scholarly journals Cryo-EM visualization of an active high open probability CFTR ion channel

2018 ◽  
Author(s):  
Jonathan F. Fay ◽  
Luba A. Aleksandrov ◽  
Timothy J. Jensen ◽  
Liying L. Cui ◽  
Joseph N. Kousouros ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Bound States ◽  
Structural Changes ◽  
Large Family ◽  
Anion Channel ◽  
List Type ◽  
Open Probability ◽  
Its Gene ◽  
Functional States ◽  
R Domain

AbstractThe Cystic fibrosis transmembrane conductance regulator (CFTR) anion channel, crucial to epithelial salt and water homeostasis, and defective due to mutations in its gene in patients with cystic fibrosis is a unique member of the large family of ATP-binding cassette transport proteins. Regulation of CFTR channel activity is stringently controlled by phosphorylation and nucleotide binding. Structural changes that underlie transitions between active and inactive functional states are not yet fully understood. Indeed the first 3D structures of dephosphorylated, ATP-free and phosphorylated ATP-bound states were only recently reported. Here we have determined the structure of inactive and active states of a thermally stabilized CFTR with very high channel open probability, confirmed after reconstitution into proteoliposomes. The unique repositioning of the TMHs and R domain density that we observe provide insights into the structural transition between active and inactive functional states of CFTR.HighlightsStructures of thermostabilized avian CFTR in dephosphorylated or phosphorylated forms at 4.3 Å and 6.6 Å resolution, respectively.Conformational differences of transmembrane helices 7 & 8 compared to zebra fish and human CFTR structures reveal an extracellular vestibule that may provide anion access to the pore.R-domain density appears to “plug” the intercellular vestibule in the dephosphorylated avian CFTR cryo-EM map.

scholarly journals Simple binding of protein kinase A prior to phosphorylation allows CFTR anion channels to be opened by nucleotides

2020 ◽  
Vol 117 (35) ◽  
pp. 21740-21746
Author(s):  
Csaba Mihályi ◽  
Iordan Iordanov ◽  
Beáta Töröcsik ◽  
László Csanády
Keyword(s):  
Cystic Fibrosis ◽  
Protein Kinase ◽  
Salt Water ◽  
Anion Channel ◽  
Large Network ◽  
Channel Activation ◽  
Incurable Disease ◽  
Cftr Mutations ◽  
In Cells ◽  
R Domain

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) anion channel is essential for epithelial salt–water balance. CFTR mutations cause cystic fibrosis, a lethal incurable disease. In cells CFTR is activated through the cAMP signaling pathway, overstimulation of which during cholera leads to CFTR-mediated intestinal salt–water loss. Channel activation is achieved by phosphorylation of its regulatory (R) domain by cAMP-dependent protein kinase catalytic subunit (PKA). Here we show using two independent approaches––an ATP analog that can drive CFTR channel gating but is unsuitable for phosphotransfer by PKA, and CFTR mutants lacking phosphorylatable serines––that PKA efficiently opens CFTR channels through simple binding, under conditions that preclude phosphorylation. Unlike when phosphorylation happens, CFTR activation by PKA binding is completely reversible. Thus, PKA binding promotes release of the unphosphorylated R domain from its inhibitory position, causing full channel activation, whereas phosphorylation serves only to maintain channel activity beyond termination of the PKA signal. The results suggest two levels of CFTR regulation in cells: irreversible through phosphorylation, and reversible through R-domain binding to PKA––and possibly also to other members of a large network of proteins known to interact with the channel.

scholarly journals Molecular pathology of the R117H cystic fibrosis mutation is explained by loss of a hydrogen bond

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Márton A Simon ◽  
László Csanády
Keyword(s):  
Cystic Fibrosis ◽  
Hydrogen Bond ◽  
Molecular Pathology ◽  
Atp Hydrolysis ◽  
Salt Water ◽  
Anion Channel ◽  
Open Probability ◽  
Binding Domains ◽  
State Dependent ◽  
Cftr Mutations

The phosphorylation-activated anion channel CFTR is gated by an ATP hydrolysis cycle at its two cytosolic nucleotide binding domains, and is essential for epithelial salt-water transport. A large number of CFTR mutations cause cystic fibrosis. Since recent breakthrough in targeted pharmacotherapy, CFTR mutants with impaired gating are candidates for stimulation by potentiator drugs. Thus, understanding the molecular pathology of individual mutations has become important. The relatively common R117H mutation affects an extracellular loop, but nevertheless causes a strong gating defect. Here we identify a hydrogen bond between the side chain of arginine 117 and the backbone carbonyl group of glutamate 1124 in the cryo-electronmicroscopic structure of phosphorylated, ATP-bound CFTR. We address the functional relevance of that interaction for CFTR gating using macroscopic and microscopic inside-out patch-clamp recordings. Employing thermodynamic double-mutant cycles, we systematically track gating-state dependent changes in the strength of the R117-E1124 interaction. We find that the H-bond is formed only in the open state, but neither in the short-lived "flickery" nor in the long-lived 'interburst' closed state. Loss of this H-bond explains the strong gating phenotype of the R117H mutant, including robustly shortened burst durations and strongly reduced intraburst open probability. The findings may help targeted potentiator design.

