Sekijima Yoshiki, Hammarström Per, Matsumura Miyuki, Shimizu Yuko, Iwata Makoto, Tokuda Takahiko, Ikeda Shu-Ichi, Kelly Jeffery W
Department of Chemistry and The Skaggs Institute of Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Lab Invest. 2003 Mar;83(3):409-17. doi: 10.1097/01.lab.0000059937.11023.1f.
Transthyretin (TTR) is a tetrameric protein that must misfold to form amyloid fibrils. Misfolding includes rate-limiting tetramer dissociation, followed by fast tertiary structural changes that enable aggregation. Amyloidogenesis of wild-type (WT) TTR causes a late-onset cardiac disease called senile systemic amyloidosis. The aggregation of one of > 80 TTR variants leads to familial amyloidosis encompassing a collection of disorders characterized by peripheral neuropathy and/or cardiomyopathy. Prominent central nervous system (CNS) impairment is rare in TTR amyloidosis. Herein, we identify a new A25T TTR variant in a Japanese patient who presented with CNS amyloidosis at age 42 and peripheral neuropathy at age 44. The A25T variant is the most destabilized and fastest dissociating TTR tetramer published to date, yet, surprising, disease onset is in the fifth decade. Quantification of A25T TTR in the serum of this heterozygote reveals low levels relative to WT, suggesting that protein concentration influences disease phenotype. Another recently characterized TTR CNS variant (D18G TTR) exhibits strictly analogous characteristics, suggesting that instability coupled with low serum concentrations is the signature of CNS pathology and protects against early-onset systemic amyloidosis. The low A25T serum concentration may be explained either by impaired secretion from the liver or by increased clearance, both scenarios consistent with A25T's low kinetic and thermodynamic stability. Liver transplantation is the only known treatment for familial amyloid polyneuropathy. This is a form of gene therapy that removes the variant protein from serum preventing systemic amyloidosis. Unfortunately, the choroid plexus would have to be resected to remove A25T from the CSF-the source of the CNS TTR amyloid. Herein we demonstrate that small-molecule tetramer stabilizers represent an attractive therapeutic strategy to inhibit A25T misfolding and CNS amyloidosis. Specifically, 2-[(3,5-dichlorophenyl)amino]benzoic acid is an excellent inhibitor of A25T TTR amyloidosis in vitro.
转甲状腺素蛋白（TTR）是一种四聚体蛋白，必须发生错误折叠才能形成淀粉样纤维。错误折叠包括限速的四聚体解离，随后是快速的三级结构变化，从而导致聚集。野生型（WT）TTR的淀粉样变会引发一种迟发性心脏病，称为老年系统性淀粉样变。80多种TTR变体之一的聚集会导致家族性淀粉样变，包括一系列以周围神经病变和/或心肌病为特征的疾病。在TTR淀粉样变中，明显的中枢神经系统（CNS）损害很少见。在此，我们在一名日本患者中鉴定出一种新的A25T TTR变体，该患者在42岁时出现中枢神经系统淀粉样变，44岁时出现周围神经病变。A25T变体是迄今为止公布的最不稳定、解离最快的TTR四聚体，但令人惊讶的是，发病年龄在五十多岁。对该杂合子血清中A25T TTR的定量分析显示，其水平相对于野生型较低，这表明蛋白质浓度会影响疾病表型。另一种最近鉴定出的TTR中枢神经系统变体（D18G TTR）表现出严格类似的特征，这表明不稳定性与低血清浓度相结合是中枢神经系统病理的特征，可预防早发性系统性淀粉样变。A25T血清浓度低可能是由于肝脏分泌受损或清除增加所致，这两种情况均与A25T的低动力学和热力学稳定性一致。肝移植是已知的治疗家族性淀粉样多神经病的唯一方法。这是一种基因治疗形式，可从血清中去除变体蛋白，预防系统性淀粉样变。不幸的是，必须切除脉络丛才能从脑脊液（中枢神经系统TTR淀粉样变的来源）中去除A25T。在此我们证明，小分子四聚体稳定剂是抑制A25T错误折叠和中枢神经系统淀粉样变的一种有吸引力的治疗策略。具体而言，2-[(3,5-二氯苯基)氨基]苯甲酸在体外是A25T TTR淀粉样变的优秀抑制剂。
