Department of Epidemiology, Preclinical Research and Advanced Diagnostics, National Institute for Infectious Diseases IRCCS 'L. Spallanzani', Rome, Italy.
Division of Medical Genetics, Fondazione IRCCS Casa Sollievo della Sofferenza, 71013, San Giovanni Rotondo, Italy.
Cell Death Dis. 2023 Aug 5;14(8):505. doi: 10.1038/s41419-023-06026-1.
Mycobacterium tuberculosis (Mtb) is known to evade host immune responses and persist in macrophages for long periods. A mechanism that the host uses to combat Mtb is xenophagy, a selective form of autophagy that targets intracellular pathogens for degradation. Ubiquitination of Mtb or Mtb-containing compartments is a key event to recruit the autophagy machinery and mediate the bacterial delivery to the lysosome. This event relies on the coordinated and complementary activity of different ubiquitin ligases, including PARKIN, SMURF1, and TRIM16. Because each of these factors is responsible for the ubiquitination of a subset of the Mtb population, it is likely that additional ubiquitin ligases are employed by macrophages to trigger a full xenophagic response during Mtb infection. In this study, we investigated the role TRIM proteins whose expression is modulated in response to Mtb or BCG infection of primary macrophages. These TRIMs were ectopically expressed in THP1 macrophage cell line to assess their impact on Mtb replication. This screening identified TRIM32 as a novel player involved in the intracellular response to Mtb infection, which promotes autophagy-mediated Mtb degradation. The role of TRIM32 in xenophagy was further confirmed by silencing TRIM32 expression in THP1 cells, which causes increased intracellular growth of Mtb associated to impaired Mtb ubiquitination, reduced recruitment of the autophagy proteins NDP52/CALCOCO2 and BECLIN 1/BECN1 to Mtb and autophagosome formation. Overall, these findings suggest that TRIM32 plays an important role in the host response to Mtb infection through the induction of autophagy, representing a promising target for host-directed tuberculosis therapies.
结核分枝杆菌（Mtb）已知逃避宿主免疫反应，并在巨噬细胞中长时间存在。宿主用于对抗 Mtb 的一种机制是异噬作用，这是一种选择性的自噬形式，可靶向细胞内病原体进行降解。Mtb 或含有 Mtb 的隔室的泛素化是招募自噬机制并介导细菌递送至溶酶体的关键事件。该事件依赖于不同泛素连接酶的协调和互补活性，包括 PARKIN、SMURF1 和 TRIM16。由于这些因子中的每一个都负责 Mtb 群体中一部分的泛素化，因此很可能巨噬细胞还利用其他泛素连接酶在 Mtb 感染期间触发完整的异噬反应。在这项研究中，我们研究了表达在受到 Mtb 或 BCG 感染的原代巨噬细胞中被调节的 TRIM 蛋白的作用。这些 TRIM 蛋白在 THP1 巨噬细胞系中被异位表达，以评估它们对 Mtb 复制的影响。该筛选鉴定了 TRIM32 作为一种新型参与者，涉及到 Mtb 感染的细胞内反应，促进自噬介导的 Mtb 降解。TRIM32 在异噬作用中的作用通过在 THP1 细胞中沉默 TRIM32 表达得到进一步证实，这导致 Mtb 的细胞内生长增加，与 Mtb 泛素化受损、自噬蛋白 NDP52/CALCOCO2 和 BECLIN 1/BECN1 向 Mtb 的募集减少以及自噬体形成减少有关。总体而言，这些发现表明，TRIM32 通过诱导自噬在宿主对 Mtb 感染的反应中发挥重要作用，代表了宿主导向性结核病治疗的有前途的靶点。
