Cholesteryl ester transfer proteins from different species do not have equivalent activities

Area of Science:

• Biochemistry
• Molecular Biology
• Lipid Metabolism

Background:

• Cholesteryl ester transfer protein (CETP) facilitates lipid transfer between lipoproteins.
• Human CETP activity is influenced by amino acid composition, affecting substrate preference.
• Homologs of CETP exist across species, but their lipid transfer activities are largely uncharacterized.

Purpose of the Study:

• To investigate the lipid transfer properties of CETP from different species.
• To compare the substrate preference (triglyceride vs. cholesteryl ester) of various CETP homologs with human CETP.
• To elucidate the functional differences in lipid transfer mechanisms mediated by different CETP species.

Main Methods:

• Recombinant CETP proteins from rabbit, monkey, and hamster were generated.
• Lipid transfer assays were performed using VLDL and HDL particles.
• CETP activity was assessed by measuring net transfer of cholesteryl ester (CE) and triglyceride (TG).
• One-way lipid transfer to an acceptor particle lacking CE and TG was also evaluated.

Main Results:

• CETP species from rabbit, monkey, and hamster exhibited significantly higher TG/CE transfer ratios compared to human CETP.
• Human and monkey CETPs mediated equimolar transfer of CE and TG between VLDL and HDL.
• Hamster CETP demonstrated a non-equimolar transfer, resulting in a net flow of TG into HDL.
• Monkey and hamster CETPs were most effective in transferring neutral lipid to an acceptor particle.

Conclusions:

• CETP proteins from human, monkey, rabbit, and hamster are functionally distinct.
• Hamster CETP exhibits a unique substrate preference, strongly favoring triglyceride transfer.
• Species-specific differences in CETP activity can significantly impact lipoprotein metabolism and lipid flow.