Human Plasma Very Low-Density Lipoproteins Are Stabilized by Electrostatic Interactions and Destabilized by Acidic pH

Figure 1

Cartoon showing metabolic remodeling of VLDL. Intact VLDL contain a core of apolar lipids, mostly triacylglycerides (TG) and some cholesterol esters (CE), surrounded by polar surface comprised mainly of phosphatidylcholines (PCs) and apolipoproteins. Exchangeable proteins, apoE (32 kD) and apoCs (6–9 kD), are comprised of amphipathic α-helical repeats and are shown in cylinders; the nonexchangeable apoB (550 kD) contains domains with predominantly α-helical or β-sheet structure. VLDL remodeling in vivo starts with TG hydrolysis by lipoprotein lipase; this produces excess surface that dissociates in the form of apoE-containing particles that join the pool of HDL [3, 4]. Similar particles are formed upon other VLDL perturbations such as heating [20]. Remodeling of VLDL eventually converts them to LDL; each LDL contains one copy of apoB as its major protein. Dissociation of apoE and some lipids from the apoB-containing particles also occurs during endosomal degradation of VLDL [10–12].