Regulation of Trigeminal Nociception by TRESK Channels

TWIK-related spinal cord K+（TRESK）channel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）中，PANs介导背景K+电流， 控制PAN的兴奋性。然而，TRESK突变引起偏头痛，但不是身体疼痛， 这表明TG神经元比DRG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突变导致TRESK蛋白的截短， 对内源性TRESK电流产生强烈的显性负效应。这促使我们使用TRESK 敲除（KO）小鼠作为模型系统以研究TRESK活性从头丧失对疼痛的影响 传输尽管TRESK电流在所有PAN中普遍丢失，但只有一个亚群TG神经元 TRESK KO小鼠变得过度兴奋。出乎意料的是，辣椒素反应神经元的百分比 在KO小鼠的TG而不是DRG中选择性地增加。TRESK KO小鼠表现出更稳健的行为 在三叉神经痛，特别是头痛的小鼠模型中，相反，野生的- 型和KO小鼠对后爪上的伤害性刺激的反应相似。这些结果表明，TRESK KO 小鼠概括了人类中TRESK突变的病理生理学。 尽管我们已经阐明了TRESK功能障碍引起偏头痛的机制， 在人类中，我们仍然不知道为什么普遍存在的TRESK缺失对TG和DRG神经元的影响不同; TRESK活性的变化是否有助于一般人群中的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。一是 研究TRESK功能障碍差异影响TG和DRG神经元的机制。我们 将鉴定选择性上调KO TG神经元中TRPV 1表达的转录调节蛋白。 我们还将鉴定补偿DRG神经元中TRESK活性损失的离子通道。 其次，基于我们的初步发现，内源性TRESK活性的变化与 雌性小鼠动情周期中TG神经元兴奋性的变化，我们将检验这一假设， 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，我们将检验频繁的偏头痛发作减少TG TRESK电流的假设，从而 增加偏头痛慢性化的风险。我们将研究内源性TRESK活性是如何受到影响， 慢性偏头痛的小鼠模型;以及改变TG神经元中的TRESK活性是否足以改变 偏头痛慢性化的过程 总的来说，这些研究的结果将阐明TRESK差异表达的新机制。 调节编码三叉神经和身体疼痛的神经元回路。这将最终导致更好的 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.