Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, UK.
Department of Biology, KU Leuven, Leuven, Belgium.
J Physiol. 2023 May;601(9):1625-1653. doi: 10.1113/JP283238. Epub 2022 Oct 23.
Acid-sensing ion channels (ASICs) are members of the diverse family of degenerin/epithelial sodium channels (DEG/ENaCs). They perform a wide range of physiological roles in healthy organisms, including in gut function and synaptic transmission, but also play important roles in disease, as acidosis is a hallmark of painful inflammatory and ischaemic conditions. We performed a screen for acid sensitivity on all 30 subunits of the Caenorhabditis elegans DEG/ENaC family using two-electrode voltage clamp in Xenopus oocytes. We found two groups of acid-sensitive DEG/ENaCs characterised by being either inhibited or activated by increasing proton concentrations. Three of these acid-sensitive C. elegans DEG/ENaCs were activated by acidic pH, making them functionally similar to the vertebrate ASICs. We also identified three new members of the acid-inhibited DEG/ENaC group, giving a total of seven additional acid-sensitive channels. We observed sensitivity to the anti-hypertensive drug amiloride as well as modulation by the trace element zinc. Acid-sensitive DEG/ENaCs were found to be expressed in both neurons and non-neuronal tissue, highlighting the likely functional diversity of these channels. Our findings provide a framework to exploit the C. elegans channels as models to study the function of these acid-sensing channels in vivo, as well as to study them as potential targets for anti-helminthic drugs. KEY POINTS: Acidosis plays many roles in healthy physiology, including synaptic transmission and gut function, but is also a key feature of inflammatory pain, ischaemia and many other conditions. Cells monitor acidosis of their surroundings via pH-sensing channels, including the acid-sensing ion channels (ASICs). These are members of the degenerin/epithelial sodium channel (DEG/ENaC) family, along with, as the name suggests, vertebrate ENaCs and degenerins of the roundworm Caenorhabditis elegans. By screening all 30 C. elegans DEG/ENaCs for pH dependence, we describe, for the first time, three acid-activated members, as well as three additional acid-inhibited channels. We surveyed both groups for sensitivity to amiloride and zinc; like their mammalian counterparts, their currents can be blocked, enhanced or unaffected by these modulators. Likewise, they exhibit diverse ion selectivity. Our findings underline the diversity of acid-sensitive DEG/ENaCs across species and provide a comparative resource for better understanding the molecular basis of their function.
酸敏离子通道（ASICs）是多样的退行性/上皮钠通道（DEG/ENaC）家族的成员。它们在健康生物中执行广泛的生理作用，包括肠道功能和突触传递，但在疾病中也发挥着重要作用，因为酸中毒是疼痛炎症和缺血等条件的标志。我们使用双电极电压钳在非洲爪蟾卵母细胞中对秀丽隐杆线虫 DEG/ENaC 家族的 30 个亚基进行了酸敏感性筛选。我们发现了两组受酸敏感的 DEG/ENaC，其特征是通过增加质子浓度被抑制或激活。这三种对酸敏感的秀丽隐杆线虫 DEG/ENaC 被酸性 pH 激活，使它们在功能上类似于脊椎动物的 ASICs。我们还鉴定了酸抑制的 DEG/ENaC 组的三个新成员，总共增加了七个额外的酸敏感通道。我们观察到对抗高血压药物阿米洛利的敏感性以及微量元素锌的调节。酸敏感的 DEG/ENaC 被发现在神经元和非神经元组织中表达，突出了这些通道的功能多样性。我们的发现为利用秀丽隐杆线虫通道作为研究体内这些酸敏通道功能的模型提供了一个框架，也为将它们作为抗寄生虫药物的潜在靶点进行研究提供了一个框架。
酸中毒在健康生理中发挥着许多作用，包括突触传递和肠道功能，但也是炎症性疼痛、缺血和许多其他疾病的关键特征。细胞通过 pH 感应通道监测周围环境的酸中毒，包括酸敏离子通道（ASICs）。这些是退行性/上皮钠通道（DEG/ENaC）家族的成员，与顾名思义的脊椎动物 ENaC 和秀丽隐杆线虫的退行性蛋白一起。通过筛选秀丽隐杆线虫所有 30 个 DEG/ENaC 对 pH 的依赖性，我们首次描述了三种酸激活成员，以及另外三种酸抑制通道。我们调查了两组对阿米洛利和锌的敏感性；与它们的哺乳动物对应物一样，它们的电流可以被这些调节剂阻断、增强或不受影响。同样，它们表现出不同的离子选择性。我们的发现强调了跨物种酸敏感的 DEG/ENaC 的多样性，并为更好地理解其功能的分子基础提供了一个比较资源。
