Differential sensitivity of TREK‐1, TREK‐2 and TRAAK background potassium channels to the polycationic dye ruthenium red. (8th January 2015)

• Record Type: Journal Article
• Authors: Braun, G; Lengyel, M; Enyedi, P; Czirják, G
• Is Part Of: British journal of pharmacology. Volume 172:Number 7(2015:Apr.)
• Page Start: 1728
• Page End: 1738
• Publication Date: 2015-01-08
• Subjects: Pharmacology -- Periodicals; Chemotherapy -- Periodicals; Drug Therapy -- Periodicals; Pharmacology -- Periodicals; 615.1
• DOI: 10.1111/bph.13019
• Languages: English
• ISSNs: 0007-1188

Abstract

Abstract : Background and Purpose: Pharmacological separation of the background potassium currents of closely related K2P channels is a challenging problem. We previously demonstrated that ruthenium red (RR) inhibits TASK‐3 (K2 P 9.1), but not TASK‐1 (K2 P 3.1) channels. RR has been extensively used to distinguish between TASK currents in native cells. In the present study, we systematically investigate the RR sensitivity of a more comprehensive set of K2 P channels. Experimental Approach: K + currents were measured by two‐electrode voltage clamp in X enopus oocytes and by whole‐cell patch clamp in mouse dorsal root ganglion (DRG) neurons. Key Results: RR differentiates between two closely related members of the TREK subfamily. TREK‐2 (K2 P 10.1) proved to be highly sensitive to RR (IC50 = 0.2 μM), whereas TREK‐1 (K2 P 2.1) was not affected by the compound. We identified aspartate 135 (D135) as the target of the inhibitor in mouse TREK‐2c. D135 lines the wall of the extracellular ion pathway (EIP), a tunnel structure through the extracellular cap characteristic for K2 P channels. TREK‐1 contains isoleucine in the corresponding position. The mutation of this isoleucine (I110D) rendered TREK‐1 sensitive to RR. The third member of the TREK subfamily, TRAAK (K2 P 4.1) was more potently inhibited by ruthenium violet, a contaminant in some RR preparations, than by RR. DRG neurons predominantly express TREK‐2 and RR‐resistant TREK‐1 and TRESK (K2 P 18.1) background K + channels. We detected the RR‐sensitive leak K + current component in DRG neurons. Conclusions and Implications: We propose that RR may be useful for distinguishing TREK‐2 (K2P 10.1) from TREK‐1 (K2P 2.1) and other RR‐resistant K2 P channels in native cells.