Influence of apolipoprotein A-V on hepatocyte lipid droplet formation

Apolipoprotein A-V (apoA-V) is postulated to modulate intra-hepatic triglyceride (TG) trafficking. Stably transfected McA-RH7777 hepatocarcinoma cells expressing human apoA-V displayed enhanced neutral lipid staining while conditioned media from these cells had 40 ± 8% less TG than cells transfected with a control vector. To obtain homogeneous cell lines expressing different amounts of apoA-V, a strategy of clonal selection was pursued. Immunoblot analysis of two distinct apoA-V stable cell lines yielded one that expresses low amounts of apoA-V and another that expresses higher amounts. Confocal fluorescence microscopy of control cells and cells expressing low levels of apoA-V had similar numbers of lipid droplets while cells expressing higher amounts of apoA-V had twice as many lipid droplets, on average. Thus, apoA-V expression promotes lipid droplet accumulation in these cells.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► McArdle 7777 hepatocarcinoma cells were transfected with human apolipoprotein (apo) A-V. ► ApoA-V expression enhances cytosolic lipid droplet (LD) formation. ► Stable transfection of apoA-V results in decreased triacylglycerol (TG) secretion. ► A molecular mechanism whereby apoA-V modulates TG trafficking is proposed. ► ApoA-V binding to ER membrane defects created by TG inhibits lumenal lipid droplet formation.