Counter-regulation mechanism of IL-4 and IFN-α signal transduction through cytosolic retention of the pY-STAT6:pY-STAT2:p48 complex.
IFN-α and IL-4 induce Th1 and Th2 responses, respectively, and often display antagonistic actions against each other. To elucidate the molecular mechanism of counter-regulation, we have investigated the signal interception by IFN-α and IL-4, employing a human B-cell line Ramos, sensitive to both cytokines. In these cells, IFN-α effectively inhibited IL-4-induced Fc epsilon receptor II (CD23) expression, whereas IL-4 suppressed IFN-α-mediated IRF7 expression. The counter-regulatory action by IL-4 and IFN-α proceeded with a delayed kinetics requiring 4 h. Notably, IFN-α did not affect the IL-4-induced tyrosine phosphorylation of STAT6, but induced a time-dependent cytoplasmic accumulation of phosphotyrosine(pY)-STAT6 and a corresponding decrease in nuclear pY-STAT6. By confocal analysis and co-immunoprecipitation assays, we demonstrated the colocalization and molecular interaction of IL-4-induced pY-STAT6 with IFN-α-induced pY-STAT2:p48 in the cytosol. In addition, the over-expression of STAT2 or STAT6 induced the concomitant cytosolic accumulation of pY-STAT6 or pY-STAT2, leading to the suppression of IL-4-induced CD23 or IFN-α-induced IRF7 gene expression, respectively. Our data suggest that the signals ensued by IFN-α and IL-4 induce cytoplasmic sequestration of IL-4-activated STAT6 and IFN-α-activated STAT2:p48 in B cells through the formation of pY-STAT6:pY-STAT2:p48 complex, which provides a novel mechanism by which IFN-α and IL-4 cross-regulate their signaling into the nucleus.
Laboratory of Immunology, Department of Biological Science, Sungkyunkwan University, Suwon, Korea.
Seol-Hee
SH
Kim
Choong-Eun
CE
Lee
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D003600:Cytosol / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit / Q000235:genetics / Q000378:metabolism*; D016898:Interferon-alpha / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology*; D007700:Kinetics; D046912:Multiprotein Complexes / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000502:physiology; D017455:Receptors, IgE / Q000235:genetics / Q000378:metabolism; D050795:STAT2 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D050800:STAT6 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism
C508598:IL4 protein, human; C494227:IRF9 protein, human; D050834:Interferon-Stimulated Gene Factor 3, gamma Subunit; D016898:Interferon-alpha; D046912:Multiprotein Complexes; D017455:Receptors, IgE; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D015847:Interleukin-4; D014443:Tyrosine; D007371:Interferon-gamma