scholarly journals Preferential Phosphorylation of R-domain Serine 768 Dampens Activation of CFTR Channels by PKA

2005 ◽  
Vol 125 (2) ◽  
pp. 171-186 ◽  
Author(s):  
László Csanády ◽  
Donna Seto-Young ◽  
Kim W. Chan ◽  
Cristina Cenciarelli ◽  
Benjamin B. Angel ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Chloride Ion ◽  
Spectrometric Analysis ◽  
Inhibitory Influence ◽  
Open Probability ◽  
Principal Mechanism ◽  
Binding Domains ◽  
Excised Patches ◽  
The Right ◽  
R Domain

CFTR (cystic fibrosis transmembrane conductance regulator), the protein whose dysfunction causes cystic fibrosis, is a chloride ion channel whose gating is controlled by interactions of MgATP with CFTR's two cytoplasmic nucleotide binding domains, but only after several serines in CFTR's regulatory (R) domain have been phosphorylated by cAMP-dependent protein kinase (PKA). Whereas eight R-domain serines have previously been shown to be phosphorylated in purified CFTR, it is not known how individual phosphoserines regulate channel gating, although two of them, at positions 737 and 768, have been suggested to be inhibitory. Here we show, using mass spectrometric analysis, that Ser 768 is the first site phosphorylated in purified R-domain protein, and that it and five other R-domain sites are already phosphorylated in resting Xenopus oocytes expressing wild-type (WT) human epithelial CFTR. The WT channels have lower activity than S768A channels (with Ser 768 mutated to Ala) in resting oocytes, confirming the inhibitory influence of phosphoserine 768. In excised patches exposed to a range of PKA concentrations, the open probability (Po) of mutant S768A channels exceeded that of WT CFTR channels at all [PKA], and the half-maximally activating [PKA] for WT channels was twice that for S768A channels. As the open burst duration of S768A CFTR channels was almost double that of WT channels, at both low (55 nM) and high (550 nM) [PKA], we conclude that the principal mechanism by which phosphoserine 768 inhibits WT CFTR is by hastening the termination of open channel bursts. The right-shifted Po-[PKA] curve of WT channels might explain their slower activation, compared with S768A channels, at low [PKA]. The finding that phosphorylation kinetics of WT or S768A R-domain peptides were similar provides no support for an alternative explanation, that early phosphorylation of Ser 768 in WT CFTR might also impair subsequent phosphorylation of stimulatory R-domain serines. The observed reduced sensitivity to activation by [PKA] imparted by Ser 768 might serve to ensure activation of WT CFTR by strong stimuli while dampening responses to weak signals.

scholarly journals Molecular pathology of a cystic fibrosis mutation is explained by loss of a hydrogen bond

2021 ◽  
Author(s):  
Márton A Simon ◽  
LászlÓ Csanády
Keyword(s):  
Cystic Fibrosis ◽  
Hydrogen Bond ◽  
Molecular Pathology ◽  
Atp Hydrolysis ◽  
Salt Water ◽  
Anion Channel ◽  
Open Probability ◽  
Binding Domains ◽  
State Dependent ◽  
Cftr Mutations

The phosphorylation-activated anion channel CFTR is gated by an ATP hydrolysis cycle at its two cytosolic nucleotide binding domains, and is essential for epithelial salt-water transport. A large number of CFTR mutations cause cystic fibrosis. Since recent breakthrough in targeted pharmacotherapy, CFTR mutants with impaired gating are candidates for stimulation by potentiator drugs. Thus, understanding the molecular pathology of individual mutations has become important. The relatively common R117H mutation affects an extracellular loop, but nevertheless causes a strong gating defect. Here we identify a hydrogen bond between the side chain of arginine 117 and the backbone carbonyl group of glutamate 1124 in the cryo-electronmicroscopic structure of phosphorylated, ATP-bound CFTR. We address the functional relevance of that interaction for CFTR gating using macroscopic and microscopic inside-out patch-clamp recordings. Employing thermodynamic double-mutant cycles, we systematically track gating-state dependent changes in the strength of the R117-E1124 interaction. We find that the H-bond is formed only in the open state, but neither in the short-lived "flickery" nor in the long-lived "interburst" closed state. Loss of this H-bond explains the entire gating phenotype of the R117H mutant, including robustly shortened burst durations and strongly reduced intraburst open probability. The findings may help targeted potentiator design.

