The defects in cAMP-regulated chloride channel CTFR are believed to be the major cause for cystic fibrosis. Regulation of CFTR protein by the surface receptor beta adrenergic receptor is mediated through the ezrin/radixin/moesin binding phosphoprotein 50 (EBP50), which binds both the C-termini CFTR and b2AR through their PDZ binding motifs. In the resting state, CFTR, b2AR, and EBP50 exist as a macromolecular complex on the apical surface of epithelial cells. Upon agonist activation of the b2AR, the adenulate cyclase is stimulated through the G protein pathway, leading to an increase in cAMP. The elevated concentration of cAMP activates PKA, which is anchored near CFTR via interaction with Ezrin. The phosphorylation of CFTR by PKA disrupts the complex and leads to compartmentalized and specific signaling of the channel.
