Regulation of Trigeminal Nociception by TRESK Channels

Twik相关的脊髓K(Tresk)通道在所有初级传入神经元中大量表达 在三叉神经节(TG)和背根神经节(DRG)，介导背景K电流和 控制锅具的兴奋性。然而，Tresk基因突变会导致偏头痛，但不会导致身体疼痛 这表明三叉神经节神经元比背根节神经元更容易受到Tresk功能障碍的影响。我们 已经发现偏头痛相关的Tresk突变会导致Tresk蛋白的截断，而Tresk蛋白 对内源性Tresk电流有很强的显性-负性效应。这促使我们使用Tresk 以基因敲除(KO)小鼠为模型系统研究Tresk活性从头开始丧失对疼痛的影响 变速箱。尽管在所有PAN中普遍存在Tresk电流的损失，但只有一个亚群的TG神经元 在特雷斯克，KO小鼠变得极度兴奋。出乎意料的是，辣椒素反应神经元的百分比 在KO小鼠的TG中选择性增加，但在DRG中不增加。Tresk KO小鼠表现出更强健的行为 在三叉神经痛，尤其是头痛的小鼠模型中，比野生型对照的反应更好。相比之下，狂野- TYPE和KO小鼠对后爪伤害性刺激的反应相似。这些结果表明，Tresk KO 小鼠重述了人类Tresk突变的病理生理学。 尽管我们已经阐明了新的Tresk功能障碍导致偏头痛的机制 在人类中，我们仍然不知道为什么Tresk的普遍缺失会对TG和DRG神经元产生不同的影响； 在一般人群中，Tresk活动的变化是否有助于发作性和慢性偏头痛。在这 我们建议采用多学科方法来解决这些知识差距。首先，我们将 研究Tresk功能障碍对TG和DRG神经元的不同影响机制。我们 将识别选择性上调KO TG神经元中TRPV1表达的转录调控蛋白。 我们还将确定补偿背根节神经元Tresk活性丧失的离子通道(S)。 其次，根据我们的初步发现，内源性Tresk活性的变化与 雌性小鼠发情周期中TG神经元兴奋性的变化，我们将检验这一假说 雌激素通过抑制TG内源性Tresk活性增加女性偏头痛易感性 神经元。最后，我们将检验这一假设，即频繁的偏头痛发作会减少TG-Tresk电流，从而 增加了偏头痛慢性化的风险。我们将研究内源性Tresk活性是如何在 慢性偏头痛的小鼠模型；以及改变TG神经元中的Tresk活动是否足以改变 偏头痛的时代化过程。 总的来说，这些研究的结果将阐明特雷斯克通过不同的 调节编码三叉神经和身体疼痛的神经回路。这最终会带来更好的结果 了解这两个系统的生理学和病理生理学。

TWIK-related spinal cord K+ (TRESK) channel is abundantly expressed in all primary afferent neurons (PANs) in trigeminal ganglion (TG) and dorsal root ganglion (DRG), mediating background K+ currents and controlling the excitability of PANs. However, TRESK mutations cause migraine headache but not body pain in humans, suggesting that TG neurons are more vulnerable to TRESK dysfunctions than DRG neurons. We have found that the migraine-associated TRESK mutation results in the truncation of TRESK protein, which exerts a strong dominant-negative effect on endogenous TRESK current. This has prompted us to use TRESK knockout (KO) mouse as a model system to study the effects of de novo loss of TRESK activity on pain transmission. Despite the ubiquitous loss of TRESK currents in all PANs, only one subpopulation TG neurons in TRESK KO mice becomes hyper-excitable. Unexpectedly, the percentage of capsaicin-responsive neurons is selectively increased in TG but not DRG of KO mice. TRESK KO mice exhibit more robust behavioral responses than wild-type controls in mouse models of trigeminal pain, especially headache. In contrast, wild- type and KO mice respond similarly to noxious stimuli on the hindpaw. These results indicate that TRESK KO mice recapitulate the pathophysiology of TRESK mutations in humans. Although we have elucidated the mechanisms through which de novo TRESK dysfunction causes migraine in humans, we still don't know why ubiquitous loss of TRESK differentially affects TG and DRG neurons; whether changes of TRESK activity contribute to episodic and chronic migraines in general populations. In this project we propose to employ a multidisciplinary approach to address these knowledge gaps. First, we will investigate the mechanisms through which TRESK dysfunction differentially affects TG and DRG neurons. We will identify transcriptional regulatory proteins that selectively upregulate TRPV1 expression in KO TG neurons. We will also identify the ion channel(s) that compensate for the loss of TRESK activity in DRG neurons. Secondly, based on our preliminary finding that changes of endogenous TRESK activity correlates with changes of the excitability of TG neurons during estrous cycles in female mice, we will test the hypothesis that estrogen increases migraine susceptibility in women through inhibition of endogenous TRESK activity in TG neurons. Finally, we will test the hypothesis that frequent migraine attacks reduce TG TRESK currents, thereby increasing the risk of migraine chronification. We will investigate how endogenous TRESK activity is affected in a mouse model of chronic migraine; and whether altering TRESK activity in TG neurons is sufficient to modify the process of migraine chronification. Collectively, results from these studies will elucidate novel mechanisms through which TRESK differentially regulates the neuronal circuits encoding trigeminal and body pain. This will ultimately leads to better understanding of the physiology and pathophysiology of both systems.