Inhibition of the human two-pore domain potassium channel, TREK-1, by fluoxetine and its metabolite norfluoxetine.
1. Block of the human two-pore domain potassium (2-PK) channel TREK-1 by fluoxetine (Prozac) and its active metabolite, norfluoxetine, was investigated using whole-cell patch-clamp recording of currents through recombinant channels in tsA 201 cells. 2. Fluoxetine produced a concentration-dependent inhibition of TREK-1 current that was reversible on wash. The IC50 for block was 19 microM. Block by fluoxetine was voltage-independent. Fluoxetine (100 microM) produced an 84% inhibition of TREK-1 currents, but only a 31% block of currents through a related 2-PK channel, TASK-3. 3. Norfluoxetine was a more potent inhibitor of TREK-1 currents with an IC50 of 9 microM. Block by norfluoxetine was also voltage-independent. 4. Truncation of the C-terminus of TREK-1 (delta89) resulted in a loss of channel function, which could be restored by intracellular acidification or the mutation E306A. The mutation E306A alone increased basal TREK-1 current and resulted in a loss of the slow phase of TREK-1 activation. 5. Progressive deletion of the C-terminus of TREK-1 had no effect on the inhibition of the channel by fluoxetine. The E306A mutation, on the other hand, reduced the magnitude of fluoxetine inhibition, with 100 microM producing only a 40% inhibition. 6. It is concluded that fluoxetine and norfluoxetine are potent inhibitors of TREK-1. Block of TREK-1 by fluoxetine may have important consequences when the drug is used clinically in the treatment of depression.
Kennard
Louise E
LE
Blackett Laboratory, Biophysics Section, Department of Biological Sciences, Imperial College London, Exhibition Road, London SW7 2AZ.
Chumbley
Justin R
JR
Ranatunga
Kishani M
KM
Armstrong
Stephanie J
SJ
Veale
Emma L
EL
Mathie
Alistair
A
D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005473:Fluoxetine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006801:Humans; D020128:Inhibitory Concentration 50; D009154:Mutation; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D024683:Potassium Channels, Tandem Pore Domain / Q000037:antagonists & inhibitors* / Q000235:genetics; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*; D014162:Transfection
D005473:Fluoxetine; D026902:Potassium Channel Blockers; D024683:Potassium Channels, Tandem Pore Domain; D017367:Selective Serotonin Reuptake Inhibitors; C103742:potassium channel protein TREK-1; C036139:norfluoxetine