PKC activators improve the function of biogenesis-deficient CFTR channels

Cystic fibrosis (CF) is a lethal genetic disease caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). The most prevalent disease-causing mutation, F508del, results in the production of misfolded CFTR proteins, which are prematurely degraded. Given the complex pathology of CF, a multimodal therapeutic strategy is essential. This underscores the urgent need to develop adjunctive modulators that synergize with existing therapies. Here, we show that protein kinase C (PKC) activators ingenol-3,20-dibenzoate and 12-deoxyphorbol 13-phenylacetate 20-acetate enhance F508del-CFTR channel function through a mechanism distinct from that of currently FDA-approved CFTR correctors. These agents enhance F508del-CFTR function as monotherapies; in combination with CFTR correctors, they largely restore the channel function in both immortalized human airway epithelial cells and Cftr^{F508del/F508del} mouse lungs. Notably, they also attenuate Cftr^{F508del/F508del} mouse pulmonary inflammation induced by infection. Furthermore, PKC activators enhance the function of CFTR harboring rare missense mutations that are refractory to existing therapies. Mechanistically, PKCε-mediated phosphorylation of nascent CFTR stabilizes the translating CFTR transcripts, thereby promoting channel synthesis. These findings reveal a previously unappreciated role of PKCε signaling in CFTR biogenesis and suggest a potential combinatorial treatment strategy to achieve a more complete functional rescue of mutant CFTR.