DSKC Bio Discovery Lab And Department of Zoology, Miranda House, University of Delhi, Delhi, 110007, India.
Apoptosis. 2023 Feb;28(1-2):136-165. doi: 10.1007/s10495-022-01778-1. Epub 2022 Oct 18.
PE/PPE proteins of Mycobacterium tuberculosis (Mtb) target the host organelles to dictate the outcome of infection. This study investigated the significance of PE6/Rv0335c protein's unique C-terminal in causing host mitochondrial perturbations and apoptosis. In-silico analysis revealed that similar to eukaryotic apoptotic Bcl2 proteins, Rv0335c had disordered, hydrophobic C-terminal and two BH3-like motifs in which one was located at C-terminal. Also, Rv0335c's N terminal had mitochondrial targeting sequence. Since, C-terminal of Bcl2 proteins are crucial for mitochondria targeting and apoptosis; it became relevant to evaluate the role of Rv0335c's C-terminal domain in modulating host mitochondrial functions and apoptosis. To confirm this, in-vitro experiments were conducted with Rv0335c whole protein and Rv0335c∆Cterm (C-terminal domain deleted Rv0335c) protein. Rv0335c∆Cterm caused significant reduction in mitochondrial perturbations and Caspase-mediated apoptosis of THP1 macrophages in comparison to Rv0335c. However, the deletion of C-terminal domain didn't affect Rv0335c's ability to localize to mitochondria. Nine Ca binding residues were predicted within Rv0335c and four of them were at the C-terminal. In-vitro studies confirmed that Rv0335c caused significant increase in intracellular calcium influx whereas Rv0335c∆Cterm had insignificant effect on Ca influx. Rv0335c has been reported to be a TLR4 agonist and, we observed a significant reduction in the expression of TLR4-HLA-DR-TNF-α in response to Rv0335c∆Cterm protein also suggesting the role of Rv0335c's C-terminal domain in host-pathogen interaction. These findings indicate the possibility of Rv0335c as a molecular mimic of eukaryotic Bcl2 proteins which equips it to cause host mitochondrial perturbations and apoptosis that may facilitate pathogen persistence.
结核分枝杆菌(Mtb)的 PE/PPE 蛋白靶向宿主细胞器,决定感染的结果。本研究探讨了 PE6/Rv0335c 蛋白独特的 C 端在引起宿主线粒体扰动和凋亡中的意义。计算机分析表明,与真核细胞凋亡 Bcl2 蛋白类似,Rv0335c 具有无序的疏水性 C 端和两个 BH3 样基序,其中一个位于 C 端。此外,Rv0335c 的 N 端具有线粒体靶向序列。由于 Bcl2 蛋白的 C 端对于线粒体靶向和凋亡至关重要,因此评估 Rv0335c 的 C 端结构域在调节宿主线粒体功能和凋亡中的作用变得相关。为了证实这一点,进行了 Rv0335c 全长蛋白和 Rv0335c∆Cterm(C 端结构域缺失的 Rv0335c)蛋白的体外实验。与 Rv0335c 相比,Rv0335c∆Cterm 导致 THP1 巨噬细胞线粒体扰动和 Caspase 介导的凋亡显著减少。然而,C 端结构域的缺失并不影响 Rv0335c 定位于线粒体的能力。在 Rv0335c 中预测到 9 个 Ca 结合残基,其中 4 个位于 C 端。体外研究证实,Rv0335c 导致细胞内钙内流显著增加,而 Rv0335c∆Cterm 对 Ca 内流无显著影响。Rv0335c 已被报道为 TLR4 激动剂,我们观察到对 Rv0335c∆Cterm 蛋白的反应中 TLR4-HLA-DR-TNF-α 的表达显著减少,这也表明 Rv0335c 的 C 端结构域在宿主-病原体相互作用中的作用。这些发现表明 Rv0335c 作为真核细胞 Bcl2 蛋白的分子模拟物的可能性,使其能够引起宿主线粒体扰动和凋亡,从而促进病原体的持续存在。