The binding of human lipoprotein lipase treated VLDL by the human hepatoma cell line HepG2

It has been suggested that besides the LDL-receptor, hepatocytes possess an apo E or remnant receptor. To evaluate which hepatic lipoprotein receptor is involved in VLDL remnant catabolism, we studied the binding of VLDL remnants to HepG2 cells. Native VLDL was obtained from type IIb hyperlipidemic patients and treated with bovine milk lipoprotein lipase (LPL). This LPL-treated VLDL (LPL-VLDL) was used as representative for VLDL remnants. Our results show that LPL-VLDL binds with high affinity to HepG2 cells. Competition experiments showed that the binding of ¹²⁵I-labelled LPL-VLDL is inhibited to about 30% of the control value by the simultaneous addition of an excess of either unlabelled LDL or LPL-VLDL. Preincubation of HepG2 cells with LDL resulted in a reduction of the binding of LDL and LPL-VLDL to 34 and 55% of the control value, whereas preincubation of the cells with heavy HDL (density between 1.16 and 1.21 g/ml) stimulated the binding of LDL and LPL-VLDL to about 230% of the control value. Preincubation of the cells with insulin (250 nM/1) also stimulated the binding of both LDL and LPL-VLDL (175 and 143% of the control value, respectively). We conclude that LPL-VLDL binds to the LDL-receptor of HepG2 cells and that no evidence has been obtained for the presence on HepG2 cells of an additional receptor that is involved in the binding of VLDL remnants.