School of Pharmacy, Binzhou Medical University, Yantai 264003, China.
Jinan Microecological Biomedicine Shandong Laboratory, Jinan 250000, China.
Soft Matter. 2022 Mar 16;18(11):2203-2210. doi: 10.1039/d1sm01791h.
Phospholipase A2 (PLA2) is a peripheral membrane protein that plays an essential role in many inflammatory responses. However, the activation mechanisms of PLA2 on the membrane surface have not been fully understood. Herein, we have combined experimental techniques and theoretical approaches to investigate the activation and association of the PLA2 protein on an artificial phospholipid membrane. Using a phosphatidylserine (PS) nanodomain containing membrane to mimic the inflammatory conditions, we found that the activity of cytosolic PLA2s (cPLA2s) increases with higher ratios of PS in the membrane. Molecular dynamics simulations reveal that significant changes in the protein structure are related to negatively charged membranes. In particular, the alteration of negatively charged residues in the C2 domain brings about an opened binding pocket and the catalytic site access to the substrate phospholipid. Meanwhile, the negative residues in the loop 650-665 facilitate the optimal interfacial orientation of the protein with a closed binding pocket on the membrane surface. These results lead us to suggest an electrostatic-switch allosteric mechanism for cPLA2 activation on the cell membrane surface under the inflammatory state.
磷脂酶 A2（PLA2）是一种外周膜蛋白，在许多炎症反应中发挥着重要作用。然而，PLA2 在膜表面的激活机制尚未完全阐明。在此，我们结合实验技术和理论方法研究了 PLA2 蛋白在人工磷脂膜上的激活和结合。我们使用含有磷脂酰丝氨酸（PS）纳米域的膜来模拟炎症条件，发现胞质 PLA2s（cPLA2s）的活性随着膜中 PS 比例的增加而增加。分子动力学模拟表明，蛋白质结构的显著变化与带负电荷的膜有关。特别是 C2 结构域中带负电荷的残基的改变导致结合口袋打开，催化位点与底物磷脂接触。同时，环 650-665 中的负电荷残基促进了蛋白与带负电荷的膜表面的最佳界面取向，此时结合口袋处于关闭状态。这些结果表明，在炎症状态下，细胞表面的 cPLA2 激活存在静电开关变构机制。
