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. / Thesis / Doctor of Philosophy (Medical Science) / The human lungs are exposed to over 10,000 litres of air each day from normal respiration, and it is the first point of contact between the outside environment and the internal anatomy. The cells on the surface of the air passages in the lungs are called human airway epithelial cells (HAECs), and they represent a critical defence against inhaled foreign objects that may include air pollution, allergens, bacteria, and viruses. HAECs have a group of proteins called ABC transporters, that are capable of different activities that are essential for maintaining normal lung health. One unique ABC transporter called ABCF1 was found to regulate defences against viral and bacterial infections in non-lung cells. It is unclear whether ABCF1 has the same function and protective capacity in HAECs.
In this Ph.D. thesis, we investigated how ABCF1 functions in HAECs to detect and respond to respiratory infections. By understanding how ABCF1 is involved in protecting the lungs against these infections, novel treatments can be developed to minimize morbidity and mortality in both healthy and vulnerable individuals. In our studies, we evaluated the changes in the response of HAECs that had normal or absent levels of the ABCF1 gene under conditions that resemble an infection. We used computational tools to help us investigate the proteins that interact with ABCF1 and predict their potential function. Our studies have concluded that ABCF1 does have a protective capacity in HAECs, however, we have yet to elucidate how and what other proteins are involved to help it function.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/29666 |
| Date | January 2024 |
| Creators | Cao, Quynh |
| Contributors | Hirota, Jeremy, Medical Sciences (Molecular Virology and Immunology Program) |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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