FIG. 4.

Effect of usnic acid on the expression of SOCE component proteins (ORAI1 and STIM1) in HepG2 cells. A, HepG2 cells or rat primary hepatocytes were treated with usnic acid at the indicated concentrations for 2 h. Western blotting analysis was performed using antibodies against ORAI1 and STIM1 in whole cell lysates. GAPDH was used as a loading control. B, Confirmation of the overexpression ORAI1 and STIM1 in HepG2 cells (ORAI1-Overexpression and STIM1-Overexpression) by Western blotting. C, D, HepG2-empty vector control cells, STIM-overexpression, and ORAI1-overexpression cells were treated with usnic acid at indicated concentrations for 24 h, then Ca²⁺ level of a single HepG2 cells was determined (C) and the ATP content was measured (D); the results shown are mean6SD of three separate experiments. *P<0.05 compared with the empty vector control. E, Western blotting analysis was performed with antibodies against CHOP and ATF-4 using lysates from ORAI-overexpression cells exposed to usnic acid at 25 µM for 24 h. GAPDH was used as a loading control.