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Cui G, Strickland KM, Vazquez Cegla AJ, McCarty NA. Comparing ATPase activity of ATP-binding cassette subfamily C member 4, lamprey CFTR, and human CFTR using an antimony-phosphomolybdate assay. Front Pharmacol 2024; 15:1363456. [PMID: 38440176 PMCID: PMC10910009 DOI: 10.3389/fphar.2024.1363456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Accepted: 02/05/2024] [Indexed: 03/06/2024] Open
Abstract
Introduction: ATP-binding cassette (ABC) transporters use the hydrolysis of ATP to power the active transport of molecules, but paradoxically the cystic fibrosis transmembrane regulator (CFTR, ABCC7) forms an ion channel. We previously showed that ATP-binding cassette subfamily C member 4 (ABCC4) is the closest mammalian paralog to CFTR, compared to other ABC transporters. In addition, Lamprey CFTR (Lp-CFTR) is the oldest known CFTR ortholog and has unique structural and functional features compared to human CFTR (hCFTR). The availability of these evolutionarily distant orthologs gives us the opportunity to study the changes in ATPase activity that may be related to their disparate functions. Methods: We utilized the baculovirus expression system with Sf9 insect cells and made use of the highly sensitive antimony-phosphomolybdate assay for testing the ATPase activity of human ABCC4 (hABCC4), Lp-CFTR, and hCFTR under similar experimental conditions. This assay measures the production of inorganic phosphate (Pi) in the nanomolar range. Results: Crude plasma membranes were purified, and protein concentration, determined semi-quantitatively, of hABCC4, Lp-CFTR, and hCFTR ranged from 0.01 to 0.36 μg/μL. No significant difference in expression level was found although hABCC4 trended toward the highest level. hABCC4 was activated by ATP with the equilibrium constant (Kd) 0.55 ± 0.28 mM (n = 8). Estimated maximum ATPase rate (Vmax) for hABCC4 was about 0.2 nmol/μg/min when the protein was activated with 1 mM ATP at 37°C (n = 7). Estimated maximum ATPase rate for PKA-phosphorylated Lp-CFTR reached about half of hCFTR levels in the same conditions. Vmax for both Lp-CFTR and hCFTR were significantly increased in high PKA conditions compared to low PKA conditions. Maximum intrinsic ATPase rate of hABCC4 in the absence of substrate was twice that of hCFTR when activated in 1 mM ATP. Conclusion: The findings here suggest that while both ABCC4 and hCFTR bear one consensus and one degenerate ATPase site, the hCFTR exhibited a reduced intrinsic ATPase activity. In addition, ATPase activity in the CFTR lineage increased from Lp-CFTR to hCFTR. Finally, the studies pave the way to purify hABCC4, Lp-CFTR, and hCFTR from Sf9 cells for their structural investigation, including by cryo-EM, and for studies of evolution in the ABC transporter superfamily.
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Affiliation(s)
| | | | | | - Nael A. McCarty
- Division of Pulmonology, Asthma, Cystic Fibrosis, and Sleep, Department of Pediatrics, Emory + Children’s Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine and Children’s Healthcare of Atlanta, Atlanta, GA, United States
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Schenkel M, Ravamehr-Lake D, Czerniak T, Saenz JP, Krainer G, Schlierf M, Deber CM. Impact of cholesterol and Lumacaftor on the folding of CFTR helical hairpins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184078. [PMID: 36279907 DOI: 10.1016/j.bbamem.2022.184078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 10/17/2022] [Accepted: 10/18/2022] [Indexed: 11/07/2022]
Abstract
Cystic fibrosis (CF) is caused by mutations in the gene that codes for the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR). Recent advances in CF treatment have included use of small-molecule drugs known as modulators, such as Lumacaftor (VX-809), but their detailed mechanism of action and interplay with the surrounding lipid membranes, including cholesterol, remain largely unknown. To examine these phenomena and guide future modulator development, we prepared a set of wild type (WT) and mutant helical hairpin constructs consisting of CFTR transmembrane (TM) segments 3 and 4 and the intervening extracellular loop (termed TM3/4 hairpins) that represent minimal membrane protein tertiary folding units. These hairpin variants, including CF-phenotypic loop mutants E217G and Q220R, and membrane-buried mutant V232D, were reconstituted into large unilamellar phosphatidylcholine (POPC) vesicles, and into corresponding vesicles containing 70 mol% POPC +30 mol% cholesterol, and studied by single-molecule FRET and circular dichroism experiments. We found that the presence of 30 mol% cholesterol induced an increase in helicity of all TM3/4 hairpins, suggesting an increase in bilayer cross-section and hence an increase in the depth of membrane insertion compared to pure POPC vesicles. Importantly, when we added the corrector VX-809, regardless of the presence or absence of cholesterol, all mutants displayed folding and helicity largely indistinguishable from the WT hairpin. Fluorescence spectroscopy measurements suggest that the corrector alters lipid packing and water accessibility. We propose a model whereby VX-809 shields the protein from the lipid environment in a mutant-independent manner such that the WT scaffold prevails. Such 'normalization' to WT conformation is consistent with the action of VX-809 as a protein-folding chaperone.
