scholarly journals Comprehensive Analysis of Combinatorial Pharmacological Treatments to Correct Nonsense Mutations in the CFTR Gene

2021 ◽  
Vol 22 (21) ◽  
pp. 11972
Author(s):  
Arianna Venturini ◽  
Anna Borrelli ◽  
Ilaria Musante ◽  
Paolo Scudieri ◽  
Valeria Capurro ◽  
...  
Keyword(s):  
Comprehensive Analysis ◽  
Cftr Gene ◽  
Loss Of Function ◽  
Pharmacological Treatments ◽  
Protein Maturation ◽  
Nonsense Mutations ◽  
Nonsense Mediated Decay ◽  
Cftr Mutations ◽  
Cftr Protein ◽  
And Function

Cystic fibrosis (CF) is caused by loss of function of the CFTR chloride channel. A substantial number of CF patients carry nonsense mutations in the CFTR gene. These patients cannot directly benefit from pharmacological correctors and potentiators that have been developed for other types of CFTR mutations. We evaluated the efficacy of combinations of drugs targeting at various levels the effects of nonsense mutations: SMG1i to protect CFTR mRNA from nonsense-mediated decay (NMD), G418 and ELX-02 for readthrough, VX-809 and VX-445 to promote protein maturation and function, PTI-428 to enhance CFTR protein synthesis. We found that the extent of rescue and sensitivity to the various agents is largely dependent on the type of mutation, with W1282X and R553X being the mutations most and least sensitive to pharmacological treatments, respectively. In particular, W1282X-CFTR was highly responsive to NMD suppression by SMG1i but also required treatment with VX-445 corrector to show function. In contrast, G542X-CFTR required treatment with readthrough agents and VX-809. Importantly, we never found cooperativity between the NMD inhibitor and readthrough compounds. Our results indicate that treatment of CF patients with nonsense mutations requires a precision medicine approach with the design of specific drug combinations for each mutation.

The first identified heterozygous nonsense mutations in podocalyxin offer new perspectives on the biology of podocytopathies

2019 ◽  
Vol 133 (3) ◽  
pp. 443-447 ◽  
Author(s):  
Ido Refaeli ◽  
Michael R. Hughes ◽  
Kelly M. McNagny
Keyword(s):  
Turning Point ◽  
Autosomal Dominant ◽  
Adult Onset ◽  
Loss Of Function ◽  
Nonsense Mutations ◽  
Cytoskeletal Organization ◽  
Nonsense Mediated Decay ◽  
Large Pool ◽  
Experimental Findings ◽  
And Function

Abstract In the last two decades, our understanding of the genetic underpinnings of inherited podocytopathies has advanced immensely. By sequencing the genomes of a large pool of families affected by focal segmental glomerulosclerosis (FSGS), researchers have identified a common theme: familial podocytopathies are frequently caused by genes selectively expressed in podocytes. Podocalyxin is a podocyte-specific surface sialomucin that has long been known to play important roles in podocyte morphogenesis and function. Few studies, however, have shown a conclusive link between mutations in the gene and FSGS complemented by functional evidence. In a fascinating new paper published in Clinical Science, Lin et al. identify two unrelated pedigrees in which dominant loss-of-function mutations in PODXL lead to adult-onset FSGS. Nonsense-mediated decay of the mutated PODXL transcripts leads to protein insufficiency, which in turn cause podocyte dysfunction through defects in motility and cytoskeletal organization. This is the first study to date that demonstrates, mechanistically, how autosomal dominant mutations in podocalyxin can lead to FSGS and renal insufficiency. Here, we summarize the experimental findings of this manuscript and propose, perhaps, a more controversial hypothesis: down-regulation of podocalyxin protein expression from podocytes is a critical turning point in the progression of most podocytopathies and may be mechanistically relevant to glomerulopathies in which podocyte damage is not necessarily induced by genetic lesions.

Oxidant stress suppresses CFTR expression

2006 ◽  
Vol 290 (1) ◽  
pp. C262-C270 ◽  
Author(s):  
André M. Cantin ◽  
Ginette Bilodeau ◽  
Cristine Ouellet ◽  
Jie Liao ◽  
John W. Hanrahan
Keyword(s):  
Gene Expression ◽  
Time Course ◽  
Oxidant Stress ◽  
Cftr Gene ◽  
T84 Cells ◽  
Gene Encoding ◽  
Glutamylcysteine Synthetase ◽  
Cftr Protein ◽  
Stressed Cells ◽  
And Function

