The transient receptor potential ion channel TRPA1 is expressed by primary afferent nerve fibres, in which it functions as a low-threshold sensor for structurally diverse electrophilic irritants, including small volatile environmental toxicants and endogenous algogenic lipids 1 . TRPA1 is also a ‘receptor-operated’ channel whose activation downstream of metabotropic receptors elicits inflammatory pain or itch, making it an attractive target for novel analgesic therapies 2 . However, the mechanisms by which TRPA1 recognizes and responds to electrophiles or cytoplasmic second messengers remain unknown. Here we use strutural studies and electrophysiology to show that electrophiles act through a two-step process in which modification of a highly reactive cysteine residue (C621) promotes reorientation of a cytoplasmic loop to enhance nucleophilicity and modification of a nearby cysteine (C665), thereby stabilizing the loop in an activating configuration. These actions modulate two restrictions controlling ion permeation, including widening of the selectivity filter to enhance calcium permeability and opening of a canonical gate at the cytoplasmic end of the pore. We propose a model to explain functional coupling between electrophile action and these control points. We also characterize a calcium-binding pocket that is highly conserved across TRP channel subtypes and accounts for all aspects of calcium-dependent TRPA1 regulation, including potentiation, desensitization and activation by metabotropic receptors. These findings provide a structural framework for understanding how a broad-spectrum irritant receptor is controlled by endogenous and exogenous agents that elicit or exacerbate pain and itch. Electrophiles activate the transient receptor potential ion channel TRPA1 by a two-step cysteine modification mechanism, which stabilizes a cytoplasmic loop that controls gating and calcium permeability.

中文翻译：

---

TRPA1 受体的刺激物诱发激活和钙调节

瞬时受体电位离子通道 TRPA1 由初级传入神经纤维表达，在其中它充当结构多样的亲电刺激物的低阈值传感器，包括小的挥发性环境毒物和内源性致痛脂质 1。TRPA1 也是一种“受体操作”通道，其在代谢型受体下游的激活会引起炎症性疼痛或瘙痒，使其成为新型镇痛疗法 2 的有吸引力的目标。然而，TRPA1 识别和响应亲电子试剂或细胞质第二信使的机制仍然未知。在这里，我们使用结构研究和电生理学来表明亲电试剂通过两步过程起作用，其中高反应性半胱氨酸残基 (C621) 的修饰促进细胞质环的重新定向以增强亲核性和附近半胱氨酸 (C665) 的修饰，从而在激活配置中稳定回路。这些作用调节控制离子渗透的两个限制，包括加宽选择性过滤器以增强钙渗透性和在孔的细胞质端打开规范门。我们提出了一个模型来解释亲电作用与这些控制点之间的功能耦合。我们还表征了一个钙结合口袋，它在 TRP 通道亚型中高度保守，并解释了钙依赖性 TRPA1 调节的所有方面，包括增效、脱敏和代谢型受体的激活。这些发现为理解广谱刺激性受体如何被引起或加剧疼痛和瘙痒的内源性和外源性因素控制提供了一个结构框架。亲电子试剂通过两步半胱氨酸修饰机制激活瞬时受体电位离子通道 TRPA1，该机制稳定控制门控和钙渗透性的细胞质环。