Mittra Bidyottam, Laranjeira-Silva Maria Fernanda, Miguel Danilo Ciccone, Perrone Bezerra de Menezes Juliana, Andrews Norma W
Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742-5815.
Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742-5815.
J Biol Chem. 2017 Jul 21;292(29):12324-12338. doi: 10.1074/jbc.M116.772624. Epub 2017 May 26.
Leishmaniasis is one of the leading globally neglected diseases, affecting millions of people worldwide. infection depends on the ability of insect-transmitted metacyclic promastigotes to invade mammalian hosts, differentiate into amastigotes, and replicate inside macrophages. To counter the hostile oxidative environment inside macrophages, these protozoans contain anti-oxidant systems that include iron-dependent superoxide dismutases (SODs) in mitochondria and glycosomes. Increasing evidence suggests that in addition to this protective role, mitochondrial SOD may also initiate HO-mediated redox signaling that regulates gene expression and metabolic changes associated with differentiation into virulent forms. To investigate this hypothesis, we examined the specific role of SODA, the mitochondrial SOD isoform in Our inability to generate null mutants and the lethal phenotype observed following RNAi-mediated silencing of the ortholog suggests that SODA is essential for trypanosomatid survival. metacyclic promastigotes lacking one allele failed to replicate in macrophages and were severely attenuated in their ability to generate cutaneous lesions in mice. Reduced expression of SODA also resulted in mitochondrial oxidative damage and failure of /Δ promastigotes to differentiate into axenic amastigotes. SODA expression above a critical threshold was also required for the development of metacyclic promastigotes, as /Δ cultures were strongly depleted in this infective form and more susceptible to reactive oxygen species (ROS)-induced stress. Collectively, our data suggest that SODA promotes virulence by protecting the parasites against mitochondrion-generated oxidative stress and by initiating ROS-mediated signaling mechanisms required for the differentiation of infective forms.
利什曼病是全球主要的被忽视疾病之一，影响着全球数百万人。感染取决于昆虫传播的循环前鞭毛体侵入哺乳动物宿主、分化为无鞭毛体并在巨噬细胞内复制的能力。为了应对巨噬细胞内恶劣的氧化环境，这些原生动物含有抗氧化系统，包括线粒体和糖体中的铁依赖性超氧化物歧化酶（SOD）。越来越多的证据表明，除了这种保护作用外，线粒体SOD还可能启动HO介导的氧化还原信号传导，调节与分化为致病形式相关的基因表达和代谢变化。为了研究这一假设，我们研究了SODA（线粒体SOD同工型）在 中的具体作用。我们无法产生 基因敲除突变体，以及在RNAi介导的直系同源基因沉默后观察到的致死表型，这表明SODA对锥虫的存活至关重要。缺乏一个 等位基因的循环前鞭毛体无法在巨噬细胞中复制，并且在小鼠中产生皮肤病变的能力严重减弱。SODA表达的降低还导致线粒体氧化损伤以及 /Δ前鞭毛体无法分化为无菌无鞭毛体。循环前鞭毛体的发育也需要SODA表达高于临界阈值，因为 /Δ培养物中这种感染形式严重减少，并且更容易受到活性氧（ROS）诱导的应激影响。总体而言，我们的数据表明，SODA通过保护寄生虫免受线粒体产生的氧化应激以及启动感染性形式分化所需的ROS介导的信号传导机制来促进 毒力。
