Heterotrimeric G proteins, vesicle trafficking, and CFTR Cl- channels.
Previously (E.M. Schwiebert, N. Kizer, D. C. Gruenert, and B. A. Stanton, Proc. Natl. Acad. Sci. USA 89: 10623-10627, 1992), we showed that heterotrimeric G proteins regulate adenosine 3',5'-cyclic monophosphate (cAMP)-activated cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels in human airway epithelial cells. The goal of the present study was to test the hypothesis that heterotrimeric G proteins regulate vesicle trafficking and exocytosis and that these events are critical for cAMP activation of CFTR-mediated Cl- secretion. We report that cAMP stimulates exocytosis and CFTR Cl- conductance (GCl) in normal but not in CF cells. Stimulation of the heterotrimeric G protein G alpha i-2 inhibited cAMP-activated CFTR GCl and exocytosis in normal cells. In contrast, inhibition of G alpha i-2 stimulated exocytosis and allowed cAMP to stimulate CFTR GCl in cells isolated from patients with cystic fibrosis (CF). Brefeldin A and nocodazol prevented cAMP-induced exocytosis and also blocked cAMP stimulation of CFTR GCl in normal airway epithelial cells. Our studies suggest that the heterotrimeric G protein G alpha i-2 regulates CFTR GCl in human airway epithelial cells by modulating vesicle trafficking and the delivery of CFTR Cl- channels from an intracellular vesicular pool to the plasma membrane. Inhibition of G alpha i-2 may be a useful therapeutic approach to target mutant delta F508 CFTR Cl- channels from an intracellular vesicular pool to the plasma membrane and thereby correct defective Cl- secretion in CF airway epithelial cells.
Schwiebert
E M
EM
Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03755.
Gesek
F
F
Ercolani
L
L
Wjasow
C
C
Gruenert
D C
DC
Karlson
K
K
Stanton
B A
BA
D002118:Calcium / Q000502:physiology; D002460:Cell Line; D018118:Chloride Channels / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D002712:Chlorides / Q000037:antagonists & inhibitors / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D003550:Cystic Fibrosis / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004553:Electric Conductivity; D004594:Electrophysiology; D005089:Exocytosis / Q000502:physiology; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
C505032:CFTR protein, human; D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D010566:Virulence Factors, Bordetella; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D002118:Calcium