A Role of hUCP2 in Mitochondrial Quality Control and Dopaminergic Neuroprotection

描述(申请人提供)：帕金森病(PD)，由黑质致密部多巴胺(DA)神经元选择性丧失引起，是最常见的运动障碍，影响1%的60岁以上人口，没有治愈或有效的治疗。尽管帕金森病的病因尚不清楚，但来自遗传和毒素模型的证据表明，线粒体重塑和转换的失调是帕金森病病理生理中突出的细胞缺陷。我们最近报道了果蝇DA神经元中hucp2的表达对鱼藤酮诱导的DA神经元死亡和头部多巴胺耗竭具有保护作用。我们扩展了我们的毒素模型，并证明了hUCP2对MPP+诱导的DA神经元变性的保护作用。为了开始了解保护机制，我们考虑了线粒体解偶联的生物能量学后果，并假设AMP激活的蛋白激酶(AMPK)是hUCP2的下游效应因子。为了支持这一观点，我们检测到当hucp2在果蝇S2R+细胞中被诱导表达时，磷酸化的AMPK表明它被激活。与我们的遗传相互作用研究揭示了hUCP2和线粒体融合分子之间的功能合作一致，我们目前的结果表明，hUCP2的神经保护作用需要线粒体融合。此外，自噬活性的增强与脑DA神经元中hucp2的表达有关。另外支持我们提出的hUCP2-AMPK轴的结果表明，在表达hUCP2或AMPK的原代DA神经元中，毒素诱导的线粒体碎裂被减弱，并且AMPK对毒素诱导的神经元丢失的保护作用与自噬受体Ref(2)P的积累减少有关。综上所述，这些初步结果使我们假设，由于hucp2表达的结果，AMPK的激活促进了线粒体融合和自噬，从而增强了线粒体的健康和DA神经元的存活。为了验证我们的假设，我们将确定：1)AMPK是否是hUCP2调控DA神经元线粒体融合/分裂的下游效应者；2)AMPK是否刺激毒素暴露的DA神经元的自噬活性和线粒体周转；3)线粒体融合和自噬是否是hUCP2-AMPK介导的DA神经元抗毒素存活的关键组成部分。

DESCRIPTION (provided by applicant): Parkinson's disease (PD), caused by selective loss of dopaminergic (DA) neurons in the substantia nigra pars compacta, is the most common movement disorder affecting 1% of the population over the age 60 with no cure or effective treatment. Although the etiology of PD remains unknown, converging evidence from genetic and toxin models points to dysregulation of mitochondrial remodeling and turnover as prominent cellular defects in PD pathophysiology. We recently reported that hucp2 expression in Drosophila DA neurons protects flies against rotenone-induced DA neuron death and head dopamine depletion. We have expanded our toxin model and demonstrated hUCP2 protective effect against MPP+-induced DA neuron degeneration. To begin to understand the protective mechanisms, we considered the bioenergetic consequences of mitochondrial uncoupling and postulated AMP activated protein kinase (AMPK) as a downstream effector of hUCP2. In supporting this idea, we detected phosphorylated AMPK¿ indicative of its activation when hucp2 expression is induced in Drosophila S2R+ cells. Consistent with our genetic interaction study revealing functional cooperation between hUCP2 and mitochondrial fusion molecules, our current results suggest hUCP2 neuroprotective effect requires mitochondrial fusion. Furthermore, increased autophagic activity is associated with hucp2 expression in brain DA neurons. Additional support for our proposed hUCP2-AMPK axis are results showing that toxin-induced mitochondrial fragmentation is attenuated in hucp2 or AMPK expressing primary DA neurons and AMPK protective effect against toxin-induced neuron loss is associated with less accumulation of the autophagy receptor Ref(2)P. Taken together, those preliminary results led us to hypothesize that activation of AMPK as the result of hucp2 expression promotes mitochondrial fusion and autophagy to enhance mitochondrial health and survival of DA neurons. To test our hypothesis, we will determine i) whether AMPK is a downstream effector of hUCP2 in regulating mitochondrial fusion/fission in DA neurons, ii) whether AMPK stimulates autophagic activity and mitochondrial turnover in DA neurons exposed to toxin and iii) whether mitochondrial fusion and autophagy are critical components in hUCP2-AMPK mediated DA neuron survival against toxin.