MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom.
PLoS One. 2020 Feb 26;15(2):e0228941. doi: 10.1371/journal.pone.0228941. eCollection 2020.
The type VI secretion system (T6SS) is a contractile injection apparatus that translocates a spike loaded with various effectors directly into eukaryotic or prokaryotic target cells. Pseudomonas aeruginosa can load either one of its three T6SSs with a variety of toxic bullets using different but specific modes. The T6SS spike, which punctures the bacterial cell envelope allowing effector transport, consists of a torch-like VgrG trimer on which sits a PAAR protein sharpening the VgrG tip. VgrG itself sits on the Hcp tube and all elements, packed into a T6SS sheath, are propelled out of the cell and into target cells. On occasion, effectors are covalent extensions of VgrG, PAAR or Hcp proteins, which are then coined "evolved" components as opposed to canonical. Here, we show how various passenger domains could be fused to the C terminus of a canonical VgrG, VgrG1a from P. aeruginosa, and be sent into the bacterial culture supernatant. There is no restriction on the passenger type, although the efficacy may vary greatly, since we used either an unrelated T6SS protein, β-lactamase, a covalent extension of an "evolved" VgrG, VgrG2b, or a Hcp-dependent T6SS toxin, Tse2. Our data further highlights an exceptional modularity/flexibility for loading the T6SS nano-weapon. Refining the parameters to optimize delivery of passenger proteins of interest would have attractive medical and industrial applications. This may for example involve engineering the T6SS as a delivery system to shuttle toxins into either bacterial pathogens or tumour cells which would be an original approach in the fight against antimicrobial resistant bacteria or cancer.
VI 型分泌系统（T6SS）是一种可收缩的注射装置，可将装载各种效应器的刺针直接输送到真核或原核靶细胞中。铜绿假单胞菌可以使用不同但特定的模式将其三种 T6SS 中的任何一种装载到各种毒性弹丸上。刺穿细菌细胞膜允许效应物转运的 T6SS 刺针由一个类似于火炬的 VgrG 三聚体组成，其上坐着一个 PAAR 蛋白，可锐化 VgrG 尖端。VgrG 本身位于 Hcp 管上，所有元件都被包装在 T6SS 鞘中，从细胞中被推出并进入靶细胞。有时，效应物是 VgrG、PAAR 或 Hcp 蛋白的共价延伸，然后被称为“进化”成分，而不是经典成分。在这里，我们展示了各种乘客结构域如何融合到铜绿假单胞菌的 T6SS 中的一个经典 VgrG（VgrG1a）的 C 末端，并被送入细菌培养上清液中。对乘客类型没有限制，尽管效力可能会有很大差异，因为我们使用了不相关的 T6SS 蛋白、β-内酰胺酶、“进化”VgrG 的共价延伸 VgrG2b 或 Hcp 依赖性 T6SS 毒素 Tse2。我们的数据进一步强调了装载 T6SS 纳米武器的异常模块化/灵活性。优化感兴趣的乘客蛋白传递的参数将具有有吸引力的医疗和工业应用。例如，这可能涉及将 T6SS 工程化为一种输送系统，将毒素输送到细菌病原体或肿瘤细胞中，这将是对抗抗微生物耐药菌或癌症的一种新方法。
