Cuddy Leah K, Seah Claudia, Pasternak Stephen H, Rylett Rebecca Jane
Molecular Medicine Research Group, Robarts Research Institute, London, Ontario, Canada.
Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
J Neurochem. 2015 Aug;134(4):769-82. doi: 10.1111/jnc.13167. Epub 2015 Jun 3.
The high-affinity choline transporter (CHT) is responsible for choline uptake into cholinergic neurons, with this being the rate-limiting step for acetylcholine production. Altering CHT protein disposition directly impacts choline uptake activity and cholinergic neurotransmission. Amyloid precursor protein (APP) interacts with CHT proteins and increases their endocytosis from the cell surface. The goal of this study was to examine regulation of CHT trafficking and activity by wild-type APP (APPwt) and determine if this differs with Swedish mutant APP (APPSwe) in SH-SY5Y human neuroblastoma cells. APPSwe differs from APPwt in its trafficking from the cell surface through endosomes. We report for the first time that CHT interacts significantly less with APPSwe than with APPwt. Surprisingly, however, CHT cell surface levels and choline uptake activity are decreased to the same extent and CHT co-localization to early endosomes increased similarly in cells expressing either APPwt or APPSwe. A critical observation is that CHT co-immunoprecipitates with βCTF from APPSwe-expressing cells. We propose that decreased CHT function is mediated differently by APPwt and APPSwe; APPwt interaction with CHT facilitates its endocytosis from the cell surface, whereas the effect of APPSwe on CHT is mediated indirectly potentially by binding to the βCTF fragment or by Aβ released from cells. High-affinity choline transporter (CHT) takes choline into cholinergic neurons for acetylcholine synthesis. Amyloid precursor protein (APP) interacts with CHT proteins, but this is decreased for Swedish mutant APP (APPSwe). CHT cell surface levels and localization to early endosomes, and choline uptake activity are changed similarly by APPwt or APPSwe. APPSwe mediates effects indirectly potentially by βCTF or Aβ.
高亲和力胆碱转运体（CHT）负责将胆碱摄取到胆碱能神经元中，这是乙酰胆碱产生的限速步骤。改变CHT蛋白的分布会直接影响胆碱摄取活性和胆碱能神经传递。淀粉样前体蛋白（APP）与CHT蛋白相互作用，并增加其从细胞表面的内吞作用。本研究的目的是研究野生型APP（APPwt）对CHT转运和活性的调节，并确定在SH-SY5Y人神经母细胞瘤细胞中，这与瑞典突变型APP（APPSwe）是否存在差异。APPSwe在从细胞表面通过内体的转运过程中与APPwt不同。我们首次报道，CHT与APPSwe的相互作用明显少于与APPwt的相互作用。然而，令人惊讶的是，在表达APPwt或APPSwe的细胞中，CHT细胞表面水平和胆碱摄取活性降低到相同程度，并且CHT与早期内体的共定位同样增加。一个关键的观察结果是，CHT在表达APPSwe的细胞中与βCTF共免疫沉淀。我们提出，APPwt和APPSwe对CHT功能降低的介导方式不同；APPwt与CHT的相互作用促进其从细胞表面的内吞作用，而APPSwe对CHT的作用可能是通过与βCTF片段结合或通过细胞释放的Aβ间接介导的。高亲和力胆碱转运体（CHT）将胆碱摄入胆碱能神经元用于乙酰胆碱合成。淀粉样前体蛋白（APP）与CHT蛋白相互作用，但瑞典突变型APP（APPSwe）的这种相互作用减少。APPwt或APPSwe对CHT细胞表面水平、早期内体定位以及胆碱摄取活性的改变相似。APPSwe可能通过βCTF或Aβ间接介导作用。
