Role of cholesteryl ester transfer protein in selective uptake of high density lipoprotein cholesteryl esters by adipocytes

• Main Authors: Gerard Vassiliou, Ruth McPherson
• Format: Article
• Language: English
• Published: Elsevier 2004-09-01
• Series: Journal of Lipid Research
• Subjects: energy depletion; monensin; scavenger receptor class B type I; SW872 liposarcoma cells
• Online Access: http://www.sciencedirect.com/science/article/pii/S0022227520312852

Previous reports attributed cholesteryl ester transfer protein (CETP)-mediated HDL cholesteryl ester (CE) selective uptake to the CETP-mediated transfer of CE from HDL to newly secreted apolipoprotein B-containing lipoproteins, which are then internalized by the LDL receptor (LDL-R). CETP has also been implicated in the remodeling of HDL, which renders it a better substrate for selective uptake by scavenger receptor class B type I (SR-BI). However, CETP-mediated selective uptake of HDL3-derived CE was not diminished in LDL-R null adipocytes, SR-BI null adipocytes, or in the presence of the receptor-associated protein. We found that monensin treatment or energy depletion of the SW872 liposarcoma cells with 2-deoxyglucose and NaN3 had no effect on CETP-mediated selective uptake, demonstrating that endocytosis is not required. This is supported by data indicating that CETP transfers CE into a compartment from which it can be extracted by unlabeled HDL. CETP could also mediate the selective uptake of HDL3-derived triacylglycerol (TG) and phospholipid (PL). The CETP-specific kinetics for TG and CE uptake were similar, and both reached saturation at ∼5 μg/ml HDL. In contrast, CETP-specific PL uptake did not attain saturation at 5 μg/ml HDL and was ∼6-fold greater than the uptake of CE.We propose two possible mechanisms to account for the role of CETP in selective uptake.