scholarly journals Structure, Gating, and Regulation of the CFTR Anion Channel

2019 ◽  
Vol 99 (1) ◽  
pp. 707-738 ◽  
Author(s):  
László Csanády ◽  
Paola Vergani ◽  
David C. Gadsby
Keyword(s):  
Cystic Fibrosis ◽  
Molecular Mechanisms ◽  
Anion Channel ◽  
Atp Binding ◽  
Electron Microscopic ◽  
Binding Domains ◽  
Cytosolic Domains ◽  
Cftr Protein ◽  
Atp Binding And Hydrolysis ◽  
R Domain

The cystic fibrosis transmembrane conductance regulator (CFTR) belongs to the ATP binding cassette (ABC) transporter superfamily but functions as an anion channel crucial for salt and water transport across epithelial cells. CFTR dysfunction, because of mutations, causes cystic fibrosis (CF). The anion-selective pore of the CFTR protein is formed by its two transmembrane domains (TMDs) and regulated by its cytosolic domains: two nucleotide binding domains (NBDs) and a regulatory (R) domain. Channel activation requires phosphorylation of the R domain by cAMP–dependent protein kinase (PKA), and pore opening and closing (gating) of phosphorylated channels is driven by ATP binding and hydrolysis at the NBDs. This review summarizes available information on structure and mechanism of the CFTR protein, with a particular focus on atomic-level insight gained from recent cryo-electron microscopic structures and on the molecular mechanisms of channel gating and its regulation. The pharmacological mechanisms of small molecules targeting CFTR’s ion channel function, aimed at treating patients suffering from CF and other diseases, are briefly discussed.

scholarly journals Inflammation in children with cystic fibrosis: contribution of bacterial production of long-chain fatty acids

2021 ◽  
Author(s):  
Erin Felton ◽  
Aszia Burrell ◽  
Hollis Chaney ◽  
Iman Sami ◽  
Anastassios C. Koumbourlis ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Fatty Acid ◽  
Antibiotic Treatment ◽  
Bacterial Production ◽  
Clinical Status ◽  
Achromobacter Xylosoxidans ◽  
List Type ◽  
Future Studies ◽  
Long Chain

Abstract Background Cystic fibrosis (CF) affects >70,000 people worldwide, yet the microbiologic trigger for pulmonary exacerbations (PExs) remains unknown. The objective of this study was to identify changes in bacterial metabolic pathways associated with clinical status. Methods Respiratory samples were collected at hospital admission for PEx, end of intravenous (IV) antibiotic treatment, and follow-up from 27 hospitalized children with CF. Bacterial DNA was extracted and shotgun DNA sequencing was performed. MetaPhlAn2 and HUMAnN2 were used to evaluate bacterial taxonomic and pathway relative abundance, while DESeq2 was used to evaluate differential abundance based on clinical status. Results The mean age of study participants was 10 years; 85% received combination IV antibiotic therapy (beta-lactam plus a second agent). Long-chain fatty acid (LCFA) biosynthesis pathways were upregulated in follow-up samples compared to end of treatment: gondoate (p = 0.012), oleate (p = 0.048), palmitoleate (p = 0.043), and pathways of fatty acid elongation (p = 0.012). Achromobacter xylosoxidans and Escherichia sp. were also more prevalent in follow-up compared to PEx (p < 0.001). Conclusions LCFAs may be associated with persistent infection of opportunistic pathogens. Future studies should more closely investigate the role of LCFA production by lung bacteria in the transition from baseline wellness to PEx in persons with CF. Impact Increased levels of LCFAs are found after IV antibiotic treatment in persons with CF. LCFAs have previously been associated with increased lung inflammation in asthma. This is the first report of LCFAs in the airway of persons with CF. This research provides support that bacterial production of LCFAs may be a contributor to inflammation in persons with CF. Future studies should evaluate LCFAs as predictors of future PExs.

scholarly journals Structure and Function of the CFTR Chloride Channel

1999 ◽  
Vol 79 (1) ◽  
pp. S23-S45 ◽  
Author(s):  
DAVID N. SHEPPARD ◽  
MICHAEL J. WELSH
Keyword(s):  
Cystic Fibrosis ◽  
Chloride Channel ◽  
Atp Hydrolysis ◽  
Current Knowledge ◽  
Structure And Function ◽  
Binding Domains ◽  
Transporter Family ◽  
Membrane Spanning ◽  
And Function ◽  
R Domain

