Cl- current activation in choroid plexus epithelial cells involves a G protein and protein kinase A.
The involvement of GTP-binding proteins (G proteins) in the regulation of the Cl- conductance in rat choroid plexus epithelial cells was investigated, using the whole cell patch-clamp technique. Intracellular application of a nonhydrolyzable GTP analogue, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; 0.1-0.2 mM), evoked a transient increase in the Cl- conductance. The activated Cl- current exhibited inward rectification and was independent of time at hyperpolarizing or depolarizing voltage pulses. The effect of GTP gamma S was inhibited by a nonhydrolyzable GDP analogue, guanosine 5'-O-(2-thiodiphosphate) (2 mM), and by an inhibitor of protein kinase A, H-89, but was not affected by chelation of cytosolic Ca2+ with 5 mM 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. GTP gamma S failed to activate the current when ATP was omitted from the pipette solution. Intracellular application of adenosine 3',5'-cyclic monophosphate (cAMP; 0.25 mM) or the catalytic subunit of protein kinase A activated a similar Cl- current. These results suggest that G proteins activate Cl- channels via a cAMP-dependent pathway in rat choroid plexus.
Kotera
T
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Department of Physiological Sciences, University of Manchester, United Kingdom.
Brown
P D
PD
D000818:Animals; D002712:Chlorides / Q000502:physiology*; D002831:Choroid Plexus / Q000166:cytology / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004553:Electric Conductivity; D004847:Epithelial Cells; D004848:Epithelium / Q000502:physiology; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D002712:Chlorides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins