维生素K2对SCA3/MJD转基因果蝇的作用及对ataxin-3蛋白降解的影响

Recently some researchers have found that vitamin K2 was necessary and sufficient to transfer electrons in Drosophila mitochondria. mitochondrial dysfunction of PD transgenic flies was rescued by vitamin K2 that serves as a mitochondrial electron carrier, helping to improve flight , increase ATP amount and a more negative mitochondrial membrane potential(Ψm). Interestingly, in previous work we have shown that vitamin K2 can rescue the lifespan of SCA3/MJD transgenic flies and significantly promote degradation of ataxin-3.But it showes a dose-dependent role, over-low and over-high doses of vitamin K2 can increase the level of ataxin-3. In this study, we will focus on the role of different doses of vitamin K2 on SCA3/MJD transgenic flies and the effects on degradation of ataxin-3 by using different methods including the immunofluorescence, immune precipitation, flow cytometryn. It is important to determine the role of mitochondrial membrane potential on degradation of ataxin-3 in the ubiquitin-proteasome system (UPS) and autophagy-lysosome pathway (ALP). We will further explore whether autophagy- lysosome acts as a compensatory degradation system when the UPS is impaired in SCA3/MJD transgenic flies and that histone deacetylase 6 (HDAC6) is an essential mechanistic link in this compensatory interaction. These results will provide strong support for studying Pathogenesis of SCA3/MJD, and pave the way for finding new medicines to cure it.

最近的研究发现，维生素K2是一种呼吸链电子载体，可提高线粒体膜电位，改善帕金森病果蝇的线粒体功能，提高果蝇飞行能力。我们在前期预实验中也发现，维生素K2不但同样可以挽救SCA3/MJD转基因果蝇，还显著促进了其致病蛋白ataxin-3的降解，但其作用效果与浓度明显相关，过高或过低反而增加了ataxin-3蛋白浓度。在本研究中，我们将通过免疫印迹，免疫荧光，流式细胞术等方法，研究不同浓度维生素K2对SCA3/MJD转基因果蝇的作用及其对ataxin-3蛋白降解的影响，明确线粒体膜电位对ataxin-3蛋白在泛素-蛋白酶体通路（UPS）和自噬-溶酶体通路（ALP）降解中的作用，进一步探讨ataxin-3蛋白降解方式是否会因线粒体膜电位改变而在UPS和ALP之间转换，UPS和ALP是否互为对方的补偿机制，以及这种互补机制是否与HDAC6有关，为研究SCA3/MJD发病机制和治疗提供新的思路。

维生素K2 能够促进致病蛋白ataxin-3的降解从而挽救SCA3/MJD 转基因果蝇，且具有明显的量效关系：维生素K2浓度的过高或过低都会导致果蝇神经变性症状的加重。维生素K2是果蝇线粒体呼吸链中转运电子的必要条件，能够提高异常线粒体的线粒体膜电位，促进线粒体的氧化磷酸化和ATP生成。实验表明，经维生素K2饲养的SCA3转基因果蝇线粒体功能明显提高，果蝇飞行能力等表型明显改善，维生素K2可能通过调控线粒体膜电位水平降解突变的ataxin-3 蛋白。抑制UPS或ALP后，维生素K2的挽救效果减弱，但仍有一定的保护作用，同时抑制UPS和ALP，维生素K2的挽救效果消失，说明在其中一个清除系统受抑制时，会相应激活另个一清除机制。维生素K2挽救SCA3/MJD 转基因果蝇为临床研究SCA3/MJD发病机制和治疗提供新的思路。

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