Division of Neurology, Department of Medicine, School of Clinical Medicine, University of Hong Kong, Hong Kong, China.
Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK.
Brain Behav. 2023 Feb;13(2):e2886. doi: 10.1002/brb3.2886. Epub 2023 Jan 9.
Leucine-rich repeat kinase 2 (LRRK2) mutation is a common genetic risk factor of Parkinson's disease (PD). Presynaptic dysfunction is an early pathogenic event associated with dopamine (DA) dysregulation in striatum of the brain. DA uptake activity of DA uptake transporter (DAT) affects synaptic plasticity and motor and non-motor behavior. Synaptogyrin-3 (SYNGR3) is part of the synaptogyrin family, especially abundant in brain. Previous in vitro studies demonstrated interaction between SYNGR3 and DAT. Reduced SYNGR3 expression was observed in human PD brains with unclear reasons.
Here, we further explored whether inducing SYNGR3 expression can influence (i) cellular DA uptake using differentiated human SH-SY5Y neuronal cells, (ii) striatal synaptosomal DA uptake in a mutant LRRK2 knockin mouse model of PD, and (iii) innate rodent behavior using the marble burying test.
Young LRRK2 mutant mice exhibited significantly lower SYNGR3 levels in striatum compared to age-matched wild-type (WT) controls, resembling level in aged WT mice. SYNGR3 is spatially co-localized with DAT at striatal presynaptic terminals, visualized by immuno-gold transmission electron microscopy and immunohistochemistry. Their protein-protein interaction was confirmed by co-immunoprecipitation. Transient overexpression of SYNGR3 in differentiated SH-SY5Y cells increased cellular DA uptake activity without affecting total DAT levels. Inducing SYNGR3 overexpression by adeno-associated virus-7 (AAV7) injection in vivo into striatum increased ex vivo synaptosomal DA uptake in LRRK2 mutant mice and improved their innate marble burying behavior.
Brain SYNGR3 expression may be an important determinant to striatal DA homeostasis and synaptic function. Our preliminary behavioral test showed improved innate behavior after SYNGR3 overexpression in LRRK2 mutant mice, advocating further studies to determine the influence of SYNGR3 in the pathophysiology of DA neurons in PD.
富含亮氨酸重复激酶 2（LRRK2）突变是帕金森病（PD）的常见遗传风险因素。 突触前功能障碍是与大脑纹状体多巴胺（DA）失调相关的早期致病事件。 DA 摄取转运体（DAT）的 DA 摄取活性影响突触可塑性和运动及非运动行为。突触糖蛋白-3（SYNGR3）是突触糖蛋白家族的一部分，在大脑中尤为丰富。 先前的体外研究表明 SYNGR3 与 DAT 之间存在相互作用。在 PD 人脑组织中观察到 SYNGR3 表达减少，但原因尚不清楚。
在这里，我们进一步探讨了诱导 SYNGR3 表达是否可以影响：（i）使用分化的人 SH-SY5Y 神经元细胞的细胞内 DA 摄取，（ii）PD 突变 LRRK2 敲入小鼠模型中的纹状体突触体 DA 摄取，以及（iii）使用大理石掩埋试验的先天啮齿动物行为。
年轻的 LRRK2 突变小鼠的纹状体中 SYNGR3 水平明显低于年龄匹配的野生型（WT）对照，类似于老年 WT 小鼠的水平。SYNGR3 与 DAT 在纹状体突触前末端空间上共定位，通过免疫金透射电子显微镜和免疫组织化学观察到。通过共免疫沉淀证实了它们的蛋白-蛋白相互作用。在分化的 SH-SY5Y 细胞中瞬时过表达 SYNGR3 可增加细胞内 DA 摄取活性，而不影响总 DAT 水平。通过腺相关病毒-7（AAV7）注射体内诱导 SYNGR3 过表达增加了 LRRK2 突变小鼠的纹状体突触体 DA 摄取，并改善了它们的先天大理石掩埋行为。
大脑 SYNGR3 表达可能是纹状体 DA 内稳态和突触功能的重要决定因素。我们的初步行为测试显示，在 LRRK2 突变小鼠中过表达 SYNGR3 后，先天行为得到改善，提倡进一步研究以确定 SYNGR3 在 PD 中 DA 神经元的病理生理学中的影响。
