Exploring the Role of ABCF1 in Mucosal Immunity of Human Airway Epithelial Cells

Abstract

Human airway epithelial cells (HAECs) play a pivotal role in creating a mechanical barrier to prevent environmental insults from entering deeper into the lung tissue and in facilitating host defence against pathogens and allergens by producing immune mediators and recruiting inflammatory cells. ABCF1, is a unique member of the ABC transporter family that it is highly expressed in the airway epithelium, however, its function in HAECs is currently not known.In this thesis, we explored the role of ABCF1 as a dsDNA viral sensor in HAECs. Our findings demonstrated that while ABCF1 is required for an immune response to a double-stranded DNA (dsDNA) viral mimic, VACV-70, our transcriptomic analysis suggested a role in pro-inflammatory responses downstream of toll-like receptors (TLR) 3 and 4 signalling pathways. We followed this outcome by investigating ABCF1 in mediating pro-inflammatory responses to TNF-α and Poly(I:C) through A20, NF-κB and IRF-3 regulated signalling pathways. Our study demonstrated that Poly(I:C) and TNF-α induced IL-8 are regulated by ABCF1 through pathways independent of NF-κB, and IRF-3 activation, although the exact mechanism remains unclear. The next approach was to run a hypothesis-free in silico investigation of the ABCF1 protein-protein interaction (PPI) network using publicly available databases and Gene Ontology (GO) term enrichment analysis. Following our in silico results of ABCF1 protein interactors, we validated a novel interaction of ABCF1 and SYK in human airway epithelial cells following Poly(I:C) stimulation. We have demonstrated that silencing ABCF1 under stimulation by VACV-70, TNF-α and Poly(I:C) in HAECs affects the induction of immune mediators, and a candidate protein interaction partner, SYK, is involved in immune signalling, however its exact mechanism is not defined. We propose that further insights into the functions of ABCF1 may aid in understanding how HAECs maintain mucosal immune homeostasis.