PCSK3 Overexpression in Sjögren's Syndrome Patients May Be Regulated by rs4932178 SNP in Its Promoter Region and Correlates with IFN-γ Gene Expression

BACKGROUND

The PCSK3 gene encodes for the protease enzyme Furin, which promotes proteolytic maturation of important regulators of the immune response, and also enhances the secretion of interferon-γ (IFN). Several studies have suggested its possible involvement in the pathogenesis of chronic inflammatory diseases.

METHODS

We investigated the PCSK3 gene expression level in peripheral blood mononuclear cells isolated from Sjögren's Syndrome (SS) patients and healthy controls and we evaluated a possible correlation with IFN-γ gene expression. Moreover, we also explored the variability of two PCSK3 genetic polymorphisms (rs4932178 and rs4702) to evaluate a possible association between these polymorphisms and the expression levels of this gene.

RESULTS

We observed, by RT-qPCR, that the PCSK3 expression level was significantly higher in SS patients compared to the controls (p = 0.028), and we confirmed a positive correlation between PCSK3 and IFN-γ expression levels (p < 0.001). Moreover, we reported that the variant homozygous genotype of rs4932178 SNP is associated with a higher expression of the PCSK3 gene (p = 0.038) and with the SS susceptibility (p = 0.016).

CONCLUSIONS

Our data suggest that Furin could play a role in SS development, also promoting IFN-γ secretion.

Conserved Expression and Functionality of Furin between Chickens and Ducks as an Activating Protease of Highly Pathogenic Avian Influenza Virus Hemagglutinins

Highly pathogenic avian influenza viruses (HPAIVs) typically emerge from low-pathogenic avian influenza viruses (LPAIVs) of the H5 and H7 subtypes upon spillover from wild aquatic birds into poultry. The conversion from LPAIV to HPAIV is characterized by the acquisition of a multibasic cleavage site (MBCS) at the proteolytic cleavage site in the viral binding and fusion protein, hemagglutinin (HA), resulting in cleavage and activation of HA by ubiquitously expressed furin-like proteases. The ensuing HPAIVs disseminate systemically in gallinaceous poultry, are endotheliotropic, and cause hemorrhagic disease with high mortality. HPAIV infections in wild aquatic birds are generally milder, often asymptomatic, and generally not associated with systemic dissemination nor endotheliotropic. As MBCS cleavage by host proteases is the main virulence determinant of HPAIVs in poultry, we set out to determine whether cleavage of HPAIV HA by host proteases might influence the observed species-specific pathogenesis and tropism. Here, we sequenced, cloned, and characterized the expression and functionality of duck furin. The furin sequence was strongly conserved between chickens and ducks, and duck furin cleaved HPAIV and tetrabasic HA in an overexpression system, confirming its functionality. Furin was expressed ubiquitously and to similar extents in duck and chicken tissues, including in primary duck endothelial cells, which sustained multicycle replication of H5N1 HPAIV but not LPAIVs. In conclusion, differences in furin-like protease biology between wild aquatic birds and gallinaceous poultry are unlikely to largely determine the stark differences observed in species-specific pathogenesis of HPAIVs. IMPORTANCE HPAIV outbreaks are a global concern due to the health risks for poultry, wildlife, and humans and their major economic impact. The number of LPAIV-to-HPAIV conversions, which is associated with spillover from wild birds to poultry, has been increasing over recent decades. Furthermore, H5 HPAIVs from the A/goose/Guangdong/1/96 lineage have been circulating in migratory birds, causing increasingly frequent epizootics in poultry and wild birds. Milder symptoms in migratory birds allow for dispersion of HPAIVs over long distances, justifying the importance of understanding the pathogenesis of HPAIVs in wild birds. Here, we examined whether host proteases are a likely candidate to explain some differences in the degree of HPAIV systemic dissemination between avian species. This is the first report to show that furin function and expression is comparable between chickens and ducks, which renders the hypothesis unlikely that furin-like protease differences influence the HPAIV species-specific pathogenesis and tropism.

COVID-19 and Genetic Variants of Protein Involved in the SARS-CoV-2 Entry into the Host Cells

The recent global COVID-19 public health emergency is caused by SARS-CoV-2 infections and can manifest extremely variable clinical symptoms. Host human genetic variability could influence susceptibility and response to infection. It is known that ACE2 acts as a receptor for this pathogen, but the viral entry into the target cell also depends on other proteins. The aim of this study was to investigate the variability of genes coding for these proteins involved in the SARS-CoV-2 entry into the cells. We analyzed 131 COVID-19 patients by exome sequencing and examined the genetic variants of TMPRSS2, PCSK3, DPP4, and BSG genes. In total we identified seventeen variants. In PCSK3 gene, we observed a missense variant (c.893G>A) statistically more frequent compared to the EUR GnomAD reference population and a missense mutation (c.1906A>G) not found in the GnomAD database. In TMPRSS2 gene, we observed a significant difference in the frequency of c.331G>A, c.23G>T, and c.589G>A variant alleles in COVID-19 patients, compared to the corresponding allelic frequency in GnomAD. Genetic variants in these genes could influence the entry of the SARS-CoV-2. These data also support the hypothesis that host genetic variability may contribute to the variability in infection susceptibility and severity.