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组织蛋白酶在结核分枝杆菌感染人巨噬细胞中的作用。

Role of Cathepsins in Mycobacterium tuberculosis Survival in Human Macrophages.

机构信息

Research Institute for Medicines, iMed-ULisboa, Faculty of Pharmacy, Universidade de Lisboa, Portugal.

Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Portugal.

出版信息

Sci Rep. 2016 Aug 30;6:32247. doi: 10.1038/srep32247.

Abstract

Cathepsins are proteolytic enzymes that function in the endocytic pathway, especially in lysosomes, where they contribute directly to pathogen killing or indirectly, by their involvement in the antigen presentation pathways. Mycobacterium tuberculosis (MTB) is a facultative intracellular pathogen that survives inside the macrophage phagosomes by inhibiting their maturation to phagolysosomes and thus avoiding a low pH and protease-rich environment. We previously showed that mycobacterial inhibition of the proinflammatory transcription factor NF-κB results in impaired delivery of lysosomal enzymes to phagosomes and reduced pathogen killing. Here, we elucidate how MTB also controls cathepsins and their inhibitors, cystatins, at the level of gene expression and proteolytic activity. MTB induced a general down-regulation of cathepsin expression in infected cells, and inhibited IFNγ-mediated increase of cathepsin mRNA. We further show that a decrease in cathepsins B, S and L favours bacterial survival within human primary macrophages. A siRNA knockdown screen of a large set of cathepsins revealed that almost half of these enzymes have a role in pathogen killing, while only cathepsin F coincided with MTB resilience. Overall, we show that cathepsins are important for the control of MTB infection, and as a response, it manipulates their expression and activity to favour its intracellular survival.

摘要

组织蛋白酶是参与内吞途径的蛋白水解酶,特别是在溶酶体中,它们直接有助于病原体的杀伤,或者通过参与抗原呈递途径间接起作用。结核分枝杆菌(MTB)是一种兼性细胞内病原体,通过抑制其向吞噬溶酶体的成熟,从而避免低 pH 值和富含蛋白酶的环境,在巨噬细胞吞噬体中存活下来。我们之前的研究表明,分枝杆菌抑制原炎症转录因子 NF-κB 的作用导致溶酶体酶向吞噬体的传递受损,从而降低了病原体的杀伤能力。在这里,我们阐明了 MTB 如何在基因表达和蛋白水解活性水平上控制组织蛋白酶及其抑制剂胱抑素。MTB 在感染细胞中诱导组织蛋白酶表达的普遍下调,并抑制 IFNγ 介导的组织蛋白酶 mRNA 的增加。我们进一步表明,组织蛋白酶 B、S 和 L 的减少有利于细菌在人原代巨噬细胞中的存活。对一大组组织蛋白酶进行 siRNA 敲低筛选表明,这些酶中的近一半在病原体杀伤中起作用,而只有组织蛋白酶 F 与 MTB 的恢复力相一致。总的来说,我们表明组织蛋白酶在控制 MTB 感染中很重要,作为一种反应,它操纵其表达和活性以有利于其细胞内存活。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/413b/5004184/630c9bdba4eb/srep32247-f1.jpg

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