| Summary: | Coronaviruses (CoVs) are known to interfere and modulate host-cell processes to promote viral replication and evade immunity. A key role presented in available literature is that CoVs can modulate autophagy, a process critical to homeostatic maintenance. This thesis investigates the role of non-structural protein 6 (NSP6) of coronaviruses, including FCoV, the cause of feline infectious peritonitis virus (FIP), human CoV-OC43 (HCoV-OC43) and serve acute respiratory syndrome CoV 2 (SARS-CoV-2) in the manipulation of autophagy. Bioinformatic analysis, including Clustal Omega multiple sequence alignment and transmembrane prediction tools, showed that NSP6 has relatively few conserved domains and transmembrane regions across the viral species, potentially suggesting functional similarities may be preserved through structural adaptations, rather than sequence conservation.
Restriction digest cloning was employed to clone the NSP6 protein of the three viral species into a pCAGGS_mCherry vector, enabling protein expression analysis to investigate its effects on autophagy. Immunoblotting and indirect immunofluorescence showed an increase in production of autophagosomes when cells expressed NSP6, whilst also appearing to impair autophagic flux, observed by the accumulation of LC3-II and p62/SQSTM1, respectively. NSP6 appeared to have an effect mTOR signalling, which is a critical regulator of autophagy induction. Additionally, NSP6 was observed to co-localise with BST-2, indicating a potential interaction that could aid in the evasion of innate immunity by coronaviruses.
This study concludes that NSP6 may have a role in the modulation of autophagy, which could enhance viral survival and replication. In addition, co-localisation with BST-2 suggests that NSP6 may also play a role in evading host immunity and enhancing the viral survival in cells. Future studies could include analysis of NSP6 in autophagy knockout cell lines (e.g. ATG5 KO) and exploring the broader implications of potential interactions between NSP6, BST-2 and the autophagy pathway, providing an insight into host immune evasion.
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