Post-Transcriptional Regulation of Toll-Interacting Protein in the Intestinal Epithelium

PLoS One. 2016 Oct 14;11(10):e0164858. doi: 10.1371/journal.pone.0164858. eCollection 2016.

Abstract

Immune responses against gut microbiota should be minimized to avoid unnecessary inflammation at mucosal surface. In this study, we analyzed the expression patterns of Toll-interacting protein (Tollip), an inhibitor of TLRs and IL-1 family cytokine-related intracellular signaling, in intestinal epithelial cells (IECs). Comparable mRNA expression was observed in murine small and large IECs (S-IECs and L-IECs). However, Tollip protein was only detected in L-IECs, but not in S-IECs. Similar results were obtained in germ-free mice, indicating that L-IEC-specific TOLLIP expression does not depend on bacterial colonization. Next, to understand the mechanisms underlying the post-transcriptional repression of Tollip, 3´-UTR-mediated translational regulation was evaluated. The region +1876/+2398 was responsible for the repression of Tollip expression. This region included the target sequence of miR-31. The inhibition of miR-31 restored the 3´-UTR-meditaed translational repression. In addition, miR-31 expression was significantly higher in S-IECs than in L-IECs, suggesting that miR-31 represses the translation of Tollip mRNA in S-IECs. Collectively, we conclude that the translation of Tollip is inhibited in S-IECs, at least in part, by miR-31 to yield L-IEC-specific high-level expression of the Tollip protein, which may contribute to the maintenance of intestinal homeostasis.

MeSH terms

  • 3' Untranslated Regions
  • Animals
  • Antagomirs / metabolism
  • Blotting, Northern
  • Cells, Cultured
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism*
  • Genes, Reporter
  • Intestinal Mucosa / cytology*
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Mice
  • Mice, Inbred BALB C
  • MicroRNAs / antagonists & inhibitors
  • MicroRNAs / genetics
  • MicroRNAs / metabolism
  • Plasmids / genetics
  • Plasmids / metabolism
  • Protein Processing, Post-Translational
  • RNA, Messenger / metabolism

Substances

  • 3' Untranslated Regions
  • Antagomirs
  • Intracellular Signaling Peptides and Proteins
  • MIRN31 microRNA, human
  • MicroRNAs
  • RNA, Messenger
  • Tollip protein, mouse

Grants and funding

This study was supported in part by grants from the Japan Society for the Promotion of Science (KAKENHI 26450165, to K.T.) and the Institute for Fermentation, Osaka (K.T.). This work was also supported by the Strategic Research Base Development Program, “International joint research and training of young researchers for zoonosis control in a globalized world”, and a matching fund subsidy from the Ministry of Education, Culture, Sports, Science and Technology of Japan (S0991023 and S1491007).