B cell antigen receptor signaling enhances IFN-gamma-induced Stat1 target gene expression through calcium mobilization and activation of multiple serine kinase pathways.
The signal transducers and activators of transcription 1 (Stat1) are essential for the majority of interferon-gamma (IFN-gamma)-regulated gene expression. Phosphorylation of serine 727 in the transcription activation domain of Stat1 is induced in response to IFN-gamma for maximal transcription activity. In this report, we show that crosslinking of B cell antigen receptor (BCR) or T cell antigen receptor (TCR) can enhance S727 phosphorylation in Stat1 and result in increased expression of Stat1 target genes. We further demonstrate that this enhancement by BCR cross-linking involves the widely used secondary messenger Ca2+ and simultaneous activation of multiple serine kinase pathways. When cells are exposed to both IFN-gamma and a Ca2+ fluxing reagent, the level of S727 phosphorylation is enhanced, resulting in increased transcription activation of Stat1 target genes. We directly demonstrate that the biochemical function of phospho-Ser-727 is to enhance the recruitment of transcription coactivator CBP/p300 to the promoters of Stat1 target genes. Furthermore, we show that both the p38 mitogen-activated protein kinase (MAPK) and the Ca(2+)/calmodulin-dependent kinase (CaMKII) are activated in response to BCR signaling to converge on Stat1 S727 for maximal gene expression. These studies demonstrate that a wide variety of noncytokine signaling pathways can modulate cytokine signaling through modulation of Stat1 serine phosphorylation.
Xu
Weifeng
W
Department of Pathology, Weill Medical College of Cornell University, New York, NY 10021, USA.
Nair
Jayasree S
JS
Malhotra
Ajay
A
Zhang
J Jillian
JJ
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology; D002118:Calcium / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D019169:Jurkat Cells; D051379:Mice; D008807:Mice, Inbred BALB C; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011946:Receptors, Antigen / Q000378:metabolism*; D050794:STAT1 Transcription Factor; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D004268:DNA-Binding Proteins; D011946:Receptors, Antigen; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; C494080:Stat1 protein, mouse; D015534:Trans-Activators; D012694:Serine; D007371:Interferon-gamma; D017346:Protein Serine-Threonine Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium