Zhao Jun-Qiang, Feng Bing-Yan, Ye Zhen-Li, Ma Xiao-Yin, Du Jing-Zhi, Li Jun-Mei, Wu Wan-Liu, Gao Jing-Jing, Li Song-Ji, Peng Shi-Yong, Huai Ji-Sen, Ge Li-Hao, Lu Cheng-Biao
First Affiliated Hospital of Xinxiang Medical University, Xinxiang, 435000, China.
School of Medical Imaging, Xinxiang Medical University, Xinxiang, 435000, China.
Acta Pharmacol Sin. 2025 Feb;46(2):338-352. doi: 10.1038/s41401-024-01377-7. Epub 2024 Sep 16.
Palmitoyl-protein thioesterase 1 (PPT1) is a lysosomal depalmitoylation enzyme that mediates protein posttranslational modifications. Loss-of-function mutation of PPT1 causes a failure of the lysosomal degradation of palmitoylated proteins and results in a congenital disease characterized by progressive neuronal degeneration referred to as infantile neuronal ceroid lipofuscinosis (INCL). A mouse knock-in model of PPT1 (PPT1-KI) was established by introducing the R151X mutation into exon 5 of the PPT1 gene, which exhibited INCL-like pathological lesions. We previously reported that hippocampal γ oscillations were impaired in PPT1 mice. Hippocampal γ oscillations can be enhanced by selective activation of the dopamine D4 receptor (DR4), a dopamine D2-like receptor. In this study, we investigated the changes in DR expression and the effects of dopamine and various DR agonists on neural network activity, cognition and motor function in PPT1KI mice. Cognition and motor defects were evaluated via Y-maze, novel object recognition and rotarod tests. Extracellular field potentials were elicited in hippocampal slices, and neuronal network oscillations in the gamma frequency band (γ oscillations) were induced by perfusion with kainic acid (200 nM). PPT1KI mice displayed progressive impairments in γ oscillations and hippocampus-related memory, as well as abnormal expression profiles of dopamine receptors with preserved expression of DR1 and 3, increased membrane expression of DR4 and decreased DR2 levels. The immunocytochemistry analysis revealed the colocalization of PPT1 with DR4 or DR2 in the soma and large dendrites of both WT and PPT1KI mice. Immunoprecipitation confirmed the interaction between PPT1 and DR4 or DR2. The impaired γ oscillations and cognitive functions were largely restored by the application of exogenous dopamine, the selective DR2 agonist quinpirole or the DR4 agonist A412997. Furthermore, the administration of A412997 (0.5 mg/kg, i.p.) significantly upregulated the activity of CaMKII in the hippocampus of 5-month-old PPT1KI mice. Collectively, these results suggest that the activation of D2-like dopamine receptors improves cognition and network activity in PPT1KI mice and that specific DR subunits may be potential targets for the intervention of neurodegenerative disorders, such as INCL.
棕榈酰蛋白硫酯酶1（PPT1）是一种溶酶体去棕榈酰化酶，介导蛋白质的翻译后修饰。PPT1的功能丧失突变导致棕榈酰化蛋白的溶酶体降解失败，并导致一种以进行性神经元变性为特征的先天性疾病，称为婴儿神经元蜡样脂褐质沉积症（INCL）。通过将R151X突变引入PPT1基因的外显子5，建立了PPT1的小鼠基因敲入模型（PPT1-KI），该模型表现出类似INCL的病理损伤。我们之前报道过，PPT1小鼠的海马γ振荡受损。海马γ振荡可通过选择性激活多巴胺D4受体（DR4，一种多巴胺D2样受体）来增强。在本研究中，我们研究了PPT1KI小鼠中DR表达的变化以及多巴胺和各种DR激动剂对神经网络活动、认知和运动功能的影响。通过Y迷宫、新物体识别和转棒试验评估认知和运动缺陷。在海马切片中诱发细胞外场电位，并用 kainic 酸（200 nM）灌注诱导γ频段的神经元网络振荡（γ振荡）。PPT1KI小鼠在γ振荡和海马相关记忆方面表现出进行性损伤，多巴胺受体表达谱异常，DR1和3表达保留，DR4膜表达增加，DR2水平降低。免疫细胞化学分析显示，在野生型和PPT1KI小鼠的胞体和大的树突中，PPT1与DR4或DR2共定位。免疫沉淀证实了PPT1与DR4或DR2之间的相互作用。外源性多巴胺、选择性DR2激动剂喹吡罗或DR4激动剂A412997的应用在很大程度上恢复了受损的γ振荡和认知功能。此外，给予A412997（0.5 mg/kg，腹腔注射）显著上调了5月龄PPT1KI小鼠海马中CaMKII的活性。总的来说，这些结果表明，激活D2样多巴胺受体可改善PPTlKI小鼠的认知和网络活动，并且特定的DR亚基可能是干预神经退行性疾病（如INCL）的潜在靶点。
