RESUMO
As a highly pathogenic human coronavirus, SARS-CoV-2 has to counteract an intricate network of antiviral host responses to establish infection and spread. The nucleic acid-induced stress response is an essential component of antiviral defense and is closely related to antiviral innate immunity. However, whether SARS-CoV-2 regulates the stress response pathway to achieve immune evasion remains elusive. In this study, SARS-CoV-2 NSP5 and N protein were found to attenuate antiviral stress granule (avSG) formation. Moreover, NSP5 and N suppressed IFN expression induced by infection of Sendai virus or transfection of a synthetic mimic of dsRNA, poly (I:C), inhibiting TBK1 and IRF3 phosphorylation, and restraining the nuclear translocalization of IRF3. Furthermore, HEK293T cells with ectopic expression of NSP5 or N protein were less resistant to vesicular stomatitis virus infection. Mechanistically, NSP5 suppressed avSG formation and disrupted RIG-I-MAVS complex to attenuate the RIG-I-mediated antiviral immunity. In contrast to the multiple targets of NSP5, the N protein specifically targeted cofactors upstream of RIG-I. The N protein interacted with G3BP1 to prevent avSG formation and to keep the cofactors G3BP1 and PACT from activating RIG-I. Additionally, the N protein also affected the recognition of dsRNA by RIG-I. This study revealed the intimate correlation between SARS-CoV-2, the stress response, and innate antiviral immunity, shedding light on the pathogenic mechanism of COVID-19.
Assuntos
Proteases 3C de Coronavírus/genética , Proteínas do Nucleocapsídeo de Coronavírus/genética , Proteína DEAD-box 58/genética , DNA Helicases/genética , Proteínas de Ligação a Poli-ADP-Ribose/genética , RNA Helicases/genética , Proteínas com Motivo de Reconhecimento de RNA/genética , Proteínas de Ligação a RNA/genética , Receptores Imunológicos/genética , SARS-CoV-2/genética , Grânulos de Estresse/genética , Animais , Chlorocebus aethiops , Proteases 3C de Coronavírus/imunologia , Proteínas do Nucleocapsídeo de Coronavírus/imunologia , Proteína DEAD-box 58/imunologia , DNA Helicases/imunologia , Regulação da Expressão Gênica , Células HEK293 , Células HeLa , Humanos , Evasão da Resposta Imune , Fosfoproteínas/genética , Fosfoproteínas/imunologia , Poli I-C/farmacologia , Proteínas de Ligação a Poli-ADP-Ribose/imunologia , Ligação Proteica , RNA Helicases/imunologia , Proteínas com Motivo de Reconhecimento de RNA/imunologia , RNA de Cadeia Dupla/genética , RNA de Cadeia Dupla/imunologia , Proteínas de Ligação a RNA/imunologia , Receptores Imunológicos/imunologia , SARS-CoV-2/imunologia , SARS-CoV-2/patogenicidade , Vírus Sendai/genética , Vírus Sendai/imunologia , Transdução de Sinais , Grânulos de Estresse/efeitos dos fármacos , Grânulos de Estresse/imunologia , Grânulos de Estresse/virologia , Células Vero , Vesiculovirus/genética , Vesiculovirus/imunologiaRESUMO
Cellular stress can induce cytoplasmic ribonucleoprotein complexes called stress granules that allow the cells to survive. Stress granules are also central to cellular responses to infections, in which they can act as platforms for viral sensing or modulate innate immune signaling through pattern recognition receptors. However, the effect of innate immune signaling on stress granules is poorly understood. In this study, we report that prior induction of innate immune signaling through TLRs inhibited stress granule assembly in a TLR ligand dose-dependent manner in murine bone marrow-derived macrophages. Time course analysis suggests that TLR stimulation can reverse stress granule assembly even after it has begun. Additionally, both MYD88- and TRIF-mediated TLR signaling inhibited stress granule assembly in response to endoplasmic reticulum stress in bone marrow-derived macrophages and the chemotherapeutic drug oxaliplatin in murine B16 melanoma cells. This inhibition was not due to a decrease in expression of the critical stress granule proteins G3BP1 and DDX3X and was independent of IRAK1/4, JNK, ERK and P38 kinase activity but dependent on IKK complex kinase activity. Overall, we have identified the TLR-IKK complex signaling axis as a regulator of stress granule assembly-disassembly dynamics, highlighting cross-talk between processes that are critical in health and disease.