The pathological Trento variant of alpha-1-antitrypsin (E75V) shows nonclassical behaviour during polymerization
The pathological Trento variant of alpha-1-antitrypsin (E75V) shows nonclassical behaviour during polymerization
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DOI：
10.1111/febs.14111
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发表时间：
2017-07-01
期刊：
影响因子：
5.4
通讯作者：
Fra, Annamaria
中科院分区：
文献类型：
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作者：
Miranda, Elena;Ferrarotti, Ilaria;Fra, Annamaria
严重的α-1-抗胰蛋白酶缺乏症（AATD）最常与α-1-抗胰蛋白酶（AAT）Z变体（E342 K）相关。ZZ纯合子表现出AAT作为聚合物在肝细胞内质网中的积累。这种蛋白质沉积可导致肝脏疾病，由于肺中弹性蛋白溶解活性的失调，导致AAT的低循环水平易诱发早发性肺气肿。在重度AATD患者中发现了越来越多的罕见AAT等位基因，通常与Z等位基因结合。在这里，我们报告了一个新的突变（E75 V）的患者严重血浆缺乏症，我们指定特伦托。与Z突变体相反，当在细胞模型中表达时，特伦托AAT被有效地分泌，但显示出受损的构象稳定性。聚丙烯酰胺凝胶电泳（PAGE）和ELISA为基础的分析的分泌蛋白揭示了存在的低聚物的电泳和免疫识别谱不同的Z和S（E264 V）AAT聚合物，包括减少识别构象单克隆抗体2C 1和4 B12。这种改变的识别不是由于对2C 1单克隆抗体的表位的直接影响，我们将其定位在螺旋E和F之间。结构分析表明，聚合物形成的可能基础是螺旋C和posthepatitis I环之间高度保守的稳定相互作用的丧失。这些结果突出了该区域对于维持天然状态稳定性是重要的，并且当受损时，导致形成与由Z和SAAT产生的那些不同的病理性聚合物。
Severe alpha-1-antitrypsin deficiency (AATD) is most frequently associated with the alpha-1-antitrypsin (AAT) Z variant (E342K). ZZ homozygotes exhibit accumulation of AAT as polymers in the endoplasmic reticulum of hepatocytes. This protein deposition can lead to liver disease, with the resulting low circulating levels of AAT predisposing to early-onset emphysema due to dysregulation of elastinolytic activity in the lungs. An increasing number of rare AAT alleles have been identified in patients with severe AATD, typically in combination with the Z allele. Here we report a new mutation (E75V) in a patient with severe plasma deficiency, which we designate Trento. In contrast to the Z mutant, Trento AAT was secreted efficiently when expressed in cellular models but showed compromised conformational stability. Polyacrylamide gel electrophoresis (PAGE) and ELISA-based analyses of the secreted protein revealed the presence of oligomeric species with electrophoretic and immunorecognition profiles different from those of Z and S (E264V) AAT polymers, including reduced recognition by conformational monoclonal antibodies 2C1 and 4B12. This altered recognition was not due to direct effects on the epitope of the 2C1 monoclonal antibody which we localized between helices E and F. Structural analyses indicate the likely basis for polymer formation is the loss of a highly conserved stabilizing interaction between helix C and the posthelix I loop. These results highlight this region as important for maintaining native state stability and, when compromised, results in the formation of pathological polymers that are different from those produced by Z and S AAT.