CFTR and respiratory system disorder: The major cause of morbidity and mortality in CF is the respiratory disorder caused by the lack of CFTR at the plasma membrane (PM) (Moskowitz et al., 2008), which decreases the anion permeability in airway cells and leads to a progressive pathophysiological cascade (Figure 4): (1) A faulty conductance of other ions, such as excessive sodium transport mediated by epithelial Na+ channel (ENaC), since it is negatively regulated by CFTR (Kunzelmann et al., 1995; Gentzsch et al., 2010).