Bendikov-Bar Inna, Rapaport Debora, Larisch Sarit, Horowitz Mia
Department of Cell Research and Immunology, Life Sciences, Tel Aviv University, Levanon St, Ramat Aviv 69978, Israel.
Orphanet J Rare Dis. 2014 Jun 16;9:86. doi: 10.1186/1750-1172-9-86.
Parkinson's disease (PD) is a movement neurodegenerative disorder characterized by death of dopaminergic neurons in the substantia nigra pars compacta of the brain that leads to movement impairments including bradykinesia, resting tremor, postural instability and rigidity. Mutations in several genes have been associated with familial PD, such as parkin, pink, DJ-1, LRKK2 and α-synuclein. Lately, mutations in the GBA gene were recognized as a major cause for the development of PD.Mutations in the GBA gene, which encodes for lysosomal β-glucocerebrosidase (GCase), lead to Gaucher disease (GD), an autosomal recessive sphingolipidosis characterized by accumulation of glucosylceramide, mainly in monocyte-derived cells. It is a heterogeneous disease, with Type 1 patients that do not present any primary neurological signs, and Type 2 or Type 3 patients who suffer from a neurological disease. The propensity of type 1 GD patients and carriers of GD mutations to develop PD is significantly higher than that of the non-GD population.We have shown in the past that parkin and mutant GCase, expressed in heterologous systems, interact with each other, and that normal but not mutant parkin mediates K48-dependent proteasomal degradation of mutant GCase variants.
We tested possible competition between mutant GCase and PARIS or ARTS on the E3 ubiquitin ligase parkin, using coimmunoprecipitation assays and quantitative real-time PCR.
We show that endogenous mutant GCase variants associate with parkin and undergo parkin-dependent degradation. Mutant GCase competes with the known parkin substrates PARIS and ARTS, whose accumulation leads to apoptosis. Dopaminergic cells expressing mutant GCase are more susceptible to apoptotic stimuli than dopaminergic cells expressing normal GCase, present increased cleavage of caspase 3 and caspase 9 levels and undergo cell death.
Our results imply that presence of mutant GCase leads to accumulation of parkin substrates like PARIS and ARTS, which may cause apoptotic death of cells.
帕金森病（PD）是一种运动性神经退行性疾病，其特征是大脑黑质致密部多巴胺能神经元死亡，导致运动障碍，包括运动迟缓、静止性震颤、姿势不稳和僵硬。几个基因的突变与家族性PD相关，如帕金森蛋白、粉色蛋白、DJ-1、富含亮氨酸重复激酶2（LRKK2）和α-突触核蛋白。最近，葡萄糖脑苷脂酶（GBA）基因突变被认为是PD发病的主要原因。GBA基因发生突变，该基因编码溶酶体β-葡萄糖脑苷脂酶（GCase），会导致戈谢病（GD），这是一种常染色体隐性鞘脂贮积症，其特征是葡萄糖神经酰胺主要在单核细胞衍生细胞中蓄积。它是一种异质性疾病，1型患者无任何原发性神经体征，2型或3型患者患有神经疾病。1型GD患者和GD突变携带者患PD的倾向明显高于非GD人群。我们过去已经表明，在异源系统中表达的帕金森蛋白和突变型GCase相互作用，并且正常而非突变型帕金森蛋白介导突变型GCase变体的K48依赖性蛋白酶体降解。
我们使用免疫共沉淀试验和定量实时聚合酶链反应（PCR），测试了突变型GCase与PARIS或ARTS在E3泛素连接酶帕金森蛋白上的可能竞争。
我们发现内源性突变型GCase变体与帕金森蛋白相关，并经历帕金森蛋白依赖性降解。突变型GCase与已知的帕金森蛋白底物PARIS和ARTS竞争，它们的蓄积会导致细胞凋亡。表达突变型GCase的多巴胺能细胞比表达正常GCase的多巴胺能细胞对凋亡刺激更敏感，半胱天冬酶3和半胱天冬酶9水平的切割增加，并发生细胞死亡。
我们的结果表明，突变型GCase的存在会导致PARIS和ARTS等帕金森蛋白底物的蓄积，这可能导致细胞凋亡死亡。
