Effects of lovastatin on trafficking of cystic fibrosis transmembrane conductance regulator in human tracheal epithelium.
Genetic defects in the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated chloride channel, cause cystic fibrosis. Most defective forms of CFTR show improper intracellular trafficking. Because isoprenylated, small GTP-binding proteins are involved in the vesicular trafficking of other integral membrane proteins, we have investigated the role of isoprenylation in the trafficking of CFTR to the apical membranes of primary cultures of human airway epithelium and of Calu-3 cells, a human lung carcinoma cell line. CFTR function was measured as short circuit current, 125I efflux, and conductance of cell sheets with permeabilized basolateral membranes. Lovastatin, an inhibitor of isoprenyl lipid biosynthesis, markedly inhibited all measures of CFTR function. The lovastatin-induced declines in CFTR function were corrected by the simultaneous addition of mevalonate or the isoprenyl lipids geranylgeranyl and farnesyl but not cholesterol. Lovastatin reduced total cellular CFTR as assessed by immunoprecipitation. Mevalonate or isoprenyl lipids protected CFTR levels from the actions of lovastatin. Together, these results suggest a role for isoprenyl lipids, presumably through the actions of small GTP-binding proteins, in the trafficking of CFTR to the apical membrane of human airway epithelium.
Shen
B Q
BQ
Cardiovascular Research Institute, University of California, San Francisco 94143-0130, USA.
Widdicombe
J H
JH
Mrsny
R J
RJ
D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D018118:Chloride Channels / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008148:Lovastatin / Q000494:pharmacology*; D017368:Protein Prenylation / Q000187:drug effects*; D014132:Trachea / Q000378:metabolism*
C505032:CFTR protein, human; D018118:Chloride Channels; D004791:Enzyme Inhibitors; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D008148:Lovastatin; D000242:Cyclic AMP