期刊
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
卷 442, 期 1, 页码 64-72出版社
SPRINGER HEIDELBERG
DOI: 10.1007/s004240000496
关键词
TRAAK K+ channels; mechanosensitivity; synergism; pressure; free fatty acids; alkali
类别
TRAAK is a member of the tandem-pore Kf channel family, and is expressed mainly in the brain. Using rat TRAAK (rTRAAK), we studied its single-channel kinetics, interactive modes of activation, and the role of the C-terminus on its pressure-, fatty-acid-and pH-sensitivity. When expressed in COS-7 cells, rTRAAK showed a mildly inwardly rectifying single-channel current/voltage relationship in symmetrical 140 mM KCl. Unlike TREK-1 and TREK-2, which are activated by acidic conditions, rTRAAK was activated by alkali conditions, such that a change in intracellular pH from 7.3 to 8.3 and 8.8 increased channel activity 5- and 14-fold, respectively. Pressure and alkali produced a strong synergistic activation, and pressure and arachidonic acid (AA) produced a mild synergistic activation. The only additive effect was observed with alkali and AA. Replacing the C-terminus of rTRAAK with that of TASK-1 or TASK-3 did not affect the response to pressure, AA or alkali. In contrast, replacing the C-terminus of TREK-2 with that of TASK-3 abolished the sensitivity to AA and acid, but not to pressure. These results show that rTRAAK is an alkali-sensing K+ channel that shows synergistic activation with pressure, and that the mechanism of activation of rTRAAK and TREK by free fatty acids are different.
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