Increasing evidence supports the hypothesis that soluble misfolded protein assemblies contribute to the degeneration of postmitotic tissue in amyloid diseases. However, there is a dearth of reliable nonantibody-based probes for selectively detecting oligomeric aggregate structures circulating in plasma or deposited in tissues, making it difficult to scrutinize this hypothesis in patients. Hence, understanding the structure-proteotoxicity relationships driving amyloid diseases remains challenging, hampering the development of early diagnostic and novel treatment strategies. We report peptide-based probes that selectively label misfolded transthyretin (TTR) oligomers circulating in the plasma of TTR hereditary amyloidosis patients exhibiting a predominant neuropathic phenotype. These probes revealed that there are much fewer misfolded TTR oligomers in healthy controls, in asymptomatic carriers of mutations linked to amyloid polyneuropathy, and in patients with TTR-associated cardiomyopathies. The absence of misfolded TTR oligomers in the plasma of cardiomyopathy patients suggests that the tissue tropism observed in the TTR amyloidoses is structure-based. Misfolded oligomers decrease in TTR amyloid polyneuropathy patients treated with disease-modifying therapies (tafamidis or liver transplant–mediated gene therapy). In a subset of TTR amyloid polyneuropathy patients, the probes also detected a circulating TTR fragment that disappeared after tafamidis treatment. Proteomic analysis of the isolated TTR oligomers revealed a specific patient-associated signature composed of proteins that likely associate with the circulating TTR oligomers. Quantification of plasma oligomer concentrations using peptide probes could become an early diagnostic strategy, a response-to-therapy biomarker, and a useful tool for understanding structure-proteotoxicity relationships in the TTR amyloidoses.

越来越多的证据支持这样的假说，即可溶性错误折叠的蛋白质组装体导致淀粉样疾病中有丝分裂后组织的变性。然而，缺乏可靠的基于非抗体的探针来选择性地检测在血浆中循环或沉积在组织中的寡聚聚集体结构，这使得难以在患者中仔细研究该假说。因此，了解驱动淀粉样蛋白疾病的结构-蛋白毒性关系仍然具有挑战性，阻碍了早期诊断和新型治疗策略的发展。我们报告基于肽的探针，选择性地标记在TTR遗传性淀粉样变性病患者血浆中表现出主要神经病性表型的错折叠的运甲状腺素蛋白（TTR）低聚物。这些探针表明，在健康对照中，与淀粉样多发性神经病有关的无症状突变携带者以及与TTR相关的心肌病患者中，错误折叠的TTR低聚物的数量要少得多。心肌病患者血浆中不存在折叠错误的TTR低聚物，这表明在TTR淀粉样糖中观察到的组织嗜性是基于结构的。用疾病改良疗法（塔法米地或肝移植介导的基因疗法）治疗的TTR淀粉样多发性神经病患者，错误折叠的寡聚体减少。在一部分TTR淀粉样多发性神经病患者中，探针还检测到了一个循环的TTR片段，在他法米地治疗后消失了。分离的TTR低聚物的蛋白质组学分析揭示了一种特定的患者相关特征，该特征由可能与循环中TTR低聚物相关的蛋白质组成。使用肽探针定量测定血浆低聚物的浓度可能成为早期诊断策略，对治疗的反应生物标志物以及了解TTR淀粉样蛋白中结构-蛋白毒性关系的有用工具。