No abstract

Edited by George DeMartinoWe previously reported that delivery of a microRNA-138 mimic or siRNA against SIN3A to cultured cystic fibrosis (⌬F508/⌬F508) airway epithelia partially restored ⌬F508-cystic fibrosis transmembrane conductance regulator (CFTR)-mediated cAMP-stimulated Cl ؊ conductance. We hypothesized that dissecting this microRNA-138/SIN3A-regulated gene network would identify individual proteins contributing to the rescue of ⌬F508-CFTR function. Among the genes in the network, we rigorously validated candidates using functional CFTR maturation and electrolyte transport assays in polarized airway epithelia. We found that depletion of the ubiquitin ligase SYVN1, the ubiquitin/proteasome system regulator NEDD8, or the F-box protein FBXO2 partially restored ⌬F508-CFTR-mediated Cl ؊ transport in primary cultures of human cystic fibrosis airway epithelia. Moreover, knockdown of SYVN1, NEDD8, or FBXO2 in combination with corrector compound 18 further potentiated rescue of ⌬F508-CFTR-mediated Cl ؊ conductance. This study provides new knowledge of the CFTR biosynthetic pathway. It suggests that SYVN1 and FBXO2 represent two distinct multiprotein complexes that may degrade ⌬F508-CFTR in airway epithelia and identifies a new role for NEDD8 in regulating ⌬F508-CFTR ubiquitination.

The most common cystic fibrosis (CF) mutation, ΔF508, causes protein misfolding, leading to proteosomal degradation. We recently showed that expression of miR-138 enhances CF transmembrane conductance regulator (CFTR) biogenesis and partially rescues ΔF508-CFTR function in CF airway epithelia. We hypothesized that a genomic signature approach can be used to identify new bioactive small molecules affecting ΔF508-CFTR rescue. The Connectivity Map was used to identify 27 small molecules with potential to restore ΔF508-CFTR function in airway epithelia. The molecules were screened in vitro for efficacy in improving ΔF508-CFTR trafficking, maturation, and chloride current. We identified four small molecules that partially restore ΔF508-CFTR function in primary CF airway epithelia. Of these, pyridostigmine showed cooperativity with corrector compound 18 in improving ΔF508-CFTR function. There are few CF therapies based on new molecular insights. Querying the Connectivity Map with relevant genomic signatures offers a method to identify new candidates for rescuing ΔF508-CFTR function.