
|
Pasyk S, Molinski S, Yu W, Eckford PDW, Bear CE. Identification and validation of hits from high throughput screens for CFTR modulators. Curr Pharm Des 2012; 18:628-41. [PMID: 22229556 DOI: 10.2174/138161212799315957] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Accepted: 11/25/2011] [Indexed: 11/22/2022]
Abstract
These are exciting times with the appearance of small molecule compounds in clinical trials which target the basic defects caused by mutation in the CFTR gene. This progress was enabled by years of basic research probing the molecular and cellular consequences caused by mutation and the development of methods by which to study the primary anion transport defect in a high-throughput manner by robotics. Future progress with the development of new, more effective corrector compounds is needed. Such discovery will require further progress in defining the molecular targets for effective intervention using a multidisciplinary approach, merging computational, molecular, proteomic and cell biological methods. There is also an urgent need to develop means to link the right therapeutic compound to the right patients given the heterogeneity of the CF patient population. We envision a time when mid to high-throughput methods will be married with stem cell biology to enable testing a compendium of compounds on cells derived from each individual patient. Given the rate of progress in this field- this scenario may exist in the not too distant future.
Collapse
Affiliation(s)
- Stan Pasyk
- Programme in Molecular Structure and Function in the Research Institute, the Hospital for Sick Children, 555 University Avenue, Toronto, Canada
| | | | | | | | | |
Collapse
|
12
|
Alkhouri B, Denning RA, Kim Chiaw P, Eckford PDW, Yu W, Li C, Bogojeski JJ, Bear CE, Viirre RD. Synthesis and properties of molecular probes for the rescue site on mutant cystic fibrosis transmembrane conductance regulator. J Med Chem 2011; 54:8693-701. [PMID: 22074181 PMCID: PMC3241338 DOI: 10.1021/jm201335c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cystic fibrosis is a genetic disease caused by mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. In vitro experiments have demonstrated that 4-methyl-2-(5-phenyl-1H-pyrazol-3-yl)phenol (VRT-532, 1) is able to partially restore the function of mutant CFTR proteins. To help elucidate the nature of the interactions between 1 and mutant CFTR, molecular probes based on the structure of 1 have been prepared. These include a photoreactive aryl azide derivative 11 and a fluorescent dansyl sulfonamide 15. Additionally, a method for hydrogen isotope exchange on 1 has been developed, which could be used for the incorporation of radioactive tritium. Using iodide efflux assays, the probe molecules have been demonstrated to modulate the activity of mutant CFTR in the same manner as 1. These probe molecules enable a number of biochemical experiments aimed at understanding how 1 rescues the function of mutant CFTR. This understanding can in turn aid in the design and development of more efficacious compounds which may serve as therapeutic agents in the treatment of cystic fibrosis.
Collapse
Affiliation(s)
- Bashar Alkhouri
- Department of Chemistry and Biology, Ryerson University, and Programme in Molecular Structure and Function, Research Institute, Hospital for Sick Children, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Affiliation(s)
- Paul D W Eckford
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | | |
Collapse
|
14
|
Eckford PDW, Sharom FJ. Interaction of the P-glycoprotein multidrug efflux pump with cholesterol: effects on ATPase activity, drug binding and transport. Biochemistry 2009; 47:13686-98. [PMID: 19049391 DOI: 10.1021/bi801409r] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Resistance to a broad spectrum of structurally diverse chemotherapeutic drugs (multidrug resistance; MDR) is a major impediment to the treatment of cancer. One cause of MDR is the expression at the tumor cell surface of P-glycoprotein (Pgp), which functions as an ATP-powered multidrug efflux pump. Since Pgp interacts with its substrates after they partition into the lipid bilayer, changes in membrane physicochemical properties may have substantial effects on its functional activity. Various interactions between cholesterol and Pgp have been suggested, including a role for the protein in transbilayer movement of cholesterol. We have characterized several aspects of Pgp-cholesterol interactions, and found that some of the previously reported effects of cholesterol result from inhibition of Pgp ATPase activity by the cholesterol-extracting reagent, methyl-beta-cyclodextrin. The presence of cholesterol in the bilayer modulated the basal and drug-stimulated ATPase activity of reconstituted Pgp in a modest fashion. Both the ability of drugs to bind to the protein and the drug transport and phospholipid flippase functions of Pgp were also affected by cholesterol. The effects of cholesterol on drug binding affinity were unrelated to the size of the compound. Increasing cholesterol content greatly altered the partitioning of hydrophobic drug substrates into the membrane, which may account for some of the observed effects of cholesterol on Pgp-mediated drug transport. Pgp does not appear to mediate the flip-flop of a fluorescent cholesterol analogue across the bilayer. Cholesterol likely modulates Pgp function via effects on drug-membrane partitioning and changes in the local lipid environment of the protein.
