Leucine rich repeat kinase 2 (LRRK2) and SNCA are genetically linked to late-onset Parkinson’s disease (PD). Aggregated α-synuclein pathologically defines PD. Recent studies identified elevated LRRK2 expression in pro-inflammatory CD16+ monocytes in idiopathic PD, as well as increased phosphorylation of the LRRK2 kinase substrate Rab10 in monocytes in some LRRK2 mutation carriers. Brain-engrafting pro-inflammatory monocytes have been implicated in dopaminergic neurodegeneration in PD models. Here we examine how α-synuclein and LRRK2 interact in monocytes and subsequent neuroinflammatory responses. Human and mouse monocytes were differentiated to distinct transcriptional states resembling macrophages, dendritic cells, or microglia, and exposed to well-characterized human or mouse α-synuclein fibrils. LRRK2 expression and LRRK2-dependent Rab10 phosphorylation were measured with monoclonal antibodies, and myeloid cell responses to α-synuclein fibrils in R1441C-Lrrk2 knock-in mice or G2019S-Lrrk2 BAC mice were evaluated by flow cytometry. Chemotaxis assays were performed with monocyte-derived macrophages stimulated with α-synuclein fibrils and microglia in Boyden chambers. α-synuclein fibrils robustly stimulate LRRK2 and Rab10 phosphorylation in human and mouse macrophages and dendritic-like cells. In these cells, α-synuclein fibrils stimulate LRRK2 through JAK-STAT activation and intrinsic LRRK2 kinase activity in a feed-forward pathway that upregulates phosphorylated Rab10. In contrast, LRRK2 expression and Rab10 phosphorylation are both suppressed in microglia-like cells that are otherwise highly responsive to α-synuclein fibrils. Corroborating these results, LRRK2 expression in the brain parenchyma occurs in pro-inflammatory monocytes infiltrating from the periphery, distinct from brain-resident microglia. Mice expressing pathogenic LRRK2 mutations G2019S or R1441C have increased numbers of infiltrating pro-inflammatory monocytes in acute response to α-synuclein fibrils. In primary cultured macrophages, LRRK2 kinase inhibition dampens α-synuclein fibril and microglia-stimulated chemotaxis. Pathologic α-synuclein activates LRRK2 expression and kinase activity in monocytes and induces their recruitment to the brain. These results predict that LRRK2 kinase inhibition may attenuate damaging pro-inflammatory monocyte responses in the brain.

中文翻译：

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病理性 α-突触核蛋白将表达 LRRK2 的促炎单核细胞招募到大脑


富含亮氨酸重复激酶 2 (LRRK2) 和 SNCA 与迟发性帕金森病 (PD) 有遗传相关性。聚集的 α-突触核蛋白在病理学上定义了 PD。最近的研究发现，特发性 PD 的促炎性 CD16+ 单核细胞中 LRRK2 表达升高，并且某些 LRRK2 突变携带者的单核细胞中 LRRK2 激酶底物 Rab10 的磷酸化增加。脑移植促炎单核细胞与 PD 模型中的多巴胺能神经变性有关。在这里，我们研究 α-突触核蛋白和 LRRK2 在单核细胞中如何相互作用以及随后的神经炎症反应。人类和小鼠单核细胞被分化为类似巨噬细胞、树突状细胞或小胶质细胞的不同转录状态，并暴露于充分表征的人类或小鼠 α-突触核蛋白原纤维。使用单克隆抗体测量 LRRK2 表达和 LRRK2 依赖性 Rab10 磷酸化，并通过流式细胞术评估 R1441C-Lrrk2 敲入小鼠或 G2019S-Lrrk2 BAC 小鼠中骨髓细胞对 α-突触核蛋白原纤维的反应。在博伊登室中用α-突触核蛋白原纤维和小胶质细胞刺激单核细胞衍生的巨噬细胞进行趋化性测定。 α-突触核蛋白原纤维强烈刺激人和小鼠巨噬细胞和树突状细胞中的 LRRK2 和 Rab10 磷酸化。在这些细胞中，α-突触核蛋白原纤维通过前馈通路中的 JAK-STAT 激活和内在 LRRK2 激酶活性刺激 LRRK2，从而上调磷酸化 Rab10。相比之下，LRRK2 表达和 Rab10 磷酸化在小胶质细胞样细胞中均受到抑制，而这些细胞对 α-突触核蛋白原纤维高度敏感。 证实了这些结果，脑实质中的 LRRK2 表达发生在从外周浸润的促炎单核细胞中，这与大脑驻留的小胶质细胞不同。表达致病性 LRRK2 突变 G2019S 或 R1441C 的小鼠在对 α-突触核蛋白原纤维的急性反应中，浸润性促炎单核细胞数量增加。在原代培养的巨噬细胞中，LRRK2 激酶抑制会抑制 α-突触核蛋白原纤维和小胶质细胞刺激的趋化性。病理性 α-突触核蛋白激活单核细胞中的 LRRK2 表达和激酶活性，并诱导其募集至大脑。这些结果预测 LRRK2 激酶抑制可能会减弱大脑中破坏性的促炎单核细胞反应。