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MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

TREK-2 (K_2P10.1) and TRESK (K_2P18.1) are major background K⁺ channels in dorsal root ganglion neurons

¹Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois; and ²Department of Physiology, College of Medicine and Institute of Health Science, Gyeongsang National University, Jinju, Korea

Submitted 15 December 2005 ; accepted in final form 15 February 2006

Dorsal root ganglion (DRG) neurons express mRNAs for many two-pore domain K⁺ (K_2P) channels that behave as background K⁺ channels. To identify functional background K⁺ channels in DRG neurons, we examined the properties of single-channel openings from cell-attached and inside-out patches from the cell bodies of DRG neurons. We found seven types of K⁺ channels, with single-channel conductance ranging from 14 to 120 pS in 150 mM KCl bath solution. Four of these K⁺ channels showed biophysical and pharmacological properties similar to TRESK (14 pS), TREK-1 (112 pS), TREK-2 (50 pS), and TRAAK (73 pS), which are members of the K_2P channel family. The molecular identity of the three other K⁺ channels could not be determined, as they showed low channel activity and were observed infrequently. Of the four K_2P channels, the TRESK-like (14 pS) K⁺ channel was most active at 24°C. At 37°C, the 50-pS (TREK-2 like) channel was the most active and contributed the most (69%) to the resting K⁺ current, followed by the TRESK-like 14-pS (16%), TREK-1-like 112-pS (12%), and TRAAK-like 73-pS (3%) channels. In DRG neurons, mRNAs of all four K_2P channels, as well as those of TASK-1 and TASK-3, were expressed, as judged by RT-PCR analysis. Our results show that TREKs and TRESK together contribute >95% of the background K⁺ conductance of DRG neurons at 37°C. As TREKs and TRESK are targets of modulation by receptor agonists, they are likely to play an active role in the regulation of excitability in DRG neurons.

two-pore domain K⁺ channel; conductance; excitability

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