NF-κB/Rel Participation in the Lymphokine-Dependent Proliferation of T Lymphoid Cells

Abstract

Proliferative responses of lymphoid cells to IL-2 and IL-4 depend on activation of the cells, but the mechanism(s) by which activation enhances cellular competence to respond to cytokines is not fully understood. The NF-κB/Rel family represents one signal transduction pathway induced during such activation. We show in this study that inhibition of NF-κB through the expression of an IκBα (inhibitory protein that dissociates from NF-κB) mutant refractory to signal-induced degradation (IκBα(ΔN)) interfered with the acquisition of competence to proliferate in response to IL-4 as well as IL-2. Thymocytes and T cells from IκBα(ΔN) transgenic mice expressed normal levels of IL-2R subunits. However, transgenic cells exhibited a dramatic defect in Stat5A activation treatment with IL-2, and a similar defect was observed for IL-4-induced Stat5. In contrast, T lymphoid cells with inhibition of NF-κB showed normal insulin receptor substrate-2 phosphorylation and only a modest decrease in Stat6 activation and insulin receptor substrate-1 phosphorylation after IL-4 stimulation. These results indicate that the NF-κB/Rel/IκBα system can regulate cytokine receptor capacitation through effects on the induction of downstream signaling by the Stat transcription factor family.