Collapse
Affiliation(s)
- Paul D W Eckford
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | | |
Collapse
|
15
|
Abstract
The Escherichia coli MsbA protein is a 65-kDa member of the ATP-binding cassette superfamily. It is thought to function as an ATP-dependent lipid translocase that transports lipid A from the inner to the outer leaflet of the cytoplasmic membrane. MsbA with high ATPase activity was isolated and found to be homodimeric in detergent solution. The protein ATPase activity was inhibited by vanadate and showed variable patterns of stimulation and inhibition by lipid A and other compounds. The intrinsic tryptophan fluorescence of the protein was characterized, and dynamic quenching using acrylamide showed that a conformational change took place on binding of lipid A. Fluorescence quenching was used to characterize the interactions of MsbA with nucleotides and various putative substrates, including lipids, lipid-like compounds, and drugs. MsbA had an apparent binding affinity for ATP of approximately 2 mm and also bound nonhydrolyzable ATP analogs and fluorescent ATP derivatives. The putative substrate lipid A interacted with the protein with an affinity of 6.4 microm. Drugs that are known to be substrates for ABC multidrug transporters also interacted with MsbA with affinities in the range 0.25-50 microm. This study represents the first use of fluorescence approaches to estimate MsbA binding affinities for nucleotides and putative transport substrates.
Collapse
Affiliation(s)
- Paul D W Eckford
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | |
Collapse
|
16
|
Eckford PDW, Sharom FJ. P-glycoprotein (ABCB1) interacts directly with lipid-based anti-cancer drugs and platelet-activating factorsThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Membrane Proteins in Health and Disease. Biochem Cell Biol 2006; 84:1022-33. [PMID: 17215888 DOI: 10.1139/o06-196] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The P-glycoprotein multidrug transporter (Pgp; ABCB1) is an ATP-binding cassette (ABC) protein that has been implicated in the multidrug resistance of human cancers. Pgp couples ATP hydrolysis to active extrusion from the cell of a broad array of amphipathic compounds via an ill-defined mechanism. Substrates are believed to interact with Pgp within the membrane. Reconstituted Pgp functions as an ATP-dependent flippase for a variety of fluorescently labelled membrane lipids. The protein may also function as a drug ‘flippase’, moving its substrates from the inner to the outer leaflet of the bilayer. We show that lipid-based anti-cancer drugs, such as miltefosine, and signaling molecules, such as platelet-activating factors, bind saturably to Pgp with Kd values in the low micromolar range, and modulate its ATPase activity. These compounds also inhibit Pgp-mediated flipping of fluorescent lipids and transport of Hoechst 33342 and tetramethylrosamine, which occupy different subsites in the drug-binding pocket. Bacterial lipid A modulates Pgp ATPase activity, and glycolipid flipping is inhibited by unlabelled glucosylceramide, suggesting that these lipids also interact with the transporter. These results indicate that Pgp treats a variety of lipid-based molecules as substrates, and likely interacts with lipids and drugs in the same manner.
Collapse
Affiliation(s)
- Paul D W Eckford
- Department of Molecular and Cellular Biology, University of Guelph, Guelph ON N1G 2W1, Canada
| | | |
Collapse
|
17
|
Sharom FJ, Lugo MR, Eckford PDW. New Insights into the Drug Binding, Transport and Lipid Flippase Activities of the P-Glycoprotein Multidrug Transporter. J Bioenerg Biomembr 2005; 37:481-7. [PMID: 16691487 DOI: 10.1007/s10863-005-9496-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The MDR1 P-glycoprotein, an ATP-binding cassette (ABC) superfamily member that functions as an ATP-driven drug efflux pump, has been linked to resistance of human tumors to multiple chemotherapeutic agents. P-glycoprotein binds and actively transports a large variety of hydrophobic drugs and peptides. P-glycoprotein in reconstituted proteoliposomes is also an outwardly directed flippase for membrane phospholipids and simple glycosphinglipids. This review focuses on recent advances in our understanding of P-glycoprotein structure and function, particularly through the use of fluorescence spectroscopic approaches. Progress is being made towards understanding the structure of the transporter, especially the spatial relationship between the two nucleotide-binding domains. Exploration of the P-glycoprotein catalytic cycle using vanadate-trapped complexes has revealed that drug transport likely takes place by concerted conformational changes linked to relaxation of a high energy intermediate. Low resolution mapping of the protein using fluorescence resonance energy transfer showed that both the H and R drug-binding sites are located within the cytoplasmic leaflet. Two drugs can bind to the R-site simultaneously, suggesting that the protein contains a large flexible binding region.
Collapse
Affiliation(s)
- Frances J Sharom
- Department of Molecular and Cellular Biology, University of Guelph, Science Complex Room 2255, Guelph, Ontario, Canada.
| | | | | |
Collapse
|
18
|
Affiliation(s)
- Frances J Sharom
- Department of Chemistry and Biochemistry, University of Guelph, Ontario, Canada
| | | |
Collapse
|