d-Amphetamine inhibits inwardly rectifying potassium channels in Xenopus oocytes expression system
Journal
NeuroToxicology
Journal Volume
29
Journal Issue
4
Pages
638-646
Date Issued
2008
Author(s)
Abstract
Effects of d-amphetamine on the renal outer medullary potassium (ROMK1) channels were tested in the Xenopus oocytes expression system. Xenopus oocytes were injected with mRNA coding for wild-type or mutant ROMK1 channels. Giant inside-out patch-clamp recordings were performed. d-Amphetamine inhibited the activity of ROMK1 channels in a manner that was concentration-dependent but voltage-independent. ROMK1 channels are regulated by intracellular pH (pHi) and protein kinase A (PKA). d-Amphetamine decreased the activity of wild-type and pHi gating residue mutant (K80M) channels over a range of pHi values. However, d-amphetamine failed to reduce channel activity in the presence of PKA inhibitors (H89 and KT 5720) and had no inhibitory effect on the mutants of PKA-phosphorylation sites (S44A, S219A, or S313A), mutants that mimicked the negative charge carried by a phosphate group bound to a serine (S44D, S219D, or S313D), or mutant channels with a positive charge (S219R). These findings suggest that d-amphetamine inhibits ROMK1 channels independently of the pHi. The effects of d-amphetamine on ROMK1 channels may be due to a conformational change induced by PKA-mediated phosphorylation, but not to charge-charge interactions. Crown Copyright ? 2008.
Other Subjects
cyclic AMP dependent protein kinase; cyclic AMP dependent protein kinase inhibitor; dexamphetamine; messenger RNA; potassium channel; protein romk1; animal cell; article; controlled study; drug inhibition; nonhuman; oocyte; priority journal; protein expression; Xenopus; Animals; Carbazoles; Dextroamphetamine; Dopamine Uptake Inhibitors; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Electric Stimulation; Enzyme Inhibitors; Female; Isoquinolines; Membrane Potentials; Microinjections; Mutagenesis, Site-Directed; Oocytes; Patch-Clamp Techniques; Potassium Channels, Inwardly Rectifying; Pyrroles; Serine; Sulfonamides; Xenopus
Type
journal article