Fig. 5

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β-catenin signaling protects hepatocytes against hypoxic injury through augmented HIF-1 signaling

  1. β-catenin alternatively binds TCF (normoxia) or HIF-1α (hypoxia) depending on oxygen availability. Binding switch was verified by co-immunoprecipitation on HepG2 cell lysates after exposure to normoxia (N) or hypoxia (H) using anti-β-catenin antibody followed by immunoblotting for HIF-1α and TCF4.
  2. Wnt1+ livers show more β-catenin/HIF-1α binding as verified by co-immunoprecipitation in sham or ischemia-treated liver lysates using anti-β-catenin antibody followed by HIF-1α immunoblotting.
  3. Augmented HIF-1α promotor binding in β-catenin mutants after 24 hours hypoxia. For EMSA, 5 µg of nuclear extracts were used for HIF-1/HRE DNA-probe binding reactions.
  4. β-catenin/TCF reporter activity can be reduced by HIF-1α stabilization with CoCl2 (150 µmol/L) under normoxia or hypoxia treatment in AML12 hepatocytes. HIF-1α induction was verified by HRE reporter assay and immunoblot. RLU= relative light units.
  5. HIF-1α inhibition under hypoxia by YC-1 pre-treatment (100 µmol/L) for 1 hour results in more apoptosis in AML12 hepatocytes as measured by MTT assay and immunoblot for caspase-cleaved K18Asp237. *p<0.05.

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