Mazzulli Joseph R, Zunke Friederike, Tsunemi Taiji, Toker Nicholas J, Jeon Sohee, Burbulla Lena F, Patnaik Samarjit, Sidransky Ellen, Marugan Juan J, Sue Carolyn M, Krainc Dimitri
Department of Neurology, Massachusetts General Hospital, Harvard Medical School, MassGeneral Institute for Neurodegeneration, Charlestown, Massachusetts 02129, The Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago IL 60611,
The Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago IL 60611.
J Neurosci. 2016 Jul 20;36(29):7693-706. doi: 10.1523/JNEUROSCI.0628-16.2016.
Parkinson's disease (PD) is characterized by the accumulation of α-synuclein (α-syn) within Lewy body inclusions in the nervous system. There are currently no disease-modifying therapies capable of reducing α-syn inclusions in PD. Recent data has indicated that loss-of-function mutations in the GBA1 gene that encodes lysosomal β-glucocerebrosidase (GCase) represent an important risk factor for PD, and can lead to α-syn accumulation. Here we use a small-molecule modulator of GCase to determine whether GCase activation within lysosomes can reduce α-syn levels and ameliorate downstream toxicity. Using induced pluripotent stem cell (iPSC)-derived human midbrain dopamine (DA) neurons from synucleinopathy patients with different PD-linked mutations, we find that a non-inhibitory small molecule modulator of GCase specifically enhanced activity within lysosomal compartments. This resulted in reduction of GCase substrates and clearance of pathological α-syn, regardless of the disease causing mutations. Importantly, the reduction of α-syn was sufficient to reverse downstream cellular pathologies induced by α-syn, including perturbations in hydrolase maturation and lysosomal dysfunction. These results indicate that enhancement of a single lysosomal hydrolase, GCase, can effectively reduce α-syn and provide therapeutic benefit in human midbrain neurons. This suggests that GCase activators may prove beneficial as treatments for PD and related synucleinopathies.
The presence of Lewy body inclusions comprised of fibrillar α-syn within affected regions of PD brain has been firmly documented, however no treatments exist that are capable of clearing Lewy bodies. Here, we used a mechanistic-based approach to examine the effect of GCase activation on α-syn clearance in human midbrain DA models that naturally accumulate α-syn through genetic mutations. Small molecule-mediated activation of GCase was effective at reducing α-syn inclusions in neurons, as well as associated downstream toxicity, demonstrating a therapeutic effect. Our work provides an example of how human iPSC-derived midbrain models could be used for testing potential treatments for neurodegenerative disorders, and identifies GCase as a critical therapeutic convergence point for a wide range of synucleinopathies.
帕金森病（PD）的特征是神经系统中路易小体包涵体内α-突触核蛋白（α-syn）的积累。目前尚无能够减少PD中α-syn包涵体的疾病修饰疗法。最近的数据表明，编码溶酶体β-葡萄糖脑苷脂酶（GCase）的GBA1基因功能丧失突变是PD的一个重要危险因素，并可导致α-syn积累。在此，我们使用一种GCase小分子调节剂来确定溶酶体内GCase的激活是否能降低α-syn水平并改善下游毒性。利用来自患有不同PD相关突变的突触核蛋白病患者的诱导多能干细胞（iPSC）衍生的人脑中脑多巴胺（DA）神经元，我们发现一种非抑制性GCase小分子调节剂特异性增强了溶酶体区室的活性。这导致GCase底物减少和病理性α-syn清除，无论致病突变如何。重要的是，α-syn的减少足以逆转由α-syn诱导的下游细胞病变，包括水解酶成熟的扰动和溶酶体功能障碍。这些结果表明，增强单一溶酶体水解酶GCase可以有效降低α-syn，并在人脑中脑神经元中提供治疗益处。这表明GCase激活剂可能被证明对PD和相关突触核蛋白病的治疗有益。
在PD脑的受影响区域中由纤维状α-syn组成的路易小体包涵体的存在已得到确凿记录，然而不存在能够清除路易小体的治疗方法。在此，我们使用基于机制的方法来研究GCase激活对通过基因突变自然积累α-syn的人脑中脑DA模型中α-syn清除的影响。小分子介导的GCase激活在减少神经元中的α-syn包涵体以及相关下游毒性方面是有效的，证明了治疗效果。我们的工作提供了一个例子，说明人iPSC衍生的中脑模型如何可用于测试神经退行性疾病的潜在治疗方法，并将GCase确定为广泛的突触核蛋白病的关键治疗汇聚点。
