ASSOCIATION OF HUMAN APOLIPOPROTEIN-E WITH LIPOPROTEINS SECRETED BY TRANSFECTED MCA RH7777 CELLS

To examine the association of apolipoprotein (apo) with nascent hepati c lipoproteins we have prepared stable transfectants of the rat hepato ma cell line McA RH7777 expressing the human apoE3 cDNA, When the nasc ent lipoproteins secreted from control cells were separated on fast pr otein liquid chromatography (FPLC) columns, rat apoE was detected in t he very lo cv density (VLDL) and high density lipoprotein (HDL) fracti ons, while rat apoA-I was found in the HDL and lipoprotein free fracti ons. Human apoE was also associated with the VLDL and HDL particles se creted from the transfected McA RH7777 cells. Expression of human apoE resulted in a significant decrease in the amount of rat apoA-I associ ated with the lipoprotein particles. Rat apoE was also displaced, but to a lesser extent, Infection of McA RH7777 cells at different multipl icities of infection with recombinant adenoviral vector containing the human apoE cDNA indicated that rat apoA-I was decreased in the HDL fr actions at lower levels of expression of human apoE than was rat apoE, The HDL particles were further examined by immunoblotting of nondenat uring gradient gels and by non-denaturing immunoprecipitation. The res ults indicate that the high density Lipoprotein (HDL) particles are he terogeneous in size and apolipoprotein composition with the majority o f the rat and human apolipoproteins being located on different particl es. These results suggest that the profile and concentration of HDL ap olipoproteins produced in hepatocytes influences the assembly of the v arious subsets of secreted HDL.