Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo , São Paulo, SP, Brazil.
Chem Res Toxicol. 2013 Oct 21;26(10):1536-44. doi: 10.1021/tx4002385. Epub 2013 Oct 11.
Mitochondrial cholesterol has been reported to be increased under specific pathological conditions associated with enhanced oxidative stress parameters. In this scenario, cholesterol oxidation would be increased, leading to the production of reactive aldehydes, including cholesterol carboxyaldehyde (ChAld). By using SDS micelles as a mitochondrial mimetic model, we have demonstrated that ChAld covalently modifies cytochrome c (cytc), a protein known to participate in electron transport and apoptosis signaling. This mimetic model induces changes in cytc structure in the same way as mitochondrial membranes do. Tryptic digestion of the cytc-ChAld adduct followed by MALDI-TOF/TOF analyses revealed that modifications occur at Lys residues (K22) localized at cytc site L, a site involved in protein-protein and protein-membrane interactions. Interestingly, ChAld ligation prevented cytc detachment from liposomes even under high ionic strength conditions. Overall, it can be concluded that ChAld ligation to Lys residues at site L creates a hydrophobic tail at cytc, which promotes cytc anchoring to the membrane. Although not investigated in detail in this study, cytc adduction to cholesterol derived aldehydes could have implications in cytc release from mitochondria under apoptotic stimuli.
已有研究报道，在与氧化应激参数增强相关的特定病理条件下，线粒体胆固醇会增加。在这种情况下，胆固醇氧化会增加，导致反应性醛的产生，包括胆固醇羧醛（ChAld）。通过使用 SDS 胶束作为线粒体模拟模型，我们已经证明 ChAld 共价修饰细胞色素 c（cytc），cytc 是一种已知参与电子传递和细胞凋亡信号的蛋白质。这种模拟模型以与线粒体膜相同的方式诱导 cytc 结构发生变化。用糜蛋白酶消化 cytc-ChAld 加合物，然后进行 MALDI-TOF/TOF 分析表明，修饰发生在 Lys 残基（K22）上，该残基位于 cytc 位点 L，该位点参与蛋白质-蛋白质和蛋白质-膜相互作用。有趣的是，即使在高离子强度条件下，ChAld 的连接也能阻止 cytc 从脂质体中脱离。总的来说，可以得出结论，ChAld 与位点 L 的 Lys 残基的连接在 cytc 上创建了一个疏水性尾巴，这促进了 cytc 与膜的锚定。尽管在本研究中没有详细研究，但 cytc 与胆固醇衍生醛的加合物可能对凋亡刺激下 cytc 从线粒体中的释放有影响。
