Beyond the Crystal: Molecular Dynamics Investigations of CETP with Varied Lipid Substrates Reveal Asymmetric Dominant Motions

Abstract

Cholesteryl Ester Transfer Protein (CETP) is a crucial therapeutic target for combating cardiovascular diseases (CVD) due to its strong influence in modulating high-density lipoprotein (HDL) levels. CETP is responsible for the bidirectional transfer of cholesteryl esters (CEs) and triglycerides (TGs) between different lipoprotein fractions. Although CETP encounters both these neutral lipid substrates when it penetrates deep into lipoprotein cores and can acquire either lipid, prior studies have examined its conformational space only in the presence of CEs or TGs individually. Here, we investigate the unexplored dynamics of CETP in heterogeneous lipid environments (CE-TG and TG-CE) using molecular dynamics simulations. Our analyses show that these mixed-lipid systems exhibit distinct behaviors compared to their homogeneous counterparts with significantly elevated flexibility and reduced compactness. Furthermore, we observed distortions in the protein's secondary structure and huge asymmetry in its dominant motions. Notably, the TGs within the mixed-lipid systems exhibit varied conformational states and adopt orientations that deviate from their reported parallel N-N orientation for lipid transfer through CETP. These local and collective structural and dynamical variations imply that the presence of mixed lipids could significantly affect the lipid transfer activity of CETP through its core hydrophobic tunnel.