Targeting autophagy as a novel strategy for facilitating the therapeutic action of potentiators on ΔF508 cystic fibrosis transmembrane conductance regulator

Abstract

Channel activators (potentiators) of cystic fibrosis (CF) transmembrane conductance regulator (CFTR), can be used for the treatment of the small subset of CF patients that carry plasma membrane-resident CFTR mutants. However, approximately 90% of CF patients carry the misfolded ΔF508-CFTR and are poorly responsive to potentiators, because ΔF508-CFTR is intrinsically unstable at the plasma membrane (PM) even if rescued by pharmacological correctors. We have demonstrated that human and mouse CF airways are autophagy deficient due to functional sequestration of BECN1 and that the tissue transglutaminase-2 inhibitor, cystamine, or antioxidants restore BECN1-dependent autophagy and reduce SQSTM1/p62 levels, thus favoring ΔF508-CFTR trafficking to the epithelial surface. Here, we investigated whether these treatments could facilitate the beneficial action of potentiators on ΔF508-CFTR homozygous airways. Cystamine or the superoxide dismutase (SOD)/catalase-mimetic EUK-134 stabilized ΔF508-CFTR at the plasma membrane of airway epithelial cells and sustained the expression of CFTR at the epithelial surface well beyond drug withdrawal, overexpressing BECN1 and depleting SQSTM1. This facilitates the beneficial action of potentiators in controlling inflammation in ex vivo ΔF508-CFTR homozygous human nasal biopsies and in vivo in mouse ΔF508-CFTR lungs. Direct depletion of Sqstm1 by shRNAs in vivo in ΔF508-CFTR mice synergized with potentiators in sustaining surface CFTR expression and suppressing inflammation. Cystamine pre-treatment restored ΔF508-CFTR response to the CFTR potentiators genistein, Vrx-532 or Vrx-770 in freshly isolated brushed nasal epithelial cells from ΔF508-CFTR homozygous patients. These findings delineate a novel therapeutic strategy for the treatment of CF patients with the ΔF508-CFTR mutation in which patients are first treated with cystamine and subsequently pulsed with CFTR potentiators.

Keywords: :

• cystic fibrosis
• autophagy
• therapy
• cystamine
• CFTR potentiators

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We thank Noboru Mizushima (The Tokyo Metropolitan Institute of Medical Sciences, Tokyo, Japan) for the gift of the pcDNA3-HA-BECN1 expression vectors, Dieter C. Gruenert (California Pacific Medical Center Research Institute, San Francisco, CA) for CFBE41o-cell lines; Eliezer Masliah and Brian Spencer (Departments of Neurosciences, University of California, San Diego, La Jolla, CA) for lentiviral vectors encoding Becn1 or GFP. This was supported by the European Institute for Research in Cystic Fibrosis and Italian Cystic Fibrosis Association (L.M.), the Programma di Ricerca Scientifica di Rilevante Interesse Nazionale (2008RMJB3A_004, 2008) of the Ministero dell'Istruzione, dell'Università e della Ricerca (L.M., V.R.), Ligue Nationale contre le Cancer, AXA Chair for Longevity Research, Agence Nationale pour la Recherche, European Commission (Active p53, Apo-Sys, ChemoRes, ApopTrain), Fondation pour la Recherche Médicale, Institut National du Cancer, Cancéropôle Ile-de-France, Fondation Bettencourt-Schueller and the LabEx Onco-Immunology (G.K.).

Supplemental Materials

Supplemental materials may be found here: www.landesbioscience.com/journals/autophagy/article/21483