Molecular basis for defective glycosylation and Pseudomonas pathogenesis in cystic fibrosis lung

The CFTR gene encodes a transmembrane conductance regulator, which is dysfu nctional in patients with cystic fibrosis (CF). The mechanism by which defe ctive CFTR (CIF transmembrane conductance regulator) leads to undersialylat ion of plasma membrane glycoconjugates, which in turn promote lung patholog y and colonization with Pseudomonas aeruginosa causing lethal bacterial inf ections in CF, is not known. Here we show by ratiometric imaging with lumen ally exposed pH-sensitive green fluorescent protein that dysfunctional CFTR leads to hyperacidification of the trans-Golgi network (TGN) in CF lung ep ithelial cells. The hyperacidification of TGN, glycosylation defect of plas ma membrane glycoconjugates, and increased P. aeruginosa adherence were cor rected by incubating CIF respiratory epithelial cells with weak bases. Stud ies with pharmacological agents indicated a role for sodium conductance, mo dulated by CFTR regulatory function, in determining the pH of TGN. These st udies demonstrate the molecular basis for defective glycosylation of lung e pithelial cells and bacterial pathogenesis in CF, and suggest a cure by nor malizing the pH of intracellular compartments.