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结核分枝杆菌 PE6(Rv0335c)蛋白 C 端结构域在宿主线粒体应激和巨噬细胞凋亡中的作用。

Role of C-terminal domain of Mycobacterium tuberculosis PE6 (Rv0335c) protein in host mitochondrial stress and macrophage apoptosis.

机构信息

DSKC Bio Discovery Lab And Department of Zoology, Miranda House, University of Delhi, Delhi, 110007, India.

出版信息

Apoptosis. 2023 Feb;28(1-2):136-165. doi: 10.1007/s10495-022-01778-1. Epub 2022 Oct 18.

Abstract

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.

摘要

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。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/806c/9579591/9a9938b3a0b2/10495_2022_1778_Fig1_HTML.jpg

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