RESUMO
The nucleotide-binding domain and leucine-rich-repeat-containing (NLR) proteins regulate innate immunity. Although the positive regulatory impact of NLRs is clear, their inhibitory roles are not well defined. We showed that Nlrx1(-/-) mice exhibited increased expression of antiviral signaling molecules IFN-ß, STAT2, OAS1, and IL-6 after influenza virus infection. Consistent with increased inflammation, Nlrx1(-/-) mice exhibited marked morbidity and histopathology. Infection of these mice with an influenza strain that carries a mutated NS-1 protein, which normally prevents IFN induction by interaction with RNA and the intracellular RNA sensor RIG-I, further exacerbated IL-6 and type I IFN signaling. NLRX1 also weakened cytokine responses to the 2009 H1N1 pandemic influenza virus in human cells. Mechanistically, Nlrx1 deletion led to constitutive interaction of MAVS and RIG-I. Additionally, an inhibitory function is identified for NLRX1 during LPS activation of macrophages where the MAVS-RIG-I pathway was not involved. NLRX1 interacts with TRAF6 and inhibits NF-κB activation. Thus, NLRX1 functions as a checkpoint of overzealous inflammation.
Assuntos
Vírus da Influenza A Subtipo H1N1/imunologia , Proteínas Mitocondriais/imunologia , Infecções por Orthomyxoviridae/imunologia , Transdução de Sinais , Proteínas Adaptadoras de Transdução de Sinal/imunologia , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Células Cultivadas , Interferon beta/biossíntese , Interferon beta/imunologia , Interleucina-6/biossíntese , Interleucina-6/imunologia , Macrófagos/imunologia , Proteínas de Membrana/imunologia , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Knockout , Proteínas Mitocondriais/deficiência , NF-kappa B/imunologia , NF-kappa B/metabolismo , Proteínas do Tecido Nervoso/imunologia , Proteínas do Tecido Nervoso/metabolismo , Receptores de Superfície Celular , Fator 6 Associado a Receptor de TNF/imunologia , Fator 6 Associado a Receptor de TNF/metabolismoRESUMO
BACKGROUND: Emergence of drug-resistant strains of influenza viruses, including avian H5N1 with pandemic potential, 1918 and 2009 A/H1N1 pandemic viruses to currently used antiviral agents, neuraminidase inhibitors and M2 Ion channel blockers, underscores the importance of developing novel antiviral strategies. Activation of innate immune pathogen sensor Retinoic Acid Inducible Gene-I (RIG-I) has recently been shown to induce antiviral state. RESULTS: In the present investigation, using real time RT-PCR, immunofluorescence, immunoblot, and plaque assay we show that 5'PPP-containing single stranded RNA (5'PPP-RNA), a ligand for the intracytoplasmic RNA sensor, RIG-I can be used as a prophylactic agent against known drug-resistant avian H5N1 and pandemic influenza viruses. 5'PPP-RNA treatment of human lung epithelial cells inhibited replication of drug-resistant avian H5N1 as well as 1918 and 2009 pandemic influenza viruses in a RIG-I and type 1 interferon dependant manner. Additionally, 5'PPP-RNA treatment also inhibited 2009 H1N1 viral replication in vivo in mice. CONCLUSIONS: Our findings suggest that 5'PPP-RNA mediated activation of RIG-I can suppress replication of influenza viruses irrespective of their genetic make-up, pathogenicity, and drug-sensitivity status.
Assuntos
RNA Helicases DEAD-box/metabolismo , Surtos de Doenças , Farmacorresistência Viral , Vírus da Influenza A Subtipo H1N1/efeitos dos fármacos , Virus da Influenza A Subtipo H5N1/efeitos dos fármacos , Influenza Humana/virologia , RNA Viral/metabolismo , Replicação Viral , Animais , Linhagem Celular , Proteína DEAD-box 58 , RNA Helicases DEAD-box/genética , Humanos , Vírus da Influenza A Subtipo H1N1/genética , Vírus da Influenza A Subtipo H1N1/fisiologia , Virus da Influenza A Subtipo H5N1/genética , Virus da Influenza A Subtipo H5N1/fisiologia , Influenza Humana/epidemiologia , Influenza Humana/genética , Camundongos , Camundongos Endogâmicos BALB C , RNA Viral/síntese química , RNA Viral/química , RNA Viral/genética , RNA Viral/farmacologia , Receptores ImunológicosRESUMO
Influenza A virus (IAV), similar to other viruses, exploits the machinery of human host cells for its survival and replication. We identified α-actinin-4, a host cytoskeletal protein, as an interacting partner of IAV nucleoprotein (NP). We confirmed this interaction using co-immunoprecipitation studies, first in a coupled in vitro transcription-translation assay and then in cells either transiently co-expressing the two proteins or infected with whole IAV. Importantly, the NP-actinin-4 interaction was observed in several IAV subtypes, including the 2009 H1N1 pandemic virus. Moreover, immunofluorescence studies revealed that both NP and actinin-4 co-localized largely around the nucleus and also in the cytoplasmic region of virus-infected A549 cells. Silencing of actinin-4 expression resulted in not only a significant decrease in NP, M2 and NS1 viral protein expression, but also a reduction of both NP mRNA and viral RNA levels, as well as viral titers, 24 h post-infection with IAV, suggesting that actinin-4 was critical for viral replication. Furthermore, actinin-4 depletion reduced the amount of NP localized in the nucleus. Treatment of infected cells with wortmannin, a known inhibitor of actinin-4, led to a decrease in NP mRNA levels and also caused the nuclear retention of NP, further strengthening our previous observations. Taken together, the results of the present study indicate that actinin-4, a novel interacting partner of IAV NP, plays a crucial role in viral replication and this interaction may participate in nuclear localization of NP and/or viral ribonucleoproteins.