Importance of the MKK6/p38 pathway for interleukin-12-induced STAT4 serine phosphorylation and transcriptional activity

Blood. 2000 Sep 1;96(5):1844-52.

Abstract

Interleukin-12 (IL-12) is a key immunoregulatory cytokine that promotes Th1 differentiation and cell-mediated immune responses. The transcription factor STAT4 (signal transducer and activator of transcription 4) is an important element in mediating IL-12 signals, as evidenced by the fact that STAT4(-/-) mice display impaired responsiveness to IL-12 and deficient Th1 differentiation. STAT4 is inducibly phosphorylated on tyrosine and serine in response to IL-12, but the kinase(s) responsible for the latter event is unknown. Here we show that IL-12 induces STAT4 phosphorylation on serine 721 and that mutation of serine 721 interferes with STAT4 transcriptional activity. In addition, we show that mutation of tyrosine 693 abrogates IL-12-induced STAT4 tyrosine phosphorylation and transcriptional activity. Although the site surrounding serine 721 is an optimum consensus sequence for mitogen-activated family of protein kinases (MAPKs)-mediated phosphorylation, we demonstrate that IL-12 does not induce extracellular signal-regulated kinase (ERK) or c-Jun N-terminal kinase (JNK) activation in T and natural killer (NK) cells and that IL-12-induced STAT4 transcriptional activity is not affected by these kinases. Rather, we show that IL-12 induces p38 activation. Moreover, we demonstrate that p38alpha and its upstream activator, MKK6, phosphorylate STAT4 on serine 721, and are required for STAT4 full transcriptional activity induced by IL-12, establishing the MKK6/p38alpha/STAT4 pathway as an important mediator of IL-12 actions. (Blood. 2000;96:1844-1852)

MeSH terms

  • 3T3 Cells
  • Animals
  • Calcium-Calmodulin-Dependent Protein Kinases / genetics
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cell Line
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Humans
  • Interleukin-12 / pharmacology*
  • Isoenzymes / metabolism
  • JNK Mitogen-Activated Protein Kinases*
  • Jurkat Cells
  • MAP Kinase Kinase 4
  • MAP Kinase Kinase 6
  • Mice
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Mitogen-Activated Protein Kinases / genetics
  • Mitogen-Activated Protein Kinases / metabolism*
  • Mutation
  • Phosphorylation / drug effects
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • STAT4 Transcription Factor
  • Serine / genetics
  • Serine / metabolism*
  • Signal Transduction / drug effects
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Transcriptional Activation / drug effects
  • Transfection
  • Tyrosine / metabolism
  • p38 Mitogen-Activated Protein Kinases

Substances

  • DNA-Binding Proteins
  • Isoenzymes
  • Recombinant Fusion Proteins
  • STAT4 Transcription Factor
  • STAT4 protein, human
  • Stat4 protein, mouse
  • Trans-Activators
  • Interleukin-12
  • Tyrosine
  • Serine
  • Calcium-Calmodulin-Dependent Protein Kinases
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 4
  • MAP Kinase Kinase 6
  • MAP2K6 protein, human
  • Map2k6 protein, mouse
  • Mitogen-Activated Protein Kinase Kinases