Binding of aflatoxins to the 20S proteasome: effects on enzyme functionality and implications for oxidative stress and apoptosis
Binding of aflatoxins to the 20S proteasome: effects on enzyme functionality and implications for oxidative stress and apoptosis
复制标题
DOI：
10.1515/bc.2007.012
复制
发表时间：
2007-01-01
影响因子：
3.7
通讯作者：
Eleuteri, Anna Maria
中科院分区：
文献类型：
--
作者：
Amici, Manila;Cecarini, Valentina;Eleuteri, Anna Maria
黄曲霉毒素（AF）是储存不当的食品污染物;它们是强有力的遗传毒性和致癌化合物，通过破坏DNA发挥其作用。它们还可以诱导增加氧化损伤的突变。本研究的目的是评估第三种机制可能参与黄曲霉毒素的致癌作用的可能性，即直接结合参与细胞周期调控途径的关键酶，从而调节酶的功能。在黄曲霉毒素B1、G1和M1存在下测定20 S组成型和免疫蛋白酶体肽酶和蛋白水解活性。所有这三种毒素激活蛋白酶体的多种肽酶活性。黄曲霉毒素（AF）M1是最有效的激活剂的蛋白酶体的活性，而组成型20 S蛋白酶体特异性刺激AFG 1。此外，还研究了黄曲霉毒素B_1对体外培养的肝癌细胞的作用，发现黄曲霉毒素B_1对肝癌细胞裂解液测定的各种蛋白酶体活性均有不同程度的影响。考虑到蛋白酶体在细胞防御氧化应激中的关键作用，分析了细胞裂解物中羰基含量和抗氧化酶活性。还通过测量caspase-3活性和p27和I κ B α的细胞水平来研究AFB 1的促凋亡作用。
Aflatoxins (AF) are contaminants of improperly stored foods; they are potent genotoxic and carcinogenic compounds, exerting their effects through damage to DNA. They can also induce mutations that increase oxidative damage. The goal of this study was to evaluate the possibility that a third mechanism could be involved in the carcinogenic action of aflatoxins, namely, direct binding to key enzymes involved in the regulatory pathways of the cell cycle, thereby modulating enzyme functionality. The 20S constitutive and immunoproteasome peptidase and proteolytic activities were assayed in the presence of aflatoxins B1, G1 and M1. All three toxins activated multiple peptidase activities of the proteasome. Aflatoxin (AF) M1 was the most potent activator of proteasome activity, while the constitutive 20S proteasome was specifically stimulated by AFG1. Furthermore, the effects of AFB1 on cultured hepatoma cells were investigated and the various proteasomal activities determined with cell lysates were differently affected. Taking into account the key role of the proteasome in cellular defense against oxidative stress, the carbonyl group content and the activities of antioxidant enzymes in cell lysates were analyzed. The proapoptotic effect of AFB1 was also investigated by measuring caspase-3 activity and cellular levels of p27 and I kappa B alpha.