title: HGF stimulation of Rac1 signaling enhances pharmacological correction of the most prevalent cystic fibrosis mutant F508del-CFTR.
abstract: Cystic fibrosis (CF), a major life-limiting genetic disease leading to severe respiratory symptoms, is caused by mutations in CF transmembrane conductance regulator (CFTR), a chloride (Cl(-)) channel expressed at the apical membrane of epithelial cells. Absence of functional CFTR from the surface of respiratory cells reduces mucociliary clearance, promoting airways obstruction, chronic infection, and ultimately lung failure. The most frequent mutation, F508del, causes the channel to misfold, triggering its premature degradation and preventing it from reaching the cell surface. Recently, novel small-molecule correctors rescuing plasma membrane localization of F508del-CFTR underwent clinical trials but with limited success. Plausibly, this may be due to the mutant intrinsic plasma membrane (PM) instability. Herein, we show that restoration of F508del-CFTR PM localization by correctors can be dramatically improved through a novel pathway involving stimulation of signaling by the endogenous small GTPase Rac1 via hepatocyte growth factor (HGF). We first show that CFTR anchors to apical actin cytoskeleton (via Ezrin) upon activation of Rac1 signaling through PIP5K and Arp2/3. We then found that such anchoring retains pharmacologically rescued F508del-CFTR at the cell surface, boosting functional restoration by correctors up to 30% of wild-type channel levels in human airway epithelial cells. Our findings reveal that surface anchoring and retention is a major target pathway for CF pharmacotherapy, namely, to achieve maximal restoration of F508del-CFTR in patients in combination with correctors. Moreover, this approach may also translate to other disorders caused by trafficking-deficient surface proteins.
authors.affiliation: Department of Genetics, National Health Institute 'Dr. Ricardo Jorge', Av. Padre Cruz, 1649-016 Lisboa, Portugal.
authors.forename: Sónia
authors.initials: S
authors.lastname: Moniz
authors.forename: Marisa
authors.initials: M
authors.lastname: Sousa
authors.forename: Bruno José
authors.initials: BJ
authors.lastname: Moraes
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: Mendes
authors.forename: Marta
authors.initials: M
authors.lastname: Palma
authors.forename: Celeste
authors.initials: C
authors.lastname: Barreto
authors.forename: José I
authors.initials: JI
authors.lastname: Fragata
authors.forename: Margarida D
authors.initials: MD
authors.lastname: Amaral
authors.forename: Paulo
authors.initials: P
authors.lastname: Matos
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003550:Cystic Fibrosis / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics* / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008954:Models, Biological; D015394:Molecular Structure; D009154:Mutation; D015398:Signal Transduction; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C107953:RAC1 protein, human; C093349:cystic fibrosis transmembrane conductance regulator delta F508; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D017228:Hepatocyte Growth Factor; D020830:rac1 GTP-Binding Protein