Torres Angie K, Rivera Bastián I, Polanco Catalina M, Jara Claudia, Tapia-Rojas Cheril
Laboratory of Neurobiology of Aging, Centro de Biología Celular y Biomedicina (CEBICEM), Facultad de Medicina y Ciencia, Universidad San Sebastián, Sede Los Leones, Santiago, Chile.
Neural Regen Res. 2022 Aug;17(8):1645-1651. doi: 10.4103/1673-5374.332125.
During normal aging, there is a decline in all physiological functions in the organism. One of the most affected organs is the brain, where neurons lose their proper synaptic function leading to cognitive impairment. Aging is one of the main risk factors for the development of neurodegenerative diseases, such as Alzheimer's disease. One of the main responsible factors for synaptic dysfunction in aging and neurodegenerative diseases is the accumulation of abnormal proteins forming aggregates. The most studied brain aggregates are the senile plaques, formed by Aβ peptide; however, the aggregates formed by phosphorylated tau protein have gained relevance in the last years by their toxicity. It is reported that neurons undergo severe mitochondrial dysfunction with age, with a decrease in adenosine 5'-triphosphate production, loss of the mitochondrial membrane potential, redox imbalance, impaired mitophagy, and loss of calcium buffer capacity. Interestingly, abnormal tau protein interacts with several mitochondrial proteins, suggesting that it could induce mitochondrial dysfunction. Nevertheless, whether tau-mediated mitochondrial dysfunction occurs indirectly or directly is still unknown. A recent study of our laboratory shows that phosphorylated tau at Ser396/404 (known as PHF-1), an epitope commonly related to pathology, accumulates inside mitochondria during normal aging. This accumulation occurs preferentially in synaptic mitochondria, which suggests that it may contribute to the synaptic failure and cognitive impairment seen in aged individuals. Here, we review the main tau modifications promoting mitochondrial dysfunction, and the possible mechanism involved. Also, we discuss the evidence that supports the possibility that phosphorylated tau accumulation in synaptic mitochondria promotes synaptic and cognitive impairment in aging. Finally, we show evidence and argue about the presence of phosphorylated tau PHF-1 inside mitochondria in Alzheimer's disease, which could be considered as an early event in the neurodegenerative process. Thus, phosphorylated tau PHF-1 inside the mitochondria could be considered such a potential therapeutic target to prevent or attenuate age-related cognitive impairment.
在正常衰老过程中，机体的所有生理功能都会下降。受影响最严重的器官之一是大脑，其中神经元失去正常的突触功能，导致认知障碍。衰老是神经退行性疾病（如阿尔茨海默病）发展的主要风险因素之一。衰老和神经退行性疾病中突触功能障碍的主要责任因素之一是形成聚集体的异常蛋白质的积累。研究最多的脑聚集体是由Aβ肽形成的老年斑；然而，近年来，由磷酸化tau蛋白形成的聚集体因其毒性而受到关注。据报道，随着年龄的增长，神经元会出现严重的线粒体功能障碍，三磷酸腺苷生成减少、线粒体膜电位丧失、氧化还原失衡、线粒体自噬受损以及钙缓冲能力丧失。有趣的是，异常的tau蛋白与几种线粒体蛋白相互作用，表明它可能诱导线粒体功能障碍。然而，tau介导的线粒体功能障碍是间接还是直接发生仍不清楚。我们实验室最近的一项研究表明，Ser396/404位点磷酸化的tau（称为PHF-1），这是一个通常与病理学相关的表位，在正常衰老过程中会在线粒体内积累。这种积累优先发生在突触线粒体中，这表明它可能导致老年个体出现的突触功能衰竭和认知障碍。在这里，我们综述了促进线粒体功能障碍的主要tau修饰及其可能涉及的机制。此外，我们讨论了支持突触线粒体中磷酸化tau积累促进衰老过程中突触和认知障碍这一可能性的证据。最后，我们展示了阿尔茨海默病中线粒体内存在磷酸化tau PHF-1的证据，并对其进行了论证，这可被视为神经退行性过程中的一个早期事件。因此，线粒体内的磷酸化tau PHF-1可被视为预防或减轻与年龄相关的认知障碍的潜在治疗靶点。
