Stress-induced phosphorylation of STAT1 at Ser727 requires p38 mitogen-activated protein kinase whereas IFN-gamma uses a different signaling pathway

P Kovarik, D Stoiber, P A Eyers, R Menghini, A Neininger, M Gaestel, P Cohen, T Decker

Research output: Journal article (peer-reviewed)Journal article

235 Citations (Scopus)

Abstract

STAT1 is an essential transcription factor for macrophage activation by IFN-gamma and requires phosphorylation of the C-terminal Ser727 for transcriptional activity. In macrophages, Ser727 phosphorylation in response to bacterial lipopolysaccharide (LPS), UV irradiation, or TNF-alpha occurred through a signaling path sensitive to the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580 whereas IFN-gamma-mediated Ser727 phosphorylation was not inhibited by the drug. Consistently, SB203580 did not affect IFN-gamma-mediated, Stat1-dependent transcription but inhibited its enhancement by LPS. Furthermore, LPS, UV irradiation, and TNF-alpha caused activation of p38 MAPK whereas IFN-gamma did not. An essential role for p38 MAPK activity in STAT1 Ser727 phosphorylation was confirmed by using cells expressing an SB203580-resistant p38 MAPK. In such cells, STAT1 Ser727 phosphorylation in response to UV irradiation was found to be SB203580 insensitive. Targeted disruption of the mapkap-k2 gene, encoding a kinase downstream of p38 MAPK with a key role in LPS-stimulated TNF-alpha production and stress-induced heat shock protein 25 phosphorylation, was without a significant effect on UV-mediated Ser727 phosphorylation. The recombinant Stat1 C terminus was phosphorylated in vitro by p38MAPKalpha and beta but not by MAPK-activated protein kinase 2. Janus kinase 2 activity, previously reported to be required for IFN-gamma-mediated Ser727 phosphorylation, was not needed for LPS-mediated Ser727 phosphorylation, and activation of Janus kinase 2 did not cause the appearance of STAT1 Ser727 kinase activity. Our data suggest that STAT1 is phosphorylated at Ser727 by a stress-activated signaling pathway either through p38 MAPK directly or through an unidentified kinase downstream of p38MAPK.

Original languageEnglish
Pages (from-to)13956-61
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume96
Issue number24
DOIs
Publication statusPublished - 23 Nov 1999
Externally publishedYes

Keywords

  • Animals
  • Cell Line
  • Cell Line, Transformed
  • DNA-Binding Proteins/metabolism
  • Enzyme Activation
  • Enzyme Inhibitors/pharmacology
  • Humans
  • Imidazoles/pharmacology
  • Interferon-gamma/metabolism
  • Intracellular Signaling Peptides and Proteins
  • Janus Kinase 2
  • Lipopolysaccharides/pharmacology
  • MAP Kinase Signaling System
  • Macrophages/cytology
  • Mitogen-Activated Protein Kinases/metabolism
  • Phosphorylation
  • Protein Serine-Threonine Kinases/metabolism
  • Protein-Tyrosine Kinases/metabolism
  • Proto-Oncogene Proteins
  • Pyridines/pharmacology
  • Rabbits
  • Recombinant Fusion Proteins/metabolism
  • STAT1 Transcription Factor
  • Serine/metabolism
  • Trans-Activators/metabolism
  • Transcription, Genetic/drug effects
  • Tumor Necrosis Factor-alpha/immunology
  • Ultraviolet Rays
  • p38 Mitogen-Activated Protein Kinases

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