Epithelial mucous membranes are repeatedly exposed to oxidants and xenobiotics. CFTR plays a role in glutathione transepithelial flux and in defining the hydration and viscoelasticity of protective mucus. We therefore hypothesized that CFTR expression and function may be modulated by oxidant stress. A sublethal oxidant stress ( tert-butylhydroquinone, BHQ) in CFTR-expressing epithelial cells (T84) induced a significant increase in cellular glutathione that was associated with an increase in expression of the gene encoding the heavy subunit of the rate-limiting enzyme for glutathione synthesis, γ-glutamylcysteine synthetase (γ-GCShs). CFTR gene expression was markedly decreased according to a time course that mirrored the changes in γ-GCShs. Western blot analysis confirmed that the decrease in CFTR gene expression was associated with a decrease in CFTR protein. cAMP-dependent iodide efflux was also decreased by the oxidant stress. Nuclear run-on assays indicated that the oxidant stress had no effect on CFTR gene transcription, but the mRNA stability in the oxidant-stressed cells was markedly reduced. Furthermore, BHQ increased γ-GCShs mRNA while decreasing CFTR mRNA in Calu-3 cells, and taurine chloramine induced similar effects in T84 cells. We conclude that suppression of CFTR expression may represent an adaptive response of mucosal epithelium to an exogenous oxidant stress.

scholarly journals CFTR mRNAs with nonsense codons are degraded by the SMG6-mediated endonucleolytic pathway

2021 ◽  
Author(s):  
Edward Sanderlin ◽  
Melissa Keenan ◽  
Martin Mense ◽  
Alexey Revenko ◽  
Brett Monia ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Exon Junction Complex ◽  
Transmembrane Conductance Regulator ◽  
Loss Of Function ◽  
Transmembrane Conductance ◽  
Nonsense Mutations ◽  
Nonsense Mediated Decay ◽  
Nonsense Codon ◽  
Translational Readthrough ◽  
Nonsense Codons

Abstract Cystic fibrosis is caused by loss of function mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene resulting in severe lung disease. Nearly 10% of cystic fibrosis patients have at least one CFTR allele with a nonsense mutation that generates a nonsense codon in the mRNA. Nonsense mutations can result in significant reduction of gene expression partially due to rapid mRNA degradation through the nonsense-mediated decay (NMD) pathway. It has not been thoroughly investigated which branch of the NMD pathway governs the decay of CFTR mRNAs containing nonsense codons. Here we utilized antisense oligonucleotides targeting NMD factors to evaluate the regulation of nonsense codon-containing CFTR mRNAs by the NMD pathway. Interestingly, we found that CFTR mRNAs with G542X, R1162X, and W1282X nonsense codons require UPF2, UPF3, and exon junction complex proteins for NMD, whereas CFTR mRNAs with the Y122X nonsense codon do not. Furthermore, we demonstrated that all evaluated CFTR mRNAs harboring nonsense codons were degraded by the SMG6-mediated endonucleolytic pathway rather than the SMG5/SMG7-mediated exonucleolytic pathway. Finally, we found that stabilization of CFTR mRNAs by NMD inhibition alone improved functional W1282X protein production, and improved the efficiency of aminoglycoside translational readthrough of CFTR-Y122X, -G542X, and -R1162X mRNAs.

CFTR is functionally active in GnRH-expressing GT1–7 hypothalamic neurons

1999 ◽  
Vol 277 (3) ◽  
pp. C563-C571 ◽  
Author(s):  
Richard T. Weyler ◽  
Karin A. Yurko-Mauro ◽  
Ronald Rubenstein ◽  
Wouter J. W. Kollen ◽  
William Reenstra ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Neuronal Cell ◽  
Cftr Gene ◽  
Gene Transcript ◽  
Transmembrane Conductance Regulator ◽  
Hypothalamic Neurons ◽  
Cftr Protein ◽  
And Function ◽  
Human Brains ◽  
Gene Mrna

