Alpha-synuclein degradation mechanisms

描述(申请人提供)：a-突触核蛋白(a-syn)突变或基因扩增导致帕金森氏病(PD)的一小部分，伴有路易小体(Lb)形成、神经退行性变和通常相关的痴呆症。在散发性帕金森病和其他肝病中也广泛存在A-syn聚集，但没有明显的转录上调。在各种动物模型中，A-SYN的过表达导致其聚集和/或神经毒性。在动物模型中，降低α-syn具有神经保护作用。这些观察表明，在治疗PD和其他LB病时，减少a-SYN具有治疗潜力。我们的长期目标是确定神经退行性疾病中a-突触核病的机制和调节，并提供新的有效的治疗策略。由于溶酶体是高容量细胞器，负责清除受损和聚集的蛋白质，并与衰老和一些神经退行性疾病有关，因此我们重点讨论溶酶体在调节神经元α-SYN聚集和毒性方面的功能。我们发现溶酶体组织蛋白酶D(CD)缺陷的小鼠表现出显著的a-syn在脑内的积聚，这表明Cd在介导a-syn代谢中起着关键作用。在体外，我们已经证明，CD的过度表达减少了a-syn的聚集，并保护了a-syn介导的毒性。为了进一步确立CD作为治疗α-突触核病的靶点，我们将检测其在体内的作用，并确定其体外作用机制。我们假设，Cd通过增加a-syn有毒物种的自噬清除来保护a-syn的神经毒性。我们将通过以下目的进行实验来验证这一假说：1.在体内验证CD单倍体不足增加对α-SYN诱导的神经毒性的敏感性的假说。2.在体内验证立体定向注射AAV-CD可减轻α-syn介导的神经毒性的假说。3.验证CD的神经保护作用是通过自噬清除a-syn的假说。这些研究的完成将确定部分Cd在α-SYN诱导的DA神经元死亡中的作用，以及Cd在体内神经保护中的作用。此外，对CD介导的神经保护的潜在分子机制以及易于聚集的蛋白质清除的分子机制和调节的深入了解，将有助于进一步完善CD的治疗策略。 公共卫生相关性：a-突触核蛋白突变或基因扩增导致帕金森病的一小部分，并聚集在其他神经退行性疾病中，伴有a-突触核素病，有时甚至在没有基因突变的情况下也会相关痴呆。我们的工作将确定自噬-溶酶体途径在降低a-syn水平和毒性方面的作用，这一策略与改进PD和其他a-突触核病的治疗相关。

DESCRIPTION (provided by applicant): a-synuclein (a-syn) mutations or gene amplification cause a small subset of Parkinson's disease (PD), with Lewy body (LB) formation, neurodegeneration and often an associated dementia. a-syn aggregation in LB is also widespread in sporadic PD and other LB diseases without apparent upregulation of transcription. a-syn overexpression leads to its aggregation and/or neurotoxicity in various animal models. Reduction of a-syn is neuroprotective in animal models. These observations suggest a therapeutic potential of reducing a-syn in treatment of PD and other LB diseases. Our long-term objective is to determine the mechanisms and regulation of a-synucleinopathy in neurodegenerative diseases, and to provide novel and effective treatment strategies. We focused on the lysosomal function in modulating neuronal a-syn aggregation and toxicity, because lysosomes are high capacity organelles responsible for clearance of damaged and aggregated proteins, and are implicated in aging and several neurodegenerative diseases. We found that mice with deficient lysosomal cathepsin D (CD) exhibited significant a-syn accumulation in the brains, indicating a critical role for CD in mediating a-syn metabolism. In vitro we have shown that overexpression of CD reduces a-syn aggregation and protects against a-syn-mediated toxicity. To further establish CD as a therapeutic target against a-synucleinopathy, we will examine its effects in vivo, and define the mechanisms of its action in vitro. We hypothesize that CD protects against a-syn neurotoxicity by increasing autophagic clearance of toxic species of a-syn. We will test this hypothesis by performing experiments with the following aims: 1. Test the hypothesis that CD haploinsufficiency increases sensitivity to a-syn-induced neurotoxicity in vivo. 2. Test the hypothesis that stereotaxic delivery of AAV-CD to the SN attenuates a-syn-mediated neurotoxicity in vivo. 3. Test the hypothesis that neuroprotection by CD is through clearance of a-syn by autophagy. Completion of these studies will determine the effect of partial loss-of-CD in a-syn-induced DA neuron death, and the effect of gain-of-function of CD in neuroprotection in vivo. Furthermore, insights into the potential molecular mechanisms of CD-mediated neuroprotection and the molecular mechanisms and regulation of clearance of aggregation-prone proteins, will be gained that will permit further refinement of CD therapeutic strategies. PUBLIC HEALTH RELEVANCE: a-synuclein mutations or gene amplification cause a small ubset of Parkinson's diseases, and aggregates in other neurodegenerative diseases with a-synucleinopathy and sometimes an associated dementia even in an absence of gene mutation. Our work will determine the function of the autophagy-lysosomal pathway in reducing a-syn level and toxicity, a strategy relevant to improving treatment of PD and other a-synucleinopathies.