Sheppard, David N., and Michael J. Welsh. Structure and Function of the CFTR Chloride Channel. Physiol. Rev. 79 , Suppl.: S23–S45, 1999. — The cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ABC transporter family that forms a novel Cl− channel. It is located predominantly in the apical membrane of epithelia where it mediates transepithelial salt and liquid movement. Dysfunction of CFTR causes the genetic disease cystic fibrosis. The CFTR is composed of five domains: two membrane-spanning domains (MSDs), two nucleotide-binding domains (NBDs), and a regulatory (R) domain. Here we review the structure and function of this unique channel, with a focus on how the various domains contribute to channel function. The MSDs form the channel pore, phosphorylation of the R domain determines channel activity, and ATP hydrolysis by the NBDs controls channel gating. Current knowledge of CFTR structure and function may help us understand better its mechanism of action, its role in electrolyte transport, its dysfunction in cystic fibrosis, and its relationship to other ABC transporters.

Using chest CT scan and unsupervised machine learning for predicting and evaluating response to lumacaftor-ivacaftor in people with cystic fibrosis

2021 ◽  
pp. 2101344
Author(s):  
Alienor Campredon ◽  
Enzo Battistella ◽  
Clémence Martin ◽  
Isabelle Durieu ◽  
Laurent Mely ◽  
...  
Keyword(s):  
Machine Learning ◽  
Cystic Fibrosis ◽  
Ct Scan ◽  
Structural Changes ◽  
Clinical Status ◽  
Chest Ct ◽  
Ct Scans ◽  
Wall Thickening ◽  
Unsupervised Machine Learning ◽  
One Year

ObjectivesLumacaftor-ivacaftor is a cystic fibrosis transmembrane conductance regulator (CFTR) modulator known to improve clinical status in people with cystic fibrosis (CF). This study aimed to assess lung structural changes after one year of lumacaftor-ivacaftor treatment, and to use unsupervised machine learning to identify morphological phenotypes of lung disease that are associated with response to lumacaftor-ivacaftor.MethodsAdolescents and adults with CF from the French multicenter real-world prospective observational study evaluating the first year of treatment with lumacaftor-ivacaftor were included if they had pretherapeutic and follow-up chest computed tomography (CT)-scans available. CT scans were visually scored using a modified Bhalla score. A k-mean clustering method was performed based on 120 radiomics features extracted from unenhanced pretherapeutic chest CT scans.ResultsA total of 283 patients were included. The Bhalla score significantly decreased after 1 year of lumacaftor-ivacaftor (−1.40±1.53 points compared with pretherapeutic CT; p<0.001). This finding was related to a significant decrease in mucus plugging (−0.35±0.62 points; p<0.001), bronchial wall thickening (−0.24±0.52 points; p<0.001) and parenchymal consolidations (−0.23±0.51 points; p<0.001). Cluster analysis identified 3 morphological clusters. Patients from cluster C were more likely to experience an increase in percent predicted forced expiratory volume in 1 sec (ppFEV1) ≥5 under lumacaftor–ivacaftor than those in the other clusters (54% of responders versus 32% and 33%; p=0.01).ConclusionOne year treatment with lumacaftor-ivacaftor was associated with a significant visual improvement of bronchial disease on chest CT. Radiomics features on pretherapeutic CT scan may help in predicting lung function response under lumacaftor-ivacaftor.

Urinary Retention Due to Severe Pseudocystic Mucoid Degeneration of the Prostatic Matrix: A Rare Urologic Manifestation of Cystic Fibrosis

2015 ◽  
Vol 95 (4) ◽  
pp. 486-488
Author(s):  
Gesa Kellermann ◽  
Aristotelis G. Anastasiadis ◽  
Desirée L. Dräger ◽  
Friedrich Prall ◽  
Oliver W. Hakenberg
Keyword(s):  
Cystic Fibrosis ◽  
Urinary Retention ◽  
Genetic Disease ◽  
Autosomal Recessive ◽  
Structural Changes ◽  
Histopathological Examination ◽  
Underlying Disease ◽  
Exocrine Glands ◽  
Mucoid Degeneration ◽  
Prostatic Enlargement

Cystic fibrosis (CF) is an autosomal recessive genetic disease, which is characterized by the production of thick mucus in exocrine glands. The main cause for morbidity and mortality in CF patients is respiratory failure. The gastrointestinal system is also commonly affected. Urologic manifestations of CF include infertility and azoospermia, nephrolithiasis, and stress urinary incontinence. In this report, we describe a 33-year-old male, who presented with recurrent urinary retention due to prostatic enlargement despite his young age. After transurethral resection, the voiding problems resolved. Histopathological examination, however, revealed a severe pseudocystic mucoid degeneration of the prostatic matrix as a cause of his subvesical obstruction. Although these structural changes are most probably due to his underlying disease, detailed histologic features have not been described in the literature.

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