Department of Biotechnology, Siddaganga Institute of Technology, Tumakuru, Karnataka, India.
Biophys Chem. 2023 Oct;301:107093. doi: 10.1016/j.bpc.2023.107093. Epub 2023 Aug 15.
Cholesteryl Ester Transfer Protein (CETP) is a plasma glycoprotein that intervenes the reverse cholesterol transport (RCT) by equimolar exchange of Cholesteryl esters (CE) and Triglycerides (TGs) between anti-atherogenic High-Density Lipoproteins (HDLs) and pro-atherogenic Low-Density Lipoproteins (LDLs) resulting in the increased concentration of CEs in LDL. This is a potential cause for the formation of atherosclerotic plaques in blood vessels leading to fatality. Therefore, blocking the function of CETP has emerged as a novel strategy for suppressing atherosclerotic plaques. The crystal structure of CETP revealed two Cholesteryl esters (CEs) in the hydrophobic tunnel and two phospholipids (PLs) plugged on the concave surface. Previous lipid transfer assay experimental studies have shown a substantial reduction in the neutral lipid transfer in [R201S] and [I443W, V198W] mutants. However, the protein conformational arrangements due to the mutations present in the CETP system leading to a decrease in the transfer rate of neutral lipids is not explored. Thus, I explored the reason behind the decreased transfer rate in mutants using molecular dynamics (MD) simulations and free energy calculations. Resulting evidences show that R201S mutant induces unfavorable bending angle to CETP with a decreased binding efficiency between N-terminal phospholipid of CETP with S201. Also, an unfavorable conformation state of TGs is formed which makes them difficult to transfer across CETP. Likewise, [I443W, V198W] mutant induces unfavorable CE, TG, and bending angle conformation to CETP impeding neutral lipid transfer. Thus, my results provide sufficient insights on the causation for a decreased transfer rate as reported earlier. The detailed understanding obtained here could help in developing a new strategy in preventing the function of CETP by blocking the role of potential hot spot residues.
胆固醇酯转移蛋白（CETP）是一种血浆糖蛋白，通过在抗动脉粥样硬化的高密度脂蛋白（HDL）和促动脉粥样硬化的低密度脂蛋白（LDL）之间等量交换胆固醇酯（CE）和甘油三酯（TGs），干预胆固醇逆转运（RCT），导致 LDL 中的 CE 浓度增加。这是血管中动脉粥样斑块形成的潜在原因，导致死亡。因此，阻断 CETP 的功能已成为抑制动脉粥样斑块的新策略。CETP 的晶体结构显示，疏水隧道中有两个胆固醇酯（CE）和两个插在凹面的磷脂（PL）。以前的脂质转移实验研究表明，[R201S]和[I443W，V198W]突变体中的中性脂质转移大量减少。然而，由于 CETP 系统中存在的突变导致蛋白质构象排列发生变化，从而降低中性脂质的转移速率，这一现象尚未得到探索。因此，我使用分子动力学（MD）模拟和自由能计算来探索突变体中转移速率降低的原因。结果表明，R201S 突变体诱导 CETP 产生不利的弯曲角度，降低 CETP 中 N 端磷脂与 S201 的结合效率。此外，形成了不利于 TG 的构象状态，使它们难以穿过 CETP。同样，[I443W，V198W]突变体诱导 CETP 中 CE、TG 和弯曲角度构象不利，阻碍中性脂质转移。因此，我的结果为先前报道的转移速率降低提供了充分的原因。这里获得的详细理解有助于通过阻断潜在热点残基的作用，开发一种新的策略来阻止 CETP 的功能。
