Combination of Correctors Rescue ΔF508-CFTR by Reducing Its Association with Hsp40 and Hsp27

Abstract

Background: Mutations in nucleotide binding domain 1 of cystic fibrosis (CF) transmembrane conductance regulator cause severe CF. Results: Correctors rescue trafficking of ⌬F508 by altering interaction with Hsp27 and Ϫ40. Conclusion: Rescue of trafficking mutants can be accomplished by combining correctors from different classes. Significance: ⌬F508 is the most common mutation. Information on the mechanism of corrector action is critical for treating the majority of patients.

Combination of Correctors Rescues CFTR Transmembrane-Domain Mutants by Mitigating their Interactions with Proteostasis

“…Atpositions 1077 and 1101, these mutations change amino acids with hydrophobic side chains for nonpolar (leucine to proline) and positively charged (methionine to lysine) amino acid residues, respectively. Cells bearing both L1077P and M1101K expressed more immature and mature forms of CFTR upon low-temperature incubation, although this increase occurred to a lesser extent than previously observed for ΔF508 [20, 21, 37]. Therefore, incubation of cells at low temperature was associated with a lesser efficiency in rectifying CFTR folding to the mutants L1077P and M1101K.…”

“…ΔF508 is a temperature-sensitive mutant, and incubation of cells at low temperature can partially restore its processing, trafficking and function [20, 21, 37]. In contrast to ΔF508, which is located at NBD1, G85E and E92K are situated at MS1 in TMD1 [11].…”

“…These results suggest that mutants with multiple defects may require drug combinations to achieve therapeutic levels that could benefit patients. Like ΔF508 [23, 37], the mutants G85E, E92K, L1077P, and M1101K are associated with multiple defects, and the greatest rescue of CFTR bearing these mutants was obtained when we applied two correctors together that have different mechanisms of action (i.e., C4+C18). C18 is a class I corrector that stabilizes the interactions between NBD1 and ICL1/4, whereas C4 is a class II corrector that restores NBD2 stability and its interdomain interactions [23].…”

“…Intriguingly, CFTR bearing G85E did not exhibit less interaction with AHSA1 and Hsp27, neither ubiquitination, after co-administration of C4 and C18. Previous studies have shown that silencing of AHSA1 [28, 30] or Hsp27 [26, 37] markedly stabilizes the folding of CFTR bearing ΔF508 and blocks protein SUMOylation, respectively. Therefore, co-administration of C4 and C18 was inefficient in rectifying the defect of CFTR bearing G85E, leading to protein retention, ubiquitination and degradation, which precluded its trafficking to the cell surface.…”

Inhibition of histone deacetylase 6 activity reduces cyst growth in polycystic kidney disease

“…Given that CFTR-mediated chloride secretion is positively regulated by cAMP, 31, 32 we added the adenylate cyclase activator forskolin (10 μM) and potentiated the CFTR-mediated chloride secretion with the tyrosine kinase inhibitor genistein (30 μM). Thiazolidonone, a specific CFTR inhibitor (CFTR inh 172), 33, 34 was added at 10 μM to inhibit the I SC , indicating that the measured current was indeed generated by the CFTR. Pretreatment with tubacin significantly reduced the CFTR-dependent I SC in MDCK.2 cells when compared to DMSO-treated cells (Fig.…”