The Structural and Functional Basis of Defective X-Gating in a Novel TASK-1 Channelopathy Associated with Sleep Apnea

一项由英国主导的研究最近发现了28个新基因，这些基因具有与发育障碍相关的高从头突变负担（Kaplanis et al，Nature，2020）。通过与这个小组的合作，我们有令人兴奋的新证据表明，这些患者中的一个特定群体也患有睡眠呼吸暂停，他们都在编码ASK-1的KCNK 3中发生突变。我们将这种新型的通道病命名为“睡眠呼吸暂停发育延迟”（DDSA）。睡眠呼吸暂停是一种常见的疾病，影响着全球数亿人，是一个重大的公共卫生负担，具有重大的经济影响。因此，临床上需要更有效的治疗方法，但其潜在的分子机制通常尚不清楚。TASK 1通道以前与睡眠呼吸暂停有关，抑制TASK-1的药物正在临床试验中用于治疗。然而，到目前为止，KCNK 3的突变目前与一种非常不同的疾病-原发性肺动脉高压-有关，因此尚未完全了解ASK-1和睡眠呼吸暂停之间的机制联系。我们现在表明，与PAH中发现的功能丧失突变不同，这些新的DDSA突变聚集在“X门”附近，我们最近在ASK-1的闭合状态晶体结构中发现了一种新的结构门控基序（Rödström et al，Nature，2020）。这些突变体都在通道活性中产生显著的功能获得。重要的是，它们还使ASK-1对GPCR介导的抑制不敏感，从而放大了功能获得效应，我们发现这些缺陷源于功能失调的X门控。幸运的是，我们还发现许多的TASK-1抑制剂，包括那些目前在临床试验中，仍然抑制突变通道，从而为这些患者和睡眠呼吸暂停患者提供可能的治疗策略。目前还不清楚GPCR途径如何调节TASK-1通道活性。也不知道X门如何打开/关闭以控制渗透，或者通道活性如何被这些临床相关的抑制剂调节。因此，需要对ASK-1通道的结构、功能和药理学进行一系列基础研究，以解决这一缺陷。基于这些发现，以及我们现有的一系列新的实验工具，本项目旨在解决BBSRC为全面了解健康而制定的世界领先的基础生物科学范围内的根本性重要问题：-ASK-1通道如何打开和关闭，以及它如何受到天然配体的调节？-新型小分子激活剂和抑制剂如何调节通道门控？X门控是如何正常调节的，在疾病状态下是如何出现缺陷的？总的来说，这个项目将产生一个步骤的变化，在我们的理解的任务-1通道和他们的调节机制的GPCR耦合途径在健康和疾病。它还将解决正在开发的针对这些通道的新药的分子作用机制。

A UK-led study recently identified 28 novel genes with a high burden of de novo mutations associated with developmental disorders (Kaplanis et al, Nature, 2020). In collaboration with this group, we have exciting new evidence that a specific group of these patients, who also suffer sleep apnea, all have mutations in KCNK3 which encodes TASK-1. We have named this novel channelopathy as "Developmental Delay with Sleep Apnea" (DDSA).Sleep apnea is a common disorder affecting hundreds of millions of people worldwide and is a major public health burden with a significant economic impact. Consequently, there is an unmet clinical need for more effective treatments, but the underlying molecular mechanisms involved are often unclear.TASK1 channels have previously been implicated in sleep apnea, and drugs which inhibit TASK-1 are in clinical trials for its treatment. However, until now, mutations in KCNK3 were currently linked to a very different disorder - Primary Pulmonary Hypertension - and so the mechanistic link between TASK-1 and sleep apnea was not fully understood.We now show that, unlike the loss-of-function mutations found in PAH, these new DDSA mutations cluster near the 'X-gate', a novel structural gating motif we recently identified in a closed-state crystal structure of TASK-1 (Rödström et al, Nature, 2020). These mutants all produce a marked gain-of-function in channel activity. Importantly, they also render TASK-1 insensitive to GPCR-mediated inhibition thereby amplifying the gain-of-function effect, and we show these defects arise from dysfunctional X-gating. Fortunately, we also discovered that many TASK-1 inhibitors, including those currently in clinical trials, still inhibit the mutant channels thereby offering possible therapeutic strategies for these patients and those with sleep apnea.It is currently unclear how GPCR pathways regulate TASK-1 channel activity. It is also unknown how theX-gate opens/closes to control permeation, or how channel activity is regulated by these clinically-relevant inhibitors. A series of fundamental studies of TASK-1 channel structure, function and pharmacology are therefore needed to address this deficit.Based on these findings, and a range of new experimental tools we also have available, this project aimsto address fundamentally important questions which fall squarely within the BBSRC remit of world-leading basic bioscience for an integrated understanding of health:-How does the TASK-1 channel open and close, and how is it regulated by natural ligands?- How do novel small molecule activators and inhibitors regulate channel gating?- How is X-gating normally regulated, and how does this become defective in the disease state?Overall this project will generate a step change in our understanding of TASK-1 channels and their mechanism of regulation by GPCR coupled pathways in both health and disease. It will also address the molecular mechanism of action of new drugs being developed to target these channels.