Department of Biology, University of Maryland, College Park, MD 20742, USA.
Biochem J. 2012 Jul 1;445(1):81-91. doi: 10.1042/BJ20112103.
The present study demonstrates the important structural features of ceramide required for proper regulation, binding and identification by both pro-apoptotic and anti-apoptotic Bcl-2 family proteins. The C-4=C-5 trans-double bond has little influence on the ability of Bax and Bcl-xL to identify and bind to these channels. The stereochemistry of the headgroup and access to the amide group of ceramide is indispensible for Bax binding, indicating that Bax may interact with the polar portion of the ceramide channel facing the bulk phase. In contrast, Bcl-xL binding to ceramide channels is tolerant of stereochemical changes in the headgroup. The present study also revealed that Bcl-xL has an optimal interaction with long-chain ceramides that are elevated early in apoptosis, whereas short-chain ceramides are not well regulated. Inhibitors specific for the hydrophobic groove of Bcl-xL, including 2-methoxyantimycin A3, ABT-737 and ABT-263 provide insights into the region of Bcl-xL involved in binding to ceramide channels. Molecular docking simulations of the lowest-energy binding poses of ceramides and Bcl-xL inhibitors to Bcl-xL were consistent with the results of our functional studies and propose potential binding modes.
本研究展示了神经酰胺的重要结构特征，这些特征对于促凋亡和抗凋亡 Bcl-2 家族蛋白的适当调节、结合和识别是必需的。C-4=C-5 反式双键对 Bax 和 Bcl-xL 识别和结合这些通道的能力几乎没有影响。神经酰胺头基的立体化学和酰胺基团的可及性对于 Bax 的结合是不可或缺的，这表明 Bax 可能与面对体相的神经酰胺通道的极性部分相互作用。相比之下，Bcl-xL 与神经酰胺通道的结合对头基的立体化学变化具有耐受性。本研究还表明，Bcl-xL 与在细胞凋亡早期升高的长链神经酰胺具有最佳相互作用，而短链神经酰胺则不能很好地调节。Bcl-xL 的疏水凹槽的抑制剂，包括 2-甲氧基安替比林 A3、ABT-737 和 ABT-263，为 Bcl-xL 与神经酰胺通道结合的区域提供了深入的了解。神经酰胺和 Bcl-xL 抑制剂与 Bcl-xL 的最低能量结合构象的分子对接模拟与我们的功能研究结果一致，并提出了潜在的结合模式。
