Protein Reactivity of 3,4-Dihydroxyphenylacetaldehyde, a Toxic Dopamine Metabolite, Is Dependent on Both the Aldehyde and the Catechol
Protein Reactivity of 3,4-Dihydroxyphenylacetaldehyde, a Toxic Dopamine Metabolite, Is Dependent on Both the Aldehyde and the Catechol
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DOI：
10.1021/tx9000557
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发表时间：
2009-07-01
影响因子：
4.1
通讯作者：
Doorn, Jonathan A.
中科院分区：
文献类型：
--
作者：
Rees, Jennifer N.;Florang, Virginia R.;Doorn, Jonathan A.
多巴胺（DA）被认为是一种内源性神经毒素，可以解释帕金森病（PD）中观察到的选择性神经变性。然而，以前的工作表明，3，4-二羟基苯乙醛（DOPAL）比DA毒性更大。DOPAL是通过单胺氧化酶的活性作为DA催化剂的一部分产生的，DOPAL毒性的机制被认为涉及蛋白质修饰。先前的研究已经证明了通过醛部分的蛋白质反应性;然而，DOPAL含有两个反应性官能团（邻苯二酚和醛），两者都具有蛋白质加合的潜力。这项工作的目的是确定蛋白质修饰DOPAL是否发生通过硫醇反应性醌产生的邻苯二酚的氧化，这是已知的DA发生，或者如果醛形成加合物与胺亲核试剂。为了实现这一目标，确定DOPAL对N-乙酰基-赖氨酸（NAL）、N-乙酰基-半胱氨酸（NAC）和两种模型蛋白的反应性。此外，获得了几种DOPAL类似物并用于比较反应性。结果表明，在pH 7.4和37 ℃下，DOPAL反应性的顺序为NAL >> NAC，并且NAL和DOPAL的产物在不存在还原剂的情况下是稳定的。此外，DOPAL将与模型蛋白质反应，但在胺选择性改性剂柠康酸酐和2-亚氨基硫杂环戊烷盐酸盐的存在下，DOPAL对蛋白质的反应性减弱。此外，当模型蛋白或蛋白混合物（即，线粒体裂解物）用浓度为5-100 μ M的DOPAL处理。在抗坏血酸的存在下，蛋白质交联减少，这表明参与的醌DOPAL介导的蛋白质修饰。这些数据表明，DOPAL对蛋白质亲核试剂具有高度反应性，具有蛋白质交联的潜力。
Dopamine (DA) has been implicated as an endogenous neurotoxin to explain selective neurodegeneration, as observed for Parkinson's disease (PD). However, previous work demonstrated that 3,4-dihydroxyphenylacetaldehyde (DOPAL) was more toxic than DA. DOPAL is generated as a part of DA catabolism via the activity of monoamine oxidase, and the mechanism of DOPAL toxicity is proposed to involve protein modification. Previous studies have demonstrated protein reactivity via the aldehyde moiety; however, DOPAL contains two reactive functional groups (catechol and aldehyde), both with the potential for protein adduction. The goal of this work was to determine whether protein modification by DOPAL occurs via a thiol-reactive quinone generated from oxidation of the catechol, which is known to occur for DA, or if the aldehyde forms adducts with amine nucleophiles. To accomplish this objective, the reactivity of DOPAL toward N-acetyl-lysine (NAL), N-acetyl-cysteine (NAC), and two model proteins was determined. In addition, several DOPAL analogues were obtained and used for comparison of reactivity. Results demonstrate that at pH 7.4 and 37 degrees C, the order of DOPAL reactivity is NAL >> NAC and the product of NAL and DOPAL is stable in the absence of reducing agent. Moreover, DOPAL will react with model proteins, but in the presence of amine-selective modifiers citraconic anhydride and 2-iminothiolane hydrochloride, the reactivity of DOPAL toward the proteins is diminished. In addition, DOPAL-mediated protein cross-linking is observed when a model protein or a protein mixture (i.e., mitochondria lysate) is treated with DOPAL at concentrations of 5-100 mu M. Protein cross-linking was diminished in the presence of ascorbate, suggesting the involvement of a quinone in DOPAL-mediated protein modification. These data indicate that DOPAL is highly reactive toward protein nucleophiles with the potential for protein cross-linking.