Molecular Genetics of Plasma Lipid Transfer Proteins

Abstract

The plasma lipoproteins are continuously modified during their metabolism in plasma, as result of the action of lipid modifying enzymes (lipases and lecithin: cholesterol acyltransferase, LCAT) and lipid transfer processes. Whereas the transfer of cholesterol between lipoproteins or between lipoproteins and cells is governed by simple diffusion, the transfer of phospholipids and neutral lipids (cholesteryl esters and triglycerides) between lipoproteins is mediated by plasma lipid transfer activities1. In plasma the cholesteryl ester transfer protein (CETP, also known as lipid transfer protein-1, LTP-1) mediates the transfer of cholesteryl esters and triglycerides between lipoproteins; the CETP can also facilitate phospholipid transfer. In addition, a separate protein or proteins without neutral lipid transfer activity, can also mediate phospholipid transfer between lipqproteins. Although not well characterized, these protein(s) are called the phospholipid transfer protein (PTP) or lipid transfer protein-2 (LTP-2). The CETP plays a particularly important role in the metabolism of HDL lipids2. In humans the HDL lipids turn over much more rapidly than the structural proteins of HDL, reflecting the continuous remodeling of HDL by lipases, LCAT and lipid transfer processes2.