We have demonstrated the expression of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, mRNA, and protein within the rat and human brains, in areas regulating sexual differentiation and function. We have found that GT1–7, a gonadotropin-releasing hormone (GnRH)-secreting hypothalamic neuronal cell line, expresses the CFTR gene, mRNA, and protein and cAMP-dependent 36Cl efflux. A linear 7-pS Cl− conductance, which is stimulated by ATP and cAMP analogs and inhibited by glibenclamide, consistent with CFTR activity, has been identified in GT1–7 cells. Antisense oligo(dN) generated against exon 10 of the CFTR gene transcript (mRNA) inhibit GnRH secretion into media [312 ± 73, 850 ± 150, 963 ± 304, and 912 ± 74 pg GnRH/4 × 106 cells for antisense, sense, missense, and no oligo(dN), respectively; P < 0.029 for antisense oligo(dN)-treated vs. normal cells]. No changes in intracellular synthesis of GnRH were noted [1,400 ± 371 and 1,395 ± 384 pg GnRH/4 × 106 cells for antisense and sense oligo(dN), respectively]. Antisense oligo(dN), but not sense or missense oligo(dN), inhibited cAMP-dependent36Cl efflux. The expression of CFTR protein, detected by Western blotting, was also inhibited 68% by preincubation of cells with antisense oligo(dN). GT1–7 hypothalamic neurons express the CFTR gene, mRNA, and protein, which modulate neurosecretion. Abnormal neuropeptide vesicle trafficking by mutant CFTR may help to explain some of the diverse manifestations of cystic fibrosis.

Cystic Fibrosis: Pathophysiology of Lung Disease

2019 ◽  
Vol 40 (06) ◽  
pp. 715-726 ◽  
Author(s):  
Christelle Bergeron ◽  
André M. Cantin
Keyword(s):  
Cystic Fibrosis ◽  
Mucociliary Clearance ◽  
Current Knowledge ◽  
Clinical Manifestations ◽  
Autosomal Recessive Disorder ◽  
Cftr Gene ◽  
Susceptibility To Infection ◽  
Life Threatening ◽  
Cftr Protein ◽  
And Function

AbstractCystic fibrosis (CF) is a common, life-threatening, multisystemic, autosomal recessive disorder. In the last few years, giant steps have been made with regard to the understanding of CF pathophysiology, allowing the scientific community to propose mechanisms that cause the myriad of CF clinical manifestations. Following the discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in 1989, the structure and function of the CFTR protein were described. Since then, more than 2,000 variants of the CFTR gene and their impact on the amount and function of the CFTR protein have been reported. The role of the CFTR protein as an ion channel transporting chloride and bicarbonate and its repercussions on different epithelial cell-lined organs and mucus are now better understood. Mechanisms behind susceptibility to infection in CF have also been proposed and include abnormalities in the composition, volume and acidity of the airway surface liquid, changes in the submucosal gland's anatomy and function, and deficiencies in the mucociliary clearance system. Numerous hypotheses explaining the excessive inflammatory response in CF are also debated and involve impaired mucociliary clearance, persistent hypoxia, lipid abnormalities, protease and antiprotease disproportion, and oxidant and antioxidant imbalance. The purpose of this review is to summarize our current knowledge of CF pathophysiology, including significant historic discoveries and most recent breakthroughs, and to improve understanding and awareness of this fatal disease.

scholarly journals Synergy between Readthrough and Nonsense Mediated Decay Inhibition in a Murine Model of Cystic Fibrosis Nonsense Mutations

2020 ◽  
Vol 22 (1) ◽  
pp. 344
Author(s):  
Daniel R. McHugh ◽  
Calvin U. Cotton ◽  
Craig A. Hodges
Keyword(s):  
Protein Function ◽  
Therapeutic Option ◽  
Genetic Disorders ◽  
Therapeutic Strategies ◽  
Primary Cells ◽  
Functional Protein ◽  
Nonsense Mutations ◽  
Nonsense Mediated Decay ◽  
Premature Termination Codons ◽  
Cftr Protein

Many heritable genetic disorders arise from nonsense mutations, which generate premature termination codons (PTCs) in transcribed mRNA. PTCs ablate protein synthesis by prematurely terminating the translation of mutant mRNA, as well as reducing mutant mRNA quantity through targeted degradation by nonsense-mediated decay (NMD) mechanisms. Therapeutic strategies for nonsense mutations include facilitating ribosomal readthrough of the PTC and/or inhibiting NMD to restore protein function. However, the efficacy of combining readthrough agents and NMD inhibitors has not been thoroughly explored. In this study, we examined combinations of known NMD inhibitors and readthrough agents using functional analysis of the CFTR protein in primary cells from a mouse model carrying a G542X nonsense mutation in Cftr. We observed synergy between an inhibitor of the NMD component SMG-1 (SMG1i) and the readthrough agents G418, gentamicin, and paromomycin, but did not observe synergy with readthrough caused by amikacin, tobramycin, PTC124, escin, or amlexanox. These results indicate that treatment with NMD inhibitors can increase the quantity of functional protein following readthrough, and that combining NMD inhibitors and readthrough agents represents a potential therapeutic option for treating nonsense mutations.

scholarly journals Nanomolar-potency ‘co-potentiator’ therapy for cystic fibrosis caused by a defined subset of minimal function CFTR mutants

