Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, Nadia, West Bengal, India.
School of Life Science, JNU, New Delhi, India.
Int J Biol Macromol. 2019 Jul 15;133:775-785. doi: 10.1016/j.ijbiomac.2019.04.026. Epub 2019 Apr 16.
Type VI secretion systems (T6SS) plays a crucial role in Vibrio cholerae mediated pathogenicity. Tip of T6SS is homologous to gp27/gp5 complex or tail spike of T4 bacteriophage. VgrG-1 of V. cholerae T6SS is unusual among other VgrG because its effector domain is trans-located into the cytosol of eukaryotic cells with an additional actin cross-linking domain (ACD) at its C terminal end. ACD of VgrG-1 (VgrG-1-ACD) causes T6SS dependent host cell cytotoxicity through actin cytoskeleton disruption to prevent bacterial engulfment by macrophages. ACD mediated actin cross-linking promotes survival of the bacteria in the small intestine of humans, along with other virulence factors; establishes successful infection with the onset of diarrhoea in humans. Our studies demonstrated VgrG-1-ACD can bind to actin besides actin cross-linking activity. Computational analysis of ACD revealed the presence of actin binding motif (ABM). Mutations in ABM lead to loss of actin binding in vitro. VgrG-1-ACD having the mutated ABM cannot cross-link actin efficiently in vitro and manifests less actin cytoskeleton disruption when transfected in HeLa cells.
VI 型分泌系统 (T6SS) 在霍乱弧菌介导的致病性中起着至关重要的作用。T6SS 的尖端与 gp27/gp5 复合物或 T4 噬菌体的尾刺同源。霍乱弧菌 T6SS 的 VgrG-1 在其他 VgrG 中是不同寻常的，因为它的效应结构域被转运到真核细胞的细胞质中，其 C 末端有一个额外的肌动蛋白交联结构域 (ACD)。VgrG-1 的 ACD（VgrG-1-ACD）通过破坏肌动蛋白细胞骨架导致 T6SS 依赖性宿主细胞细胞毒性，从而防止巨噬细胞吞噬细菌。ACD 介导的肌动蛋白交联促进了细菌在人类小肠中的存活，以及其他毒力因子的存活；随着腹泻的发作，在人类中建立了成功的感染。我们的研究表明，VgrG-1-ACD 除了具有肌动蛋白交联活性外，还可以与肌动蛋白结合。对 ACD 的计算分析显示存在肌动蛋白结合基序 (ABM)。ABM 中的突变导致体外肌动蛋白结合丧失。具有突变 ABM 的 VgrG-1-ACD 不能在体外有效地交联肌动蛋白，并且在转染 HeLa 细胞时表现出较少的肌动蛋白细胞骨架破坏。
