GSK3β调控结核菌诱导巨噬细胞凋亡与坏死转换的机制研究

Macrophage plays a pivotal role in the infection of Mycobacterium tuberculosis (MTB) and the pathogenesis of tuberculosis (TB). The fate infected macrophages will affect clearance of the pathogens and the process of disease. Apoptosis and necrosis are two most common cell death pattern of MTB infected macrophages, the former will effectively eradicate the bacteria while the later will lead to the release of the bacteria from infected cells and infection of other cells. Therefore, identification of the switcher of the process of apoptosis and necrosis of the MTB-infected macrophages will reveal novel targets for future intervention of MTB infection.By application of a platform for high-throughput simultaneous detection of apoptosis and necrosis for screening of more than 1000 compounds, we observed that inhibition of glycogen synthase kinase 3β (Gsk3β) significantly enhanced MTB-induced macrophage cell death. Furtherly, we found that RNAi-mediated knockdown the expression of GSK3β inhibited apoptosis and enhanced necrosis of infected macrophages, which indicated that Gsk3β may shift the necrotic response of MTB infected macrophages to apoptosis. Here, we will characterize function and mechanism of Gsk3β in the shift of the necrosis of MTB infected macrophages to apoptosis and the pathogenesis of TB by employing molecular and cell biology technology, mouse MTB aerosol infection model and clinical samples analysis integratively. We would therefore expect that this study will provide novel molecular target and intervention strategies for the treatment of TB, especially multi-drug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB).

巨噬细胞在结核菌感染免疫应答过程中起关键作用。结核菌诱导巨噬细胞凋亡或坏死对于病原体清除及疾病进程的影响截然不同：凋亡可以非常有效的清除病原菌，而坏死会造成病原菌散播。因此，凋亡与坏死过程之间转换的机制研究可为结核病的干预提供新的策略。我们前期研究发现：1) 结核菌感染可以激活糖原合成酶激酶(GSK)3β信号通路； 2) GSK3β抑制剂可以显著增加结核菌感染引起的巨噬细胞死亡；3) RNAi下调GSK3β表达可抑制结核菌感染引起的巨噬细胞凋亡, 并促进坏死。 这些结果提示GSK3β可能参与调控结核菌感染引起的巨噬细胞凋亡与坏死的转换。为此, 本项目将从分子、细胞、动物模型和临床样本等不同层次研究GSK3β调控结核菌诱导巨噬细胞凋亡与坏死之间转换的作用机制，并明确其对结核菌感染过程的调节作用。研究结果可为结核病特别是耐药结核病的治疗提供新的分子靶标和干预手段。

巨噬细胞在结核菌感染免疫应答过程中起关键作用。结核菌诱导巨噬细胞凋亡或坏死对于病原体清除及疾病进程的影响截然不同：凋亡可以非常有效的清除病原菌，而坏死会造成病原菌散播。因此，凋亡与坏死过程之间转换的机制研究可为结核病的干预提供新的策略。本项目主要从分子、细胞、动物模型和临床样本等不同层次研究GSK3β调控结核菌诱导巨噬细胞凋亡与坏死之间转换的作用机制，研究发现MTB可通过TLR2受体诱导GSK3β Ser9位点磷酸化，抑制其Ser/Thr蛋白激酶活性。此外，GSK3β可与线粒体分裂调节子Drp1（Dynamin-related protein 1）直接相互作用，并促进Ser637发生磷酸化，抑制其GTPase活性。MTB抑制GSK3β蛋白激酶活性后，可抑制Drp1 Ser639位点的磷酸化，激活Drp1，导致成串排列的线粒体发生线性断裂，进而造成细胞坏死，最终加重MTB感染过程。研究结果提示GSK3β可以作为有效的抗MTB感染的分子靶标，可为结核病特别是耐药结核病的治疗提供新的干预手段。