African swine fever virus ubiquitin-conjugating enzyme pI215L inhibits IFN-I signaling pathway through STAT2 degradation

Abstract

African swine fever virus (ASFV) is the causative agent of one of the most lethal diseases affecting domestic pig and wild boar, which is endangering the swine industry due to its rapid expansion. ASFV has developed different mechanisms to evade the host immune response, including inhibition of type I IFN (IFN-I) production and signaling, since IFN-I is a key element in the cellular antiviral response. Here, we report a novel mechanism of evasion of the IFN-I signaling pathway carried out by the ASFV ubiquitin-conjugating enzyme pI215L. Our data showed that pI215L inhibited IFN-stimulated response element (ISRE) activity and the consecutive mRNA induction of the IFN-stimulated genes ISG15 and IFIT1 through the ubiquitination and proteasomal degradation of STAT2. Additionally, by immunofluorescence, co-immunoprecipitation and nucleus-cytoplasm fractionation approaches, we have confirmed the interaction and colocalization of STAT2 and pI215L, in ectopic experiments and during ASFV infection. Moreover, expression of the catalytic mutant (I215L-C85A) did not inhibit the induction of ISG15 and IFIT1, nor the activity of ISRE. Furthermore, we confirmed that STAT2 degradation by pI215L is dependent on its catalytic activity, since expression of the pI215L-C85A mutant did not affect STAT2 levels, compared to the wild-type protein. Yet, our data reveal that the interaction of pI215L with STAT2 does not require the integrity of its catalytic domain since the pI215L-C85A mutant co-immunoprecipitates with STAT2. All these findings reveal, for the first time, the involvement of E2-ubiquitin-conjugating enzyme activity of pI215L in the immune response modulation.

The African swine fever virus MGF300-4L protein is associated with viral pathogenicity by promoting the autophagic degradation of IKK β and increasing the stability of I κ B α

“…The further analysis unveiled that the interaction of MGF300-4L with IKK β results in the autophagic degradation of IKK β . The immune regulatory protein of ASFV degrades key molecules involved in the IFNs and NF- κ B signaling pathway via the autophagy pathway, a commonly employed immunoevasion mechanism by ASFV [ 44 ]. For example, the virulence-associated factor A137R protein of ASFV can inhibit the production of IFNs by mediating the autophagy-induced lysosomal degradation of TBK1 [ 45 ].…”

Deletion of MGF505-2R Gene Activates the cGAS-STING Pathway Leading to Attenuation and Protection against Virulent African Swine Fever Virus

“…Monoclonal antibody anti-tubulin (B-5-1-2) (T-5168) was purchased by Sigma, Kanagawa, Japan. Polyclonal antibody anti-I125L was previously generated in our lab [24]. Monoclonal antibody anti-p32(S-5C1) was previously generated [34].…”

“…The type I IFN-induced JAK/STAT pathway has also been described as being controlled by ASFV [20], further relating type I IFN to virulence. Some of the viral factors that control this pathway during ASFV infection [21][22][23][24][25] have also been identified. The identification and study of these factors are fundamental for the development of live attenuated vaccines (LAVs), which are currently the most realistic strategy for developing a vaccine against ASFV.…”

Antagonisms of ASFV towards Host Defense Mechanisms: Knowledge Gaps in Viral Immune Evasion and Pathogenesis

“…ASFV pI215L (UBCv1) can interact with IRF9 and mediate the degradation of IRF9 via autophagy-lysosome pathway, which is independent of its ubiquitin-conjugating enzyme activity [ 85 ]. Additionally, ASFV pI215L (UBCv1) can also mediate the degradation of STAT2 via ubiquitin-proteasome pathway, which is dependent on its ubiquitin-conjugating enzyme activity [ 86 ]. In addition, Zhang et al identified pMGF360-9L as also working as an inhibitor of JAK/STAT pathway [ 87 ].…”