The nucleoprotein of influenza A virus inhibits the innate immune response by inducing mitophagy.

Mitophagy is a form of autophagy that plays a key role in maintaining the homeostasis of functional mitochondria in the cell. Viruses have evolved various strategies to manipulate mitophagy to escape host immune responses and promote virus replication. In this study, the nucleoprotein (NP) of H1N1 virus (PR8 strain) was identified as a regulator of mitophagy.

Comparative transcriptome analysis reveals molecular adaptations underlying distinct immunity and inverted resting posture in bats.

Understanding how natural selection shapes unique traits in mammals is a central topic in evolutionary biology. The mammalian order Chiroptera (bats) is attractive for biologists as well as the general public due to their specific traits of extraordinary immunity and inverted resting posture. However, genomic resources for bats that occupy key phylogenetic positions are not sufficient, which hinders comprehensive investigation of the molecular mechanisms underpinning the origin of specific traits in bats.

Tankyrases inhibit innate antiviral response by PARylating VISA/MAVS and priming it for RNF146-mediated ubiquitination and degradation.

During viral infection, sensing of viral RNA by retinoic acid-inducible gene-I-like receptors (RLRs) initiates an antiviral innate immune response, which is mediated by the mitochondrial adaptor protein VISA (virus-induced signal adaptor; also known as mitochondrial antiviral signaling protein [MAVS]). VISA is regulated by various posttranslational modifications (PTMs), such as polyubiquitination, phosphorylation, -linked β-d--acetylglucosaminylation (O-GlcNAcylation), and monomethylation. However, whether other forms of PTMs regulate VISA-mediated innate immune signaling remains elusive.

USP19 exacerbates lipogenesis and colorectal carcinogenesis by stabilizing ME1.

Lipogenesis plays a critical role in colorectal carcinogenesis, but precisely how remains unclear. Here, we show that ERK2 phosphorylates ME1 at T103, thereby inhibiting its polyubiquitination and proteasomal degradation and enhancing its interaction with USP19. USP19 antagonizes RNF1-mediated ME1 degradation by deubiquitination, which in turn promotes lipid metabolism and NADPH production and suppresses ROS.

The RNA-binding protein LUC7L2 mediates MITA/STING intron retention to negatively regulate innate antiviral response.

MITA (also known as STING) is an ER-located adaptor protein, which mediates DNA-triggered innate immune response and is critically involved in autoimmune diseases and tumorigenesis. MITA is regulated by post-translational modifications, but how post-transcriptional mechanisms are involved in the regulation of MITA is still largely unknown. Here, we identified the RNA-binding protein LUC7L2 as a negative regulator of DNA virus-triggered innate immune response.

The PB1 protein of influenza A virus inhibits the innate immune response by targeting MAVS for NBR1-mediated selective autophagic degradation.

Influenza A virus (IAV) has evolved various strategies to counteract the innate immune response using different viral proteins. However, the mechanism is not fully elucidated. In this study, we identified the PB1 protein of H7N9 virus as a new negative regulator of virus- or poly(I:C)-stimulated IFN induction and specifically interacted with and destabilized MAVS.

TAK1-TABs Complex: A Central Signalosome in Inflammatory Responses.

Transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) is a member of the MAPK kinase kinase (MAPKKK) family and has been implicated in the regulation of a wide range of physiological and pathological processes. TAK1 functions through assembling with its binding partners TAK1-binding proteins (TAB1, TAB2, and TAB3) and can be activated by a variety of stimuli such as tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), and toll-like receptor ligands, and they play essential roles in the activation of NF-κB and MAPKs. Numerous studies have demonstrated that post-translational modifications play important roles in properly controlling the activity, stability, and assembly of TAK1-TABs complex according to the indicated cellular environment.

The Nucleoprotein of H7N9 Influenza Virus Positively Regulates TRAF3-Mediated Innate Signaling and Attenuates Viral Virulence in Mice.

H7N9 influenza A virus (IAV) is an emerged contagious pathogen that may cause severe human infections, even death. Understanding the precise cross talk between virus and host is vital for the development of effective vaccines and therapeutics. In the present study, we identified the nucleoprotein (NP) of H7N9 IAV as a positive regulator of RIG-I like receptor (RLR)-mediated signaling.

