Lipid Transfer Mechanism of CETP between HDL and LDL: A Coarse-Grained Simulation Study

Abstract

Cholesteryl ester transfer protein (CETP) mediates the bidirectional exchange of cholesteryl esters (CEs) and triglycerides between HDL and LDL (1)⁠. Animal models along with early clinical studies have demonstrated that the impairment of CETP's functionality is important for the efficient treatment of cardiovascular diseases. Despite the pharmacological interest, CETP's lipid transfer mechanism is poorly understood. Recent cryo-electron microscopy studies suggested that CETP penetrates its N-and C-terminal β-barrel domains into HDL and LDL respectively to form a ternary complex (2)⁠. Further it was proposed that the hydrophobic tunnel of CETP can simultaneously interact with the core of HDL and LDL for continuous lipid exchange. However, the detailed lipid transfer process is still inconclusive. In this study, we employed coarse-grained molecular dynamics simulations to illuminate the lipid transfer mechanism of CETP in HDL-CETP-LDL ternary complex. The extent of penetration of CETP into HDL and LDL in our ternary complex model corroborated well with the experimental findings. Further, the results demonstrated that the ejection of C-terminal plug-in phospholipid (PLC) and subsequently the diffusion of CETP-bound CEs into LDL droplet through PLC opening. A detailed analysis on interactions of PLC pocket lining residues with the discharged lipids revealed residues with significant role in CE transfer. The detailed mechanism of lipid transfer by CETP as explored in this study might help designing future CETP research and subsequent CETP therapeutics.