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

ABSTRACT: Interleukin-3 (IL-3) receptor ? (IL-3R?) is the ? 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-3R? ubiquitination and degradation in the proteasome. In vitro, IL-3 stimulation promoted IL-3R? proteasomal degradation dependent on RNFT2, and we identified IL-3R? lysine 357 as a ubiquitin acceptor site. We determined that LPS priming reduces RNFT2 abundance, extends IL-3R? 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-3R? 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-3R? and show a potential role for the RNFT2/IL-3R?/IL-3 axis in regulating innate immune responses in the lung.

SUBMITTER: Tong Y 

PROVIDER: S-EPMC7098800 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature