High density lipoprotein subfractions isolated by heparin-Sepharose affinity chromatography and their role in cholesteryl ester transfer to very low density lipoproteins.

Normal human plasma HDL was applied to a column of heparin-Sepharose in the presence of MnCl(2) and three fractions were obtained by stepwise elution with increasing NaCl concentrations: a non-retained fraction (NR, 78% of protein) and two retained fractions (R(1) and R(2), 18 and 2.5% of protein, respectively). Both unesterified and esterified cholesterol increased from NR to R(1) to R(2) but the increment was more pronounced for unesterified cholesterol. ApoA-II to apoA-I ratio was-lower in R(1) compared to NR but R(1) contained more apoC than NR. ApoE increased from NR to R(1) to R(2) (0.07, 0.4, and 14% of protein in each fraction, respectively) while apoB was found only in R(2). Agarose gel electrophoresis and immunoadsorbers for apoB and apoE showed that R(2) consisted of two major lipoprotein populations, one containing apoB and some apoE and the other containing apoE and no apoB. Cholesteryl ester transfer between each HDL subfraction and VLDL in the presence of partially purified cholesterol ester transfer protein was studied. NR and R(1) gave the highest initial rates of transfer for labeled cholesteryl ester which were corroborated by significant mass transfer of cholesteryl esters. From these results, we concluded that there is no connection between cholesteryl ester transfer and apoE. On the other hand, transfer from R(2) to VLDL followed different kinetics with a high zero hour transfer but with subsequently lower rates when compared to NR and R(1). The cholesteryl ester transfer activity in R(2) was mainly due to the presence of apoE-containing lipoproteins whereas those containing apoB had minimal transfer activity. However, because this transfer of label was not translated into significant mass transfer of cholesteryl ester to VLDL, the apoE-containing lipoproteins appear involved mainly in the equilibration of cholesteryl esters.-Marcel, Y. L., C. Vézina, D. Emond, R. B. Verdery, and R. W. Milne. High density lipoprotein subfractions isolated by heparin-Sepharose affinity chromatography and their role in cholesteryl ester transfer to very low density lipoproteins.