Wang Ruizhi, Palavicini Juan Pablo, Wang Hongjie, Maiti Panchanan, Bianchi Elisabetta, Xu Shaohua, Lloyd B N, Dawson-Scully Ken, Kang David E, Lakshmana Madepalli K
Section of Neurobiology, Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port Saint Lucie, FL 34987, USA.
University of Tennessee Health Science Center, Department of Neurology, 415 Link Building, TN, USA.
Neurobiol Dis. 2014 Sep;69:169-79. doi: 10.1016/j.nbd.2014.05.029. Epub 2014 Jun 2.
We previously demonstrated that RanBP9 overexpression increased Aβ generation and amyloid plaque burden, subsequently leading to robust reductions in the levels of several synaptic proteins as well as deficits in the learning and memory skills in a mouse model of Alzheimer's disease (AD). In the present study, we found striking reduction of spinophilin-immunoreactive puncta (52%, p<0.001) and spinophilin area (62.5%, p<0.001) in the primary cortical neurons derived from RanBP9 transgenic mice (RanBP9-Tg) compared to wild-type (WT) neurons. Similar results were confirmed in WT cortical neurons transfected with EGFP-RanBP9. At 6-months of age, the total spine density in the cortex of RanBP9 single transgenic, APΔE9 double transgenic and APΔE9/RanBP9 triple transgenic mice was similar to WT mice. However, in the hippocampus the spine density was significantly reduced (27%, p<0.05) in the triple transgenic mice compared to WT mice due to reduced number of thin spines (33%, p<0.05) and mushroom spines (22%, p<0.05). This suggests that RanBP9 overexpression in the APΔE9 mice accelerates loss of spines and that the hippocampus is more vulnerable. At 12-months of age, the cortex showed significant reductions in total spine density in the RanBP9 (22%, p<0.05), APΔE9 (19%, p<0.05) and APΔE9/RanBP9 (33%, p<0.01) mice compared to WT controls due to reductions in mushroom and thin spines. Similarly, in the hippocampus the total spine density was reduced in the RanBP9 (23%, p<0.05), APΔE9 (26%, p<0.05) and APΔE9/RanBP9 (39%, p<0.01) mice due to reductions in thin and mushroom spines. Most importantly, RanBP9 overexpression in the APΔE9 mice further exacerbated the reductions in spine density in both the cortex (14%, p<0.05) and the hippocampus (16%, p<0.05). Because dendritic spines are considered physical traces of memory, loss of spines due to RanBP9 provided the physical basis for the learning and memory deficits. Since RanBP9 protein levels are increased in AD brains, RanBP9 might play a crucial role in the loss of spines and synapses in AD.
我们先前证明，在阿尔茨海默病（AD）小鼠模型中，RanBP9过表达会增加Aβ生成和淀粉样斑块负荷，随后导致几种突触蛋白水平大幅降低以及学习和记忆能力缺陷。在本研究中，我们发现，与野生型（WT）神经元相比，源自RanBP9转基因小鼠（RanBP9-Tg）的原代皮质神经元中亲嗜素免疫反应性斑点显著减少（52%，p<0.001），亲嗜素面积减少（62.5%，p<0.001）。在转染了EGFP-RanBP9的WT皮质神经元中也证实了类似结果。在6个月大时，RanBP9单转基因、APΔE9双转基因和APΔE9/RanBP9三转基因小鼠皮质中的总棘密度与WT小鼠相似。然而，在海马体中，三转基因小鼠的棘密度与WT小鼠相比显著降低（27%，p<0.05），原因是细棘数量减少（33%，p<0.05）和蘑菇状棘数量减少（22%，p<0.05）。这表明APΔE9小鼠中RanBP9过表达会加速棘的丢失，且海马体更易受损。在12个月大时，与WT对照组相比，RanBP9小鼠（22%，p<0.05）、APΔE9小鼠（19%，p<0.05）和APΔE9/RanBP9小鼠（33%，p<0.01）皮质中的总棘密度显著降低，原因是蘑菇状棘和细棘减少。同样，在海马体中，RanBP9小鼠（23%，p<0.05）、APΔE9小鼠（26%，p<0.05）和APΔE9/RanBP9小鼠（39%，p<0.01）的总棘密度也因细棘和蘑菇状棘减少而降低。最重要的是，APΔE9小鼠中RanBP9过表达进一步加剧了皮质（14%，p<0.05）和海马体（16%，p<0.05）棘密度的降低。由于树突棘被认为是记忆的物理痕迹，RanBP9导致的棘丢失为学习和记忆缺陷提供了物理基础。由于AD大脑中RanBP9蛋白水平升高，RanBP9可能在AD中棘和突触的丢失中起关键作用。
