Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica.
Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica.
Infect Immun. 2018 Mar 22;86(4). doi: 10.1128/IAI.00713-17. Print 2018 Apr.
is a facultative extracellular-intracellular pathogen belonging to a group of that establishes close interactions with animal cells. This bacterium enters host cells in a membrane-bound compartment, avoiding the lysosomal route and reaching the endoplasmic reticulum through the action of the type IV secretion system, VirB. In this work, we demonstrate that the BvrR/BvrS two-component system senses the intracellular environment to mount the transcriptional response required for intracellular life adaptation. By combining a method to purify intracellularly extracted bacteria with a strategy that allows direct determination of BvrR phosphorylation, we showed that upon entrance to host cells, the regulatory protein BvrR was activated (BvrR-P) by phosphorylation at aspartate 58. This activation takes place in response to intracellular cues found in early compartments, such as low pH and nutrient deprivation. Furthermore, BvrR activation was followed by an increase in the expression of VjbR and VirB. The activation of this BvrR-P/VjbR/VirB virulence circuit rescued from the inhibition of intracellular replication induced by bafilomycin treatment of cells, demonstrating the relevance of this mechanism for intracellular bacterial survival and replication. All together, our results indicate that senses the transition from the extracellular to the intracellular milieu through BvrR/BvrS, allowing the bacterium to transit safely to its replicative niche. These results serve as a working model for understanding the role of this family of two-component systems in the adaptation to intracellular life of .
是一种兼性细胞内外病原体，属于一组与动物细胞建立密切相互作用的细菌。这种细菌通过 IV 型分泌系统 VirB 的作用，进入宿主细胞的膜结合隔室，避免了溶酶体途径，并到达内质网。在这项工作中，我们证明了 BvrR/BvrS 双组分系统感知细胞内环境，以启动适应细胞内生活所需的转录反应。通过结合一种纯化细胞内提取细菌的方法和一种允许直接测定 BvrR 磷酸化的策略，我们表明，进入宿主细胞后，调节蛋白 BvrR 通过天冬氨酸 58 的磷酸化被激活（BvrR-P）。这种激活发生在早期隔室中发现的细胞内信号的响应，例如低 pH 值和营养剥夺。此外，BvrR 激活伴随着 VjbR 和 VirB 的表达增加。这种 BvrR-P/VjbR/VirB 毒力回路的激活挽救了 免受细胞用巴弗洛霉素处理诱导的细胞内复制抑制，证明了这种机制对于细胞内细菌存活和复制的相关性。总之，我们的结果表明，通过 BvrR/BvrS 感知从细胞外到细胞内环境的转变，使细菌能够安全地过渡到其复制生态位。这些结果为理解这组双组分系统在适应细胞内生活中的作用提供了一个工作模型。
