24S-hydroxycholesterol alters activity of large-conductance Ca2+-dependent K+ (slo1 BK) channel through intercalation into plasma membrane
24S-hydroxycholesterol alters activity of large-conductance Ca2+-dependent K+ (slo1 BK) channel through intercalation into plasma membrane
复制标题
24S-羟基胆固醇通过嵌入质膜改变大电导 Ca2 依赖性 K (slo1 BK) 通道的活性
DOI：
10.1016/j.bbalip.2019.05.010
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Kato Nobuo
中科院分区：
文献类型：
--
作者：
Tajima Nobuyoshi;Xiaoyan Liu;Taniguchi Makoto;Kato Nobuo
氧化甾醇是胆固醇的氧化产物，被认为是影响多种生理功能的生物活性脂类。然而，人们对它们对离子通道的影响知之甚少。利用内向外膜片钳记录，我们发现天然存在的侧链氧化氧甾醇，20S羟基胆固醇，22R羟基胆固醇，24S羟基胆固醇，25羟基胆固醇和27羟基胆固醇，诱导电流减少大电导Ca2+和电压激活K+(slo1 BK)通道异源表达在HEK293T细胞中。与侧链氧化的氧甾醇相比，天然存在的环氧化的，7α -羟基胆固醇和7 -酮胆固醇没有影响。利用脑内主要的氧甾醇24S‑羟基胆固醇（24S‑HC），探讨其抑制机制。24S‑HC抑制Slo1 BK通道的ic50为~2 μM，使宏观电流降低~60%。这种显著的电流减少伴随着电导-电压关系的右移和激活动力学的减慢，而失活动力学不变。此外，膜甾醇清除剂γ -环糊精被发现可以将slo1 BK通道从抑制中拯救出来，这表明24S-HC可能嵌入质膜中影响通道。这些发现从涉及离子通道调节的新角度揭示了氧化甾醇的新生理重要性。
Oxysterols, oxidization products of cholesterol, are regarded as bioactive lipids affecting various physiological functions. However, little is known of their effects on ion channels. Using inside-out patch clamp recording, we found that naturally occurring side-chain oxidized oxysterols, 20S‑hydroxycholesterol, 22R‑hydroxycholesterol, 24S‑hydroxycholestero, 25‑hydroxycholesterol, and 27‑hydroxycholesterol, induced current reduction of large-conductance Ca2+- and voltage-activated K+(slo1 BK) channels heterologously expressed in HEK293T cells. In contrast with side-chain oxidized oxysterols, naturally occurring ring oxidized ones, 7α‑hydroxycholesterol and 7‑ketocholesterol were without effect. By using 24S‑hydroxycholesterol (24S‑HC), the major brain oxysterol, we explored the inhibition mechanism. 24S‑HC inhibited Slo1 BK channels with an IC50of ~2 μM, and decreased macroscopic current by ~60%. This marked current decrease was accompanied by a rightward shift in the conductance-voltage relationship and a slowed activation kinetics, with the deactivation kinetics unaltered. Furthermore, the membrane sterol scavenger γ‑cyclodextrin was found to rescue slo1 BK channels from the inhibition, implicating that 24S-HC may be intercalated into the plasma membrane to affect the channel. These findings unveil a novel physiological importance of oxysterols from a new angle that involves ion channel regulation.