In silico, in vitro and ex vivo characterization of cystic fibrosis transmembrane conductance regulator pathogenic variants localized in the fourth intracellular loop and their rescue by modulators.

Background And Purpose: Cystic fibrosis (CF) is due to loss-of-function variants of the CF transmembrane conductance regulator (CFTR) channel. The most effective treatment for people with CF carrying the F508del mutation is the triple combination of elexacaftor-tezacaftor-ivacaftor (ETI). ETI can correct the underlying defect(s) in other CFTR mutants.

Prime editing functionally corrects cystic fibrosis-causing CFTR mutations in human organoids and airway epithelial cells.

Prime editing is a recent, CRISPR-derived genome editing technology capable of introducing precise nucleotide substitutions, insertions, and deletions. Here, we present prime editing approaches to correct L227R- and N1303K-CFTR, two mutations that cause cystic fibrosis and are not eligible for current market-approved modulator therapies. We show that, upon DNA correction of the CFTR gene, the complex glycosylation, localization, and, most importantly, function of the CFTR protein are restored in HEK293T and 16HBE cell lines.

Role of KCNK3 Dysfunction in Dasatinib-associated Pulmonary Arterial Hypertension and Endothelial Cell Dysfunction.

Pulmonary arterial (PA) hypertension (PAH) is a severe cardiopulmonary disease that may be triggered by exposure to drugs such as dasatinib or facilitated by genetic predispositions. The incidence of dasatinib-associated PAH is estimated at 0.45%, suggesting individual predispositions.

Effects of skin-to-skin contact in supported diagonal flexion positioning on movement quality in very preterm infants at term age.

Background: Preterm birth is associated with a high risk of long-term neuromotor disabilities such as coordination of movements, deficient antigravity limb movement, less adaptive postural control strategies, head deformities… AIMS: The aim of the present study was to examine the potential positive impact of a Supported Diagonal Flexion (SDF) skin-to-skin contact (SSC) positioning on the neuromotor development and movement quality of very preterm infants at term age.

Study Design: Monocentric prospective matched-pair case-control study.

Subjects: Thirty very preterm infants and their mother were proposed either SDF SSC positioning (n = 15) or Vertical SSC positioning (n = 15).

Putting bicarbonate on the spot: pharmacological insights for CFTR correction in the airway epithelium.

Cystic fibrosis (CF) is caused by defective Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) proteins. CFTR controls chloride (Cl) and bicarbonate (HCO ) transport into the Airway Surface Liquid (ASL). We investigated the impact of F508del-CFTR correction on HCO secretion by studying transepithelial HCO fluxes.

Theratyping cystic fibrosis patients to guide elexacaftor/tezacaftor/ivacaftor out-of-label prescription.

Background: Around 20% of people with cystic fibrosis (pwCF) do not have access to the triple combination elexacaftor/tezacaftor/ivacaftor (ETI) in Europe because they do not carry the F508del allele on the CF transmembrane conductance regulator () gene. Considering that pwCF carrying rare variants may benefit from ETI, including variants already validated by the US Food and Drug Administration (FDA), a compassionate use programme was launched in France. PwCF were invited to undergo a nasal brushing to investigate whether the pharmacological rescue of CFTR activity by ETI in human nasal epithelial cell (HNEC) cultures was predictive of the clinical response.

Nonsense mutations accelerate lung disease and decrease survival of cystic fibrosis children.

Rationale: Limited information is available on the clinical status of people with Cystic Fibrosis (pwCF) carrying 2 nonsense mutations (PTC/PTC). The main objective of this study was to compare disease severity between pwCF PTC/PTC, compound heterozygous for F508del and PTC (F508del/PTC) and homozygous for F508del (F508del+/+).

Methods: Based on the European CF Society Patient Registry clinical data of pwCF living in high and middle income European and neighboring countries, PTC/PTC (n = 657) were compared with F508del+/+ (n = 21,317) and F508del/PTC(n = 4254).

Design of Crotoxin-Based Peptides with Potentiator Activity Targeting the ΔF508NBD1 Cystic Fibrosis Transmembrane Conductance Regulator.

We have previously shown that the CBb subunit of crotoxin, a β-neurotoxin with phospholipase A (PLA) activity, targets the human ΔF508CFTR chloride channel implicated in cystic fibrosis (CF). By direct binding to the nucleotide binding domain 1 (NBD1) of ΔF508CFTR, this neurotoxic PLA acts as a potentiator increasing chloride channel current and corrects the trafficking defect of misfolded ΔF508CFTR inside the cell. Here, for a therapeutics development of new anti-cystic fibrosis agents, we use a structure-based in silico approach to design peptides mimicking the CBb-ΔF508NBD1 interface.

Acting on the CFTR Membrane-Spanning Domains Interface Rescues Some Misfolded Mutants.

ABC transporters are large membrane proteins sharing a complex architecture, which comprises two nucleotide-binding domains (NBDs) and two membrane-spanning domains (MSDs). These domains are susceptible to mutations affecting their folding and assembly. In the CFTR (ABCC7) protein, a groove has been highlighted in the MSD1 at the level of the membrane inner leaflet, containing both multiple mutations affecting folding and a binding site for pharmaco-chaperones that stabilize this region.

