Protein disulfide isomerases (PDIs) are a family of chaperone enzymes within the eukaryotic endoplasmic reticulum that facilitate creation of disulfide (-S-S-) bonds in proteins. PDIA3 is a PDI which has been found to interact with influenza virus A hemagglutinin (IHA), a protein found on the viral coat which facilitates infection by binding with sialic acid on the host cells’ membranes (Gamblin & Skehel, 2010). Previous in vitro studies have found that PDIA3 is required for proper IHA folding (Solda et al. 2006). This study examined PDIA3 regulation in both infection and non-infection conditions, both with and without the addition of external PDI inhibitor LOC14 as well as via deletion of PDIA3 in mice.
Primary mouse tracheal epithelial cells (MTECs) were cultured as previously described (Hoffman et al. 2016) for in vitro exposures and transgenic conditional KO mice for Pdia3 (ΔEpi-Pdia3), were developed with selective deletion of Pdia3 in lung epithelial cells. Mice fed a diet with the antibiotic doxycycline to activate the KO phenotype 7 days prior to the study’s start and until its completion. Non-KO littermates fed the same diet served as controls. Lung inflammatory response, total viral load, and airway mechanics including Newtonian resistance (Rn), tissue dampening (G), elastance (H) and airway hyperresponsiveness were measured using the flexiVent FX.
Infection with active virus in vivo resulted in upregulated PDIA3 transcription and expression when compared to irradiated virus controls, and relative to other PDI family members. Following infection with influenza A, ΔEpi-Pdia3 mice showed decreased viral burden, and had improved lung mechanics compared to control subjects. During methacholine hypersensitive tests, control mice in this study showed elevated peripheral airway resistance (G) following influenza infection as expected (Chang et al., 2011), however increased sensitivity was not observed in ΔEpi-Pdia3 subjects.
Chamberlain et al.’s study was able to evaluate the importance of the chaperone enzyme PDIA3 during Influenza A infection in a murine model. The flexiVent allowed for highly sensitive evaluation of changes in subject respiratory physiology using small groups (6-10 mice/ group) in response to both removal of PDIA3 (ΔEpi-Pdia3) and infection with influenza A, in both native and stressed hyperresponsive conditions. Their results were able to suggest the importance of lung epithelial PDIA3 in formation of -S-S bonds of IHA and in the subsequent establishment of influenza infection, airway inflammation, and AHR.
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