Structural and functional studies of the TRPM2 channel

体温严格保持在一个狭窄的范围内，以保护大脑和其他神经系统中的脆弱神经。 身体组织，因为不适当的体温会引起发烧，脑损伤和中风。TRPM 2是 大脑中主要的温度感应受体，调节核心体温，防止过热， 出现发热。TRPM 2是一种Ca 2+可渗透的非选择性离子通道，在脑中高度表达，但在脑中表达不明显。 也存在于心脏、血管和平滑肌以及免疫细胞中。它被Ca 2+唯一激活， ADP核糖（ADPR）是NAD+代谢的产物，是NAD+代谢后释放的第二信使。 氧化应激TRPM 2的激活导致Ca 2+穿过质膜进入细胞， 从溶酶体中释放。因此，TRPM 2在Ca 2+依赖的生理性细胞凋亡中起着重要作用。 从胰岛素分泌到对细胞死亡的免疫反应的过程和细胞功能。已经 与阿尔茨海默病、中风和其他神经退行性疾病有关。 TRPM 2属于TRP超家族的TRPM（melastin-like transient receptor potential）亚家族。 尽管共有TRPM N-末端同源区（MHR）和C-末端卷曲螺旋区， 结构域，TRPM 2独特地与C-末端NHDT 9-H结构域组装，NHDT 9-H结构域是人TRPM 2的同源物。 线粒体ADP-核糖焦磷酸酶NUDT 9.功能研究，包括结合试验， 电生理学和分子模拟，提供了一个共识的观点，ADPR结合NUDT 9-H 结构域，但缺乏ADPR结合位点的证据，激动剂作用的分子基础 在钙存在下TRPM 2上的ADPR仍然未知。TRPM 2的门控被进一步调节， 许多分子和离子，从质子到核苷酸（环ADPR，AMP，8-Br-cADPR）， 姜黄素（从姜黄的根茎中分离），通过多种机制起作用。在 目前，我们不知道这些分子和离子在哪里与TRPM 2结合，或者它们如何激活通道， 调节其功能。我们已经获得了两个cryo-EM结构的斑马鱼TRPM 2在apo/关闭和ADPR/Ca 2+结合的开放状态，后者代表的第一个活跃状态的TRPM家族成员。我们发现了一个新的ADPR结合位点，它位于NUDT 9-H结构域之外，以前完全未知。基于这些初步数据，我们建议继续结合互补的电生理学实验，结合试验和X射线晶体学对TRPM 2进行结构研究，这将为全面的门控机制和药理学定义分子基础。这些进步将提供一个坚实的 基金会，用于开发针对神经退行性疾病的新药，并加深对神经退行性疾病的了解 整个TRPM家族的功能。

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.