Moafian Zeinab, Khoshaman Kazem, Oryan Ahmad, Kurganov Boris I, Yousefi Reza
Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran.
Department of Pathology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
PLoS One. 2016 Oct 5;11(10):e0164139. doi: 10.1371/journal.pone.0164139. eCollection 2016.
Various post-translational lens crystallins modifications result in structural and functional insults, contributing to the development of lens opacity and cataract disorders. Lens crystallins are potential targets of homocysteinylation, particularly under hyperhomocysteinemia which has been indicated in various eye diseases. Since both homocysteinylation and acetylation primarily occur on protein free amino groups, we applied different spectroscopic methods and gel mobility shift analysis to examine the possible preventive role of acetylation against homocysteinylation. Lens crystallins were extensively acetylated in the presence of acetic anhydride and then subjected to homocysteinylation in the presence of homocysteine thiolactone (HCTL). Extensive acetylation of the lens crystallins results in partial structural alteration and enhancement of their stability, as well as improvement of α-crystallin chaperone-like activity. In addition, acetylation partially prevents HCTL-induced structural alteration and aggregation of lens crystallins. Also, acetylation protects against HCTL-induced loss of α-crystallin chaperone activity. Additionally, subsequent acetylation and homocysteinylation cause significant proteolytic degradation of crystallins. Therefore, further experimentation is required in order to judge effectively the preventative role of acetylation on the structural and functional insults induced by homocysteinylation of lens crystallins.
晶状体蛋白的各种翻译后修饰会导致结构和功能损伤，促进晶状体混浊和白内障疾病的发展。晶状体蛋白是同型半胱氨酸化的潜在靶点，尤其是在高同型半胱氨酸血症的情况下，高同型半胱氨酸血症已在多种眼部疾病中有所体现。由于同型半胱氨酸化和乙酰化主要发生在蛋白质的游离氨基上，我们应用了不同的光谱方法和凝胶迁移率变动分析来研究乙酰化对同型半胱氨酸化可能的预防作用。晶状体蛋白在乙酸酐存在的情况下被广泛乙酰化，然后在同型半胱氨酸硫内酯（HCTL）存在的情况下进行同型半胱氨酸化。晶状体蛋白的广泛乙酰化导致部分结构改变并增强其稳定性，同时提高α-晶状体蛋白的伴侣样活性。此外，乙酰化部分地防止了HCTL诱导的晶状体蛋白结构改变和聚集。而且，乙酰化可防止HCTL诱导的α-晶状体蛋白伴侣活性丧失。此外，随后的乙酰化和同型半胱氨酸化会导致晶状体蛋白发生显著的蛋白水解降解。因此，需要进一步的实验来有效判断乙酰化对晶状体蛋白同型半胱氨酸化诱导的结构和功能损伤的预防作用。
