Iannuzzi Clara, Maritato Rosa, Irace Gaetano, Sirangelo Ivana
Department of Biochemistry, Biophysics and General Pathology, Second University of Naples, Naples, Italy.
PLoS One. 2013 Dec 4;8(12):e80768. doi: 10.1371/journal.pone.0080768. eCollection 2013.
Neurodegenerative diseases are associated with misfolding and deposition of specific proteins, either intra or extracellularly in the nervous system. Advanced glycation end products (AGEs) originate from different molecular species that become glycated after exposure to sugars. Several proteins implicated in neurodegenerative diseases have been found to be glycated in vivo and the extent of glycation is related to the pathologies of the patients. Although it is now accepted that there is a direct correlation between AGEs formation and the development of neurodegenerative diseases, several questions still remain unanswered: whether glycation is the triggering event or just an additional factor acting on the aggregation pathway. To this concern, in the present study we have investigated the effect of glycation on the aggregation pathway of the amyloidogenic W7FW14F apomyoglobin. Although this protein has not been related to any amyloid disease, it represents a good model to resemble proteins that intrinsically evolve toward the formation of amyloid aggregates in physiological conditions. We show that D-ribose, but not D-glucose, rapidly induces the W7FW14F apomyoglobin to generate AGEs in a time-dependent manner and protein ribosylation is likely to involve lysine residues on the polypeptide chain. Ribosylation of the W7FW14F apomyoglobin strongly affects its aggregation kinetics producing amyloid fibrils within few days. Cytotoxicity of the glycated aggregates has also been tested using a cell viability assay. We propose that ribosylation in the W7FW14F apomyoglobin induces the formation of a cross-link that strongly reduces the flexibility of the H helix and/or induce a conformational change that favor fibril formation. These results open new perspectives for AGEs biological role as they can be considered not only a triggering factor in amyloidosis but also a player in later stages of the aggregation process.
神经退行性疾病与特定蛋白质在神经系统内或细胞外的错误折叠和沉积有关。晚期糖基化终产物（AGEs）源自不同的分子种类，这些分子在接触糖类后会发生糖基化。已发现几种与神经退行性疾病相关的蛋白质在体内发生了糖基化，且糖基化程度与患者的病理状况有关。尽管现在人们普遍认为AGEs的形成与神经退行性疾病的发展之间存在直接关联，但仍有几个问题尚未得到解答：糖基化是触发事件还是仅仅是作用于聚集途径的一个附加因素。针对这一问题，在本研究中，我们研究了糖基化对淀粉样蛋白生成性W7FW14F脱辅基肌红蛋白聚集途径的影响。尽管这种蛋白质与任何淀粉样疾病都没有关联，但它是一个很好的模型，类似于在生理条件下自然会形成淀粉样聚集体的蛋白质。我们发现，D-核糖而非D-葡萄糖能迅速诱导W7FW14F脱辅基肌红蛋白以时间依赖性方式生成AGEs，蛋白质核糖基化可能涉及多肽链上的赖氨酸残基。W7FW14F脱辅基肌红蛋白的核糖基化强烈影响其聚集动力学，在几天内就产生了淀粉样纤维。还使用细胞活力测定法测试了糖基化聚集体的细胞毒性。我们提出，W7FW14F脱辅基肌红蛋白中的核糖基化诱导形成了一种交联，这种交联强烈降低了H螺旋的柔韧性和/或诱导了有利于纤维形成的构象变化。这些结果为AGEs的生物学作用开辟了新的视角，因为它们不仅可以被视为淀粉样变性的触发因素，还可以被视为聚集过程后期的一个参与者。
