Plasminogen activation triggers transthyretin amyloidogenesis in vitro.
Plasminogen activation triggers transthyretin amyloidogenesis in vitro.
复制标题
DOI：
10.1074/jbc.ra118.003990
复制
发表时间：
2018-09-14
期刊：
影响因子：
--
通讯作者：
Bellotti V
中科院分区：
文献类型：
--
作者：
Mangione PP;Verona G;Corazza A;Marcoux J;Canetti D;Giorgetti S;Raimondi S;Stoppini M;Esposito M;Relini A;Canale C;Valli M;Marchese L;Faravelli G;Obici L;Hawkins PN;Taylor GW;Gillmore JD;Pepys MB;Bellotti V
系统性淀粉样变性是由可溶性球状血浆蛋白前体的错误折叠和聚集所衍生的异常蛋白纤维（淀粉样原纤维）的细胞外积累引起的通常致命的疾病。正常血浆蛋白甲状腺素运载蛋白（TTR）的WT和遗传变体都形成淀粉样蛋白，但导致纤维形成的错误折叠和TTR淀粉样蛋白沉积的解剖学定位都不清楚。我们先前已经表明，在生理条件下，胰蛋白酶在机械酶促机制中切割人TTR，在体外产生丰富的淀粉样纤维。与此形成鲜明对比的是，广泛使用的TTR通过长时间暴露于pH 4.0的变性和聚集的体外模型几乎没有产生明确定义的淀粉样蛋白原纤维。然而，胰蛋白酶的唯一十二指肠位置意味着这种酶不能促进体内全身性细胞外TTR淀粉样蛋白沉积。在这里，我们因此进行了生物信息学搜索系统活性胰蛋白酶与适当的组织分布，意外地确定纤溶酶作为主要候选人。我们证实，纤溶酶，就像胰蛋白酶，选择性切割之间的残基48和49人TTR在体外生理条件下。然后从天然同源四聚体释放截短的全长原聚体，并迅速聚集成与离体TTR淀粉样蛋白难以区分的丰富原纤维。我们的研究结果表明，生理性纤维蛋白溶解可能在体内TTR淀粉样蛋白的形成中发挥关键作用。这两个迄今为止不相关的途径之间令人惊讶的交叉点的鉴定为阐明TTR淀粉样变性的机制，寻找易感风险因素和治疗创新开辟了新的途径。
Systemic amyloidosis is a usually fatal disease caused by extracellular accumulation of abnormal protein fibers, amyloid fibrils, derived by misfolding and aggregation of soluble globular plasma protein precursors. Both WT and genetic variants of the normal plasma protein transthyretin (TTR) form amyloid, but neither the misfolding leading to fibrillogenesis nor the anatomical localization of TTR amyloid deposition are understood. We have previously shown that, under physiological conditions, trypsin cleaves human TTR in a mechano-enzymatic mechanism that generates abundant amyloid fibrils in vitro. In sharp contrast, the widely used in vitro model of denaturation and aggregation of TTR by prolonged exposure to pH 4.0 yields almost no clearly defined amyloid fibrils. However, the exclusive duodenal location of trypsin means that this enzyme cannot contribute to systemic extracellular TTR amyloid deposition in vivo. Here, we therefore conducted a bioinformatics search for systemically active tryptic proteases with appropriate tissue distribution, which unexpectedly identified plasmin as the leading candidate. We confirmed that plasmin, just as trypsin, selectively cleaves human TTR between residues 48 and 49 under physiological conditions in vitro. Truncated and full-length protomers are then released from the native homotetramer and rapidly aggregate into abundant fibrils indistinguishable from ex vivo TTR amyloid. Our findings suggest that physiological fibrinolysis is likely to play a critical role in TTR amyloid formation in vivo. Identification of this surprising intersection between two hitherto unrelated pathways opens new avenues for elucidating the mechanisms of TTR amyloidosis, for seeking susceptibility risk factors, and for therapeutic innovation.