The design of a potent amyloid-β protein (Aβ) inhibitor plays a pivotal role in the prevention and treatment of Alzheimer’s disease (AD). Despite endogenous transthyretin (TTR) being recognized as an Aβ inhibitor, the weak inhibitory and blood brain barrier (BBB) crossing capabilities hinder it for Aβ aggregation inhibition and transport. Therefore, we have herein designed a recombinant TTR by conjugating a cationic cell penetrating peptide (penetratin, Pen), which not only enabled the fusion protein, TTR-Pen (TP), to present high BBB penetration but also greatly enhanced the potency of Aβ inhibition. Namely, the protein fusion made TP positively charged, leading to a potent suppression of Aβ₄₀ fibrillization at a low concentration (1.5 μM), while a TTR concentration as high as 12.5 μM was required to gain a similar function. Moreover, TP could mitigate Aβ-induced neuronal death, increase cultured cell viability from 72% to 92% at 2.5 μM, and extend the lifespan of AD nematodes from 14 to 18 d. Thermodynamic studies revealed that TP, enriched in positive charges, presented extensive electrostatic interactions with Aβ₄₀. Importantly, TP showed excellent BBB penetration performance, with a 10 times higher BBB permeability than TTR, which would allow TP to enter the brain of AD patients and participate in the transport of Aβ species out of the brain. Thus, it is expected that the fusion protein has great potential for drug development in AD treatment.

中文翻译：

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甲状腺素运载蛋白-渗透素：一种有效的融合蛋白抑制剂，可抑制阿尔茨海默氏症淀粉样蛋白-β 纤维形成，具有高血脑屏障穿越能力

有效的β淀粉样蛋白（Aβ）抑制剂的设计在预防和治疗阿尔茨海默病（AD）中发挥着关键作用。尽管内源性转甲状腺素蛋白（TTR）被认为是一种 Aβ 抑制剂，但其较弱的抑制性和血脑屏障（BBB）穿越能力阻碍了其对 Aβ 聚集的抑制和运输。因此，我们通过缀合阳离子细胞穿透肽（penetratin，Pen）设计了重组TTR，不仅使融合蛋白TTR-Pen（TP）具有高BBB穿透性，而且大大增强了Aβ的效力抑制。也就是说，蛋白质融合使TP带正电，从而在低浓度（1.5μM）下有效抑制Aβ40_原纤维化，而TTR浓度需要高达12.5μM才能获得类似的功能。此外，TP 可以减轻 Aβ 诱导的神经元死亡，将培养细胞活力在 2.5 μM 下从 72% 提高到 92%，并将 AD 线虫的寿命从 14 天延长到 18 天。热力学研究表明，富含正电荷的 TP 与 Aβ ₄₀表现出广泛的静电相互作用。重要的是，TP表现出优异的BBB渗透性能，其BBB渗透性比TTR高10倍，这将使得TP能够进入AD患者的大脑并参与Aβ物质从大脑的转运。因此，预计该融合蛋白在AD治疗药物开发方面具有巨大潜力。