Hepatocyte KLF6 regulates autophagy in a p53 dependent manner

Autophagy regulates turnover of long-lived or damaged organelles and proteins, which promotes survival and regeneration by maintaining intracellular energy production. In acute liver injury, autophagy helps to reduce cellular stress and tissue damage in hepatocytes. KLF6 is a transcription factor and tumor suppressor gene belonging to the family of zinc finger proteins that regulate potential target genes and mechanisms by binding to specific DNA motifs. In patients and several models of acute liver injury, we observed a consistent induction of hepatic KLF6 expression that was accompanied by an induction of autophagy. Here, we aimed to investigate a potential interaction of KLF6 and autophagy related molecules by transfecting HepG2 cells with a specific KLF6 expressing vector. In this model, KLF6 overexpression led to a significant induction of autophagy as assessed by LC3-II Western blot. In order to elucidate a potential interaction of KLF6 with the autophagy related molecules Atg7 and Beclin1, we performed co-transfection studies with specific Atg7 or Beclin1 luciferase reporter plasmids in KLF6 overexpressing cells. KLF6 overexpression led to a significant transcriptional activation of Atg7. In HepG2 cells, we did not observe a significant induction of Beclin1. Using chromatin immunoprecipitation (ChIP) we could show that KLF6 actively binds to the promoter region of Atg7. Since p53 is an important mediator in autophagy induction, we used p53-deficient HepG2 – 303 cells and repeated luciferase reporter experiments. Interestingly, in KLF6 overexpressing HepG2 – 303 cells, Atg7 luciferase activity was not altered, while Beclin1 luciferase activity was significantly induced in KLF6 overexpressing p53 knockout cells. These experiments demonstrate, that KLF6 activates autophagy by binding directly to Atg7 promoter region or Beclin1 and therefore influencing autophagy induction in a p53 dependent manner.

No conflict of interest has been declared by the author(s).

Sydor, Svenja

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