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Affiliation(s)
- Mathias Schenkel
- B CUBE - Center for Molecular Bioengineering, TU Dresden, Tatzberg 41, 01307 Dresden, Germany
| | - Dorna Ravamehr-Lake
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Tomasz Czerniak
- B CUBE - Center for Molecular Bioengineering, TU Dresden, Tatzberg 41, 01307 Dresden, Germany
| | - James P Saenz
- B CUBE - Center for Molecular Bioengineering, TU Dresden, Tatzberg 41, 01307 Dresden, Germany
| | - Georg Krainer
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW Cambridge, UK.
| | - Michael Schlierf
- B CUBE - Center for Molecular Bioengineering, TU Dresden, Tatzberg 41, 01307 Dresden, Germany.
| | - Charles M Deber
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
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Kim MD, Chung S, Dennis JS, Yoshida M, Aguiar C, Aller SP, Mendes ES, Schmid A, Sabater J, Baumlin N, Salathe M. Vegetable glycerin e-cigarette aerosols cause airway inflammation and ion channel dysfunction. Front Pharmacol 2022; 13:1012723. [PMID: 36225570 PMCID: PMC9549247 DOI: 10.3389/fphar.2022.1012723] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 09/08/2022] [Indexed: 02/02/2023] Open
Abstract
Vegetable glycerin (VG) and propylene glycol (PG) serve as delivery vehicles for nicotine and flavorings in most e-cigarette (e-cig) liquids. Here, we investigated whether VG e-cig aerosols, in the absence of nicotine and flavors, impact parameters of mucociliary function in human volunteers, a large animal model (sheep), and air-liquid interface (ALI) cultures of primary human bronchial epithelial cells (HBECs). We found that VG-containing (VG or PG/VG), but not sole PG-containing, e-cig aerosols reduced the activity of nasal cystic fibrosis transmembrane conductance regulator (CFTR) in human volunteers who vaped for seven days. Markers of inflammation, including interleukin-6 (IL6), interleukin-8 (IL8) and matrix metalloproteinase-9 (MMP9) mRNAs, as well as MMP-9 activity and mucin 5AC (MUC5AC) expression levels, were also elevated in nasal samples from volunteers who vaped VG-containing e-liquids. In sheep, exposures to VG e-cig aerosols for five days increased mucus concentrations and MMP-9 activity in tracheal secretions and plasma levels of transforming growth factor-beta 1 (TGF-β1). In vitro exposure of HBECs to VG e-cig aerosols for five days decreased ciliary beating and increased mucus concentrations. VG e-cig aerosols also reduced CFTR function in HBECs, mechanistically by reducing membrane fluidity. Although VG e-cig aerosols did not increase MMP9 mRNA expression, expression levels of IL6, IL8, TGFB1, and MUC5AC mRNAs were significantly increased in HBECs after seven days of exposure. Thus, VG e-cig aerosols can potentially cause harm in the airway by inducing inflammation and ion channel dysfunction with consequent mucus hyperconcentration.
