The role of IGF2BP3 in Type 2 signalling in bronchial epithelium: a novel player in severe asthma

Background: Despite extensive mechanistic research into T2 inflammation, which drive severe asthma (SA) pathogenesis, little is currently known about the role of RNA binding proteins (RBP). Methods: Subcellular fractionation and RNA-sequencing was undertaken to compare total and polyribosome-bound mRNAs in bronchial epithelium from healthy control and SA patients. Knock-down employing siRNAs and shRNAs in bronchial epithelial cells were undertaken to demonstrate the role of the RBP Insulin like Growth Factor-II mRNA binding protein III (IGF2BP3) in T2-signalling. Western blots were used to measure protein expression and phosphorylation. RNA immunoprecipitation was performed to determine the binding of mRNAs to IGF2BP3. Results: IGF2BP3 expression was increased in airway epithelial cells from SA patients compared to healthy controls. We validated these data in publicly available microarray datasets from peripheral blood and nasal lavage from asthmatic children and bronchial epithelial cells of asthma patients compared to healthy controls. Employing a constitutive cell line, down regulation of IGF2BP3 resulted in increased IL-13-dependent phosphorylation of STAT-6 and increased transcriptional levels of CCL26; as well as basal over-expression of GATA3 mRNA. RNA immunoprecipitation showed direct interaction between IGF2BP3 and several mRNAs encoding genes that are involved up and downstream of IL-4 and IL-13 signalling; namely IL4R, IL13RA1, CCL26 and SOCS1. Conclusions: Our data show IGF2BP3 plays a central role in T2 signalling as a potential novel inhibitor of IL-13-dependent signalling. Our data uncover novel roles for RBPs as mediators of IL-4 and IL-13 signalling.