TP53INP1 (tumor protein 53-induced nuclear protein 1) is a tumor suppressor, whose expression is downregulated in cancers from different organs. It was described as a p53 target gene involved in cell death, cell-cycle arrest and cellular migration. In this work, we show that TP53INP1 is also able to interact with ATG8-family proteins and to induce autophagy-dependent cell death. In agreement with this finding, we observe that TP53INP1, which is mainly nuclear, relocalizes in autophagosomes during autophagy where it is eventually degraded. TP53INP1-LC3 interaction occurs via a functional LC3-interacting region (LIR). Inactivating mutations of this sequence abolish TP53INP1-LC3 interaction, relocalize TP53INP1 in autophagosomes and decrease TP53INP1 ability to trigger cell death. Interestingly, TP53INP1 binds to ATG8-family proteins with higher affinity than p62, suggesting that it could partially displace p62 from autophagosomes, modifying thereby their composition. Moreover, silencing the expression of autophagy related genes (ATG5 or Beclin-1) or inhibiting caspase activity significantly decreases cell death induced by TP53INP1. These data indicate that cell death observed after TP53INP1-LC3 interaction depends on both autophagy and caspase activity. We conclude that TP53INP1 could act as a tumor suppressor by inducing cell death by caspasedependent autophagy. Increased resistance to cell death participates in pancreatic cancer progression. Cells unable to undergo self elimination accumulate mutations and epigenetic modifications that in turn induce uncontrolled replication. 1 Various concomitant mechanisms exist in normal cells to induce death and, as consequence, a number of known cell-death regulators are missing in cancer cells. One of the most studied is the tumor suppressor TP53, which is inactivated in 450% of pancreatic tumors. 2 p53 induces cell death by both direct permeabilization of the outer mitochondrial membrane or translocation to the nucleus where it activates the transcription of several target genes. One of the p53 target genes is TP53INP1 (tumor protein 53-induced nuclear protein 1). 3-6 p53-dependent expression of TP53INP1 is triggered in response to several stress agents such as mutagens, ethanol, heat shock or conditions promoting reactive oxygen species formation (i.e., exposure to UV light or g-irradiation). 4,6 TP53INP1 interacts with kinases, HIPK2 and PKCd, which in turn phosphorylate p53 creating a positive feedback loop between p53 and TP53INP1. 7,8 Our laboratory demonstrated that TP53INP1 is a tumor suppressor on the basis of the following observations: (i) TP53INP1 deficient mice present with an increased susceptibility to tumor development; (ii) TP53INP1 is lost at very early stages of pancreatic carcinogenesis through a mechanism involving the oncogenic miR-155 microRNA and (iii) when TP53INP1 expression is restored in pancreatic cells, it suppresses xenograft growth by increasing apoptotic cell death through a caspase-dependent mechanism. 3,9,10 More recently, in an attempt t...

The metabolic syndrome covers metabolic abnormalities including obesity and type 2 diabetes (T2D). T2D is characterized by insulin resistance resulting from both environmental and genetic factors. A genome-wide association study (GWAS) published in 2010 identified TP53INP1 as a new T2D susceptibility locus, but a pathological mechanism was not identified. In this work, we show that mice lacking TP53INP1 are prone to redox-driven obesity and insulin resistance. Furthermore, we demonstrate that the reactive oxygen species increase in TP53INP1-deficient cells results from accumulation of defective mitochondria associated with impaired PINK/PARKIN mitophagy. This chronic oxidative stress also favors accumulation of lipid droplets. Taken together, our data provide evidence that the GWAS-identified TP53INP1 gene prevents metabolic syndrome, through a mechanism involving prevention of oxidative stress by mitochondrial homeostasis regulation. In conclusion, this study highlights TP53INP1 as a molecular regulator of redox-driven metabolic syndrome and provides a new preclinical mouse model for metabolic syndrome clinical research.