Honoré Eric, Patel Amanda Jane, Chemin Jean, Suchyna Thomas, Sachs Frederick
Single Molecule Biophysics, 301 Cary Hall, University at Buffalo, State University of New York, Buffalo, NY 14214, USA.
Proc Natl Acad Sci U S A. 2006 May 2;103(18):6859-64. doi: 10.1073/pnas.0600463103. Epub 2006 Apr 24.
The neuronal mechano-gated K2P channels TREK-1 and TRAAK show pronounced desensitization within 100 ms of membrane stretch. Desensitization persists in the presence of cytoskeleton disrupting agents, upon patch excision, and when channels are expressed in membrane blebs. Mechanosensitive currents evoked with a variety of complex stimulus protocols were globally fit to a four-state cyclic kinetic model in detailed balance, without the need to introduce adaptation of the stimulus. However, we show that patch stress can be a complex function of time and stimulation history. The kinetic model couples desensitization to activation, so that gentle conditioning stimuli do not cause desensitization. Prestressing the channels with pressure, amphipaths, intracellular acidosis, or the E306A mutation reduces the peak-to-steady-state ratio by changing the preexponential terms of the rate constants, increasing the steady-state current amplitude. The mechanical responsivity can be accounted for by a change of in-plane area of approximately 2 nm2 between the closed and open conformations. Desensitization and its regulation by chemical messengers is predicted to condition the physiological role of K2P channels.
神经元机械门控K2P通道TREK - 1和TRAAK在膜拉伸100毫秒内表现出明显的脱敏现象。在存在破坏细胞骨架的试剂时、膜片切除后以及通道在膜泡中表达时，脱敏现象持续存在。用各种复杂刺激方案诱发的机械敏感电流整体符合详细平衡的四态循环动力学模型，无需引入刺激适应性。然而，我们表明膜片应力可能是时间和刺激历史的复杂函数。动力学模型将脱敏与激活耦合，因此温和的预处理刺激不会引起脱敏。用压力、两亲分子、细胞内酸中毒或E306A突变对通道进行预应激，通过改变速率常数的指数前项来降低峰 - 稳态比，增加稳态电流幅度。机械响应性可由关闭和开放构象之间平面内面积约2 nm²的变化来解释。预计脱敏及其受化学信使的调节将决定K2P通道的生理作用。
