Mechanisms of LRRK2 Mediated Neurotoxicity

 描述（由申请人提供）：帕金森病（PD）是第二常见的神经退行性疾病。预计到2030年，全球将有超过1000万人患有PD，目前还没有已知的治疗方法可以减缓或阻止疾病的无情进展。富亮氨酸重复激酶2（LRRK 2）基因中的显性错义突变是PD最常见的已知原因，在美国有多达4万至6万例致病性G2019 S-LRRK 2突变携带者。在德系犹太人或柏柏尔人后裔中，PD患者中G2019 S-LRRK 2突变的频率可高达20-30%。在我们的上一个项目期间，我们证明了G2019 S-LRRK 2表达促进由α-突触核蛋白过度表达引起的多巴胺能神经变性，并且LRRK 2激酶抑制剂阻断了这些作用。然而，LRRK 2与α-突触核蛋白神经毒性的联系机制尚不清楚。进一步剖析LRRK 2在PD中的作用可能会加速发现靶向LRRK 2和相关神经保护通路的新疗法。 我们发现，LRRK 2在健康大脑中的许多神经元中表达，但在具有α-突触核蛋白包涵体的患病大脑中，LRRK 2也在髓样细胞中表达，这些细胞可以指导神经毒性细胞因子和活性氧的产生。在该竞争性更新请求中，我们假设LRRK 2表达和激酶活性促进骨髓细胞募集到具有α-突触核蛋白包涵体的神经元，从而加剧神经变性和α-突触核蛋白包涵体的扩散。使用在骨髓细胞中诱导过表达G2019 S-LRRK 2的条件性转基因，我们将测试G2019 S-LRRK 2是否可以通过促进骨髓细胞募集来上调由神经元α-突触核蛋白包涵体引起的细胞因子应答和氧化损伤。使用条件性缺失技术，我们将测试髓系细胞中的LRRK 2敲除是否会通过抑制髓系细胞募集来下调神经毒性细胞因子和氧化损伤以响应α-突触核蛋白包涵体。我们将探讨LRRK 2蛋白如何通过作为Arp 2/3的新型支架来控制肌动蛋白聚合，从而控制髓系细胞的运动性和趋化性。我们预测，LRRK 2与Arp 2/3相互作用，以激酶依赖的方式，以促进肌动蛋白微刺在移动的髓样细胞的前端，以增强运动性。这些研究的完成应该允许进一步深入了解LRRK 2如何导致PD，LRRK 2在髓样细胞中的表达如何有助于神经变性，以及定义一种对髓样细胞趋化性重要的新型肌动蛋白成核复合物。

 DESCRIPTION (provided by applicant): Parkinson disease (PD) is the second most common neurodegenerative disorder. More than 10 million individuals worldwide are expected to have PD by the year 2030, and currently there are no known therapies that slow or halt the relentless progression of the disease. Dominant missense mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common known cause of PD, with up to 40 to 60 thousand carriers of the pathogenic G2019S-LRRK2 mutation in the United States. In individuals of Ashkenazi or Berber descent, frequencies of the G2019S-LRRK2 mutation can be as high as 20-30% in PD patients. In our last project period, we demonstrated that G2019S- LRRK2 expression promotes dopaminergic neurodegeneration caused by α-synuclein over- expression and that LRRK2 kinase inhibitors blocked these effects. However, the mechanisms linking LRRK2 to α-synuclein neurotoxicity are not clear. Further dissection of LRRK2 action in PD may expedite the discovery of new therapies that target LRRK2 and related pathways for neuroprotection. We found that LRRK2 is expressed in many neurons tougher with α-synuclein in healthy brains, but in diseased brains that have α-synuclein inclusions, LRRK2 is also expressed in myeloid cells that can direct the production of neurotoxic cytokines and reactive-oxygen species. In this competitive renewal request, we hypothesize that LRRK2 expression and kinase activity promotes myeloid cell recruitment to neurons that have α-synuclein inclusions to exacerbate neurodegeneration and the spread of α-synuclein inclusions. Using conditional transgenics that inducibly over-express G2019S-LRRK2 in myeloid cells, we will test whether G2019S-LRRK2 can upregulate cytokine responses and oxidative damage caused by neuronal α-synuclein inclusions through promoting myeloid cell recruitment. Using conditional deletion technology, we will test whether LRRK2 knockout in myeloid cells will downregulate neurotoxic cytokines and oxidative damage in response to α- synuclein inclusions through inhibiting myeloid cell recruitment. We will explore how LRRK2 protein can control myeloid cell motility and chemotaxis by acting as a novel scaffold for Arp2/3 to control actin polymerization. We predict that LRRK2 interacts with Arp2/3, in a kinase-dependent manner, to facilitate actin microspikes at the leading front of mobile myeloid cells to enhance motility. Completion of these studies should allow for further insight into how LRRK2 can cause PD, how LRRK2 expression in myeloid cells might contribute to neurodegeneration, and definition of a novel actin nucleation complex important for myeloid cell chemotaxis.