Inhibition of Smurf2 translation by miR-322/503 modulates TGF-β/Smad2 signaling and intestinal epithelial homeostasis

Mol Biol Cell. 2014 Apr;25(8):1234-43. doi: 10.1091/mbc.E13-09-0560. Epub 2014 Feb 19.

Abstract

Smad ubiquitin regulatory factor 2 (Smurf2) is an E3 ubiquitin ligase that regulates transforming growth factor β (TGF-β)/Smad signaling and is implicated in a wide variety of cellular responses, but the exact mechanisms that control Smurf2 abundance are largely unknown. Here we identify microRNA-322 (miR-322) and miR-503 as novel factors that regulate Smurf2 expression posttranscriptionally. Both miR-322 and miR-503 interact with Smurf2 mRNA via its 3'-untranslated region (UTR) and repress Smurf2 translation but do not affect total Smurf2 mRNA levels. Studies using heterologous reporter constructs reveal a greater repressive effect of miR-322/503 through a single binding site in the Smurf2 3'-UTR, whereas point mutation of this site prevents miR-322/503-induced repression of Smurf2 translation. Increased levels of endogenous Smurf2 via antagonism of miR-322/503 inhibits TGF-β-induced Smad2 activation by increasing degradation of phosphorylated Smad2. Furthermore, the increase in Smurf2 in intestinal epithelial cells (IECs) expressing lower levels of miR-322/503 is associated with increased resistance to apoptosis, which is abolished by Smurf2 silencing. These findings indicate that miR-322/503 represses Smurf2 translation, in turn affecting intestinal epithelial homeostasis by altering TGF-β/Smad2 signaling and IEC apoptosis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • 3' Untranslated Regions / genetics
  • Animals
  • Apoptosis / genetics
  • Cell Line
  • Cycloheximide / pharmacology
  • Intestinal Mucosa / metabolism
  • MicroRNAs / antagonists & inhibitors
  • MicroRNAs / genetics*
  • Phosphorylation
  • Protein Biosynthesis / genetics
  • RNA, Messenger / genetics
  • Rats
  • Signal Transduction
  • Smad2 Protein / metabolism*
  • Transforming Growth Factor beta / antagonists & inhibitors
  • Transforming Growth Factor beta / metabolism*
  • Transforming Growth Factor beta / pharmacology
  • Ubiquitin-Protein Ligases / biosynthesis*
  • Ubiquitin-Protein Ligases / genetics

Substances

  • 3' Untranslated Regions
  • MIRN322 microRNA, rat
  • MIRN503 microRNA, rat
  • MicroRNAs
  • RNA, Messenger
  • Smad2 Protein
  • Smad2 protein, rat
  • Transforming Growth Factor beta
  • Cycloheximide
  • Smurf2 protein, rat
  • Ubiquitin-Protein Ligases