Kim Y, Gnatenco C, Bang H, Kim D
Department of Physiology and Biophysics, Finch University of Health Sciences, The Chicago Medical School, IL 60064, USA.
Pflugers Arch. 2001 Sep;442(6):952-60. doi: 10.1007/s004240100626.
TREK-2, a member of the tandem-pore K+ channel family, is activated by membrane stretch, unsaturated free fatty acids and acidic conditions, and exhibits unique open channel kinetics. To identify the regions responsible for these properties, we studied the role of the cytoplasmic regions of TREK-2. Deletion of the N-terminus had no effect on any aspect of TREK-2 function. Deletion of the C-terminus or its substitution with that of TASK-3 abolished the sensitivity to free fatty acids and intracellular pH (pHi), and reduced the sensitivity to pressure. The regions that allow activation by free fatty acids and low pHi were localized to 25- and 10-amino-acid domains, respectively, close to the fourth transmembrane segment. Substitution of KKTKEE, a charged region near the proximal C-terminus, with uncharged amino acids produced little change in TREK-2 function; however, its deletion abolished sensitivity to fatty acids and low pH, indicating that this region is structurally very important. The TREK-2 C-terminus was also found to be critical for its channel opening in bursts as well as for its increased basal activity. Thus, the C-terminus endows TREK-2 with unique channel kinetics and the ability to be gated by free fatty acids and low pHi, and with increased mechanosensitivity.
TREK-2是双孔钾通道家族的一员，可被膜拉伸、不饱和游离脂肪酸和酸性条件激活，并呈现出独特的开放通道动力学。为了确定负责这些特性的区域，我们研究了TREK-2胞质区域的作用。N端缺失对TREK-2功能的任何方面均无影响。C端缺失或用TASK-3的C端替代后，消除了对游离脂肪酸和细胞内pH（pHi）的敏感性，并降低了对压力的敏感性。分别允许被游离脂肪酸和低pHi激活的区域定位于靠近第四个跨膜段的25个和10个氨基酸的结构域。将靠近C端近端的带电荷区域KKTKEE替换为不带电荷的氨基酸，TREK-2功能几乎没有变化；然而，该区域缺失后消除了对脂肪酸和低pH的敏感性，表明该区域在结构上非常重要。还发现TREK-2的C端对于其成簇开放通道以及增加的基础活性也至关重要。因此，C端赋予TREK-2独特的通道动力学以及被游离脂肪酸和低pHi门控的能力，并提高了机械敏感性。
