A novel mechano-enzymatic cleavage mechanism underlies transthyretin amyloidogenesis.
A novel mechano-enzymatic cleavage mechanism underlies transthyretin amyloidogenesis.
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DOI：
10.15252/emmm.201505357
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发表时间：
2015-10
影响因子：
11.1
通讯作者：
Bellotti V
中科院分区：
文献类型：
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作者：
Marcoux J;Mangione PP;Porcari R;Degiacomi MT;Verona G;Taylor GW;Giorgetti S;Raimondi S;Sanglier-Cianférani S;Benesch JL;Cecconi C;Naqvi MM;Gillmore JD;Hawkins PN;Stoppini M;Robinson CV;Pepys MB;Bellotti V
体内转甲状腺素蛋白相关淀粉样变性的机制仍不清楚。离体沉积物中 49-127 运甲状腺素蛋白片段的丰度表明，蛋白水解切割在破坏四聚体稳定性和释放高度淀粉样蛋白生成的 49-127 截短原聚体方面发挥着至关重要的作用。在这里，我们研究了原型 S52P 变体中 49-127 片段的裂解和释放机制，并且我们表明，蛋白水解/原纤维形成途径是甲状腺素运载蛋白的几种淀粉样变体所共有的，并且需要生理液流剪切应力提供的生物力学力的作用。至关重要的是，非淀粉样蛋白生成和保护性 T119M 变体在这些条件下既不会被裂解，也不会产生原纤维。我们提出机械酶机制介导体内转甲状腺素蛋白淀粉样蛋白原纤维的形成。这对于剪切应力最大的心脏尤其重要。事实上，49-127 运甲状腺素蛋白片段在心脏淀粉样蛋白中特别丰富。最后，我们表明现有的转甲状腺素蛋白稳定剂，包括他法米迪，在不同变体中以不同的效率抑制蛋白水解介导的转甲状腺素蛋白原纤维形成；然而，只有当两个结合位点都被占据时，抑制才完全。
The mechanisms underlying transthyretin-related amyloidosis in vivo remain unclear. The abundance of the 49–127 transthyretin fragment in ex vivo deposits suggests that a proteolytic cleavage has a crucial role in destabilizing the tetramer and releasing the highly amyloidogenic 49–127 truncated protomer. Here, we investigate the mechanism of cleavage and release of the 49–127 fragment from the prototypic S52P variant, and we show that the proteolysis/fibrillogenesis pathway is common to several amyloidogenic variants of transthyretin and requires the action of biomechanical forces provided by the shear stress of physiological fluid flow. Crucially, the non-amyloidogenic and protective T119M variant is neither cleaved nor generates fibrils under these conditions. We propose that a mechano-enzymatic mechanism mediates transthyretin amyloid fibrillogenesis in vivo. This may be particularly important in the heart where shear stress is greatest; indeed, the 49–127 transthyretin fragment is particularly abundant in cardiac amyloid. Finally, we show that existing transthyretin stabilizers, including tafamidis, inhibit proteolysis-mediated transthyretin fibrillogenesis with different efficiency in different variants; however, inhibition is complete only when both binding sites are occupied.