Markovich Samuel W, Frey Brian L, Scalf Mark, Shortreed Michael R, Smith Lloyd M
Department of Chemistry, University of Wisconsin-Madison; Madison, WI 53706, USA.
Brain Commun. 2025 Jan 16;7(1):fcaf019. doi: 10.1093/braincomms/fcaf019. eCollection 2025.
Alzheimer's disease (AD) is characterized by the accumulation of protein aggregates, which are thought to be influenced by posttranslational modifications (PTMs). Dehydroamino acids (DHAAs) are rarely observed PTMs that contain an electrophilic alkene capable of forming protein-protein crosslinks, which may lead to protein aggregation. We report here the discovery of DHAAs in the protein aggregates from AD, constituting an unknown and previously unsuspected source of extensive proteomic complexity. We used mass spectrometry-based proteomics to discover 404 sites of DHAA formation in 171 proteins from protein aggregate-enriched human brain samples, 6-fold more sites than observed in the soluble protein fractions. The DHAA modifications are observed both directly and in the form of conjugates after reacting with abundant cellular nucleophiles or crosslinking to nucleophilic amino acid residues. We report 11 such crosslinks, including three in the Tau protein, which are 10-fold more abundant in AD samples compared with age-matched controls. Many of the proteins found to contain DHAAs and their conjugates are involved in protein aggregation or pathways dysregulated in AD. DHAAs are prevalent modifications in the AD brain proteome and give rise to protein crosslinks that may contribute to protein aggregation.
阿尔茨海默病（AD）的特征是蛋白质聚集体的积累，人们认为这受翻译后修饰（PTM）的影响。脱氢氨基酸（DHAA）是罕见的翻译后修饰，其包含能够形成蛋白质-蛋白质交联的亲电烯烃，这可能导致蛋白质聚集。我们在此报告了在AD患者的蛋白质聚集体中发现了DHAA，这构成了广泛蛋白质组复杂性的一个未知且先前未被怀疑的来源。我们使用基于质谱的蛋白质组学方法，在富含蛋白质聚集体的人脑样本中的171种蛋白质上发现了404个DHAA形成位点，比在可溶性蛋白质组分中观察到的位点多6倍。DHAA修饰既可以直接观察到，也可以在与丰富的细胞亲核试剂反应或与亲核氨基酸残基交联后以缀合物的形式观察到。我们报告了11种这样的交联，其中包括Tau蛋白中的三种，与年龄匹配的对照相比，这些交联在AD样本中的丰度高10倍。许多被发现含有DHAA及其缀合物的蛋白质都参与了AD中蛋白质聚集或失调的途径。DHAA是AD脑蛋白质组中普遍存在的修饰，并产生可能导致蛋白质聚集的蛋白质交联。
