CETP is capable of proatherogenic activities during remodeling through both triglyceride and cholesteryl ester (CE) pathways. CETP mediates transfer of triglycerides from VLDL-1 to HDL and/or LDL in exchange for CE, resulting in larger, relatively triglyceride-enriched HDL and LDL species ( 3,4 ). Hepatic lipase remodels these larger lipoprotein species into i ) smaller and denser HDL remnants destined for removal from the circulation by the hepatic holo receptor and/or by renal clearance ( 5 ) and ii ) smaller, denser LDL destined for the subendothelial space of arteries to initiate plaque formation, as these LDL species react weakly with LDL receptors, thus prolonging their half-lives ( 6-8 ). These pathological endpoints are observed clinically as circulating i ) high normal to moderately elevated triglyceride levels, ii ) low total HDL cholesterol (HDL-C) levels, and iii ) high levels of small, dense LDL. This triad is referred to as the atherogenic lipid profi le, which is observed in ف 25% of the general population in Western countries due to insulin resistance, including type 2 diabetes ( 9, 10 ).Further, but related, proatherogenic activity for CETP involves its redirection of CE to more atherogenic lipoprotein species, rather than to direct CE disposal by the liver via SRB-1 or the LDL receptor ( 4, 6 ). The latter two, in part, mediate reverse cholesterol transport (RCT), in which cholesterol obtained from peripheral tissue is esterifi ed by LCAT. Most CEs derived from LCAT do not return to the liver via the HDL SRB-1 pathway but, rather, through more atherogenic pathways ( 4, 7 ). CETP mediates the transfer of most CE from HDL to VLDL or to other more atherogenic intermediate-density lipoproteins and remnants ( 3 ). Apolipoprotein F may inhibit direct transfer of some, but not all, of CE from HDL to the potentially more atherogenic LDL ( 11 ). Inhibiting the above two proatherogenic remodeling events could be advantageous. Indeed, in vitro studies using human plasma indicate an anti- Recent innovative X-ray crystallographic, electron microscopic (EM), and bioinformatics observations signifi cantly improve our understanding of the physical relationships of cholesteryl ester transfer protein's (CETP) interactions with lipoproteins and lipid transfer processes ( 1, 2 ). Two major observations derived using these novel methods are i ) CETP connects with or forms bridges between two lipoproteins, e.g., HDL and LDL, with resultant neutral lipid transfer, and ii ) CETP appears to contain a hydrophobic tunnel along its entire long axis capable of neutral lipid transfer. Using this new paradigm, prior data regarding CETP and lipoprotein interactions can be reevaluated from current perspectives. Here, we focus on molecular details of CETP that appear relevant to its interactions with lipoproteins, including sensing, penetration, docking, selectivity, ternary complex formation, lipid transfer, and HDL dissociation.
Abstract Cholesteryl ester transfer protein (CETP) is im-First, a summary of the biological and ...