Hemoglobin Subunit Beta Interacts with the Capsid Protein and Antagonizes the Growth of Classical Swine Fever Virus

Abstract

The capsid (C) protein of the Flaviviridae family members is involved in nucleocapsid formation and virion assembly. However, the influence of C protein-interacting partners on the outcome of pestivirus infections is poorly defined. In this study, hemoglobin subunit beta (HB) was identified as a C protein-binding protein by glutathione S-transferase pulldown and subsequent mass spectrometry analysis of PK-15 cells, which are permissive cells for classical swine fever virus (CSFV). Coimmunoprecipitation and confocal microscopy confirmed that HB interacts and colocalizes with the C protein in the cytoplasm. Silencing of HB with small interfering RNAs promoted CSFV growth and replication, whereas overexpression of HB suppressed CSFV replication and growth. Interestingly, HB was found to interact with retinoic acid-inducible gene I and increase its expression, resulting in increased production of type I interferon (IFN). However, HB was unable to suppress CSFV growth when the RIG-I pathway was blocked. Overall, our results suggest that cellular HB antagonizes CSFV growth and replication by triggering IFN signaling, and might represent a novel antiviral restriction factor. This study reports for the first time the novel role of HB in innate immunity.

Mitogen-Activated Protein Kinase Kinase 2, a Novel E2-Interacting Protein, Promotes the Growth of Classical Swine Fever Virus via Attenuation of the JAK-STAT Signaling Pathway

“…However, the cross-linking function between the Raf/MEK1/2/ERK1/2 and JAK-STAT pathways has not been illustrated in different cell lines. We have previously shown that addition of recombinant IFN-β to CSFV-infected cells dramatically decreases the yields of progeny virus (46). In the present work, we show that the expression of p-STAT1 in PK-15 cells is induced during the early phase of CSFV infection, indicating that CSFV can activate the JAK-STAT pathway.…”

Swine Host Protein Coiled-Coil Domain-Containing 115 (CCDC115) Interacts with Classical Swine Fever Virus Structural Glycoprotein E2 during Virus Replication

“…Through mechanisms mediated by interaction between virus and host proteins, the virus could modulate the host cell response, permitting the virus to manipulate host metabolic pathways to facilitate its replication. In that regard, we have already reported that structural CSFV Core protein interacts with host SUMO1, IQGAP1, UBC9 and OS9 [11][12][13][14]; the interaction of nonstructural protein p7, a viroporin, with CAMLG [28]; recently, we characterized the interaction of major structural glycoprotein E2 with host proteins PPP1CB and DCNT6 [20,21]. Interestingly, some of these host-virus protein-protein interactions also play a role determining virus virulence in swine [11][12][13]21].…”

“…Therefore, the identification of host cell proteins specifically interacting with these virus proteins during infection is a relatively new field of CSFV research. CSFV Core protein has been shown to interact with IQ motif-containing GTPase activating protein 1 (IQGAP1), ubiquitin-conjugating enzyme 9 (UBC9), small ubiquitin-related modifier 1 (SUMO1), and hemoglobin subunit beta (HB) [11][12][13][14]. E rns has been demonstrated to interact with the Laminin receptor [15].…”

Effects of the nuclear localization of the N pro protein of classical swine fever virus on its virulence in pigs

“…CSFV has developed different strategies to subvert the innate immune system to facilitate its replication in the host cell. These include the proteasomal degradation of IRF3 mediated by N pro (Ruggli et al, 2003;La Rocca et al, 2005), RNase activity of E rns (Bauhofer et al, 2005;Matzener et al, 2009), and the antagonism of the hemoglobin b-subunit (HB)-induced interferon production by the CSFV C protein (Li et al, 2013b), etc. This may explain why vSM-IRF3 and EGFP-CSFV did not induce the IFN-b production.…”