Structure-function relationships of human cholesteryl ester transfer protein: analysis using monoclonal antibodies

Area of Science:

• Biochemistry
• Molecular Biology
• Lipid Metabolism

Background:

• Cholesteryl ester transfer protein (CETP) is a glycoprotein that facilitates lipid transfer between lipoproteins.
• A previously identified antibody (mAb TP2) blocks CETP activity by targeting its C-terminal region.

Purpose of the Study:

• To investigate the structure-function relationships of CETP using a new panel of monoclonal antibodies (mAbs).
• To identify specific epitopes on CETP that, when bound by mAbs, inhibit cholesteryl ester (CE) transfer activity.

Main Methods:

• Generated and characterized 16 anti-human CETP mAbs.
• Mapped antibody epitopes using CETP variants with deletions or substitutions.
• Assessed the inhibitory effects of mAbs on CETP-mediated CE transfer from HDL to LDL.
• Analyzed mAb binding competition to determine CETP structural conformation.

Main Results:

• Nine of the 16 mAbs partially inhibited CETP-mediated CE transfer (24-43%).
• Neutralizing epitopes were mapped to four distinct regions of CETP, including residues 410-450, 184-260, and 332-366.
• Antibody competition assays indicated that the C-terminal 60% of CETP forms a compact structure.
• Non-neutralizing epitopes were mapped to regions 184-260, 261-331, and 367-409.

Conclusions:

• Inhibitory activity against CETP-mediated CE transfer can be achieved by targeting multiple, distinct epitopes across the protein.
• The compact structure of CETP's C-terminus suggests proximity between neutral lipid and lipoprotein binding sites.
• These findings provide insights into CETP structure and potential therapeutic strategies for modulating lipid transfer.