Duke Center for Neurodegeneration Research, Duke University, Durham, NC, 27710, USA.
Department of Pharmacology and Cancer Biology, Duke University, 3 Genome Court, Durham, NC, 27710, USA.
Mol Neurodegener. 2022 Jan 10;17(1):7. doi: 10.1186/s13024-021-00509-5.
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.
富含亮氨酸重复激酶 2（LRRK2）和 SNCA 与迟发性帕金森病（PD）在遗传上有关。聚集的α-突触核蛋白病理性地定义了 PD。最近的研究在特发性 PD 中发现了促炎 CD16+单核细胞中 LRRK2 表达的升高，以及一些 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已被牵连到 PD 模型中的多巴胺能神经退行性变中。在这里，我们研究了α-突触核蛋白和 LRRK2 如何在单核细胞中相互作用以及随后的神经炎症反应。
将人源和鼠源单核细胞分化为类似于巨噬细胞、树突状细胞或小胶质细胞的不同转录状态，并将其暴露于经过充分表征的人源或鼠源α-突触核蛋白纤维中。使用单克隆抗体测量 LRRK2 表达和 LRRK2 依赖性 Rab10 磷酸化，并用 R1441C-Lrrk2 敲入小鼠或 G2019S-Lrrk2 BAC 小鼠中的流式细胞术评估 LRRK2 敲入小鼠或 G2019S-Lrrk2 BAC 小鼠中 LRRK2 对α-突触核蛋白纤维的反应。用α-突触核蛋白纤维刺激单核细胞来源的巨噬细胞和 Boyden 室中的小胶质细胞进行趋化性测定。
α-突触核蛋白纤维在人源和鼠源巨噬细胞和树突状样细胞中强烈刺激 LRRK2 和 Rab10 磷酸化。在这些细胞中，α-突触核蛋白纤维通过 JAK-STAT 激活和内在的 LRRK2 激酶活性刺激 LRRK2，形成一个正反馈通路，上调磷酸化的 Rab10。相比之下，LRRK2 表达和 Rab10 磷酸化在对α-突触核蛋白纤维高度反应的小胶质细胞样细胞中均受到抑制。这些结果得到了证实，LRRK2 在浸润外周的促炎单核细胞中的脑实质表达，与脑内固有小胶质细胞不同。表达致病性 LRRK2 突变 G2019S 或 R1441C 的小鼠在急性对α-突触核蛋白纤维的反应中，浸润的促炎单核细胞数量增加。在原代培养的巨噬细胞中，LRRK2 激酶抑制减弱了α-突触核蛋白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，并诱导其向大脑募集。这些结果预测 LRRK2 激酶抑制可能会减弱大脑中有害的促炎单核细胞反应。
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