Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, 3601 4th Street, Lubbock, Texas, 79430-6540, USA.
Pharm Res. 2020 May 17;37(6):98. doi: 10.1007/s11095-020-02835-7.
A Na-coupled transport system in mammalian cells is responsible for the uptake of oligopeptides consisting of 5 or more amino acids. Here we investigated if this transport system is expressed in brain cells and transports the 42-amino-acid β-amyloid peptide (Aβ).
The human and mouse neuronal cell lines SK-N-SH and HT22, human microglial cell line HMC-3, and human blood-brain barrier endothelial cell line hCMEC/D3 were used to monitor the uptake of [H]-deltorphin II (a heptapeptide) and fluorescence-labeled Aβ.
All four cell lines exhibited Na-coupled uptake of deltorphin II. Aβ competed with deltorphin II for the uptake. Uptake of fluorescence-labeled Aβ was detectable in these cell lines, and the uptake was Na-dependent and inhibitable by deltorphin II. The Na-coupled uptake disappeared at high concentrations of Aβ due to oligomerization of the peptide. Exposure of the cells to excess iron abolished the uptake. In hCMEC/D3 cells cultured on Transwell filters, the uptake was localized preferentially to the abluminal membrane.
A Na-coupled transport system mediates the uptake of Aβ monomers in neuronal and microglial cells. The same system is also responsible for the uptake of Aβ from brain into blood-brain barrier endothelial cells. These findings have relevance to Alzheimer's disease.
哺乳动物细胞中的 Na 偶联转运系统负责摄取由 5 个或更多氨基酸组成的寡肽。在这里，我们研究了该转运系统是否在脑细胞中表达，并转运 42 个氨基酸的β-淀粉样肽（Aβ）。
使用人神经母细胞瘤细胞系 SK-N-SH 和 HT22、人小胶质细胞系 HMC-3 和人血脑屏障内皮细胞系 hCMEC/D3 来监测 [H]-delta 啡肽 II（七肽）和荧光标记的 Aβ 的摄取。
所有四种细胞系均表现出 Na 偶联的 delta 啡肽 II 摄取。Aβ 与 delta 啡肽 II 竞争摄取。这些细胞系中可检测到荧光标记的 Aβ 的摄取，摄取是 Na 依赖性的，可被 delta 啡肽 II 抑制。由于肽的寡聚化，高浓度的 Aβ 会导致 Na 偶联摄取消失。细胞暴露于过量的铁会破坏摄取。在 Transwell 滤器上培养的 hCMEC/D3 细胞中，摄取优先定位于基底外侧膜。
Na 偶联转运系统介导神经元和小胶质细胞中 Aβ 单体的摄取。同样的系统也负责将 Aβ 从大脑摄取到血脑屏障内皮细胞。这些发现与阿尔茨海默病有关。
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