RNA-binding protein RBM3 negatively regulates innate lymphoid cells (ILCs) and lung inflammation

Innate lymphoid cells (ILCs) promote lung inflammation through cytokine production in diseases such as asthma. RNA-binding proteins (RBPs) are critical post-transcriptional regulators of cellular function, including inflammatory responses, though the role of RBPs in innate lymphoid cells is unknown. Here, we demonstrate that RNA-binding motif 3 (RBM3) is one of the most highly expressed RBPs in Thy1.2+ lung ILCs after fungal allergen challenge and is further induced by epithelial cytokines TSLP and IL-33 in both human and mouse ILCs. Single (rbm3-/-) and double (rbm3-/-rag2-/-) knockout mice exposed via the airway to the asthma-associated fungal allergen Alternaria alternata displayed increases in eosinophilic lung inflammation and ILC activation compared to control mice. In addition to increased Th2 cytokine production, rbm3-/- ILCs produced elevated IL-17A. The negative regulation by RBM3 in ILC responses was direct as purified rbm3-/- ILCs were hyperinflammatory in vitro and in vivo after stimulation with IL-33. Transcriptomic analysis by RNA-sequencing of rbm3-/- lung ILCs showed increased type 2 and 17 cytokines as well as global expression differences in critical cytokines, receptors, transcription factors, and survival transcripts compared with WT ILCs. Intriguingly, these transcript changes did not correlate with the presence of AU-rich elements (AREs), which RBM3 is known to bind. Thus, regulation of ILC responses by RNA-binding proteins offers novel mechanistic insight into lung ILC biology and ILC-driven inflammatory diseases.