Severe acute respiratory syndrome coronavirus papain-like protease suppressed alpha interferon-induced responses through downregulation of extracellular signal-regulated kinase 1-mediated signalling pathways

Abstract

Severe acute respiratory syndrome coronavirus (SARS-CoV) papain-like protease (PLpro), a deubiquitinating enzyme, reportedly blocks poly I : C-induced activation of interferon regulatory factor 3 and nuclear factor kappa B, reducing interferon (IFN) induction. This study investigated type I IFN antagonist mechanism of PLpro in human promonocytes. PLpro antagonized IFN-ainduced responses such as interferon-stimulated response element-and AP-1-driven promoter activation, protein kinase R, 29-59-oligoadenylate synthetase (OAS), interleukin (IL)-6 and IL-8 expression, and signal transducers and activators of transcription (STAT) 1 (Tyr701), STAT1 (Ser727) and c-Jun phosphorylation. A proteomics approach demonstrated downregulation of extracellular signal-regulated kinase (ERK) 1 and upregulation of ubiquitin-conjugating enzyme (UBC) E2-25k as inhibitory mechanism of PLpro on IFN-a-induced responses. IFN-a treatment significantly induced mRNA expression of UBC E2-25k, but not ERK1, causing time-dependent decrease of ERK1, but not ERK2, in PLpro-expressing cells. Poly-ubiquitination of ERK1 showed a relationship between ERK1 and ubiquitin proteasome signalling pathways associated with IFN antagonism by PLpro. Combination treatment of IFN-a and the proteasome inhibitor MG-132 showed a time-dependent restoration of ERK1 protein levels and significant increase of ERK1, STAT1 and c-Jun phosphorylation in PLpro-expressing cells. Importantly, PD098059 (an ERK1/2 inhibitor) treatment significantly reduced IFN-a-induced ERK1 and STAT1 phosphorylation, inhibiting IFN-a-induced expression of 29-59-OAS in vector control cells and PLpro-expressing cells. Overall results proved downregulation of ERK1 by ubiquitin proteasomes and suppression of interaction between ERK1 and STAT1 as type I IFN antagonist function of SARS-CoV PLpro.

SARS coronavirus papain-like protease up-regulates the collagen expression through non-Samd TGF-β1 signaling

“…Human alveolar basal epithelial A549 cells grew in Dulbecco's Modified Eagle's Medium (HyClone Laboratories) and were transfected with control vector pcDNA3.1/His C (Invitrogen), or pSARS-PLpro containing SARS-CoV PLpro gene, as described in our prior reports (Li et al, 2011(Li et al, , 2012(Li et al, , 2016a(Li et al, , 2016b. In addition, pSARS-PLpro (H273A) that had the alanine substitution for histidine at position 273 by Ala within PLpro gene was constructed using PCR-based sitedirected mutagenesis with a mutated primer pair (5′-GGTAACT ATC-AGTGTGGTGCTTACACTCATATAACTGCTAAG-3′ and 5′-CTTAGCAGT TATATGAGTGTAAGCACCACACTGATAGTTACC-3′).…”

“…The largest ORFs ORF1a and ORF1ab encode for the polyprotein replicases 1a and 1ab mainly involving in the SARS-CoV replication, as cleaved in cis and in trans by ORF1a-encoded papain-like protease (PLpro) and 3C-like protease (3CLpro). PLpro, a de-ubiquitinating/de-ISGylating enzyme (Barretto et al, 2005;Ratia et al, 2006), has the antagonistic activities of Type I interferon (IFN) via blocking IRF-3 and ERK1 phosphorylation, preventing the IκBα degradation, and de-ubiquitinating the STING-TRAF3-TBK1 complex (Li et al, 2011;Frieman et al, 2009;Sun et al, 2012). Recently, PLpro shows the inhibitory effect on Tolllike receptor 7 (TLR7) mediated cytokine production through removing Lys63-linked ubiquitin chains of TRAF3 and TRAF6 (Li et al, 2016a).…”

Proteomic analysis forTypeIinterferon antagonism ofJapanese encephalitis virusNS5 protein

“…JEV NS5 Flag‐tagged pCR3.1 and its empty control vectors were supplied by Dr. Yi‐Ling Lin (Genomics Research Center, Academia Sinica, Taiwan), as described in a prior report . TE671 cells at 60–90% confluency in 6‐well plates were transfected with a mixture of GenePorter reagent and recombinant vector containing NS5 gene or empty vector for 5 h, then maintained in 2 mL of MEM containing 20% bovine serum for 2 days, as described previously . Transfected cell line was selected with a long‐term incubation of MEM containing 10% FBS and 800 μg/mL of G418.…”

Some research advances of immune mechanism during infection in China

“…As deubiquitinating enzymes, PLPs block polyI:C-induced activation of Interferon regulatory factor 3 (IRF3) and NF-κB, thus reducing IFN induction. Meanwhile, PLPs deactivate ERIS, an endoplasmic reticulum IFN stimulator, by inhibiting the ERIS dimerization [36][37][38][39][40][41]. Another mechanism involved in pathogen evasion is induced by IbeT, an E. coli K1 pathogenicity island gene.…”