Proto William R, Jones Nathaniel G, Coombs Graham H, Mottram Jeremy C
Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK.
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, UK.
Microb Cell. 2014 Jan 6;1(1):9-20. doi: 10.15698/mic2014.01.120.
Autophagy is a lysosome-dependent degradation mechanism that sequesters target cargo into autophagosomal vesicles. The genome contains apparent orthologues of several autophagy-related proteins including an ATG8 family. These ubiquitin-like proteins are required for autophagosome membrane formation, but our studies show that ATG8.3 is atypical. To investigate the function of other ATG proteins, RNAi compatible were modified to function as autophagy reporter lines by expressing only either YFP-ATG8.1 or YFP-ATG8.2. In the insect procyclic lifecycle stage, independent RNAi down-regulation of ATG3 or ATG7 generated autophagy-defective mutants and confirmed a pro-survival role for autophagy in the procyclic form nutrient starvation response. Similarly, RNAi depletion of ATG5 or ATG7 in the bloodstream form disrupted autophagy, but did not impede proliferation. Further characterisation showed bloodstream form autophagy mutants retain the capacity to undergo the complex cellular remodelling that occurs during differentiation to the procyclic form and are equally susceptible to dihydroxyacetone-induced cell death as wild type parasites, not supporting a role for autophagy in this cell death mechanism. The RNAi reporter system developed, which also identified TOR1 as a negative regulator controlling YFP-ATG8.2 but not YFP-ATG8.1 autophagosome formation, will enable further targeted analysis of the mechanisms and function of autophagy in the medically relevant bloodstream form of
自噬是一种依赖溶酶体的降解机制,它将靶标货物隔离到自噬体小泡中。该基因组包含几种自噬相关蛋白的明显直系同源物,包括一个ATG8家族。这些类泛素蛋白是自噬体膜形成所必需的,但我们的研究表明ATG8.3是不典型的。为了研究其他ATG蛋白的功能,通过仅表达YFP-ATG8.1或YFP-ATG8.2,将RNAi兼容载体修饰为自噬报告株系。在昆虫前循环生命周期阶段,对ATG3或ATG7进行独立的RNAi下调产生了自噬缺陷型突变体,并证实了自噬在前循环形式的营养饥饿反应中具有促生存作用。同样,在血流形式中对ATG5或ATG7进行RNAi敲低会破坏自噬,但不会阻碍增殖。进一步的表征表明,血流形式的自噬突变体保留了在分化为前循环形式过程中发生复杂细胞重塑的能力,并且与野生型寄生虫一样容易受到二羟基丙酮诱导的细胞死亡的影响,这并不支持自噬在这种细胞死亡机制中起作用。所开发的RNAi报告系统还确定TOR1是控制YFP-ATG8.2而非YFP-ATG8.1自噬体形成的负调节因子,这将有助于对医学上相关的血流形式中自噬的机制和功能进行进一步的靶向分析。