The interferon-stimulated
gene, Viperin (RSAD2) is
significantly expressed following viral infection and has been characterised as
broad antiviral protein against a range of viruses including hepatitis C virus (HCV), dengue virus (DENV), HIV
and HCMV. We have previously reported
that viperin has anti-HCV activity and showed that viperin interacts with the
HCV non-structural protein NS5A a protein essential for HCV replication and
virion assembly. These interactions
occur at sites of HCV replication (replication complex) and at the lipid
droplet interface the site of HCV assembly. Furthermore, viperin interacts with
the host HCV pro-viral factor VAP-A. In
addition to viperins antiviral role against a broad range of viral infections it
also modulates innate immune signaling. However, the molecular mechanisms that
underpin these observations are not well understood and we hypothesise that
viperin exerts it diverse range of functions through interaction with other
cellular proteins. Therefore, the goal of this study was to identify and characterise novel interacting
partners of viperin. A yeast two-hybrid system was employed in which we
used a cDNA library generated from Huh-7 cells stimulated with interferon-a and
viperin as the bait protein to identify novel viperin interacting partners. We identified
2 novel interacting partners of viperin, peroxisomal biogenesis factor 19
(PEX19) and apolipoprotein A-I (ApoAI). PEX19 is a cellular chaperone protein
that plays an important role in peroxisome biogenesis. The interaction of
viperin and PEX19 was confirmed by both proximity ligation assay (PLA) and
co-immunoprecipitation (Co-IP) analysis while immunofluorescence microscopy
analysis demonstrated that viperin and PEX19 colocalised to the lipid droplet
interface. Interestingly we also noted that in the presence of viperin
expression the localisation of PEX19 changed from its characteristic staining
pattern at the peroxisome to the lipid droplet in association with viperin. The
peroxisome is a key organelle in cholesterol/lipid metabolism and more recently
it has been identified as important in innate immune signaling in response to
viral infection. Thus, the interaction between viperin and PEX19 may play an important
role in modulation of host cholesterol/lipid biosynthesis that may impact viral
replication while concurrently modulation innate immune antiviral signaling.