PCBP1 modulates the innate immune response by facilitating the binding of cGAS to DNA.

Cyclic GMP-AMP synthase (cGAS) is a key sensor critical for the recognition of DNA in the cytosol and catalyzes the synthesis of the second messenger cyclic GMP-AMP (cGAMP), which binds to the adapter protein MITA (also known as STING, MPYS, and ERIS) to initiate the innate immune response. How the binding of DNA to and the activation of cGAS are regulated remains poorly understood. Using a biochemical purification approach, we identified poly(rC)-binding protein 1 (PCBP1) as a cGAS-associated protein.

Phosphoproteomics Analysis Reveals a Potential Role of CHK1 in Regulation of Innate Immunity through IRF3.

Inhibitors of checkpoint kinase 1 (CHK1), a central component of DNA damage and cell cycle checkpoint response, represent a promising new cancer therapy, but the global cellular functions they regulate through phosphorylation are poorly understood. To elucidate the CHK1-regulated phosphorylation network, we performed a global quantitative phosphoproteomics analysis, which revealed 142 phosphosites whose phosphorylation levels were significantly different following treatment with the CHK1 inhibitor SCH 900776. Bioinformatics analysis identified phosphoproteins that function in ATR-CHK1 signaling, DNA replication, and DNA repair.

ZFYVE1 negatively regulates MDA5- but not RIG-I-mediated innate antiviral response.

The retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), including RIG-I and melanoma differentiation-associated gene 5 (MDA5), sense cytoplasmic viral RNA and initiate innate antiviral responses. How RIG-I and MDA5 are differentially regulated remains enigmatic. In this study, we identified the guanylate-binding protein (GBP) and zinc-finger FYVE domain-containing protein ZFYVE1 as a negative regulator of MDA5- but not RIG-I-mediated innate antiviral responses.

Regulation of TRIF-mediated innate immune response by K27-linked polyubiquitination and deubiquitination.

TIR domain-containing adaptor inducing interferon-β (TRIF) is an essential adaptor protein required for innate immune responses mediated by Toll-like receptor (TLR) 3- and TLR4. Here we identify USP19 as a negative regulator of TLR3/4-mediated signaling. USP19 deficiency increases the production of type I interferons (IFN) and proinflammatory cytokines induced by poly(I:C) or LPS in vitro and in vivo.

The zinc-finger protein ZFYVE1 modulates TLR3-mediated signaling by facilitating TLR3 ligand binding.

Recognition of viral dsRNA by Toll-like receptor 3 (TLR3) leads to the induction of downstream antiviral effectors and the innate antiviral immune response. Here, we identified the zinc-finger FYVE domain-containing protein ZFYVE1, a guanylate-binding protein (GBP), as a positive regulator of TLR3-mediated signaling. Overexpression of ZFYVE1 promoted the transcription of downstream antiviral genes upon stimulation with the synthetic TLR3 ligand poly(I:C).

USP19 Inhibits TNF-α- and IL-1β-Triggered NF-κB Activation by Deubiquitinating TAK1.

The dynamic regulations of ubiquitination and deubiquitination play important roles in TGF-β-activated kinase 1 (TAK1)-mediated NF-κB activation, which regulates various physiological and pathological events. We identified ubiquitin-specific protease (USP)19 as a negative regulator of TNF-α- and IL-1β-triggered NF-κB activation by deubiquitinating TAK1. Overexpression of USP19 but not its enzymatic inactive mutant inhibited TNF-α- and IL-1β-triggered NF-κB activation and transcription of downstream genes, whereas USP19 deficiency had the opposite effects.

Global phosphoproteomic analysis reveals ARMC10 as an AMPK substrate that regulates mitochondrial dynamics.

AMP-activated protein kinase (AMPK) is a key regulator of cellular energy homeostasis. Although AMPK has been studied extensively in cellular processes, understanding of its substrates and downstream functional network, and their contributions to cell fate and disease development, remains incomplete. To elucidate the AMPK-dependent signaling pathways, we performed global quantitative phosphoproteomic analysis using wild-type and AMPKα1/α2-double knockout cells and discovered 160 AMPK-dependent phosphorylation sites.