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Affiliation(s)
- Michael D. Kim
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - Samuel Chung
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - John S. Dennis
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - Makoto Yoshida
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - Carolina Aguiar
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - Sheyla P. Aller
- Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Eliana S. Mendes
- Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Andreas Schmid
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - Juan Sabater
- Department of Research, Mount Sinai Medical Center, Miami Beach, FL, United States
| | - Nathalie Baumlin
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - Matthias Salathe
- Department of Internal Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of Kansas Medical Center, Kansas City, KS, United States,*Correspondence: Matthias Salathe,
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Vasconcelos-Cardoso M, Batista-Almeida D, Rios-Barros LV, Castro-Gomes T, Girao H. Cellular and molecular mechanisms underlying plasma membrane functionality and integrity. J Cell Sci 2022; 135:275922. [PMID: 35801807 DOI: 10.1242/jcs.259806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The plasma membrane not only protects the cell from the extracellular environment, acting as a selective barrier, but also regulates cellular events that originate at the cell surface, playing a key role in various biological processes that are essential for the preservation of cell homeostasis. Therefore, elucidation of the mechanisms involved in the maintenance of plasma membrane integrity and functionality is of utmost importance. Cells have developed mechanisms to ensure the quality of proteins that inhabit the cell surface, as well as strategies to cope with injuries inflicted to the plasma membrane. Defects in these mechanisms can lead to the development or onset of several diseases. Despite the importance of these processes, a comprehensive and holistic perspective of plasma membrane quality control is still lacking. To tackle this gap, in this Review, we provide a thorough overview of the mechanisms underlying the identification and targeting of membrane proteins that are to be removed from the cell surface, as well as the membrane repair mechanisms triggered in both physiological and pathological conditions. A better understanding of the mechanisms underlying protein quality control at the plasma membrane can reveal promising and unanticipated targets for the development of innovative therapeutic approaches.
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Affiliation(s)
- Maria Vasconcelos-Cardoso
- University of Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, 3000-548 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology (CIBB), 3000-548 Coimbra, Portugal.,Clinical Academic Centre of Coimbra (CACC), 3000-548 Coimbra, Portugal
| | - Daniela Batista-Almeida
- University of Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, 3000-548 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology (CIBB), 3000-548 Coimbra, Portugal.,Clinical Academic Centre of Coimbra (CACC), 3000-548 Coimbra, Portugal
| | - Laura Valeria Rios-Barros
- Department of Parasitology, Federal University of Minas Gerais, Belo Horizonte, CEP 31270-901, Brazil
| | - Thiago Castro-Gomes
- Department of Parasitology, Federal University of Minas Gerais, Belo Horizonte, CEP 31270-901, Brazil
| | - Henrique Girao
- University of Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, 3000-548 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology (CIBB), 3000-548 Coimbra, Portugal.,Clinical Academic Centre of Coimbra (CACC), 3000-548 Coimbra, Portugal
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Hanssens LS, Duchateau J, Casimir GJ. CFTR Protein: Not Just a Chloride Channel? Cells 2021; 10:2844. [PMID: 34831067 PMCID: PMC8616376 DOI: 10.3390/cells10112844] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 10/15/2021] [Accepted: 10/19/2021] [Indexed: 12/17/2022] Open
Abstract
Cystic fibrosis (CF) is a recessive genetic disease caused by mutations in a gene encoding a protein called Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). The CFTR protein is known to acts as a chloride (Cl-) channel expressed in the exocrine glands of several body systems where it also regulates other ion channels, including the epithelial sodium (Na+) channel (ENaC) that plays a key role in salt absorption. This function is crucial to the osmotic balance of the mucus and its viscosity. However, the pathophysiology of CF is more challenging than a mere dysregulation of epithelial ion transport, mainly resulting in impaired mucociliary clearance (MCC) with consecutive bronchiectasis and in exocrine pancreatic insufficiency. This review shows that the CFTR protein is not just a chloride channel. For a long time, research in CF has focused on abnormal Cl- and Na+ transport. Yet, the CFTR protein also regulates numerous other pathways, such as the transport of HCO3-, glutathione and thiocyanate, immune cells, and the metabolism of lipids. It influences the pH homeostasis of airway surface liquid and thus the MCC as well as innate immunity leading to chronic infection and inflammation, all of which are considered as key pathophysiological characteristics of CF.
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Affiliation(s)
- Laurence S. Hanssens
- Department of Pediatric Pulmonology and Cystic Fibrosis Clinic, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Avenue J.J. Crocq 15, 1020 Brussels, Belgium;
| | - Jean Duchateau
- Laboratoire Académique de Pédiatrie, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Avenue J.J. Crocq 15, 1020 Brussels, Belgium;
| | - Georges J. Casimir
- Department of Pediatric Pulmonology and Cystic Fibrosis Clinic, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Avenue J.J. Crocq 15, 1020 Brussels, Belgium;
- Laboratoire Académique de Pédiatrie, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Avenue J.J. Crocq 15, 1020 Brussels, Belgium;
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