Biology subjects

Vergani, P.

Publications and source records attributed to Vergani, P..

4 recordsLinked to original sources

bioRxiv2022

K978C CFTR restores essential epithelial function with greater efficiency than wildtype CFTR when expressed in CF airway cells.

Class Ia/b CFTR variants cause severe cystic fibrosis (CF) lung disease in ~10% of CF patients and are untreatable with small molecule pharmaceuticals. Genetic replacement strategies offer a potential cure for all patients but so far, have displayed limited efficiency in vivo. We hypothesised that increasing protein abundance and/or activity of introduced CFTRs would more effectively restore function to CF bronchial epithelial cells (CFBE) in the presence of CF sputum (CFS) than wildtype (WT)-CFTR. We investigated codon optimised CFTR (hCAI), increased open probability CFTR (K978C) and codon optimised plus K978C (h^K978C) as candidates for gene therapy. Transfection of HEK293T with hCAI and h^K978C produced ~10-fold more CFTR protein than WT or K978C CFTRs. hCAI and h^K978C also displayed ~4-fold greater anion transport than WT in a halide-sensitive YFP quenching assay. However, functionality of modified CFTR cDNAs expressed in CFBE were profoundly different. 10% transduction of CFBE with K978C, compared to 22% transduction with WT, restored Cl- transport to similar levels as that recorded from non-CF cells. K978C increased ASL height and pH more effectively than WT-CFTR, while hCAI and h^K978C had limited impact. Further investigation indicated that codon optimised CFTRs mis-localised in CFBE and compromised vectoral Cl- transport. These data provide further evidence that codon optimised CFTR cDNAs may be unsuitable for gene therapy practices that employ high activity promoters. However, increased activity CFTR cDNAs such as K978C, that potentially mimic the effect of potentiators, may provide more potent recovery of function than WT-CFTR cDNA in CF airways. Significance StatementCystic fibrosis (CF) disease is associated with genetic malfunction of the Cl- channel CFTR, leading to dehydration and decreased pH in the fluid lining the airways. Replacement of CFTR by gene therapy/gene editing offers potential therapeutic benefit but efficiency is poor. We show that gain of activity K978C CFTR under the control of a high activity promoter fully restored Cl- transport, hydration and pH to CF bronchial epithelial cells (CFBE) in the presence of CF sputum and more efficiently than wild type CFTR. Codon optimised forms of CFTR were much less effective and proteins were mis-localised/mis-processed in CFBE. Thus, K978C could offer improved therapeutic potential.

molecular biology↗

bioRxiv2021

Can two wrongs make a right? F508del-CFTR ion channel rescue by second-site mutations in its transmembrane domains

Deletion of phenylalanine 508 (F508del), in the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel, is the most common cause of cystic fibrosis (CF). F508 is located on nucleotide-binding domain 1 (NBD1) in contact with cytosolic extensions of transmembrane helices, in particular intracellular loop 4 (ICL4). We carried out a mutagenesis scan of ICL4 by introducing five or six second-site mutations at eleven positions in cis with F508del, and quantifying changes in membrane proximity and ion-channel function of CFTR. The scan strongly validated the effectiveness of R1070W at rescuing F508del defects. Molecular dynamics simulations highlighted two features characterizing the ICL4/NBD1 interface of F508del/R1070W-CFTR: flexibility, with frequent transient formation of interdomain hydrogen bonds, and loosely stacked aromatic sidechains, (F1068, R1070W, and F1074, mimicking F1068, F508 and F1074 in wild-type CFTR). F508del-CFTR had a distorted aromatic stack, with F1068 displaced towards space vacated by F508. In F508del/R1070F-CFTR, which largely retained F508del defects, R1070F could not form hydrogen bonds, and the interface was less flexible. Other ICL4 second-site mutations which partially rescued F508del-CFTR are F1068M and F1074M. Methionine side chains allow hydrophobic interactions without the steric rigidity of aromatic rings, possibly conferring flexibility to accommodate the absence of F508 and retain a dynamic interface. Finally, two mutations identified in a yeast scan (A141S and R1097T, on adjacent transmembrane helices linked to ICL1 and ICL4) also partially rescued F508del-CFTR function. These studies highlight the importance of hydrophobic interactions and conformational flexibility at the ICL4/NBD1 interface, advancing understanding of the structural underpinning of F508del dysfunction.

biophysics↗

bioRxiv2019

High-content assay for precision medicine discovery in cystic fibrosis.

CFTR, a plasma membrane anion channel, plays a key role in controlling transepithelial fluid movement. Excessive activation results in intestinal fluid loss during secretory diarrhoeas, while CFTR mutations underlie cystic fibrosis (CF). Anion permeability depends both on how well CFTR channels work (permeation/gating) and on how many are present at the membrane (reflecting folding, trafficking, metabolic stability). Recently, treatments with two drug classes targeting CFTR - one boosting ion-channel function (potentiators), the other increasing plasma membrane density (correctors) - have provided significant health benefits to CF patients. Here we present an image-based fluorescence assay that can rapidly and simultaneously estimate both CFTR ion-channel function and the proteins proximity to the membrane. We monitor F508del-CFTR, the most common CF-causing variant, and confirm rescue by low temperature, CFTR-targeting drugs and second-site revertant mutation R1070W. In addition, we characterize a panel of 62 CF-causing mutations. Our measurements correlate well with published data (electrophysiology and biochemistry), further confirming validity of the assay. Finally, we profile effects of acute treatment with approved potentiator drug VX-770 on the rare-mutation panel. Mapping the potentiation profile on CFTR structures raises mechanistic hypotheses on drug action, suggesting that VX-770 might allow an open-channel conformation with an alternative arrangement of domain interfaces around site 1. The assay is a valuable tool for investigation of CFTR molecular mechanisms, allowing accurate inferences on gating/permeation. In addition, by providing a two-dimensional characterization of the CFTR protein, it could better inform development of single-drug and precision therapies addressing the root cause of CF disease.

pharmacology and toxicology↗

bioRxiv2017

Structure of transmembrane helix 8 and possible membrane defects in CFTR

The cystic fibrosis transmembrane conductance regulator (CFTR) is an ion channel that regulates the flow of anions across epithelia. Mutations in CFTR cause cystic fibrosis. CFTR belongs to the ATP-Binding Cassette (ABC) transporter superfamily, and gating is controlled by phosphorylation and ATP binding and hydrolysis. Recent ATP-free and ATP-bound structures of zebrafish CFTR revealed an unwound segment of transmembrane helix (TM) 8, which appears to be a unique feature of CFTR not present in other ABC transporter structures. Here, by means of 1 s long molecular dynamics simulations, we investigate the interactions formed by this TM8 segment with nearby helices, in both ATP-free and ATP-bound states. We highlight the structural role of TM8 in maintaining the functional architecture of the pore and we describe a distinct membrane defect that is found near TM8 only in the ATP-free state. The results of the MD simulations are discussed in the context of the gating mechanism of CFTR.

biochemistry↗