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1.
Microbiol Spectr ; 9(2): e0090821, 2021 10 31.
Article in English | MEDLINE | ID: covidwho-1452921

ABSTRACT

Emerging coronaviruses (CoVs) can cause severe diseases in humans and animals, and, as of yet, none of the currently available broad-spectrum drugs or vaccines can effectively control these diseases. Host antiviral proteins play an important role in inhibiting viral proliferation. One of the isoforms of cytoplasmic poly(A)-binding protein (PABP), PABPC4, is an RNA-processing protein, which plays an important role in promoting gene expression by enhancing translation and mRNA stability. However, its function in viruses remains poorly understood. Here, we report that the host protein, PABPC4, could be regulated by transcription factor SP1 and broadly inhibits the replication of CoVs, covering four genera (Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus) of the Coronaviridae family by targeting the nucleocapsid (N) protein through the autophagosomes for degradation. PABPC4 recruited the E3 ubiquitin ligase MARCH8/MARCHF8 to the N protein for ubiquitination. Ubiquitinated N protein was recognized by the cargo receptor NDP52/CALCOCO2, which delivered it to the autolysosomes for degradation, resulting in impaired viral proliferation. In addition to regulating gene expression, these data demonstrate a novel antiviral function of PABPC4, which broadly suppresses CoVs by degrading the N protein via the selective autophagy pathway. This study will shed light on the development of broad anticoronaviral therapies. IMPORTANCE Emerging coronaviruses (CoVs) can cause severe diseases in humans and animals, but none of the currently available drugs or vaccines can effectively control these diseases. During viral infection, the host will activate the interferon (IFN) signaling pathways and host restriction factors in maintaining the innate antiviral responses and suppressing viral replication. This study demonstrated that the host protein, PABPC4, interacts with the nucleocapsid (N) proteins from eight CoVs covering four genera (Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus) of the Coronaviridae family. PABPC4 could be regulated by SP1 and broadly inhibits the replication of CoVs by targeting the nucleocapsid (N) protein through the autophagosomes for degradation. This study significantly increases our understanding of the novel host restriction factor PABPC4 against CoV replication and will help develop novel antiviral strategies.


Subject(s)
Autophagy/physiology , Blood Proteins/metabolism , Coronavirus Nucleocapsid Proteins/metabolism , Coronavirus/growth & development , Poly(A)-Binding Proteins/metabolism , Virus Replication/physiology , Animals , Cell Line , Chlorocebus aethiops , HEK293 Cells , Humans , Infectious bronchitis virus/growth & development , Murine hepatitis virus/growth & development , Nuclear Proteins/metabolism , Porcine epidemic diarrhea virus/growth & development , Proteolysis , Sp1 Transcription Factor/metabolism , Swine , Ubiquitin-Protein Ligases/metabolism , Ubiquitination , Vero Cells
2.
Virol J ; 17(1): 46, 2020 04 03.
Article in English | MEDLINE | ID: covidwho-827237

ABSTRACT

BACKGROUND: Porcine epidemic diarrhea virus (PEDV) infection causes an acute enteric tract infectious disease characterized by vomiting, anorexia, dehydration, weight loss and high mortality in neonatal piglets. During PEDV infection, the spike protein (S) is a major virion structural protein interacting with receptors and inducing neutralizing antibodies. However, the neutralizing B-cell epitopes within PEDV S protein have not been well studied. METHODS: To accurately identify the important immunodominant region of S1, the purified truncated S1 proteins (SA, SB, SC, SD and SE) were used to immunize BALB/c mice to prepare polyclonal antibodies. The antisera titers were determined by indirect ELISA, western blot and IFA after four immunizations to find the important immunodominant region of S1, and then purified the immunodominant region of S1 protein and immunized mice to generate the special antibodies, and then used recombinant peptides to determine the B-cell epitopes of monoclonal antibodies. RESULTS: Five antisera of recombinant proteins of the spike protein region of PEDV were generated and we found that only the polyclonal antibody against part of the S1 region (signed as SE protein, residues 666-789) could recognize the native PEDV. Purified SE protein was used to immunize BALB/c mice and generate mAb 2E10. Pepscan of the SE protein demonstrated that SE16 (722SSTFNSTREL731) is the minimal linear epitope required for reactivity with the mAb 2E10. Further investigation indicated that the epitope SE16 was localized on the surface of PEDV S protein in the 3D structure. CONCLUSIONS: A mAb 2E10 that is specifically bound to PEDV was generated and identified a specific linear B-cell epitope (SE16, 722SSTFNSTREL731) of the mAb. The epitope region of PEDV S1 localized in the different regions in comparison with the earlier identified epitopes. These findings enhance the understanding of the PEDV spike protein structure for vaccine design and provide a potential use for developing diagnostic methods to detect PEDV.


Subject(s)
Epitopes, B-Lymphocyte/immunology , Immunodominant Epitopes/immunology , Porcine epidemic diarrhea virus/immunology , Spike Glycoprotein, Coronavirus/immunology , Animals , Antibodies, Monoclonal/immunology , Antibodies, Neutralizing/immunology , Chlorocebus aethiops , Female , Mice , Mice, Inbred BALB C , Porcine epidemic diarrhea virus/chemistry , Vero Cells
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