Dual NDP52 Function in Persistent CSFV Infection

Abstract

Viruses have evolved many mechanisms to escape host antiviral responses. Previously, we found that classical swine fever virus (CSFV) infection induces autophagy using the autophagosome as a self-replication site, thereby evading the host immune response and promoting long-term infection. However, the underlying mechanisms used by CSFV to enter autophagosomes and the mechanism by which autophagy promotes viral replication remain unclear. We found that CSFV infection inhibited autophagy receptor nuclear dot protein 52 kDa (NDP52) expression, ubiquitination, and SUMO2-4 modification. Further analyses revealed that CSFV mediated ubiquitination and SUMOylation of NDP52 via Pten-induced kinase 1 (PINK1)-Parkin. Moreover, NDP52 inhibition also inhibited CSFV replication and the induction of mitophagy marker proteins expression. Inhibition of NDP52 reduced CD63 expression and binding to CSFV E2 protein, which has an essential role in persistent CSFV infection. As NDP52 has a close relationship with the NF-κB innate immunity pathway and plays an important role in the antiviral response, we investigated whether NDP52 inhibited CSFV replication through the release of immune factors and antivirus signals. Our results showed that inhibiting NDP52 boosted interferon and TNF release and promoted NF-κB pathway activation. In summary, we found that NDP52 inhibition not only reduces CSFV binding and entry into autophagic vesicles, but also inhibits CSFV replication by active NF-κB antiviral immune pathways. Our data reveal a novel mechanism by which NDP52, an autophagy receptor, mediates CSFV infection, and provide new avenues for the development of antiviral strategies.

The Role of Autophagy and Autophagy Receptor NDP52 in Microbial Infections

“…Our results show that inhibiting NDP52 boosts interferon and release and promotes NF-κB pathway activation. In summary, we found that NDP52 inhibition not only reduces CSFV binding and entry into autophagic vesicles, but also inhibits CSFV replication by active NF-κB antiviral immune pathways [100] (Figure 4). Our data reveal a novel mechanism by which NDP52, an autophagy receptor, mediates CSFV infection, and provides new avenues for the development of antiviral strategies.…”

Anti-Classical Swine Fever Virus Strategies

“…(7) Proteins related to MAPK signaling pathways, such as TRAF5 [80] and MEK2 [81,82], could promote CSFV replication. (8) Some proteins involved in autophagy or apoptosis, such as BECN1, LC3 [83], NDP52 [84], and FHC [85], also could regulate CSFV replication. (9) Other proteins were also reported to be involved in the CSFV replication, such as FKBP8 [86], Jiv90 [87], HSP70 [88], HO-1 [89], and AIF1 [90].…”

Autophagy receptors as viral targets

“…The classical swine fever virus (CSFV) was recently reported to cause down-regulation of CALCOCO2/NDP52 as well as decreased ubiquitination and SUMOylation (small ubiquitin-like modifier) of the receptor or its binding partners in a Parkin dependent manner [ 25 ]. Parkin was upregulated and Parkin, or Parkin associated proteins, were ubiquitinated as a response to CSFV infection.…”

“…Parkin was upregulated and Parkin, or Parkin associated proteins, were ubiquitinated as a response to CSFV infection. CALCOCO2/NDP52 silencing decreased CSFV replication measured by viral titers, RNA copy numbers and reduction of viral protein N pro , indicating a positive role for CALCOCO2/NDP52 in CSFV replication [ 25 ]. CSFV structural protein E2 was observed colocalizing with CALCOCO2/NDP52 in PK-15 cells.…”

“…CALCOCO2/NDP52 silencing also decreased the autophagic markers CD63, LC3 and BECN1; however, colocalization between LC3 and ubiquitin was also decreased. CALCOCO2/NDP52 silencing during CSFV infection revealed that CALCOCO2/NDP52 promotes the colocalization between CSFV E2 protein and CD63 as well as ubiquitin [ 25 ]. The viral protein responsible for the CALCOCO2/NDP52 ubiquitin modulation is yet to be discovered.…”