Pharmacological chaperone-rescued cystic fibrosis CFTR-F508del mutant overcomes PRAF2-gated access to endoplasmic reticulum exit sites.

The endoplasmic reticulum exit of some polytopic plasma membrane proteins (PMPs) is controlled by arginin-based retention motifs. PRAF2, a gatekeeper which recognizes these motifs, was shown to retain the GABA-receptor GB1 subunit in the ER. We report that PRAF2 can interact on a stoichiometric basis with both wild type and mutant F508del Cystic Fibrosis (CF) Transmembrane Conductance Regulator (CFTR), preventing the access of newly synthesized cargo to ER exit sites.

Keratin 8 is a scaffolding and regulatory protein of ERAD complexes.

Early recognition and enhanced degradation of misfolded proteins by the endoplasmic reticulum (ER) quality control and ER-associated degradation (ERAD) cause defective protein secretion and membrane targeting, as exemplified for Z-alpha-1-antitrypsin (Z-A1AT), responsible for alpha-1-antitrypsin deficiency (A1ATD) and F508del-CFTR (cystic fibrosis transmembrane conductance regulator) responsible for cystic fibrosis (CF). Prompted by our previous observation that decreasing Keratin 8 (K8) expression increased trafficking of F508del-CFTR to the plasma membrane, we investigated whether K8 impacts trafficking of soluble misfolded Z-A1AT protein. The subsequent goal of this study was to elucidate the mechanism underlying the K8-dependent regulation of protein trafficking, focusing on the ERAD pathway.

Differential CFTR-Interactome Proximity Labeling Procedures Identify Enrichment in Multiple SLC Transporters.

Proteins interacting with CFTR and its mutants have been intensively studied using different experimental approaches. These studies provided information on the cellular processes leading to proper protein folding, routing to the plasma membrane, recycling, activation and degradation. Recently, new approaches have been developed based on the proximity labeling of protein partners or proteins in close vicinity and their subsequent identification by mass spectrometry.

Pharmacological chaperones improve intra-domain stability and inter-domain assembly via distinct binding sites to rescue misfolded CFTR.

Protein misfolding is involved in a large number of diseases, among which cystic fibrosis. Complex intra- and inter-domain folding defects associated with mutations in the cystic fibrosis transmembrane regulator (CFTR) gene, among which p.Phe508del (F508del), have recently become a therapeutical target.

New insights into structure and function of bis-phosphinic acid derivatives and implications for CFTR modulation.

C407 is a compound that corrects the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein carrying the p.Phe508del (F508del) mutation. We investigated the corrector effect of c407 and its derivatives on F508del-CFTR protein.

Modulators of CFTR. Updates on clinical development and future directions.

Cystic fibrosis (CF) is the most frequent life-limiting autosomal recessive disorder in the Caucasian population. It is due to mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. Current symptomatic CF therapies, which treat the downstream consequences of CFTR mutations, have increased survival.

Targeting different binding sites in the CFTR structures allows to synergistically potentiate channel activity.

Recent evidence shows that combination of correctors and potentiators, such as the drug ivacaftor (VX-770), can significantly restore the functional expression of mutated Cystic Fibrosis Transmembrane conductance Regulator (CFTR), an anion channel which is mutated in cystic fibrosis (CF). The success of these combinatorial therapies highlights the necessity of identifying a broad panel of specific binding mode modulators, occupying several distinct binding sites at structural level. Here, we identified two small molecules, SBC040 and SBC219, which are two efficient cAMP-independent potentiators, acting at low concentration of forskolin with EC close to 1 μM and in a synergic way with the drug VX-770 on several CFTR mutants of classes II and III.

The influence of CFTR complex alleles on precision therapy of cystic fibrosis.

CFTR is an extensively studied gene and multiple sequence variants have been identified, many of which still need to be defined as neutral or disease causing. Complex alleles are defined when at least two variants are identified on the same allele. Each pathogenic variant can affect distinct steps of the CFTR biogenesis.

The "one airway, one disease" concept in light of Th2 inflammation.

In line with the pathophysiological continuum described between nose and bronchus in allergic respiratory diseases, we assessed whether nasal epithelium could mirror the Type 2 T-helper cell (Th2) status of bronchial epithelium.Nasal and bronchial cells were collected by brushing from healthy controls (C, n=13), patients with allergic rhinitis and asthma (AR, n=12), and patients with isolated allergic rhinitis (R, n=14). Cellular composition was assessed by flow cytometry, gene expression was analysed by RNA sequencing and Th2, Type 17 T-helper cell (Th17) and interferon (IFN) signatures were derived from the literature.

Factors influencing readthrough therapy for frequent cystic fibrosis premature termination codons.

Premature termination codons (PTCs) are generally associated with severe forms of genetic diseases. Readthrough of in-frame PTCs using small molecules is a promising therapeutic approach. Nonetheless, the outcome of preclinical studies has been low and variable.

Cis variants identified in F508del complex alleles modulate CFTR channel rescue by small molecules.

Molecules correcting the trafficking (correctors) and gating defects (potentiators) of the cystic fibrosis causing mutation c.1521_1523delCTT (p.Phe508del) begin to be a useful treatment for CF patients bearing p.