靶向BK（α+β4）通道的多肽martentoxin抗癫痫分子机制研究

癫痫是神经元异常放电引起的脑功能紊乱，影响1%人口健康。治疗癫痫主要依靠化学药物，但效果有限, 副作用明显。大电导钙激活钾离子（BK）通道在神经系统中大量表达，使神经元放电。BK通道β4亚基在大脑中大量表达，缺失β4会导致小鼠表现出显著的惊厥发作症状，故神经型BK（α+β4）通道是调控癫痫发作重要功能元件，治疗癫痫潜在靶标。毒素martentoxin通过与BK通道β4亚基胞外区（即hβ4-loop）作用，选择性阻断BK（α+β4）通道K+电流。本项目首先利用核磁共振技术研究毒素与人源hβ4-loop作用机制，继而考察毒素及其突变体对BK（α+β4）通道阻断K+电流影响。通过γ-氨基丁酸受体拮抗剂戊四唑诱发大鼠发生BK通道功能获得型癫痫，考察毒素对惊厥复发行为影响，对海马神经元脑损伤及C-fos表达影响，以考察该毒素靶向BK(α+β4)通道发挥抗癫痫药效,为设计新的多肽抗癫痫药物奠定基础。

Epilepsy is a most frequent neurological disorder affecting round 1% of the population in the world. Large conductance, Ca2+- and Voltage activated K+ (BK) channels, broadly expressed in the central nervous system, contribute to generating the fast-afterhyperpolarization, which helps set neuronal firing rates at the single-cell as well as network level. Gain-of-function in BK channels or knockout of its β4 subunit, a BK inhibitory subunit enriched in brain, is associated with spontaneous epilepsy in both animal models and humans. So far, no studies on the efficacy of BK (α+β4) channel modulators in preventing epilepsy were reported. Here, we first show that peptide martentoxin selectively inhibits BK (α+β4) channel through hydrogen-bond interactions with the extracellular loop of BK channel β4 subunit, which represents a novel interaction model between potassium channels and their specific ligands. We then demonstrate that, by this inhibition, intrahippocampal infusion of martentoxin significantly increases latency time of seizure, reduces the seizure duration and seizure numbers on pentylenetetrazole-induced pre-sensitized rats, inhibits hippocampal hyperexcitability as well as c-Fos expression, and displays neuroprotective effects on hippocampal neurons. These results suggest that BK (α+β4) channel can be regarded as a novel therapeutic target of intractable epilepsy, and martentoxin contributes to the rational drug-design for epilepsy treatment.