Apolipoprotein A-V association with intracellular lipid droplets.
Apolipoprotein A-V (apoA-V) plays a key role in the regulation of triglyceride (TG) metabolism. Given the very low concentration of apoA-V in plasma, we hypothesized that apoA-V may influence plasma TG levels by affecting the assembly and/or secretion of apoB-containing lipoproteins. When apoA-V was overexpressed in cultured Hep3B cells, neither the amount of apoB secreted nor the density distribution of apoB-containing lipoproteins was affected. Fluorescence microscopy and cell lysate immunoprecipitation studies revealed that apoA-V is not associated with apoB intracellularly, yet immunoprecipitation of apoA-V from the cell culture medium resulted in coprecipitation of apoB. These data suggest that the apoA-V association with apoB-containing lipoproteins is a postsecretory event. Confocal fluorescence microscopy revealed the presence of apoA-V in distinct cellular structures. Based on Nile Red staining, we identified these structures to be intracellular lipid droplets. These data suggest that apoA-V has a unique association with cellular lipids and, therefore, may be involved in the storage or mobilization of intracellular lipids.
Shu
Xiao
X
Center for Prevention of Obesity, Diabetes, and Cardiovascular Diseases, Children's Hospital Oakland Research Institute, Oakland, CA 94609, USA.
Chan
Joanne
J
Ryan
Robert O
RO
Forte
Trudy M
TM
D000072040:Apolipoprotein A-V; D001054:Apolipoproteins A / Q000032:analysis* / Q000096:biosynthesis; D001055:Apolipoproteins B / Q000032:analysis; D045744:Cell Line, Tumor; D003600:Cytosol / Q000737:chemistry*; D006801:Humans; D047468:Immunoprecipitation; D008079:Lipoproteins, VLDL / Q000032:analysis; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence
C437704:APOA5 protein, human; D000072040:Apolipoprotein A-V; D001054:Apolipoproteins A; D001055:Apolipoproteins B; D008079:Lipoproteins, VLDL