Velmurugan Kamalakannan, Chen Bing, Miller Jessica L, Azogue Sharon, Gurses Serdar, Hsu Tsungda, Glickman Michael, Jacobs William R, Porcelli Steven A, Briken Volker
Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America.
PLoS Pathog. 2007 Jul;3(7):e110. doi: 10.1371/journal.ppat.0030110.
The survival and persistence of Mycobacterium tuberculosis depends on its capacity to manipulate multiple host defense pathways, including the ability to actively inhibit the death by apoptosis of infected host cells. The genetic basis for this anti-apoptotic activity and its implication for mycobacterial virulence have not been demonstrated or elucidated. Using a novel gain-of-function genetic screen, we demonstrated that inhibition of infection-induced apoptosis of macrophages is controlled by multiple genetic loci in M. tuberculosis. Characterization of one of these loci in detail revealed that the anti-apoptosis activity was attributable to the type I NADH-dehydrogenase of M. tuberculosis, and was mainly due to the subunit of this multicomponent complex encoded by the nuoG gene. Expression of M. tuberculosis nuoG in nonpathogenic mycobacteria endowed them with the ability to inhibit apoptosis of infected human or mouse macrophages, and increased their virulence in a SCID mouse model. Conversely, deletion of nuoG in M. tuberculosis ablated its ability to inhibit macrophage apoptosis and significantly reduced its virulence in mice. These results identify a key component of the genetic basis for an important virulence trait of M. tuberculosis and support a direct causal relationship between virulence of pathogenic mycobacteria and their ability to inhibit macrophage apoptosis.
结核分枝杆菌的存活与持续存在取决于其操控多种宿主防御途径的能力，包括主动抑制受感染宿主细胞凋亡死亡的能力。这种抗凋亡活性的遗传基础及其对分枝杆菌毒力的影响尚未得到证实或阐明。通过一项新型的功能获得性遗传筛选，我们证明结核分枝杆菌中多个基因位点控制着对感染诱导的巨噬细胞凋亡的抑制。对其中一个位点的详细表征显示，抗凋亡活性归因于结核分枝杆菌的I型NADH脱氢酶，主要是由于该多亚基复合物中由nuoG基因编码的亚基。结核分枝杆菌nuoG在非致病性分枝杆菌中的表达赋予它们抑制受感染的人或小鼠巨噬细胞凋亡的能力，并在SCID小鼠模型中增强了它们的毒力。相反，结核分枝杆菌中nuoG的缺失消除了其抑制巨噬细胞凋亡的能力，并显著降低了其在小鼠中的毒力。这些结果确定了结核分枝杆菌一个重要毒力特征的遗传基础的关键组成部分，并支持致病性分枝杆菌的毒力与其抑制巨噬细胞凋亡能力之间存在直接因果关系。
