Direct blockade of both cloned rat rod photoreceptor cyclic nucleotide-gated non-selective cation (CNG) channel alpha-subunit and native CNG channels from Xenopus rod outer segments by H-8, a non-specific cyclic nucleotide-dependent protein kinase inhibitor.
Using excised inside-out patch techniques, a non-specific cyclic nucleotide-dependent protein kinase inhibitor, H-8 (N-2-(methylamino)ethyl-5-isoquinolinesulfonamide), has been shown to suppress directly the activities of both rat rod photoreceptor cyclic GMP-gated channel alpha-subunits expressed in Xenopus oocytes and native cGMP-gated channels from Xenopus rod outer segments. When co-applied with 100 microM cGMP on the cytoplasmic side of the patches, current suppression by H-8 increased with membrane depolarization. Blockade by H-8 was not relieved by supersaturating concentrations of cGMP (1 mM). In addition, blockade by H-8 showed significant inhibition of channel activity at negative holding potentials when acting from the extracellular side of the channel. The results were consistent with the conclusion that H-8 can act as an open channel blocker from either side of the channel. Even though H-8 is a much more effective kinase inhibitor, it is frequently used at concentrations that cause inhibition of cGMP-gated channels and this effect needs to be taken into account when evaluating results obtained with this compound.
Wei
J Y
JY
Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, CT 06520, USA.
Cohen
E D
ED
Barnstable
C J
CJ
D000818:Animals; D002412:Cations / Q000378:metabolism; D003001:Cloning, Molecular; D018844:Cyclin-Dependent Kinases / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects*; D007546:Isoquinolines / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects; D051381:Rats; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects*; D014981:Xenopus
D002412:Cations; D004791:Enzyme Inhibitors; D007473:Ion Channels; D007546:Isoquinolines; D018844:Cyclin-Dependent Kinases