清华大学贾怡昌、中科院上海药物所高召兵等发现，由内质网阴离子通道氯通道CLIC样1 (CLCC1)维持的内质网离子稳态的破坏导致肌萎缩侧索硬化症(ALS)样病理。这一研究成果于2023年5月4日发表在国际顶尖学术期刊《细胞研究》上。

他们将CLCC1的罕见变异与ALS样病理联系起来。他们证明CLCC1是ER阴离子通道的成孔组分，ALS相关突变损害通道电导率。CLCC1形成同聚体，其通道活性被腔内Ca2+抑制，但被磷脂酰肌醇4,5-二磷酸(PIP2)促进。他们发现CLCC1 N端负责Ca2+结合和腔内Ca2+介导的通道打开概率抑制的保守残基D25和D181, CLCC1腔内环中的K298是关键的PIP2感应残基。CLCC1维持稳态[Cl -]ER和[K+]ER和ER形态，调节ER Ca2+稳态，包括内部Ca2+释放和稳态[Ca2+]ER。

ALS相关的CLCC1突变形式增加稳态[Cl -]ER并损害ER Ca2+稳态，具有ALS相关突变的动物对应激挑战诱导的蛋白质错误折叠敏感。多种Clcc1功能缺失等位基因的表型比较，包括ALS相关突变，揭示了体内疾病表型严重程度的CLCC1剂量依赖性。与CLCC1罕见变异在ALS中占主导地位类似，10%的K298A杂合小鼠出现了ALS样症状，这表明由功能丧失突变显性负性诱导的通道病变机制。Clcc1细胞的条件性敲除自主导致运动神经元丢失和内质网应激，错误折叠蛋白积累，以及脊髓的特征性ALS病理。因此，他们的研究结果支持CLCC1维持的ER离子稳态的破坏有助于ALS样病理。

据介绍，虽然阴离子通道在肌浆网/内质网(SR/ER)中具有活性，但其分子特性和功能尚不清楚。

附：英文原文

Title: Disruption of ER ion homeostasis maintained by an ER anion channel CLCC1 contributes to ALS-like pathologies

Author: Guo, Liang, Mao, Qionglei, He, Ji, Liu, Xiaoling, Piao, Xuejiao, Luo, Li, Hao, Xiaoxu, Yu, Hanzhi, Song, Qiang, Xiao, Bailong, Fan, Dongsheng, Gao, Zhaobing, Jia, Yichang

Issue&Volume: 2023-05-04

Abstract: Although anion channel activities have been demonstrated in sarcoplasmic reticulum/endoplasmic reticulum (SR/ER), their molecular identities and functions remain unclear. Here, we link rare variants of Chloride Channel CLIC Like 1 (CLCC1) to amyotrophic lateral sclerosis (ALS)-like pathologies. We demonstrate that CLCC1 is a pore-forming component of an ER anion channel and that ALS-associated mutations impair channel conductance. CLCC1 forms homomultimers and its channel activity is inhibited by luminal Ca2+ but facilitated by phosphatidylinositol 4,5-bisphosphate (PIP2). We identified conserved residues D25 and D181 in CLCC1 N-terminus responsible for Ca2+ binding and luminal Ca2+-mediated inhibition on channel open probability and K298 in CLCC1 intraluminal loop as the critical PIP2-sensing residue. CLCC1 maintains steady-state [Cl–]ER and [K+]ER and ER morphology and regulates ER Ca2+ homeostasis, including internal Ca2+ release and steady-state [Ca2+]ER. ALS-associated mutant forms of CLCC1 increase steady-state [Cl–]ER and impair ER Ca2+ homeostasis, and animals with the ALS-associated mutations are sensitized to stress challenge-induced protein misfolding. Phenotypic comparisons of multiple Clcc1 loss-of-function alleles, including ALS-associated mutations, reveal a CLCC1 dosage dependence in the severity of disease phenotypes in vivo. Similar to CLCC1 rare variations dominant in ALS, 10% of K298A heterozygous mice developed ALS-like symptoms, pointing to a mechanism of channelopathy dominant-negatively induced by a loss-of-function mutation. Conditional knockout of Clcc1 cell-autonomously causes motor neuron loss and ER stress, misfolded protein accumulation, and characteristic ALS pathologies in the spinal cord. Thus, our findings support that disruption of ER ion homeostasis maintained by CLCC1 contributes to ALS-like pathologies.

DOI: 10.1038/s41422-023-00798-z

Source: https://www.nature.com/articles/s41422-023-00798-z