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Puay-Wah Phuan ◽  
Joseph-Anthony Tan ◽  
Amber A. Rivera ◽  
Lorna Zlock ◽  
Dennis W. Nielson ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Class Ii ◽  
Bronchial Epithelial Cell ◽  
Therapeutic Benefit ◽  
Initial Structure ◽  
Transmembrane Conductance Regulator ◽  
Loss Of Function ◽  
Nonsense Mutations ◽  
Minimal Function ◽  
Cftr Mutations

AbstractAvailable CFTR modulators provide no therapeutic benefit for cystic fibrosis (CF) caused by many loss-of-function mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel, including N1303K. We previously introduced the concept of ‘co-potentiators’ (combination-potentiators) to rescue CFTR function in some minimal function CFTR mutants. Herein, a screen of ~120,000 drug-like synthetic small molecules identified active co-potentiators of pyrazoloquinoline, piperidine-pyridoindole, tetrahydroquinoline and phenylazepine classes, with EC50 down to ~300 nM following initial structure-activity studies. Increased CFTR chloride conductance by up to 8-fold was observed when a co-potentiator (termed ‘Class II potentiator’) was used with a classical potentiator (‘Class I potentiator’) such as VX-770 or GLPG1837. To investigate the range of CFTR mutations benefitted by co-potentiators, 14 CF-associated CFTR mutations were studied in transfected cell models. Co-potentiator efficacy was found for CFTR missense, deletion and nonsense mutations in nucleotide binding domain-2 (NBD2), including W1282X, N1303K, c.3700A > G and Q1313X (with corrector for some mutations). In contrast, CFTR mutations G85E, R334W, R347P, V520F, R560T, A561E, M1101K and R1162X showed no co-potentiator activity, even with corrector. Co-potentiator efficacy was confirmed in primary human bronchial epithelial cell cultures generated from a N1303K homozygous CF subject. The Class II potentiators identified here may have clinical benefit for CF caused by mutations in the NBD2 domain of CFTR.

scholarly journals Alterations in ZnT1 expression and function lead to impaired intracellular zinc homeostasis in cancer

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Adrian Israel Lehvy ◽  
Guy Horev ◽  
Yarden Golan ◽  
Fabian Glaser ◽  
Yael Shammai ◽  
...  
Keyword(s):  
Malignant Tumors ◽  
Zinc Homeostasis ◽  
Healthy Population ◽  
Missense Mutations ◽  
Protein Alignment ◽  
Loss Of Function ◽  
Intracellular Zinc ◽  
Dismal Prognosis ◽  
Zinc Levels ◽  
And Function

Abstract Zinc is vital for the structure and function of ~3000 human proteins and hence plays key physiological roles. Consequently, impaired zinc homeostasis is associated with various human diseases including cancer. Intracellular zinc levels are tightly regulated by two families of zinc transporters: ZIPs and ZnTs; ZIPs import zinc into the cytosol from the extracellular milieu, or from the lumen of organelles into the cytoplasm. In contrast, the vast majority of ZnTs compartmentalize zinc within organelles, whereas the ubiquitously expressed ZnT1 is the sole zinc exporter. Herein, we explored the hypothesis that qualitative and quantitative alterations in ZnT1 activity impair cellular zinc homeostasis in cancer. Towards this end, we first used bioinformatics to analyze inactivating mutations in ZIPs and ZNTs, catalogued in the COSMIC and gnomAD databases, representing tumor specimens and healthy population controls, respectively. ZnT1, ZnT10, ZIP8, and ZIP10 showed extremely high rates of loss of function mutations in cancer as compared to healthy controls. Analysis of the putative functional impact of missense mutations in ZnT1-ZnT10 and ZIP1-ZIP14, using homologous protein alignment and structural predictions, revealed that ZnT1 displays a markedly increased frequency of predicted functionally deleterious mutations in malignant tumors, as compared to a healthy population. Furthermore, examination of ZnT1 expression in 30 cancer types in the TCGA database revealed five tumor types with significant ZnT1 overexpression, which predicted dismal prognosis for cancer patient survival. Novel functional zinc transport assays, which allowed for the indirect measurement of cytosolic zinc levels, established that wild type ZnT1 overexpression results in low intracellular zinc levels. In contrast, overexpression of predicted deleterious ZnT1 missense mutations did not reduce intracellular zinc levels, validating eight missense mutations as loss of function (LoF) mutations. Thus, alterations in ZnT1 expression and LoF mutations in ZnT1 provide a molecular mechanism for impaired zinc homeostasis in cancer formation and/or progression.

Sign in / Sign up

Export Citation Format

Share Document