Relationship between auxiliary gamma subunits and mallotoxin on BK channel modulation.
Relationship between auxiliary gamma subunits and mallotoxin on BK channel modulation.
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DOI：
10.1038/srep42240
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发表时间：
2017-02-06
影响因子：
4.6
通讯作者：
Yan J
中科院分区：
文献类型：
--
作者：
Guan X;Li Q;Yan J
大电导、钙和电压激活的 K+(BK) 通道由成孔 α 亚基 (BKα) 和辅助亚基组成。辅助 γ1-3 亚基通过将通道激活的电压依赖性向超极化方向移动约 145 mV (γ1)、100 mV (γ2) 和 50 mV (γ3) 来有效调节 BK 通道。 Mallotoxin 是一种有效的小分子 BK 通道激活剂。我们分析了从 HEK-293 细胞切下的膜片中马洛毒素和 γ 亚基在 BK 通道激活作用中的关系。我们发现，当在细胞外应用马洛毒素时，BKα通道的半激活电压（V1/2）移动了-72 mV。当存在 γ1、γ2 或 γ3 亚基时，马洛毒素的通道激活作用大大减弱，所得 ΔV1/2（+/- 马洛毒素）值分别为 -9、-28 或 -15mV。大多数研究的γ1突变亚基拮抗马洛毒素的通道激活作用，其方式在很大程度上取决于其自身的调节功能。然而，马洛毒素导致 γ1-F273S 突变体与 BK 通道发生不可逆的功能和结构脱离。我们推断，辅助 γ 亚基通过直接空间竞争或对 Mallotoxin 对 BKα 的结合和作用的间接变构影响，有效干扰 Mallotoxin 对 BK 通道的调制。
The large-conductance, calcium- and voltage-activated K+(BK) channel consists of the pore-forming α subunits (BKα) and auxiliary subunits. The auxiliary γ1-3 subunits potently modulate the BK channel by shifting its voltage-dependence of channel activation toward the hyperpolarizing direction by approximately 145 mV (γ1), 100 mV (γ2), and 50 mV (γ3). Mallotoxin is a potent small-molecule BK channel activator. We analyzed the relationship between mallotoxin and the γ subunits in their BK channel-activating effects in membrane patches excised from HEK-293 cells. We found that mallotoxin, when applied extracellularly, shifted the half-activation voltage (V1/2) of BKα channels by −72 mV. The channel-activating effect of mallotoxin was greatly attenuated in the presence of the γ1, γ2, or γ3 subunit, with resultant ΔV1/2 (+/− mallotoxin) values of −9, −28, or −15 mV, respectively. Most examined γ1 mutant subunits antagonized mallotoxin’s channel-activating effect in a manner that was largely dependent on its own modulatory function. However, mallotoxin caused an irreversible functional and structural disengagement of the γ1-F273S mutant from BK channels. We infer that the auxiliary γ subunit effectively interferes with mallotoxin on BK channel modulation via either a direct steric competition or an indirect allosteric influence on mallotoxin’s binding and action on BKα.