Elevated Hapln2 Expression Contributes to Protein Aggregation and Neurodegeneration in an Animal Model of Parkinson's Disease
Elevated Hapln2 Expression Contributes to Protein Aggregation and Neurodegeneration in an Animal Model of Parkinson's Disease
复制标题
Hapln2 表达升高会导致帕金森病动物模型中的蛋白质聚集和神经变性。
DOI：
10.3389/fnagi.2016.00197
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发表时间：
2016-08-23
影响因子：
4.8
通讯作者：
Zhou, Jiawei
中科院分区：
文献类型：
--
作者：
Wang, Qinqin;Zhou, Qinbo;Zhou, Jiawei
帕金森病（Parkinson's disease，PD）是第二常见的与年龄相关的进行性神经退行性疾病，其特征在于黑质（substantia nigra pars rectata，SN）中的多巴胺（dopaminergic，DA）神经元的损失。PD的发病机制和DA神经元变性的机制尚未完全清楚。我们先前的定量蛋白质组学研究显示，透明质酸和蛋白聚糖结合连接蛋白2（Hapln 2）是PD患者和健康对照者黑质组织中差异表达的蛋白质之一。然而，Hapln 2在PD发病机制中的潜在作用仍然难以捉摸。在本研究中，我们表征了Hapln 2的表达模式。原位杂交结果显示，Hapln 2 mRNA在成年大鼠脑内广泛表达，在黑质中表达丰度较高。免疫印迹显示，与健康对照相比，Hapln 2的表达水平在患有帕金森病的人类受试者的黑质中显著上调。同样，在神经毒素6-羟基多巴胺处理的大鼠中Hapln 2表达显著增加。Hapln 2在体外过表达增加了多巴胺能细胞系MES23.5细胞对6-羟基多巴胺的脆弱性。此外，Haplon 2过表达导致细胞质聚集体的形成，这些聚集体在体外与泛蛋白和E3连接酶（包括Parkin、Gp 78和Hrd 1）共定位。内源性α-突触核蛋白也定位于含Hapln 2的聚集体中，并且与对照相比，Hapln 2的消融导致不溶性级分中α-突触核蛋白的显著降低。因此，Hapln 2被鉴定为导致PD中神经变性的新因子。我们的数据为PD发病机制的细胞机制提供了新的见解。
Parkinson's disease (PD), the second most common age-associated progressive neurodegenerative disorder, is characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SN). The pathogenesis of PD and the mechanisms underlying the degeneration of DA neurons are still not fully understood. Our previous quantitative proteomics study revealed that hyaluronan and proteoglycan binding link protein 2 (Hapln2) is one of differentially expressed proteins in the substantia nigra tissues from PD patients and healthy control subjects. However, the potential role of Hapln2 in PD pathogenesis remains elusive. In the present study, we characterized the expression pattern of Hapln2. In situ hybridization revealed that Hapln2 mRNA was widely expressed in adult rat brain with high abundance in the substantia nigra. Immunoblotting showed that expression levels of Hapln2 were markedly upregulated in the substantia nigra of either human subjects with Parkinson's disease compared with healthy control. Likewise, there were profound increases in Hapln2 expression in neurotoxin 6-hydroxydopamine-treated rat. Overexpression of Hapln2 in vitro increased vulnerability of MES23.5 cells, a dopaminergic cell line, to 6-hydroxydopamine. Moreover, Hapln2 overexpression led to the formation of cytoplasmic aggregates which were co-localized with ubiquitin and E3 ligases including Parkin, Gp78, and Hrd1 in vitro. Endogenous alpha-synuclein was also localized in Hapln2-containing aggregates and ablation of Hapln2 led to a marked decrease of alpha-synuclein in insoluble fraction compared with control. Thus, Hapln2 is identified as a novel factor contributing to neurodegeneration in PD. Our data provides new insights into the cellular mechanism underlying the pathogenesis in PD.