钙稳态调节蛋白2 Q87A突变增加抑郁易感性

钙稳态调节蛋白2（calcium homeostasis modulator 2，Calhm2）参与钙离子活动和ATP释放的调控. 本实验室的前期工作已经证实，Calhm2可以介导星形胶质细胞ATP的释放，在抑郁症的发生发展中起到重要作用. 为了进一步探究Calhm2在抑郁症发生发展中的分子机制，本文首先预测了Calhm2的ATP结合位点，即位于第87位点的谷氨酰胺（Q87），并将其突变为丙氨酸（A），建立了一个携带calhm2突变（Q87A）的小鼠品系. 随后，通过对原代星形胶质细胞的胞内和胞外ATP检测，发现Calhm2 Q87A突变导致星形胶质细胞ATP的释放下降；此外，通过对小鼠大脑海马切片的ATP检测，发现Calhm2 Q87A突变小鼠海马组织的ATP释放较正常小鼠下降；最后，通过给予慢性温和不可预知应激（chronic unpredictable mild stress，CUMS）来诱发小鼠抑郁样行为，发现Calhm2 Q87A突变小鼠抑郁样行为相对野生型小鼠表现得更为严重. 综上所述，本文发现Q87位点对Calhm2介导的星形胶质细胞ATP释放发挥重要作用，该位点的突变增加了外界压力刺激诱导抑郁样行为的易感性，进一步明确了Calhm2蛋白在抑郁症发生发展中的分子机制，为抑郁症相关疾病的诊断和治疗提供了新的理论基础.

Calcium Homeostasis Modulator 2 Q87A Mutation Promotes Depression Susceptibility

Calcium homeostasis modulator 2 (Calhm2) is involved in the modulation of Ca²⁺ activity and ATP release. Our previous work has demonstrated that Calhm2 plays a crucial role in the progression of depression by regulating the astrocytic ATP release. In order to further explore the role and mechanism of Calhm2 in the development of depression, we firstly predicted the ATP binding site (glutamine, amino acid 87) of Calhm2, and established a mouse line that carried calhm2 mutation by mutating the glutamine to alanine (Q87A). Secondly, by using the primary culture of astrocyte and ATP detection analysis, we found that Calhm2 Q87A mutation resulted in a significant decrease of ATP release in astrocytes. Furthermore, we found that the ATP release decreased in hippocampal slice from Calhm2 Q87A mutated mice. Importantly, Calhm2 Q87A mutated mice showed a higher susceptibility to develop depression-like symptoms than that of wild type mice when exposed to chronic unpredictable mild stress (CUMS). Taken together, we identified that Q87 site is important for Calhm2-mediated ATP release in astrocytes and this point mutation of Calhm2 promotes depression susceptibility induced by stress in mice. The present work further defines the molecular mechanism of Calhm2 in the development of depression, with the implication of a potential avenues for the diagnosis and therapeutics of depression-related diseases.