Identification of a novel interleukin-9 receptor complex in non-hematopoietic cells

This study aimed to explore the possibility that like the type II IL-4Rα, the IL-9Rα chain can pair with the IL-13Rα1 chain, forming a type II IL-9R and can mediate IL-9 responses in epithelial cells. We demonstrated that the IL-9Rα /IL-13Rα1 complex was detected in situ in mouse tracheal epithelial cells and human small airway epithelial cells (SAEC) using proximity ligation assay. STAT3 was activated after exposure to IL-9 in vitro in SAEC when co-cultured with neutralizing antibody targeting γc chain but STAT3 activity returned to its basal level in the presence of anti-IL-13Rα1 antibody, providing further evidence of a type II IL-9R on epithelial cells.

Strikingly, asthma-associated genes are upregulated in SAEC upon IL-9 stimulation in RNA-seq analysis. Collectively, our results identify a putative receptor complex - a type II IL-9R composed of IL-9Rα and IL-13Rα1, providing a mechanism for responses of structural cells to IL-9 and a potential role in asthma.