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Damage-regulated autophagy modulator 1(DRAM1),a novel p53 target gene,is an evolutionarily conserved lysosomal protein and plays an essential role in p53-dependent autophagy activation and apoptosis(Crighton et al,2006).The mechanisms through which DRAM1 promotes autophagy and apoptosis are not clear.Uncovering the molecular mechanism through which DRAM1 regulates autophagy and apoptosis would provide a better understanding of the role of p53 in the regulation of cell death and survival.In in vivo studies,we have shown that 3-nitropropionic acid(3-NP),an inhibitor of mitochondrial respiratory complexⅡ,induces autophagy activation and cell death in rat striatum through p53.p53 activates autophagy through up-regulation of DRAM1.p53-mediated autophagy activation contributes to 3-NP-induced cell death.In in vitro studies,we investigated the mechanisms by which DRAM1 regulates autophagy and cell death.In A549 cells,3-NP increased the protein levels of DRAM1,BAX,LC3-Ⅱ,and cytochrome c(cyt-c) release.3-NP-induced cell death was inhibited by knock-down of ATG5 and the pan-caspase inhibitor Z-Vad-FMK.Knock-down of DRAM1 with siRNA inhibited autophagic activity and BAX expression as well as reduced 3-NP-induced cyt-c release and cell death.DRAM1 siRNA impaired the clearance of autophagosomes,acidification of lysosomes and activation of lysosomal cathepsin D.Similarly,lysosomal inhibitors E64d and chloroquine inhibited autophagosome clearance,cyt-c release and cell death after 3-NP treatment.Furthermore,inhibiting BAX expression also reduced 3-NP-induced cathepsin D activation and cyt-c release.These data suggest that DRAM1 plays important roles in autophagy activation and apoptosis induced by mitochondria dysfunction.DRAM1 affects autophagy flux and apoptosis via lysosomes.
Damage-regulated autophagy modulator 1 (DRAM1), a novel p53 target gene, is an evolutionarily conserved lysosomal protein and plays an essential role in p53-dependent autophagy activation and apoptosis (Crighton et al, 2006). The mechanisms through which DRAM1 promoted autophagy and apoptosis are not clear. Uncovering the molecular mechanism through which DRAM1 regulates autophagy and apoptosis would provide a better understanding of the role of p53 in the regulation of cell death and survival. In vivo studies, we have shown that 3-nitropropionic acid ( 3-NP), an inhibitor of mitochondrial respiratory complexⅡ, induces autophagy activation and cell death in rat striatum through p53. P53-mediated autophagy through up-regulation of DRAM1.p53-mediated autophagy activation contributes to 3-NP-induced cell death. in vitro studies, we investigated the mechanisms by which DRAM1 regulates autophagy and cell death. A549 cells, 3-NP increased the protein levels of DRAM1, BAX, LC3-II, and cytochrome c (cy tc) release.3-NP-induced cell death was inhibited by knock-down of ATG5 and the pan-caspase inhibitor Z-Vad-FMK. Knock-down of DRAM1 with siRNA inhibited autophagic activity and BAX expression as well as reduced 3- NP-induced cyt-c release and cell death. DRAM1 siRNA impaired the clearance of autophagosomes, acidification of lysosomes and activation of lysosomal cathepsin D. Similar, lysosomal inhibitors E64d and chloroquine inhibited autophagosome clearance, cyt-c release and cell death after 3- NP treatment.Furthermore, inhibiting BAX expression also reduced 3-NP-induced cathepsin D activation and cyt-c release.These data suggest that DRAM1 plays important roles in autophagy activation and apoptosis induced by mitochondria dysfunction. DRAM1 affects autophagy flux and apoptosis via lysosomes .