Abstract

TREK-1 is a member of the two-pore domain potassium channel family that is known as a leak channel and plays a key role in many physiological and pathological processes. The conformational transition of the selectivity filter is considered as an effective strategy for potassium channels to control the course of potassium efflux. It is well known that TREK-1 is regulated by a large volume of extracellular and intracellular signals. However, until now, little was known about the selectivity filter gating mechanism of the channel. In this research, it was found that Ba(2+) blocked the TREK-1 channel in a concentration- and time-dependent manner. A mutagenesis analysis showed that overlapped binding of Ba(2+) at the assumed K(+) binding site 4 (S4) within the selectivity filter was responsible for the inhibitory effects on TREK-1. Then, Ba(2+) was used as a probe to explore the conformational transition in the selectivity filter of the channel. It was confirmed that collapsed conformations were induced by extracellular K(+)-free and acidification at the selectivity filters, leading to nonconductive to permeable ions. Further detailed characterization demonstrated that the two conformations presented different properties. Additionally, the N-terminal truncated isoform (ΔN41), a product derived from alternative translation initiation, was identified as a constitutively nonconductive variant. Together, these results illustrate the important role of selectivity filter gating in the regulation of TREK-1 by the extracellular K(+) and proton.

Highlights

  • Ba2ϩ Blocks TREK-1 in a Concentration- and Time-dependent Manner—It has been reported that the 426 amino acid of TREK-1 (TREK-1426) is subjected to the alternative translation initiation (ATI) mechanism because of the suboptimal sequence context flanking the first start codon compared with the second one [34]

  • These results indicate that there is very little, if any, ⌬N41 variant that was produced by TREK-1

  • Relatively little is known in the field of its gate mechanism, which may be due to the complex structure in the pore region compared with its voltage-gated brethren

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Summary

Introduction

Extracellular acid could depress the TREK-1 current by facilitating C-type inactivation, in which conformational modification of the pore region could be involved [20]. External Kϩ Impedes the Blocking Effect of Ba2ϩ on TREK-1 Currents—Ba2ϩ inhibition of some potassium channels resulted from its docking properties in the SF [21,22,23]. It was found that the macroscopic currents of TREK-1 were enhanced by increasing [Kϩ]o from 0 to 20 mM (Fig. 5A), implying a conformational transition of the SF from nonconductive to conductive.

Results
Conclusion
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