Department of Pathology, Microbiology, and Immunology, University of Nebraska Medical Center, Omaha, Nebraska, USA.
Paul G. Allen School for Global Health, Washington State University, Pullman, Washington, USA.
J Bacteriol. 2024 Aug 22;206(8):e0015024. doi: 10.1128/jb.00150-24. Epub 2024 Jul 26.
is a highly infectious, Gram-negative, obligate intracellular bacterium and the causative agent of human Q fever. The Containing Vacuole (CCV) is a modified phagolysosome that forms through fusion with host endosomes and lysosomes. While an initial acidic pH < 4.7 is essential to activate metabolism, the mature, growth-permissive CCV has a luminal pH of 5.2 that remains stable throughout infection. Inducing CCV acidification to a lysosomal pH (4.7) causes degradation, suggesting that regulates CCV pH. Supporting this hypothesis, blocks host lysosomal biogenesis, leading to fewer host lysosomes available to fuse with the CCV. Host cell lysosome biogenesis is primarily controlled by the transcription factor EB (TFEB), which binds Coordinated Lysosomal Expression And Regulation (CLEAR) motifs upstream of genes involved in lysosomal biogenesis and function. TFEB is a member of the microphthalmia/transcription factor E (MiT/TFE) protein family, which also includes MITF, TFE3, and TFEC. This study examines the roles of MiT/TFE proteins during infection. We found that in cells lacking TFEB, both growth and CCV size increase. Conversely, TFEB overexpression or expression in the absence of other family members leads to significantly less bacterial growth and smaller CCVs. TFE3 and MITF do not appear to play a significant role during infection. Surprisingly, we found that actively blocks TFEB nuclear translocation in a Type IV Secretion System-dependent manner, thus decreasing lysosomal biogenesis. Together, these results suggest that inhibits TFEB nuclear translocation to limit lysosomal biogenesis, thus avoiding further CCV acidification through CCV-lysosomal fusion.
The obligate intracellular bacterial pathogen causes the zoonotic disease Q fever, which is characterized by a debilitating flu-like illness in acute cases and life-threatening endocarditis in patients with chronic disease. While survives in a unique lysosome-like vacuole called the Containing Vacuole (CCV), the bacterium inhibits lysosome biogenesis as a mechanism to avoid increased CCV acidification. Our results establish that transcription factor EB (TFEB), a member of the microphthalmia/transcription factor E (MiT/TFE) family of transcription factors that regulate lysosomal gene expression, restricts infection. Surprisingly, blocks TFEB translocation from the cytoplasm to the nucleus, thus downregulating the expression of lysosomal genes. These findings reveal a novel bacterial mechanism to regulate lysosomal biogenesis.
是一种高度传染性的革兰氏阴性需氧细胞内细菌，也是人类 Q 热的病原体。包含空泡（CCV）是一种通过与宿主内体和溶酶体融合形成的改良吞噬溶酶体。虽然初始酸性 pH 值<4.7 对于激活代谢至关重要，但成熟的、允许生长的 CCV 的腔 pH 值约为 5.2，在整个感染过程中保持稳定。诱导 CCV 酸化至溶酶体 pH（~4.7）会导致降解，这表明 调节 CCV pH 值。这一假说得到了支持，因为 阻止了宿主溶酶体生物发生，导致与 CCV 融合的宿主溶酶体减少。宿主细胞溶酶体生物发生主要由转录因子 EB（TFEB）控制，TFEB 结合参与溶酶体生物发生和功能的基因上游的协调溶酶体表达和调节（CLEAR）基序。TFEB 是小眼/转录因子 E（MiT/TFE）蛋白家族的成员，该家族还包括 MITF、TFE3 和 TFEC。本研究探讨了 MiT/TFE 蛋白在 感染过程中的作用。我们发现，在缺乏 TFEB 的细胞中，和 CCV 大小均增加。相反，TFEB 过表达或在缺乏其他家族成员的情况下表达会导致细菌生长显著减少和 CCV 变小。TFE3 和 MITF 在 感染过程中似乎没有发挥重要作用。令人惊讶的是，我们发现通过 IV 型分泌系统依赖性方式主动阻止 TFEB 核易位，从而减少溶酶体生物发生。综上所述，这些结果表明，通过阻止 TFEB 核易位，避免了进一步的 CCV 酸化和 CCV-溶酶体融合，从而限制了溶酶体生物发生。
