CFTR and cystic fibrosis: Therefore, the inverted funnel-shaped ion permeation pathway is highly positive and lined with polar and charged residues, which provide a high affinity for anions and offer an electrostatic barrier to the entry of cations into the channel pore (Fig. 1b).6 The dysfunction of CFTR will lead to dysregulation of anion transport, which is associated with a number of diseases known as “channelopathies”, such as cystic fibrosis (CF).7