Association of the interleukin-4 receptor α chain with p47(phox), an activator of the phagocyte NADPH oxidase in B cells

Interleukin (IL)-4 plays an important role in IgE synthesis in B cells and in Th2 differentiation in T cells, IL-4 conducts its biological activities through binding to the IL-4 receptor (IL-4R) on the surface of target cells. IL-4R are thought to be composed of the IL-4R α chain (IL- 4Rα) and either the IL-2R γ chain or the IL-13R α chain. We have previously shown that the membrane-proximal portion in the cytoplasmic domain of the human IL-4Rα (hIL-4Rα) is critical for proliferation, generation of germline ε transcript, and activation of STAT6, based on analyses of truncated hIL-4Rαs. In this study, we found that p47p(phox), an activator of the phagocyte NADPH oxidase, binds to this portion by the two-hybrid system. Furthermore, we observed the association of p47(phox) with the hIL-4Rα in B cells derived from a normal donor. These results suggest that p47(phox) is involved in the signal transduction of IL-4 in B cells. However, activation of STAT6, CD23 expression, and IgE synthesis induced by IL-4 were not affected in p47(phox)-deficient patients, which raises the possibility that p47(phox) may be important in other signaling activities as well in B cells.