Suppression of premature termination codons (PTCs) with aminoglycosides and other agents has the potential to treat an underlying cause of cystic fibrosis (CF) and other genetic diseases including Duchenne's muscular dystrophy, Hurler's syndrome, and spinal muscular atrophy. While initial studies with gentamicin, amikacin, and the novel small molecule PTC124 indicate significant promise to the approach, successfully employing the strategy in CF and other diseases will require overcoming important challenges identified by our laboratory, including the need for a better understanding of basic mechanisms of action, defining patient populations most responsive to treatment (in particular, the molecular basis underlying increased response observed for the W1282X cystic fibrosis transmembrane conductance regulator (CFTR) mutation), and identifying pathways to augment rescue of CFTR nonsense codons. Approaches to repair CFTR mutations that confer dysfuction at the plasma membrane (as opposed to those caused by PTCs) have also received increasing attention in multicenter clinical trials. Interim results testing VX-770, a novel small molecule and CFTR modulator that potentiates gating of mutant CFTR localized to the cell surface, indicated improved CFTR activity and lung function in CF patients harboring G551D CFTR (a mutation resident at the cell surface but inactive due to a channel gating defect). These results indicate that correction of basic CF defects by protein repair therapy is feasible, and can result in clinically beneficial effects, even in a short (2 week) time frame. Recent evidence from our laboratory establishes that CFTR potentiators (such as VX-770) also potently activate W1282X CFTR, a relatively common premature stop mutation. Moreover, we observed significantly enhanced Cl- transport when a CFTR potentiator was used in combination with an aminoglycoside to induce translational readthrough of CFTR premature termination codons. These results provide preliminary data for an innovative therapeutic approach to treat CF patients harboring premature termination codons in CFTR. This proposal will test the hypothesis that certain CFTR nonsense mutants such as W1282X exhibit residual activity, even in the truncated state, and may respond to small molecule potentiators that enhance channel gating and restore CFTR activity. The proposed studies will capitalize on data emerging from an international clinical trial testing the stop codon suppressor PTC124 in CF patients (led by Dr. Rowe), and will also examine the combination of stop codon suppression and potentiation of CFTR readthrough product in experimental models, including primary human bronchial epithelial cells and G542X CFTR human transgenic mice. Results will lend insight regarding the mechanistic underpinnings of premature stop codon suppression, an emerging treatment strategy applicable to patients with a variety of genetic diseases, and provide preliminary data necessary to justify clinical testing of a novel approach to restore mutant CFTR function and ameliorate the basic defect in the disease. Correction of nonsense mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) represents a novel treatment strategy to correct a fundamental defect underlying cystic fibrosis (CF). However, a better understanding of the mechanistic basis of the approach is needed to overcome important challenges identified in human clinical trials. These experiments will define mechanisms underlying response to stop codon suppression, and examine whether potentiation of CFTR truncation mutants (and readthrough product following suppression of these mutations) represents a viable approach to restore CFTR function and thus ameliorate disease.

Public Health Relevance

Correction of nonsense mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) represents a novel treatment strategy to correct a fundamental defect underlying cystic fibrosis (CF). However, a better understanding of the mechanistic basis of the approach is needed to overcome important challenges identified in human clinical trials. These experiments will define mechanisms underlying response to stop codon suppression, and examine whether potentiation of CFTR truncation mutants (and readthrough product following suppression of these mutations) represents a viable approach to restore CFTR function and thus ameliorate disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Small Research Grants (R03)
Project #
1R03DK084110-01
Application #
7706429
Study Section
Diabetes, Endocrinology and Metabolic Diseases B Subcommittee (DDK)
Program Officer
Hyde, James F
Project Start
2009-08-25
Project End
2011-06-30
Budget Start
2009-08-25
Budget End
2010-06-30
Support Year
1
Fiscal Year
2009
Total Cost
$73,188
Indirect Cost
Name
University of Alabama Birmingham
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
063690705
City
Birmingham
State
AL
Country
United States
Zip Code
35294
Xue, Xiaojiao; Mutyam, Venkateshwar; Tang, Liping et al. (2014) Synthetic aminoglycosides efficiently suppress cystic fibrosis transmembrane conductance regulator nonsense mutations and are enhanced by ivacaftor. Am J Respir Cell Mol Biol 50:805-16
Chaaban, Mohamad R; Kejner, Alexandra; Rowe, Steven M et al. (2013) Cystic fibrosis chronic rhinosinusitis: a comprehensive review. Am J Rhinol Allergy 27:387-95
Conger, Bryant T; Zhang, Shaoyan; Skinner, Daniel et al. (2013) Comparison of cystic fibrosis transmembrane conductance regulator (CFTR) and ciliary beat frequency activation by the CFTR Modulators Genistein, VRT-532, and UCCF-152 in primary sinonasal epithelial cultures. JAMA Otolaryngol Head Neck Surg 139:822-7
Troxler, Robert Bradley; Hoover, Wynton C; Britton, LaCrecia J et al. (2012) Clearance of initial mucoid Pseudomonas aeruginosa in patients with cystic fibrosis. Pediatr Pulmonol 47:1113-22
McClure, Michelle; DeLucas, Lawrence J; Wilson, Landon et al. (2012) Purification of CFTR for mass spectrometry analysis: identification of palmitoylation and other post-translational modifications. Protein Eng Des Sel 25:7-14
Pyle, Louise C; Ehrhardt, Annette; Mitchell, Lisa High et al. (2011) Regulatory domain phosphorylation to distinguish the mechanistic basis underlying acute CFTR modulators. Am J Physiol Lung Cell Mol Physiol 301:L587-97
Rowe, Steven M; Clancy, John Paul; Wilschanski, Michael (2011) Nasal potential difference measurements to assess CFTR ion channel activity. Methods Mol Biol 741:69-86
Rowe, Steven M; Sloane, Peter; Tang, Li Ping et al. (2011) Suppression of CFTR premature termination codons and rescue of CFTR protein and function by the synthetic aminoglycoside NB54. J Mol Med (Berl) 89:1149-61
Solomon, George M; Konstan, Michael W; Wilschanski, Michael et al. (2010) An international randomized multicenter comparison of nasal potential difference techniques. Chest 138:919-28
Pyle, Louise C; Fulton, Jennifer C; Sloane, Peter A et al. (2010) Activation of the cystic fibrosis transmembrane conductance regulator by the flavonoid quercetin: potential use as a biomarker of ?F508 cystic fibrosis transmembrane conductance regulator rescue. Am J Respir Cell Mol Biol 43:607-16

Showing the most recent 10 out of 13 publications