DRAM1 protects neuroblastoma cells from oxygen-glucose deprivation/reperfusion-induced injury via autophagy

Int J Mol Sci. 2014 Oct 23;15(10):19253-64. doi: 10.3390/ijms151019253.

Abstract

DNA damage-regulated autophagy modulator protein 1 (DRAM1), a multi-pass membrane lysosomal protein, is reportedly a tumor protein p53 (TP53) target gene involved in autophagy. During cerebral ischemia/reperfusion (I/R) injury, DRAM1 protein expression is increased, and autophagy is activated. However, the functional significance of DRAM1 and the relationship between DRAM1 and autophagy in brain I/R remains uncertain. The aim of this study is to investigate whether DRAM1 mediates autophagy activation in cerebral I/R injury and to explore its possible effects and mechanisms. We adopt the oxygen-glucose deprivation and reperfusion (OGD/R) Neuro-2a cell model to mimic cerebral I/R conditions in vitro, and RNA interference is used to knock down DRAM1 expression in this model. Cell viability assay is performed using the LIVE/DEAD viability/cytotoxicity kit. Cell phenotypic changes are analyzed through Western blot assays. Autophagy flux is monitored through the tandem red fluorescent protein-Green fluorescent protein-microtubule associated protein 1 light chain 3 (RFP-GFP-LC3) construct. The expression levels of DRAM1 and microtubule associated protein 1 light chain 3II/I (LC3II/I) are strongly up-regulated in Neuro-2a cells after OGD/R treatment and peaked at the 12 h reperfusion time point. The autophagy-specific inhibitor 3-Methyladenine (3-MA) inhibits the expression of DRAM1 and LC3II/I and exacerbates OGD/R-induced cell injury. Furthermore, DRAM1 knockdown aggravates OGD/R-induced cell injury and significantly blocks autophagy through decreasing autophagosome-lysosome fusion. In conclusion, our data demonstrate that DRAM1 knockdown in Neuro-2a cells inhibits autophagy by blocking autophagosome-lysosome fusion and exacerbated OGD/R-induced cell injury. Thus, DRAM1 might constitute a new therapeutic target for I/R diseases.

MeSH terms

  • Adenine / analogs & derivatives
  • Adenine / pharmacology
  • Animals
  • Apoptosis Regulatory Proteins / metabolism
  • Autophagy / drug effects
  • Autophagy / physiology*
  • Brain Ischemia / metabolism*
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • Glucose / metabolism*
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Membrane Proteins / metabolism*
  • Mice
  • Microtubule-Associated Proteins / metabolism
  • Neuroblastoma / metabolism*
  • Oxygen / metabolism*
  • Reperfusion Injury / metabolism*
  • Up-Regulation / drug effects

Substances

  • Apoptosis Regulatory Proteins
  • DRAM-1 protein, mouse
  • Membrane Proteins
  • Microtubule-Associated Proteins
  • 3-methyladenine
  • Glucose
  • Adenine
  • Oxygen