Department of Neurology, Shandong Provincial Hospital, Shandong University, No. 324 Jingwuweiqi Road, Jinan, Shandong 250021, PR China.
Department of Neurology, Shandong Provincial Hospital, Shandong University, No. 324 Jingwuweiqi Road, Jinan, Shandong 250021, PR China; Department of Neurology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, PR China; Shandong Provincial Clinical Research Center for Neurological Diseases, Jinan, Shandong, PR China.
EBioMedicine. 2022 Apr;78:103980. doi: 10.1016/j.ebiom.2022.103980. Epub 2022 Apr 1.
Previous research has revealed that KIBRA controls secretion of extracellular vesicles (EVs) by inhibiting the proteasomal degradation of Rab27a and EVs play an important role in amyloid β (Aβ) metabolism and transmission during Alzheimer's disease (AD) pathogenesis. Here, we further test the hypothesis that KIBRA regulates Aβ metabolism via the endosomal-lysosomal system.
We generated KIBRA knockout mice on a 5XFAD background and KIBRA knockdown cells in murine HT22 cells with stably overexpressing APP. Various forms of Aβ and quantification of EVs were analyzed by biochemical methods and nanoparticle tracking analysis, respectively. Multivesicular bodies (MVBs) were visualized by electron microscopy and confocal fluorescent microscopy. In a population-based cohort (n = 1419), KIBRA genotypes and plasma Aβ levels were analyzed using multiple-PCR amplification and Simoa, respectively.
Multiple forms of Aβ were dramatically attenuated in KIBRA knockout mouse brain, including monomers, oligomers, and extracellular deposition, but KIBRA knockout had no effect on intraneuronal APP C-terminal fragment β (APP-CTFβ)/Aβ levels. KIBRA depletion also decreased APP-CTFβ/Aβ-associated EVs secretion and subsequently enhanced MVBs number. Furthermore, we found that excessive accumulation of MVBs harboring APP-CTFβ/Aβ promoted the MVBs-lysosome fusion for degradation and inhibition of lysosomal function rescued secretion of APP-CTFβ/Aβ-associated EVs. More importantly, whole exon sequencing of KIBRA in a large population-based cohort identified the association of KIBRA rs28421695 polymorphism with plasma Aβ levels.
These results demonstrate that KIBRA regulates Aβ metabolism via controlling the secretion of APP-CTFβ/Aβ-associated EVs.
National Key R&D Program of China, and National Natural Science Foundation of China.
先前的研究表明，KIBRA 通过抑制 Rab27a 的蛋白酶体降解来控制细胞外囊泡（EVs）的分泌，EVs 在阿尔茨海默病（AD）发病机制中淀粉样β（Aβ）代谢和传递中发挥着重要作用。在这里，我们进一步验证了 KIBRA 通过内体溶酶体系统调节 Aβ 代谢的假说。
我们在 5XFAD 背景下生成了 KIBRA 敲除小鼠和在稳定过表达 APP 的鼠 HT22 细胞中敲低 KIBRA 的细胞。通过生化方法和纳米颗粒跟踪分析分别分析各种形式的 Aβ 和 EV 的定量。通过电子显微镜和共聚焦荧光显微镜观察多泡体（MVBs）。在基于人群的队列（n=1419）中，使用多重-PCR 扩增和 Simoa 分别分析 KIBRA 基因型和血浆 Aβ 水平。
KIBRA 敲除小鼠大脑中的多种形式的 Aβ（包括单体、寡聚体和细胞外沉积）明显减少，但 KIBRA 敲除对神经元内 APP C 端片段β（APP-CTFβ）/Aβ水平没有影响。KIBRA 耗竭也减少了 APP-CTFβ/Aβ 相关 EVs 的分泌，随后增加了 MVBs 的数量。此外，我们发现，过多的含有 APP-CTFβ/Aβ 的 MVBs 的积累促进了 MVBs-溶酶体融合降解，抑制溶酶体功能可挽救 APP-CTFβ/Aβ 相关 EVs 的分泌。更重要的是，在一个基于人群的大队列中对 KIBRA 的全外显子测序鉴定出 KIBRA rs28421695 多态性与血浆 Aβ 水平的关联。
这些结果表明，KIBRA 通过控制 APP-CTFβ/Aβ 相关 EVs 的分泌来调节 Aβ 代谢。
国家重点研发计划和国家自然科学基金。
