Heat stress induces AMPK dephosphorylation through activation of PP2A.

<p><b>A.</b> HepG2 cells were exposed to 42°C (HS) for 0–1 h or 1 h followed by recovery at 37°C for 1–6 h. <b>B.</b> Various types of cells were exposed to 42°C (HS) for 30 min, then examined for AMPKα phosphorylation by Western blot. <b>C–D.</b> HepG2 cells pretreated with or without 1 mM AICAR for 15 min were exposed to 42°C (HS) for 30 min (<b>C</b>) or 1 h (<b>D</b>), then examined for ACC phosphorylation by Western blot (<b>C</b>), or PEPCK expression by real-time PCR (<b>D</b>). mean ± SEM, n = 3. **P<0.01 vs. cells without heat stress; ^#P<0.05 vs. cells cultured in control medium under heat stress. <b>E.</b> HepG2 cells were exposed to 42°C (HS) for indicated times and measured intracellular ATP levels. mean ± SEM, n = 3. <b>F.</b> HepG2 cells pretreated with 100 nM okadaic acid (OA) for 30 min or 1 mM AICAR for 15 min were exposed to 42°C (HS) for 30 min, then examined for AMPKα phosphorylation by Western blot. <b>G–H.</b> bEend.3 cells transfected with PP2Ac specific siRNA or control siRNA for 48 h were exposed to 42°C (HS) for 30 min. PP2Ac protein level (G) and AMPKα phosphorylation (H) were examined by Western blot. <b>A–C and F</b>–<b>H:</b> experiments were performed at least three times and the representative results are shown.