The RNFT2/IL-3Rα axis regulates IL-3 signaling and innate immunity.

Abstract

Interleukin-3 (IL-3) receptor α (IL-3Rα) is the α subunit of the ligand-specific IL-3R and initiates intracellular signaling in response to IL-3. IL-3 amplifies proinflammatory signaling and cytokine storm in murine sepsis models. Here we found that RNFT2 (RING finger transmembrane-domain containing protein 2, also TMEM118), a previously uncharacterized RING finger ubiquitin E3 ligase, negatively regulated IL-3-dependent cellular responses through IL-3Rα ubiquitination and degradation in the proteasome. In vitro, IL-3 stimulation promoted IL-3Rα proteasomal degradation dependent on RNFT2, and we identified IL-3Rα lysine 357 as a ubiquitin acceptor site. We determined that LPS priming reduces RNFT2 abundance, extends IL-3Rα half-life, and sensitizes cells to the effects of IL-3, acting synergistically to increase proinflammatory signaling. In vivo, IL-3 synergized with LPS to exacerbate lung inflammation in LPS and Pseudomonas aeruginosa-challenged mice; conversely, IL-3 neutralization reduced LPS-induced lung injury. Further, RNFT2 overexpression reduced lung inflammation and injury, whereas Rnft2 knockdown exacerbated inflammatory responses in LPS-induced murine lung injury. Last, we examined RNFT2 and IL-3Rα in human lung explants from patients with cystic fibrosis and also showed that IL-3 is elevated in mechanically ventilated critically ill humans at risk for acute respiratory distress syndrome. These results identify RNFT2 as a negative regulator of IL-3Rα and show a potential role for the RNFT2/IL-3Rα/IL-3 axis in regulating innate immune responses in the lung.

• Authors: Yao Tong, Travis B Lear, John Evankovich, Yanwen Chen, James D Londino, Michael M Myerburg, Yingze Zhang, Iulia D Popescu, John F McDyer, Bryan J McVerry, Karina C Lockwood, Michael J Jurczak, Yuan Liu, Bill B Chen
• Journal: JCI insight (JCI Insight) Vol. 5 Issue 3 (02 13 2020) ISSN: 2379-3708 [Electronic] United States
• PMID: 31990690 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• IL3 protein, human
• Interleukin-3
• Interleukin-3 Receptor alpha Subunit
• Membrane Proteins
• RNFT2 protein, human
• Ubiquitin
• Proteasome Endopeptidase Complex

Topics

• Animals
• Humans
• Immunity, Innate
• Interleukin-3 (metabolism)
• Interleukin-3 Receptor alpha Subunit (metabolism)
• Membrane Proteins (metabolism)
• Mice
• Proteasome Endopeptidase Complex (metabolism)
• RAW 264.7 Cells
• Signal Transduction
• Ubiquitin (metabolism)
• Ubiquitination