The Zinc-Finger Protein ZCCHC3 Binds RNA and Facilitates Viral RNA Sensing and Activation of the RIG-I-like Receptors.

Recognition of viral RNA by the retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) initiates innate antiviral immune response. How the binding of viral RNA to and activation of the RLRs are regulated remains enigmatic. In this study, we identified ZCCHC3 as a positive regulator of the RLRs including RIG-I and MDA5.

ZCCHC3 is a co-sensor of cGAS for dsDNA recognition in innate immune response.

Cyclic GMP-AMP synthase (cGAS) senses double-strand (ds) DNA in the cytosol and then catalyzes synthesis of the second messenger cGAMP, which activates the adaptor MITA/STING to initiate innate antiviral response. How cGAS activity is regulated remains enigmatic. Here, we identify ZCCHC3, a CCHC-type zinc-finger protein, as a positive regulator of cytosolic dsDNA- and DNA virus-triggered signaling.

A Naturally Occurring Deletion in the Effector Domain of H5N1 Swine Influenza Virus Nonstructural Protein 1 Regulates Viral Fitness and Host Innate Immunity.

Nonstructural protein 1 (NS1) of influenza A virus regulates innate immune responses via various mechanisms. We previously showed that a naturally occurring deletion (the EALQR motif) in the NS1 effector domain of an H5N1 swine-origin avian influenza virus impairs the inhibition of type I interferon (IFN) in chicken fibroblasts and attenuates virulence in chickens. Here we found that the virus bearing this deletion in its NS1 effector domain showed diminished inhibition of IFN-related cytokine expression and attenuated virulence in mice.

TRIM8 Negatively Regulates TLR3/4-Mediated Innate Immune Response by Blocking TRIF-TBK1 Interaction.

TLR-mediated signaling pathways play critical roles in host defense against microbials. However, dysregulation of innate immune and inflammatory responses triggered by TLRs would result in harmful damage to the host. Using a gene-knockout mouse model, we show that tripartite motif (TRIM) 8 negatively regulates TLR3- and TLR4-mediated innate immune and inflammatory responses.

IFITM3 inhibits virus-triggered induction of type I interferon by mediating autophagosome-dependent degradation of IRF3.

Interferon-induced transmembrane protein 3 (IFITM3) is a restriction factor that can be induced by viral infection and interferons (IFNs). It inhibits the entry and replication of many viruses, which are independent of receptor usage but dependent on processes that occur in endosomes. In this study, we demonstrate that IFITM3 plays important roles in regulating the RNA-virus-triggered production of IFN-β in a negative-feedback manner.

Duck Tembusu Virus Nonstructural Protein 1 Antagonizes IFN-β Signaling Pathways by Targeting VISA.

Duck Tembusu virus (DTMUV) is an emergent infectious pathogen that has caused severe disease in ducks and huge economic losses to the poultry industry in China since 2009. Previously, we showed that DTMUV inhibits IFN-β induction early in infection; however, the mechanisms of the inhibition of innate immune responses remain poorly understood. In this study, we screened DTMUV-encoded structural and nonstructural proteins using reporter assays and found that DTMUV NS1 markedly suppressed virus-triggered IFN-β expression by inhibiting retinoic acid-inducible gene I-like receptor signaling.

Foot-and-mouth disease virus non-structural protein 3A inhibits the interferon-β signaling pathway.

Foot-and-mouth disease virus (FMDV) is the etiological agent of FMD, which affects cloven-hoofed animals. The pathophysiology of FMDV has not been fully understood and the evasion of host innate immune system is still unclear. Here, the FMDV non-structural protein 3A was identified as a negative regulator of virus-triggered IFN-β signaling pathway.

The VP3 structural protein of foot-and-mouth disease virus inhibits the IFN-β signaling pathway.

Foot-and-mouth disease is a frequently occurring disease of cloven-hoofed animals that is caused by infection with the foot-and-mouth virus (FMDV). FMDV circumvents the type-I IFN response by expressing proteins that antagonize cellular innate immunity, such as leader protease and 3C protease. We identified the FMDV structural protein VP3 as a negative regulator of the virus-triggered IFN-β signaling pathway.