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

英国领导的一项研究最近确定了28个新基因，这些基因具有与发育障碍相关的从头突变的高负担(KaPlanis等人，《自然》，2020)。与这个小组合作，我们有了令人兴奋的新证据，这些患者中的一个特定组，他们也患有睡眠呼吸暂停，都有编码TASK-1的KCNK3突变。我们将这种新的经络病命名为发育迟缓伴睡眠呼吸暂停(DDSA)。睡眠呼吸暂停是一种影响全球数亿人的常见疾病，是一种主要的公共卫生负担，具有重大的经济影响。因此，临床上对更有效的治疗方法的需求还没有得到满足，但涉及的潜在分子机制往往不清楚。TASK1通道以前被认为与睡眠呼吸暂停有关，抑制TASK-1的药物正在进行其治疗的临床试验。然而，到目前为止，KCNK3的突变与一种非常不同的疾病--原发性肺动脉高压--有关，因此TASK-1和睡眠呼吸暂停之间的机制联系还不完全清楚。我们现在表明，与在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，这是我们最近在TASK-1的闭态晶体结构中发现的一种新的结构门控基序(Rödström等人，“自然”，2020)。这些突变体都在通道活动中产生了显着的功能增益。重要的是，它们也使TASK-1对GPCR介导的抑制不敏感，从而放大了功能增益效应，我们证明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TASK-1抑制剂，包括那些目前正在进行临床试验的药物，仍然抑制突变的通道，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。目前尚不清楚GPCR通路如何调节TASK-1通道的活性。也不知道X门如何开启/关闭以控制渗透，或者这些临床相关的抑制物如何调节通道活动。因此，需要对TASK-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，该项目旨在解决根本上的重要问题，这些问题正好属于BBSRC对健康的综合理解：-TASK-1通道是如何打开和关闭的，它是如何被天然配体调节的？-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，这是如何在疾病状态下变得有缺陷的？总体而言，这个项目将在我们对TASK-1通道及其在健康和疾病中由GPCR耦合通路调节的机制的理解上产生阶段性的变化。它还将解决正在开发的针对这些渠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.