A Role of hUCP2 in Mitochondrial Quality Control and Dopaminergic Neuroprotection

描述（由申请人提供）：帕金森病（PD）是由黑质致密部多巴胺能（DA）神经元的选择性丧失引起的，是最常见的运动障碍，影响了1%的60岁以上人群，目前尚无治愈或有效治疗方法。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，线粒体重塑和周转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的表达保护果蝇免受鱼藤酮诱导的DA神经元死亡和头部多巴胺耗竭。我们扩大了毒素模型，证明了hUCP2对MPP+诱导的DA神经元变性具有保护作用。为了开始理解保护机制，我们考虑了线粒体解偶联的生物能量后果，并假设AMP激活的蛋白激酶（AMPK）是hUCP2的下游效应物。为了支持这一观点，我们在果蝇S2R+细胞中检测到磷酸化的AMPK¿，表明当诱导hucp2表达时，AMPK¿被激活。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，我们目前的研究结果表明，hUCP2的神经保护作用需要线粒体融合。此外，自噬活性的增加与脑DA神经元中hucp2的表达有关。对我们提出的hucp2 -AMPK轴的进一步支持是，结果显示毒素诱导的线粒体片段在表达hucp2或AMPK的初级DA神经元中减弱，AMPK对毒素诱导的神经元损失的保护作用与自噬受体Ref(2)P的积累较少有关。综上所述，这些初步结果使我们假设，hucp2表达导致AMPK活化，促进线粒体融合和自噬，从而增强DA神经元的线粒体健康和存活。为了验证我们的假设，我们将确定i) AMPK是否在调节DA神经元线粒体融合/裂变中是hUCP2的下游效应者，ii) AMPK是否刺激暴露于毒素的DA神经元的自噬活性和线粒体更新，iii)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成分。

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.