Analysis of the life cycle of stat6. Continuous cycling of STAT6 is required for IL-4 signaling.
Signal transducer and activator of transcription (Stat)6 is a transcription factor important for the development of Th2 cells and regulation of gene expression by IL-4 and IL-13. It is known that Stat6 is rapidly activated in response to IL-4; however, the fate of activated Stat6 is less clear. We examined the fate of activated Stat6 and found that during continuous exposure to IL-4, Stat6 activity was sustained for 72 h and that the maintenance of a constant level of activated Stat6 did not require new protein synthesis. In contrast, when cells were pulsed with IL-4 and then incubated in the absence of IL-4, the half-life of Stat6 phosphorylation and DNA binding activity was less than 1 h. Stat6 did not accumulate in the nucleus, and protein degradation did not play a major role in the disappearance of activated Stat6. Inhibition of kinase activity by staurosporine or the JAK inhibitor, AG490, revealed that maintenance of Stat6 activation in the continuous presence of IL-4 required ongoing phosphorylation of latent cytoplasmic Stat6 molecules. Cells treated with an inhibitor of nuclear export, leptomycin B, were unable to maintain Stat6 activation. Thus, the maintenance of Stat6 activation requires a constant cycle of activation, deactivation, nuclear export, and reactivation.
Division of Allergy and Immunology, Department of Pediatrics, Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
Ryan P
RP
Andrews
Mark B
MB
Ericksen
Christie M
CM
Cunningham
Michael O
MO
Daines
Gurjit K Khurana
GK
Hershey
D021581:Active Transport, Cell Nucleus; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004789:Enzyme Activation; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005434:Flow Cytometry; D015151:Immunoblotting; D018793:Interleukin-13 / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D050800:STAT6 Transcription Factor; D015398:Signal Transduction; D018418:Th2 Cells / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D015854:Up-Regulation
D000903:Antibiotics, Antineoplastic; D005231:Fatty Acids, Unsaturated; D018793:Interleukin-13; D050800:STAT6 Transcription Factor; C494100:Stat6 protein, mouse; D015534:Trans-Activators; D015847:Interleukin-4; D014443:Tyrosine; D004247:DNA; C038753:leptomycin B