Differential Regulation of c-Rel Translocation in Activated B and T Cells

c-Rel induction in activated lymphocytes is suppressed by the immunosuppressive drug, FK506. Here we show that FK506-suppressible, delayed c-Rel induction is similar in B and T cells and is regulated by mRNA production. In contrast, rapid nuclear translocation of pre-existing cytoplasmic c-Rel occurs only in B cells, but not in T cells. Analysis of 1-κBα and -β in these cells showed that both 1-κBα and I-κBβ were rapidly degraded in response to stimulation in B cells, but only 1-κBα was affected in T cells. These observations suggest that 1) different Rel proteins in the same cell may be sequestered in the cytoplasm differently, 2) the sequestration mechanism is cell-type specific, and 3) differential sensitivities of 1-κBα and β in B and T cells may regulate, in part, the rapid response of family members. We propose that subunit-specific and cell-specific regulation of nuclear translocation may help determine the varied cellular responses to different stimuli.