title: External Ba2+ block of the two-pore domain potassium channel TREK-1 defines conformational transition in its selectivity filter.
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.
authors.affiliation: Department of Biochemical Pharmacology, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China.
authors.forename: Xiao-Yun
authors.initials: XY
authors.lastname: Ma
authors.forename: Jin-Mei
authors.initials: JM
authors.lastname: Yu
authors.forename: Shu-Zhuo
authors.initials: SZ
authors.lastname: Zhang
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Liu
authors.forename: Bao-Hong
authors.initials: BH
authors.lastname: Wu
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Wei
authors.forename: Jia-Qing
authors.initials: JQ
authors.lastname: Yan
authors.forename: Hong-Liang
authors.initials: HL
authors.lastname: Sun
authors.forename: Hai-Tao
authors.initials: HT
authors.lastname: Yan
authors.forename: Jian-Quan
authors.initials: JQ
authors.lastname: Zheng
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology*; D001665:Binding Sites / Q000235:genetics; D002413:Cations, Divalent / Q000494:pharmacology; D002414:Cations, Monovalent / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D017136:Ion Transport / Q000502:physiology; D016296:Mutagenesis; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D024683:Potassium Channels, Tandem Pore Domain / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D014982:Xenopus laevis
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D026902:Potassium Channel Blockers; D024683:Potassium Channels, Tandem Pore Domain; D020033:Protein Isoforms; C103742:potassium channel protein TREK-1; D001464:Barium; D011188:Potassium