Mitochondrial fission in Huntington's Disease

亨廷顿病中的线粒体裂变

• 批准号: 9222045
• 负责人: Ella R Bossy-Wetzel
• 金额: $ 31.35万
• 依托单位: UNIVERSITY OF CENTRAL FLORIDA
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-02-01 至 2019-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9222045
• 关键词: ATP Synthesis Pathway; Address; Affect; American; Apoptosis; Axonal Transport; Binding; Bioenergetics; Buffers; Cell Death; Cell Survival; Cells; Cellular biology; Chorea; Complex; Corpus striatum structure; Data; Defect; Dementia; Development; Disease; Dynamin; Emotional; Energy Metabolism; Event; Exhibits; Functional disorder; Funding; Goals; Guanosine Triphosphate; Guanosine Triphosphate Phosphohydrolases; Health; Homeostasis; Human; Huntington Disease; Huntington gene; Hydrolysis; Hyperactive behavior; In Vitro; Inherited; Injury; Knockout Mice; Lead; Mediating; Mitochondria; Mitosis; Molecular Conformation; Morphology; Motor; Mus; Mutation; Nerve Degeneration; Neurodegenerative Disorders; Neuronal Injury; Neurons; Patients; Phosphorylation; Phosphotransferases; Physiological; Play; Post-Translational Protein Processing; Process; Proteins; Role; Site; Structure; Substrate Specificity; Synapses; Synaptic Transmission; System; Testing; Therapeutic; caregiving; cognitive ability; cost; cytochrome c; effective therapy; experience; experimental study; improved; in vivo; insight; knock-down; mitochondrial dysfunction; mutant; neuron loss; neurotoxicity; novel therapeutics; particle; polyglutamine; progressive chorea; public health relevance; respiratory; self assembly; synaptic function; targeted treatment; three dimensional structure

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a neurodegenerative disease caused by an abnormal expansion of a poly- glutamine (poly-Q) repeats in huntingtin (Htt), a 350 kDa protein. People with HD experience chorea, dementia, and psychiatric disturbances. In HD, long projection neurons of the cortex and striatum degenerate by an unknown mechanism. There is currently no cure or effective treatment for this devastating disease. Neurons depend on mitochondria to provide energy to fuel specialized processes, e.g., synaptic transmission, channel activity, and axonal transport. To meet the constantly changing energy needs of neurons, mitochondria undergo frequent fission and fusion. These dynamic processes stimulate ATP synthesis, maintain Ca2+ homeostasis, and mediate cell survival. However, excessive fission without counterbalancing fusion causes fragmented mitochondrial morphology, neuronal injury, and apoptosis. Fission and fusion is regulated by large conserved GTPases of the dynamin super-family. Dynamin-related protein 1 (DRP1) is required for mitochondrial fission. Under physiological conditions, DRP1 GTPase activity is kept in check. Posttranslational modifications (PTMs) including phosphorylation can activate DRP1. For example, transient DRP1 Ser616 phosphorylation by Cdk1-CyclinB activates mitochondrial fission. There is strong evidence that mitochondrial dysfunction occurs early and plays a causal role in HD. For example, mitochondria from HD patients and HD mice exhibit fragmented morphology, respiratory complex inhibition, diminished Ca2+ buffering capacity, and a sensitized induction towards cytochrome c release and apoptosis. In addition, mutant Htt (mHtt) localizes to mitochondrial fission sites, directly binds DRP1, activates DRP1 GTPase activity, and alters its oligomeric ring-like structure. We have shown that decreasing DRP1 GTPase activity rescues cultured neurons from mHtt-induced excessive mitochondrial fission, axonal transport defects, synaptic injury, and cell death. Persistent Cdk5 activation by p25 and aberrant Cdk5 subcellular localization and substrate specificity also contribute to neurodegeneration. Whether Cdk5-p25 aberrantly phosphorylates DRP1 at Ser616, thereby promoting excessive mitochondrial fission in HD, is unknown. Therefore, the specific questions that will be addressed here are: (1) Does Cdk5-p25 cause DRP1 Ser616 hyperphosphorylation and mitochondrial fission in HD? (2) Does DRP1 Ser616 hyperphosphorylation play a causal role in mHtt-mediated neuronal cell death? (3) By which mechanism does mHtt interaction and Ser616 phosphorylation stimulate DRP1 activity? Results obtained here may provide a mechanistic explanation for DRP1 hyperactivity in neurodegeneration and form the basis for new therapies.

描述(申请人提供)：亨廷顿病(HD)是一种神经退行性疾病，由亨廷顿蛋白(Htt)中的多谷氨酰胺(Poly-Q)重复序列异常扩张引起，亨廷顿蛋白是一种350 kDa的蛋白质。患有多动症的人会有舞蹈症、痴呆症和精神障碍。在HD中，皮质和纹状体的长投射神经元以一种未知的机制退化。目前还没有治愈或有效治疗这种毁灭性疾病的方法。神经元依赖线粒体提供能量，为突触传递、通道活动和轴突运输等特殊过程提供能量。为了满足神经元不断变化的能量需求，线粒体经历了频繁的分裂和融合。这些动态过程刺激了ATP的合成，维持了钙离子的稳态，并调节了细胞的存活。然而，过度的分裂而不平衡的融合会导致线粒体形态的碎裂、神经元损伤和细胞凋亡。核分裂和融合是由动力蛋白超家族的大保守GTP酶调控的。动力蛋白相关蛋白1(Drp1)是线粒体分裂所必需的。在生理条件下，Drp1 GTP酶的活性处于受控状态。包括磷酸化在内的翻译后修饰(PTM)可以激活DRp1。例如，CDK1-CyclinB对Drp1 Ser616的瞬时磷酸化激活了线粒体的分裂。有强有力的证据表明，线粒体功能障碍发生在早期，并在HD中起到因果作用。例如，HD患者和HD小鼠的线粒体表现出形态碎裂、呼吸复合体抑制、钙缓冲能力减弱以及对细胞色素c释放和细胞凋亡的敏化诱导。此外，突变体Htt(MHTT)定位于线粒体的分裂位点，直接与Drp1结合，激活Drp1 GTPase活性，改变其寡聚体环状结构。我们已经证明，降低Drp1 GTPase活性可以将培养的神经元从mHTT诱导的过度线粒体分裂、轴突运输缺陷、突触损伤和细胞死亡中拯救出来。由p25持续激活的CDK5和异常的CDK5亚细胞定位和底物特异性也是神经退行性变的原因。CDK5-p25是否异常地磷酸化了Ser616处的Drp1，从而促进了HD患者线粒体的过度分裂，目前尚不清楚。因此，这里要解决的具体问题是：(1)CDK5-p25是否导致HD中Drp1 Ser616过度磷酸化和线粒体分裂？(2)Drp1 Ser616过度磷酸化是否在mHTT介导的神经细胞死亡中起因果作用？(3)mHTT相互作用和Ser616磷酸化通过什么机制刺激Drp1活性？本研究的结果可能为神经退行性变中Drp1的过度活动提供一个机制上的解释，并形成新的治疗方法的基础。

项目成果

Molecular mechanism of DRP1 assembly studied in vitro by cryo-electron microscopy.

• DOI: 10.1371/journal.pone.0179397
• 发表时间: 2017
• 期刊: PloS one
• 影响因子: 3.7
• 作者: Basu K;Lajoie D;Aumentado-Armstrong T;Chen J;Koning RI;Bossy B;Bostina M;Sik A;Bossy-Wetzel E;Rouiller I
• 通讯作者: Rouiller I