MG132 Attenuates the Replication of Classical Swine Fever Virus in vitro.

Yuming Chen,Shaofeng Deng,Shuangqi Fan,Shengming Ma,Mengpo Zhao,Jingyuan Zhang,Hailuan Xu,Lin Yi,Mingqiu Zhao,Keke Wu,Erpeng Zhu,Jinding Chen,Hongxing Ding,Wencheng He

doi:10.3389/fmicb.2020.00852

Abstract

The 26S proteasome, in charge of intracellular protein degradation, plays significant roles in the modulation of various cellular activities as well as in the interplay between virus and host. However, studies about the relationship between 26S proteasome and classical swine fever virus (CSFV) is limited up to now. MG132 is a proteasome inhibitor and has been extensively used in studies about replication of many viruses. Herein, we investigated the role of MG132 in CSFV replication and results showed that MG132 significantly decreased virus titers and viral RNA copies in CSFV-infected PK-15 cells. Further studies demonstrated that MG132 upregulated the expression of several interferon-stimulated genes (ISGs), in CSFV-infected cells. Since the activation of ISGs is controlled by the JAK-STAT signal pathway, we next examined the effect of MG132 on the expression and localization of key molecular STAT1 in the infected cells using Western blot and confocal laser scanning microscopy, respectively. Results showed that CSFV infection and viral NS4A protein decreased the protein level of STAT1, and MG132 promoted the accumulation of STAT1 in the nucleus of cells adjacent to the CSFV-infected cells. Besides, MG132 did not affect the expressions of IFN-α, STAT1, Mx1, OAS1, and PKR genes in cells without CSFV. In conclusion, we identify that MG132 significantly inhibits CSFV replication in vitro, in which the activation of the JAK-STAT pathway and the subsequent upregulation of expressions of ISGs might play significant roles, providing a potential preventive method for CSF.

Highlights

The 26S proteasome, which consists of a 20S catalytic core and two 19S regulatory subunits at the end (Kim et al, 2011), plays important roles in the regulation of various fundamental cellular processes including cell cycle, cell apoptosis, signal transduction, innate immune, etc. (Goldberg, 2007)
We decided to assess the role of MG132 in classical swine fever virus (CSFV) replication in PK-15 cells
We identified that CSFV infection promoted the transcription levels of Mx1, PKR, and OAS1, and MG132 further upregulated expressions of Mx1 and OAS1 compared with the CSFV group, though PKR was not significantly affected (Figure 3B)

Summary

Introduction

The 26S proteasome, which consists of a 20S catalytic core and two 19S regulatory subunits at the end (Kim et al, 2011), plays important roles in the regulation of various fundamental cellular processes including cell cycle, cell apoptosis, signal transduction, innate immune, etc. (Goldberg, 2007). There is a close relationship between 26S proteasome and the ubiquitin reaction cascade, since most proteins degraded by 26S proteasome are modified by ubiquitin. 26S proteasome together with the ubiquitin reaction cascade constitutes the ubiquitin proteasome system (UPS), mediating the degradation of both cellular and viral proteins. The 26S proteasome has been reported to be involved in the infection of various viruses by regulating levels of viral proteins and relevant cellular proteins (Rajsbaum and Garcia-Sastre, 2013; Davis and Gack, 2015; Luo, 2016). The genome of CSFV encodes a viral polyprotein which could be cleaved to form four structural proteins (Erns, E1, E2, and C) and eight non-structural proteins (Npro, p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B) by enzymes (Lamp et al, 2011; Ji et al, 2015)

Methods

Results

Conclusion