G protein G alpha i-2 inhibits outwardly rectifying chloride channels in human airway epithelial cells.
Previously we demonstrated that the heterotrimeric G protein, G alpha i-2, inhibits cystic fibrosis transmembrane conductance regulator (CFTR) chloride (Cl-) channels in human airway epithelial cells (E. M. Schwiebert, F. Gesek, L. Ercolani, C. Wjasow, D. C. Gruenert, and B. A. Stanton. Am. J. Physiol. 267 (Cell Physiol. 36): C272-C281, 1994, and E. M. Schwiebert, N. L. Kizer, D. C. Gruenert, and B. A. Stanton. Proc. Natl. Acad. Sci. USA 89: 10623-10627, 1992). The goal of the present study was to determine if G proteins also regulate outwardly rectifying Cl- channels (ORCC), a distinct class of Cl- channels regulated defectively by protein kinase A (PKA) in cystic fibrosis (CF). To this end, we used the patch-clamp technique to study ORCC in a normal human airway epithelial cell line (9HTEo-) that expresses CFTR and ORCC. Stimulation of G proteins with GTP and GTP gamma S decreased the single-channel open probability (Po) of ORCC, whereas inhibition of G proteins by GDP beta S increased the Po. Moreover, pertussis toxin (PTX), an uncoupler of Gi and G(o) subclasses of heterotrimeric G proteins, also increased the Po. Purified G alpha i-2 decreased the Po. In contrast, other PTX-sensitive G proteins, G alpha i-1, G alpha i-3, and G alpha o, had no effect on Po. We propose that G alpha i-2 couples to a receptor whose agonist negatively regulates ORCC in human airway epithelial cells.
Schwiebert
E M
EM
Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03755-3830, USA.
Gruenert
D C
DC
Guggino
W B
WB
Stanton
B A
BA
D000255:Adenosine Triphosphate / Q000494:pharmacology; D002384:Catalysis; D002460:Cell Line; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000187:drug effects / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin; D014132:Trachea / Q000166:cytology / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
C505032:CFTR protein, human; D018118:Chloride Channels; D008565:Membrane Proteins; D010566:Virulence Factors, Bordetella; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000255:Adenosine Triphosphate; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins