The aim of this study was to investigate the role of S100
calcium binding protein A16 (S100A16) in lipid metabolism in hepatocytes and its possible biological mechanism. HepG2 cells (human
hepatoma cell line) were cultured with
fatty acid to establish
fatty acid culture model. The control model was cultured without
fatty acid. Each model was divided into three groups and transfected with S100a16 over-expression,
shRNA and vector plasmids, respectively. The concentration of
triglyceride (TG) in the cells was measured by kit, and the lipid droplets was observed by
oil red O staining. Immunoprecipitation and mass spectrometry were used to find the interesting
proteins interacting with S100A16, and the interaction was verified by immunoprecipitation. The further mechanism was studied by Western blot and qRT-PCR. The results showed that the intracellular lipid droplet and TG concentrations in the
fatty acid culture model were significantly higher than those in the control model. The accumulation of intracellular fat in the S100a16 over-expression group was significantly higher than that in the vector plasmid transfection group. There was an interaction between
heat shock protein A5 (HSPA5) and S100A16. Over-expression of S100A16 up-regulated
protein expression levels of HSPA5,
inositol-requiring
enzyme 1α (IRE1α) and pIREα1, which belong to endoplasmic reticulum stress HSPA5/IRE1α-XBP1 pathway. Meanwhile, over-expression of S100A16 up-regulated the
mRNA expression levels of adipose synthesis-related gene Srebp1c, Acc and Fas. In the S100a16
shRNA plasmid transfection group, the above-mentioned
protein and
mRNA levels were lower than those of vector plasmid transfection group. These results suggest that S100A16 may promote
lipid synthesis in HepG2 cells through endoplasmic reticulum stress HSPA5/IRE1α-XBP1 pathway.