GTP-binding proteins inhibit cAMP activation of chloride channels in cystic fibrosis airway epithelial cells.

AUTOR(ES)

Schwiebert, E M

RESUMO

Cystic fibrosis (CF) is a genetic disease characterized, in part, by defective regulation of Cl- secretion by airway epithelial cells. In CF, cAMP does not activate Cl- channels in the apical membrane of airway epithelial cells. We report here whole-cell patch-clamp studies demonstrating that pertussis toxin, which uncouples heterotrimeric GTP-binding proteins (G proteins) from their receptors, and guanosine 5'-[beta-thio]diphosphate, which prevents G proteins from interacting with their effectors, increase Cl- currents and restore cAMP-activated Cl- currents in airway epithelial cells isolated from CF patients. In contrast, the G protein activators guanosine 5'-[gamma-thio]triphosphate and AlF4- reduce Cl- currents and inhibit cAMP from activating Cl- currents in normal airway epithelial cells. In CF cells treated with pertussis toxin or guanosine 5'-[beta-thio]diphosphate and in normal cells, cAMP activates a Cl- conductance that has properties similar to CF transmembrane-conductance regulator Cl- channels. We conclude that heterotrimeric G proteins inhibit cAMP-activated Cl- currents in airway epithelial cells and that modulation of the inhibitory G protein signaling pathway may have the therapeutic potential for improving cAMP-activated Cl- secretion in CF.

Documentos Relacionados

• Beta gamma subunits of GTP-binding proteins inhibit muscarinic receptor stimulation of phospholipase C.
• Calcium and cAMP activate different chloride channels in the apical membrane of normal and cystic fibrosis epithelia.
• cAMP stimulates bicarbonate secretion across normal, but not cystic fibrosis airway epithelia.
• Characterization of cDNAs encoding small GTP-binding proteins from maize.
• GTP-binding proteins in rat liver nuclear envelopes.