Importance of the MKK6/p38 pathway for interleukin-12-induced STAT4 serine phosphorylation and transcriptional activity.
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)
Visconti
R
R
Lymphocyte Cell Biology Section, Arthritis and Rheumatism Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892-1820, USA. viscontr@exchange.nih.gov
Gadina
M
M
Chiariello
M
M
Chen
E H
EH
Stancato
L F
LF
Gutkind
J S
JS
O'Shea
J J
JJ
D016475:3T3 Cells; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018664:Interleukin-12 / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D048670:MAP Kinase Kinase 4; D048669:MAP Kinase Kinase 6; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050797:STAT4 Transcription Factor; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D004268:DNA-Binding Proteins; D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D050797:STAT4 Transcription Factor; C494090:STAT4 protein, human; C494091:Stat4 protein, mouse; D015534:Trans-Activators; D018664:Interleukin-12; D014443:Tyrosine; D012694:Serine; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D048669:MAP Kinase Kinase 6; C482566:MAP2K6 protein, human; C482567:Map2k6 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases