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Shen J, Ji XZ, Han L, Yao J, Liang Y, Yuan M, Xu S, Li Z. Activation of NF-κB/MAPK signaling and induction of apoptosis by salicylate synthase NbtS in Nocardia farcinica promotes neuroinflammation development. mSystems 2024:e0089324. [PMID: 39240104 DOI: 10.1128/msystems.00893-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2024] [Accepted: 07/17/2024] [Indexed: 09/07/2024] Open
Abstract
Nocardia farcinica can cause a rare, yet potentially fatal, central nervous system infection. NbtS protein may be a key virulence factor in N. farcinica infection of the brain. In this study, we investigated the function of the virulence-associated factor NbtS in microglial cells in vitro and in infected mice in vivo. We explored the interactions between NbtS and microglial cells (BV2 and human microglial clone 3), revealing that NbtS activates the toll-like receptor 4-dependent MyD88-IRAK4-IRAK1 and MAPK/nuclear factor kappa B (NF-κB) pathways, significantly enhancing pro-inflammatory responses as indicated by increased levels of tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β), as measured by ELISA and quantitative PCR. Apoptosis was elevated in these cells, as shown by increased expression of Bax and caspase-3 and decreased Bcl-2 levels. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay also confirmed the occurrence of apoptosis. In vivo, mice infected with an RS03155-deficient strain of N. farcinica exhibited higher survival rates and reduced brain inflammation, suggesting a pivotal role for the NbtS protein in the pathogenesis of Nocardia. Conservation of the RS03155 gene across Nocardia spp. was verified by PCR, and the immunogenic potential of NbtS was confirmed by Western blot analysis using sera from infected mice. These findings suggest that targeting NbtS may offer a novel therapeutic strategy against Nocardia infection. IMPORTANCE The study presented in this article delves into the molecular underpinnings of Nocardia farcinica-induced neuroinflammation. By focusing on the salicylate synthase gene, RS03155, and its encoded protein, NbtS, we uncover a pivotal virulence factor that triggers a cascade of immunological responses leading to apoptosis in microglial cells. This research not only enhances our comprehension of the pathogenesis of Nocardia infections but also provides a potential therapeutic target. Given the rising importance of understanding host-microbe interactions within the context of the central nervous system, especially in immunocompromised individuals, the findings are of significant relevance to the field of microbiology and could inform future diagnostic and treatment modalities for Nocardia-associated neurological disorders. Our work emphasizes the need for continued research into the intricate mechanisms of microbial pathogenesis and the development of novel strategies to combat life-threatening infections.
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Affiliation(s)
- Jirao Shen
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Xing Zhao Ji
- Department of Pulmonary and Critical Care Medicine, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Lichao Han
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Jiang Yao
- School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China
| | - Yihe Liang
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Min Yuan
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Shuai Xu
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Zhenjun Li
- National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
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Zhu H, Wang L, Wang Y, Jiang X, Qin Q, Song M, Huang Q. Directed-evolution mutations enhance DNA-binding affinity and protein stability of the adenine base editor ABE8e. Cell Mol Life Sci 2024; 81:257. [PMID: 38874784 PMCID: PMC11335294 DOI: 10.1007/s00018-024-05263-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 04/28/2024] [Accepted: 05/02/2024] [Indexed: 06/15/2024]
Abstract
Adenine base editors (ABEs), consisting of CRISPR Cas nickase and deaminase, can chemically convert the A:T base pair to G:C. ABE8e, an evolved variant of the base editor ABE7.10, contains eight directed evolution mutations in its deaminase TadA8e that significantly increase its base editing activity. However, the functional implications of these mutations remain unclear. Here, we combined molecular dynamics (MD) simulations and experimental measurements to investigate the role of the directed-evolution mutations in the base editing catalysis. MD simulations showed that the DNA-binding affinity of TadA8e is higher than that of the original deaminase TadA7.10 in ABE7.10 and is mainly driven by electrostatic interactions. The directed-evolution mutations increase the positive charge density in the DNA-binding region, thereby enhancing the electrostatic attraction of TadA8e to DNA. We identified R111, N119 and N167 as the key mutations for the enhanced DNA binding and confirmed them by microscale thermophoresis (MST) and in vivo reversion mutation experiments. Unexpectedly, we also found that the directed mutations improved the thermal stability of TadA8e by ~ 12 °C (Tm, melting temperature) and that of ABE8e by ~ 9 °C, respectively. Our results demonstrate that the directed-evolution mutations improve the substrate-binding ability and protein stability of ABE8e, thus providing a rational basis for further editing optimisation of the system.
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Affiliation(s)
- Haixia Zhu
- State Key Laboratory of Genetic Engineering, Shanghai Engineering Research Center of Industrial Microorganisms, MOE Engineering Research Center of Gene Technology, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Lei Wang
- State Key Laboratory of Genetic Engineering, Shanghai Engineering Research Center of Industrial Microorganisms, MOE Engineering Research Center of Gene Technology, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Ying Wang
- State Key Laboratory of Genetic Engineering, Shanghai Engineering Research Center of Industrial Microorganisms, MOE Engineering Research Center of Gene Technology, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Xinyi Jiang
- State Key Laboratory of Genetic Engineering, Shanghai Engineering Research Center of Industrial Microorganisms, MOE Engineering Research Center of Gene Technology, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Qin Qin
- State Key Laboratory of Genetic Engineering, Shanghai Engineering Research Center of Industrial Microorganisms, MOE Engineering Research Center of Gene Technology, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Menghua Song
- State Key Laboratory of Genetic Engineering, Shanghai Engineering Research Center of Industrial Microorganisms, MOE Engineering Research Center of Gene Technology, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Qiang Huang
- State Key Laboratory of Genetic Engineering, Shanghai Engineering Research Center of Industrial Microorganisms, MOE Engineering Research Center of Gene Technology, School of Life Sciences, Fudan University, Shanghai, 200438, China.
- Multiscale Research Institute of Complex Systems, Fudan University, Shanghai, 201203, China.
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