The cystic fibrosis transmembrane regulator is present and functional in endosomes. Role as a determinant of endosomal pH.

作者：Gergely L. Lukács, Xiaowei Chang, Norbert Kartner, Ori D. Rotstein, J.R. Riordan, Sergio Grinstein · 发表于：Journal of Biological Chemistry · 年份：1992 · DOI：10.1016/s0021-9258(18)42078-9 · 被引用次数：119 · 研究领域：Cystic Fibrosis Research Advances、Cellular transport and secretion、Neonatal Respiratory Health Research

Cystic fibrosis is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), which lead to defective Cl- conductance in epithelial cells. While the CFTR gene product has been detected in the plasma membrane, its presence and functional role in the membranes of intracellular compartments remain to be established. The purpose of the present experiments was to functionally localize CFTR in the endosomal membrane and to test the role of the associated Cl- conductance in the regulation of endosomal pH (pH(en)). When using conductive protonophores, the net H+ flux across the endosomal membrane of Chinese hamster ovary (CHO) cells is limited by the movement of counterions. Thus, ionic permeability could be estimated indirectly, from the changes in pH(en) determined fluorimetrically. Measurements in situ and in a cell-free microsomal preparation indicate the presence of a protein kinase A (PKA)-activated anion conductance in endosomes from CHO cells transfected with CFTR, but not in endosomes from wild-type or mock-transfected cells. In endosomes isolated from CFTR-expressing cells, the stimulatory effect of PKA was diminished by a specific peptide inhibitor of PKA, by alkaline phosphatase treatment or by a monoclonal antibody against the second nucleotide binding fold of CFTR. Increasing counterion permeability by phosphorylation of CFTR or by addition of valinomycin failed to alter the rate or extent of endosomal acidification in situ....