Kschonsak Marc, Chua Han Chow, Weidling Claudia, Chakouri Nourdine, Noland Cameron L, Schott Katharina, Chang Timothy, Tam Christine, Patel Nidhi, Arthur Christopher P, Leitner Alexander, Ben-Johny Manu, Ciferri Claudio, Pless Stephan Alexander, Payandeh Jian
Department of Structural Biology, Genentech Inc., South San Francisco, CA, USA.
Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
Nature. 2022 Mar;603(7899):180-186. doi: 10.1038/s41586-021-04313-5. Epub 2021 Dec 20.
Depolarizing sodium (Na) leak currents carried by the NALCN channel regulate the resting membrane potential of many neurons to modulate respiration, circadian rhythm, locomotion and pain sensitivity. NALCN requires FAM155A, UNC79 and UNC80 to function, but the role of these auxiliary subunits is not understood. NALCN, UNC79 and UNC80 are essential in rodents, and mutations in human NALCN and UNC80 cause severe developmental and neurological disease. Here we determined the structure of the NALCN channelosome, an approximately 1-MDa complex, as fundamental aspects about the composition, assembly and gating of this channelosome remain obscure. UNC79 and UNC80 are massive HEAT-repeat proteins that form an intertwined anti-parallel superhelical assembly, which docks intracellularly onto the NALCN-FAM155A pore-forming subcomplex. Calmodulin copurifies bound to the carboxy-terminal domain of NALCN, identifying this region as a putative modulatory hub. Single-channel analyses uncovered a low open probability for the wild-type complex, highlighting the tightly closed S6 gate in the structure, and providing a basis to interpret the altered gating properties of disease-causing variants. Key constraints between the UNC79-UNC80 subcomplex and the NALCN DI-DII and DII-DIII linkers were identified, leading to a model of channelosome gating. Our results provide a structural blueprint to understand the physiology of the NALCN channelosome and a template for drug discovery to modulate the resting membrane potential.
由NALCN通道携带的去极化钠（Na）泄漏电流调节许多神经元的静息膜电位，以调节呼吸、昼夜节律、运动和疼痛敏感性。NALCN需要FAM155A、UNC79和UNC80才能发挥作用，但这些辅助亚基的作用尚不清楚。NALCN、UNC79和UNC80在啮齿动物中至关重要，人类NALCN和UNC80的突变会导致严重的发育和神经疾病。在这里，我们确定了NALCN通道体的结构，这是一种约1兆道尔顿的复合物，因为关于该通道体的组成、组装和门控的基本方面仍然不清楚。UNC79和UNC80是大量的HEAT重复蛋白，它们形成一个相互缠绕的反平行超螺旋组装体，在细胞内对接在NALCN-FAM155A孔形成亚复合物上。钙调蛋白与NALCN的羧基末端结构域共纯化，确定该区域为一个假定的调节中心。单通道分析发现野生型复合物的开放概率很低，突出了结构中紧密关闭的S6门，并为解释致病变体改变的门控特性提供了基础。确定了UNC79-UNC80亚复合物与NALCN DI-DII和DII-DIII连接子之间的关键限制，从而得出通道体门控模型。我们的结果提供了一个结构蓝图，以了解NALCN通道体的生理学，并为调节静息膜电位的药物发现提供了一个模板。
