BACKGROUND Misfolding and aggregation of the presynaptic protein alpha-synuclein (αsyn) is a hallmark of Parkinson's disease (PD) and related synucleinopathies. Although predominantly localized in the cytosol, a body of evidence has shown that αsyn localizes to mitochondria and contributes to the disruption of key mitochondrial processes. Mitochondrial dysfunction is central to the progression of PD and mutations in mitochondrial-associated proteins are found in familial cases of PD. The sirtuins are highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent enzymes that play a broad role in cellular metabolism and aging. Interestingly, mitochondrial sirtuin 3 (SIRT3) plays a major role in maintaining mitochondrial function and preventing oxidative stress, and is downregulated in aging and age-associated diseases such as neurodegenerative disorders. Herein, we hypothesize that αsyn is associated with decreased SIRT3 levels contributing to impaired mitochondrial dynamics and biogenesis in PD. METHODS The level of mitochondrial SIRT3 was assessed in cells expressing oligomeric αsyn within the cytosolic and mitochondrial-enriched fractions. Mitochondrial integrity, respiration, and health were examined using several markers of mitochondrial dynamics and stress response and by measuring the rate of oxygen consumption (OCR). Our findings were validated in a rodent model of PD as well as in human post-mortem Lewy body disease (LBD) brain tissue. RESULTS Here, we demonstrate that αsyn associates with mitochondria and induces a decrease in mitochondrial SIRT3 levels and mitochondrial biogenesis. We show that SIRT3 downregulation is accompanied by decreased phosphorylation of AMPK and cAMP-response element binding protein (CREB), as well as increased phosphorylation of dynamin-related protein 1 (DRP1), indicative of impaired mitochondrial dynamics. OCR was significantly decreased suggesting a mitochondria respiratory deficit. Interestingly treatment with AMPK agonist 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) restores SIRT3 expression, improves mitochondrial function, and decreases αsyn oligomer formation in a SIRT3-dependent manner. CONCLUSIONS Together, our findings suggest that pharmacologically increasing SIRT3 levels can counteract αsyn-induced mitochondrial dysfunction by reducing αsyn oligomers and normalizing mitochondrial bioenergetics. These data support a protective role for SIRT3 in PD-associated pathways and contribute significant mechanistic insight into the interplay of SIRT3 and αsyn.

中文翻译：

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α-突触核蛋白诱导的线粒体功能障碍是通过 Sirtuin 3 依赖性途径介导的。


背景技术突触前蛋白α-突触核蛋白(αsyn)的错误折叠和聚集是帕金森病(PD)和相关突触核蛋白病的标志。尽管主要定位于细胞质，但大量证据表明 αsyn 定位于线粒体并有助于破坏关键的线粒体过程。线粒体功能障碍是帕金森病进展的核心，在帕金森家族病例中发现了线粒体相关蛋白的突变。 Sirtuins 是高度保守的烟酰胺腺嘌呤二核苷酸 (NAD+) 依赖性酶，在细胞代谢和衰老中发挥广泛作用。有趣的是，线粒体 Sirtuin 3 (SIRT3) 在维持线粒体功能和预防氧化应激方面发挥着重要作用，并且在衰老和与年龄相关的疾病（如神经退行性疾病）中表达下调。在此，我们假设 αsyn 与 SIRT3 水平降低有关，导致 PD 中线粒体动力学和生物合成受损。方法 在细胞质和线粒体富集部分中表达寡聚 αsyn 的细胞中评估线粒体 SIRT3 的水平。使用线粒体动力学和应激反应的多种标记以及测量耗氧率 (OCR) 来检查线粒体完整性、呼吸和健康状况。我们的研究结果在 PD 啮齿动物模型以及人类死后路易体病 (LBD) 脑组织中得到了验证。结果在这里，我们证明 αsyn 与线粒体结合并诱导线粒体 SIRT3 水平和线粒体生物合成降低。 我们发现 SIRT3 下调伴随着 AMPK 和 cAMP 反应元件结合蛋白 (CREB) 磷酸化的减少，以及动力相关蛋白 1 (DRP1) 磷酸化的增加，表明线粒体动力学受损。 OCR 显着下降，表明线粒体呼吸缺陷。有趣的是，用 AMPK 激动剂 5-氨基咪唑-4-甲酰胺-1-β-d-呋喃核苷 (AICAR) 治疗可恢复 SIRT3 表达，改善线粒体功能，并以 SIRT3 依赖性方式减少 αsyn 寡聚体形成。结论 总之，我们的研究结果表明，药理学上增加 SIRT3 水平可以通过减少 αsyn 寡聚体和使线粒体生物能正常化来抵消 αsyn 诱导的线粒体功能障碍。这些数据支持 SIRT3 在 PD 相关通路中的保护作用，并有助于深入了解 SIRT3 和 αsyn 的相互作用。