title: MIR376A is a regulator of starvation-induced autophagy.
abstract: BACKGROUND
  Autophagy is a vesicular trafficking process responsible for the degradation of long-lived, misfolded or abnormal proteins, as well as damaged or surplus organelles. Abnormalities of the autophagic activity may result in the accumulation of protein aggregates, organelle dysfunction, and autophagy disorders were associated with various diseases. Hence, mechanisms of autophagy regulation are under exploration.
  
  
  METHODS
  Over-expression of hsa-miR-376a1 (shortly MIR376A) was performed to evaluate its effects on autophagy. Autophagy-related targets of the miRNA were predicted using Microcosm Targets and MIRanda bioinformatics tools and experimentally validated. Endogenous miRNA was blocked using antagomirs and the effects on target expression and autophagy were analyzed. Luciferase tests were performed to confirm that 3' UTR sequences in target genes were functional. Differential expression of MIR376A and the related MIR376B was compared using TaqMan quantitative PCR.
  
  
  RESULTS
  Here, we demonstrated that, a microRNA (miRNA) from the DLK1/GTL2 gene cluster, MIR376A, played an important role in autophagy regulation. We showed that, amino acid and serum starvation-induced autophagy was blocked by MIR376A overexpression in MCF-7 and Huh7 cells. MIR376A shared the same seed sequence and had overlapping targets with MIR376B, and similarly blocked the expression of key autophagy proteins ATG4C and BECN1 (Beclin 1). Indeed, 3' UTR sequences in the mRNA of these autophagy proteins were responsive to MIR376A in luciferase assays. Antagomir tests showed that, endogenous MIR376A was participating to the control of ATG4C and BECN1 transcript and protein levels. Moreover, blockage of endogenous MIR376A accelerated starvation-induced autophagic activity. Interestingly, MIR376A and MIR376B levels were increased with different kinetics in response to starvation stress and tissue-specific level differences were also observed, pointing out to an overlapping but miRNA-specific biological role.
  
  
  CONCLUSIONS
  Our findings underline the importance of miRNAs encoded by the DLK1/GTL2 gene cluster in stress-response control mechanisms, and introduce MIR376A as a new regulator of autophagy.
authors.affiliation: Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey.
authors.forename: Gozde
authors.initials: G
authors.lastname: Korkmaz
authors.affiliation: Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey.
authors.forename: Kumsal Ayse
authors.initials: KA
authors.lastname: Tekirdag
authors.affiliation: Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey.
authors.forename: Deniz Gulfem
authors.initials: DG
authors.lastname: Ozturk
authors.affiliation: Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey.
authors.forename: Ali
authors.initials: A
authors.lastname: Kosar
authors.affiliation: Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey.
authors.forename: Osman Ugur
authors.initials: OU
authors.lastname: Sezerman
authors.affiliation: Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey.
authors.forename: Devrim
authors.initials: D
authors.lastname: Gozuacik
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001343:Autophagy / Q000235:genetics*; D000071183:Autophagy-Related Proteins; D000071186:Beclin-1; D045744:Cell Line, Tumor; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D013217:Starvation / Q000235:genetics*
chemical_list: D051017:Apoptosis Regulatory Proteins; D000071183:Autophagy-Related Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; C573498:MIRN376C microRNA, human; D008565:Membrane Proteins; D035683:MicroRNAs; C474025:ATG4A protein, human; D003546:Cysteine Endopeptidases