Acylation of Lens Proteins

胞浆蛋白的 N-酰化在组织中很常见，它调节蛋白质的结构和 功能。细胞中主要的N-酰化类型是乙酰化、丙酰化、琥珀酰化和丙二酰化， 由乙酰辅酶A、丙酰辅酶A、琥珀酰辅酶A的酶促或非酶促转移引发 和丙二酰辅酶A分别转化为赖氨酸残基。晶状体蛋白的寿命很长，很少或没有更新，并且 因此，翻译后修饰（PTM）会随着年龄的增长而积累。缺乏酶活性蛋白质， 特别是在晶状体的核心，禁止 PTM 的逆转。因此，如果晶状体中的脱酰基酶较弱， 酰化主要是一种单向反应，导致晶状体蛋白的永久修饰，这似乎 情况确实如此（基于我们的初步数据）。酰化对晶状体蛋白的影响仍然很大 未知。正如我们之前的研究所示，乙酰化使 α-晶状体蛋白成为更好的伴侣。此外， 我们的初步数据表明，晶状体蛋白也被丙酰化、琥珀酰化和丙二酰化，并且 乙酰化和琥珀酰化增加了蛋白质的热稳定性和溶解度。因此，我们 假设晶状体蛋白的酰化是一种有益的 PTM，有助于维持 α- 的伴侣活性 晶状体蛋白以及晶状体蛋白在老化过程中的稳定性和溶解度。我们将在 三个目标。在目标 1 中，我们将通过质量确定人晶状体 α-晶状体蛋白中的主要酰化位点 光谱分析并确定年龄对这些修饰的影响。在目标 2 中，我们将确定 酰化对α-晶状体蛋白结构和功能的影响。在目标 3 中，我们将评估以下效果： 酰化对晶状体蛋白稳定性和溶解度的影响，并确定酰化是否可用于 改善老年人晶状体受损的弹性。

N-acylation of cytosolic proteins is a common occurrence in tissues, and it regulates protein structure and function. The major N-acylation types in cells are acetylation, propionylation, succinylation and malonylation, which are initiated by the enzymatic or non-enzymatic transfer of acetyl CoA, propionyl CoA, succinyl CoA and malonyl CoA to lysine residues, respectively. Lens proteins are long lived with little or no turnover, and thus, post-translational modifications (PTMs) accumulate with age. The lack of enzymatically active proteins, particularly in the core of the lens, prohibits the reversal of PTMs. Thus, if deacylases are weak in the lens, acylation is mostly a one-way reaction that leads to permanent modifications of lens proteins, which appears to be the case (based on our preliminary data). The effects of acylation on lens proteins remain largely unknown. As shown in our previous study, the acetylation makes α-crystallin a better chaperone. In addition, our preliminary data show that lens proteins are also propionylated, succinylated and malonylated and that acetylation and succinylation increase the thermal stability and solubility of the proteins. Thus, we hypothesize that acylation of lens proteins is a beneficial PTM that helps maintain the chaperone activity of α- crystallin as well as the stability and solubility of lens proteins during aging. We will test this hypothesis in three aims. In Aim 1, we will determine the major acylation sites in human lens α-crystallin by mass spectrometric analyses and determine the effect of age on these modifications. In Aim 2, we will determine effects of acylation on the structure and function of α-crystallin. In Aim 3, we will evaluate the effects of acylation on the stability and solubility of lens proteins and determine whether acylation can be used to improve the compromised resilience of aged human lenses.