ABSTRACT
DExD/H box RNA helicases, such as the RIG-I-like receptors (RLR), are important components of the innate immune system. Here we demonstrate a pivotal and sex-specific role for the heterosomal isoforms of the DEAD box RNA helicase DDX3 in the immune system. Mice lacking DDX3X during hematopoiesis showed an altered leukocyte composition in bone marrow and spleen and a striking inability to combat infection with Listeria monocytogenes. Alterations in innate immune responses resulted from decreased effector cell availability and function as well as a sex-dependent impairment of cytokine synthesis. Thus, our data provide further in vivo evidence for an essential contribution of a non-RLR DExD/H RNA helicase to innate immunity and suggest it may contribute to sex-related differences in resistance to microbes and resilience to inflammatory disease.
Subject(s)
Listeriosis/immunology , RNA Helicases/immunology , Animals , DEAD-box RNA Helicases/metabolism , Disease Resistance/immunology , Female , Fibroblasts/immunology , Fibroblasts/pathology , HEK293 Cells , Hematopoiesis/immunology , Humans , Immunity, Innate , Killer Cells, Natural/immunology , Listeria monocytogenes/immunology , Listeriosis/pathology , Lymphocytes/immunology , Male , Mice , Mice, Knockout , NF-kappa B/immunology , RNA Helicases/deficiency , RNA Helicases/genetics , Sex Factors , Signal TransductionABSTRACT
Signal transducer and activator of transcription 1 (STAT1) plays a pivotal role in the innate immune system by directing the transcriptional response to interferons (IFNs). STAT1 is activated by Janus kinase (JAK)-mediated phosphorylation of Y701. To determine whether STAT1 contributes to cellular responses without this phosphorylation event, we generated mice with Y701 mutated to a phenylalanine (Stat1(Y701F)). We show that heterozygous mice do not exhibit a dominant-negative phenotype. Homozygous Stat1(Y701F) mice show a profound reduction in Stat1 expression, highlighting an important role for basal IFN-dependent signaling. The rapid transcriptional response to type I IFN (IFN-I) and type II IFN (IFNγ) was absent in Stat1(Y701F) cells. Intriguingly, STAT1Y701F suppresses the delayed expression of IFN-I-stimulated genes (ISG) observed in Stat1(-/-) cells, mediated by the STAT2/IRF9 complex. Thus, Stat1(Y701F) macrophages are more susceptible to Legionella pneumophila infection than Stat1(-/-) macrophages. Listeria monocytogenes grew less robustly in Stat1(Y701F) macrophages and mice compared to Stat1(-/-) counterparts, but STAT1Y701F is not sufficient to rescue the animals. Our studies are consistent with a potential contribution of Y701-unphosphorylated STAT1 to innate antibacterial immunity.
