Immunoreactivity of apolipoprotein B-100 and binding to LDL-receptor of phospholipase A(2)-treated low density lipoproteins

Lipid-protein particles were obtained by treatment of low density lipoprote ins (LDL) with phospholipase A, from bee venom. Under these conditions, hal f of the phosphatidylcholine (PC) of LDL tvas changed to lysophosphatidylch oline (LPC). At the same time, the composition of other lipids and the apop rotein structure were unaffected. Three monoclonal antibodies (MAbs) agains t various apo B epitopes were used to test immunoreactivity of phospholipas e A(2)-treated LDL (pl-LDL). The apo B epitope interacting with MAb 4C11 (a mino acid residues 2377-2658) showed significantly decreased immunoreactivi ty. Increase in MAb 4C11 binding was demonstrated to depend on oxidation de gree of LDL. Thus, changing of half of PC to LPC modified apo B translocati on in the lipoprotein globule in an opposite manner as compared with change s induced by oxidative modification. A minor increase in imununoreactivity of pl-LDL with 1D1 MAb against a large middle part of apo B (residues 1297- 3249) may be due to the effect of the change of surface lipid composition o n the extent of immersion of apo B into the hydrophobic phase. No changes i n the interaction of pl-LDL with MAb Cs (residues 3748-4306) were observed in comparison with native LDL, This fact demonstrates that 50% phospholipol ysis of LDL does not affect the expression of apo B C-terminal residues in pl-LDL. Twofold increase in pl-LDL affinity to immobilized LDL-receptor was shown in contrast to LDL. The data indicate that LPC accumulation in LDL r esults in better elimination of LDL from the blood stream than in case of a ccumulation of oxidative products.