Structural and functional studies of the TRPM2 channel

体温严格维持在一个狭窄的范围内，以保护大脑和其他脆弱的神经 身体组织，因为体温不当会引起发烧、脑损伤和中风。 TRPM2 是 大脑中主要的温感受体，调节核心体温并防止过热 出现发烧现象。 TRPM2 是一种 Ca2 渗透性、非选择性离子通道，在大脑中高度表达，但 还存在于心脏、血管和平滑肌以及免疫细胞中。它独特地被 Ca2 激活， ADP 核糖 (ADPR) 是 NAD 代谢的产物，是细胞释放的第二信使。 氧化应激。 TRPM2 的激活导致 Ca2+ 穿过质膜和 Ca2+ 从溶酶体中释放。因此，TRPM2 在 Ca2 依赖的一系列生理功能中发挥着重要作用。 从胰岛素分泌到免疫反应再到细胞死亡的过程和细胞功能。已经是 与阿尔茨海默病、中风和其他神经退行性疾病有关。 TRPM2 属于 TRP 超家族的 TRPM（类褪黑素瞬时受体电位）亚家族。 尽管共享 TRPM N 端同源区 (MHR) 和 C 端卷曲螺旋的特征 TRPM2 独特地与 C 端 NHDT9-H 结构域组装在一起，该结构域与人类 线粒体 ADP-核糖焦磷酸酶 NUDT9。功能研究，包括结合测定， 电生理学和分子模拟提供了 ADPR 与 NUDT9-H 结合的共识 域，但缺乏 ADPR 结合位点的证据，并且缺乏激动剂作用的分子基础 ADPR 在钙存在下对 TRPM2 的影响仍然未知。 TRPM2 的门控进一步调制 由从质子到核苷酸（环状 ADPR、AMP、8-Br-cADPR）的许多分子和离子 姜黄素（从姜黄根茎中分离出来），通过多种机制发挥作用。在 目前，我们不知道这些分子和离子在哪里与 TRPM2 结合，也不知道它们如何激活通道或 调节其功能。我们获得了斑马鱼TRPM2在apo/闭合状态和ADPR/Ca2结合开放状态下的两种冷冻电镜结构，后者代表了TRPM家族成员的第一个活性状态。我们发现了一个新的 ADPR 结合位点，该位点位于 NUDT9-H 结构域之外，之前是完全未知的。基于这些初步数据，我们建议结合互补的电生理学实验、结合测定和 X 射线晶体学继续进行 TRPM2 的结构研究，这将为全面的门控机制和药理学定义分子基础。这些进步将为 开发抗神经退行性疾病新药和更深入了解的基础 整个 TRPM 系列的功能。

Body temperature is strictly maintained in a narrow range to protect the delicate nerves in the brain and other body tissues, because improper body temperature gives rise to fever, brain injury, and stroke. TRPM2 is the major warmth-sensing receptor in the brain regulating core body temperature and preventing overheating as fever occurs. TRPM2 is a Ca2+-permeable, nonselective ion channel that is highly expressed in brain but is also found in the heart, vascular and smooth muscle, and immune cells. It is uniquely activated by Ca2+ and ADP ribose (ADPR), a product of the metabolism of NAD+ and a secondary messenger released upon oxidative stress. The activation of TRPM2 results in both Ca2+ entry across the plasma membrane and Ca2+ release from lysosomes. Therefore, TRPM2 plays fundamental role in Ca2+-dependent array of physiological processes and cellular functions from insulin secretion to immune response to cell death. It has been implicated in Alzheimer disease, stroke, and other neurodegenerative diseases. TRPM2 belongs to the TRPM (melastatin-like transient receptor potential) subfamily of the TRP superfamily. Despite sharing the characteristic TRPM N-terminal homology regions (MHRs) and C-terminal coiled-coil domains, TRPM2 is uniquely assembled with a C-terminal NHDT9-H domain, a homolog to the human mitochondrial ADP-ribose pyrophosphatase NUDT9. Functional studies, including binding assays, electrophysiology, and molecular simulations, provided a consensus view that ADPR binds to the NUDT9-H domain, but proof of the ADPR binding site is lacking, and the molecular basis for the action of the agonist ADPR on TRPM2 in the presence of calcium remains unknown. The gating of TRPM2 is further modulated by many molecules and ions that range from protons to nucleotides (cyclic ADPR, AMP, 8-Br-cADPR) to curcumin (which is isolated from rhizomes of Curcuma longa), acting by way of multiple mechanisms. At present, we don't know where these molecules and ions bind to TRPM2 or how they activate the channel or modulate its function. We have obtained two cryo-EM structures of zebrafish TRPM2 in the apo/closed and ADPR/Ca2+-bound open state, with the latter representing the first active state of TRPM family members. We identified a novel ADPR binding site that is located outside the NUDT9-H domain and was completely unknown before. Building on this preliminary data, we propose to continue the structural studies of TRPM2 combined with complementary electrophysiology experiments, binding assays, and X-ray crystallography, which will define the molecular basis for a comprehensive gating mechanism and pharmacology. These advances will provide a solid foundation for developing new drugs against neurodegenerative diseases and for a deeper understanding the function of the entire TRPM family.