MicroRNA-93 Regulates Hypoxia-Induced Autophagy by Targeting ULK1

Oxid Med Cell Longev. 2017:2017:2709053. doi: 10.1155/2017/2709053. Epub 2017 Oct 3.

Abstract

The expression of the core autophagy kinase, Unc51-like kinase 1 (ULK1), is regulated transcriptionally and translationally by starvation-induced autophagy. However, how ULK1 is regulated during hypoxia is not well understood. Previously, we showed that ULK1 expression is induced by hypoxia stress. Here, we report a new ULK1-modulating microRNA, miR-93; its transcription is negatively correlated with the translation of ULK1 under hypoxic condition. miR-93 targets ULK1 and reduces its protein levels under hypoxia condition. miR-93 also inhibits hypoxia-induced autophagy by preventing LC3-I to LC3-II transition and P62 degradation; these processes are reversed by the overexpression of an endogenous miR-93 inhibitor. Re-expression of ULK1 without miR-93 response elements restores the hypoxia-induced autophagy which is inhibited by miR-93. Finally, we detected the effects of miR-93 on cell viability and apoptosis in noncancer cell lines and cancer cells. We found that miR-93 sustains the viability of MEFs (mouse embryonic fibroblasts) and inhibits its apoptosis under hypoxia. Thus, we conclude that miR-93 is involved in hypoxia-induced autophagy by regulating ULK1. Our results provide a new angle to understand the complicated regulation of the key autophagy kinase ULK1 during different stress conditions.

MeSH terms

  • Animals
  • Autophagy
  • Autophagy-Related Protein-1 Homolog / genetics*
  • Autophagy-Related Protein-1 Homolog / metabolism
  • CHO Cells
  • Cell Hypoxia / genetics
  • Cricetulus
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / genetics*
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Mice
  • MicroRNAs / genetics*
  • MicroRNAs / metabolism
  • Protein Biosynthesis
  • Stress, Physiological / genetics
  • Transcription, Genetic
  • Transfection

Substances

  • Intracellular Signaling Peptides and Proteins
  • MIRN93 microRNA, human
  • MicroRNAs
  • Mirn93 microRNA, mouse
  • Autophagy-Related Protein-1 Homolog
  • ULK1 protein, human
  • Ulk1 protein, mouse