Bhatt Parul, Joshi Hemant, Sharma Sadhna, Sharma Monika
DSKC BioDiscovery Laboratory and Department of Zoology, Miranda House, University of Delhi, Delhi, India.
DSKC BioDiscovery Laboratory and Department of Zoology, Miranda House, University of Delhi, Delhi, India.
Microb Pathog. 2023 Mar;176:106021. doi: 10.1016/j.micpath.2023.106021. Epub 2023 Feb 3.
Mitochondria are the powerhouse of the cell and a critical cell signalling hub that decides the fate of the cell. Mycobacterium tuberculosis (Mtb) being a successful pathogen targets and controls the host mitochondria for pathogenesis. Various effector proteins of Mtb are also known to target host mitochondria which include few proteins of a unique Proline-Glutamate/Proline-Proline-Glutamate (PE/PPE) family exclusively present in pathogenic mycobacteria, but many of them are still uncharacterized. The present study investigates one such late expressing Rv0109 (PE_PGRS1) protein of Mtb. In-silico analysis predicted the presence of mitochondria targeting signal sequences in Rv0109 and its role in regulation of cysteine type endopeptidase (caspase) activity during apoptosis. Recombinant Rv0109 gets localized to mitochondria of THP1 macrophages as shown by confocal microscopy. Rv0109 was observed to induce mitochondrial stress which resulted in mitochondrial membrane depolarization, upregulation of mitochondrial superoxides and release of Cytochrome-C in the cytoplasm through flow cytometry. Depleted intracellular ATP was observed in THP1 macrophages in response to Rv0109. This mitochondrial stress in response to Rv0109 was observed to culminate in increased expression of pro-apoptotic Bax and Bim factors and caspase activation leading to macrophage apoptosis. Since Rv0109 is a late stage specific protein expressed within granuloma; mitochondria mediated apoptosis induced by Rv0109 may be explored for its role in granuloma maintenance and pathogen persistence.
线粒体是细胞的动力源，也是决定细胞命运的关键细胞信号枢纽。结核分枝杆菌作为一种成功的病原体，会靶向并控制宿主线粒体以实现致病作用。已知结核分枝杆菌的多种效应蛋白会靶向宿主线粒体，其中包括一些独特的脯氨酸 - 谷氨酸/脯氨酸 - 脯氨酸 - 谷氨酸（PE/PPE）家族的蛋白，这些蛋白仅存在于致病性分枝杆菌中，但其中许多仍未被表征。本研究调查了结核分枝杆菌的一种这样的晚期表达蛋白Rv0109（PE_PGRS1）。计算机分析预测Rv0109中存在线粒体靶向信号序列及其在细胞凋亡过程中对半胱氨酸型内肽酶（半胱天冬酶）活性的调节作用。共聚焦显微镜显示重组Rv0109定位于THP1巨噬细胞的线粒体。通过流式细胞术观察到Rv0109诱导线粒体应激，导致线粒体膜去极化、线粒体超氧化物上调以及细胞质中细胞色素C的释放。在THP1巨噬细胞中观察到响应Rv0109时细胞内ATP减少。观察到这种对Rv0109的线粒体应激最终导致促凋亡因子Bax和Bim的表达增加以及半胱天冬酶激活，从而导致巨噬细胞凋亡。由于Rv0109是在肉芽肿内表达的晚期特异性蛋白，因此可以探索Rv0109诱导的线粒体介导的凋亡在肉芽肿维持和病原体持续存在中的作用。
