Response to interferons and antibacterial innate immunity in the absence of tyrosine-phosphorylated STAT1

Andrea Majoros, Ekaterini Platanitis, Daniel Szappanos, Hyeonjoo Cheon, Claus Vogl, Priyank Shukla, George R. Stark, Veronika Sexl, Robert Schreiber, Christian Schindler, Mathias Müller, Thomas Decker

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

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 (Stat1Y701F). We show that heterozygous mice do not exhibit a dominant-negative phenotype. Homozygous Stat1Y701F 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 Stat1Y701F cells. Intriguingly, STAT1Y701F suppresses the delayed expression of IFN-I-stimulated genes (ISG) observed in Stat1-/- cells, mediated by the STAT2/IRF9 complex. Thus, Stat1Y701F macrophages are more susceptible to Legionella pneumophila infection than Stat1-/- macrophages. Listeria monocytogenes grew less robustly in Stat1Y701F 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. Synopsis This study shows that cells and mice expressing an unphosphorylated STAT1Y701F mutant are immunodeficient, but phenotypically distinguishable from Stat1-/- animals. STAT1Y701F expression alters innate immunity to the bacterial pathogens Listeria monocytogenes and Legionella pneumophila. High levels of cellular STAT1 protein require STAT1 tyrosine phosphorylation-dependent tonic signaling (A). Heterozygosity of the Stat1Y701F mutation reduces STAT1 protein expression and interferon-induced tyrosine phosphorylation of the WT allele. STAT1Y701F inhibits nuclear translocation of STAT2 and reduces interferon-induced transcription through STAT2/IRF9 complexes (B). This study shows that cells and mice expressing an unphosphorylated STAT1Y701F mutant are immunodeficient, but phenotypically distinguishable from Stat1-/- animals.

Original languageEnglish
Pages (from-to)367-382
Number of pages16
JournalEMBO Reports
Volume17
Issue number3
DOIs
StatePublished - Mar 1 2016

Keywords

  • STAT1
  • innate immunity
  • interferon
  • pathogen
  • phosphorylation

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