Vol. 61, Issue 1, 177-185, January 2002

Evidence for Unique Calmodulin-Dependent Nuclear Factor-B Regulation in WEHI-231 B Cells

Stuart D. Shumway, Craig M. Berchtold, Michael N. Gould, and Shigeki Miyamoto

Program in Cellular and Molecular Biology, Department of Pharmacology (S.D.S., S.M), and McArdle Laboratory for Cancer Research (C.M.B., M.N.G.), University of Wisconsin, Madison, Wisconsin

Immature B cells express constitutive nuclear factor-B (NF-B) activity and inhibition of this activity is associated with the induction of apoptotic cell death. Previous studies have implicated a calcium-dependent proteolysis of the NF-B inhibitory protein IB as critical in the maintenance of constitutive NF-B activity in these cells. We tested whether modulation of diverse calcium-dependent processes affects the maintenance of constitutive NF-B activity in the WEHI-231 immature B cell line. Calmodulin inhibitors, but not calcineurin inhibition, blocked both IB turnover and the maintenance of constitutive NF-B activity. Inhibition of NF-B DNA binding activity by the calmodulin antagonist W13 also resulted in a loss of the expression of the NF-B target gene, IB. However, prolonged inhibition of NF-B activity for up to 8 h did not lead to apoptotic induction in the WEHI-231 cells. Moreover, removal of calmodulin inhibitors resulted in the reappearance of constitutive NF-B activity and the renewed expression of the IB gene. Thus, calmodulin activity is a requirement for the continual turnover of IB and the maintenance of constitutive NF-B function in WEHI-231 cells. In addition, our findings suggest that inhibition of NF-B activity does not lead to the immediate onset of apoptosis, indicating that prolonged inhibition of NF-B-dependent gene expression is required to cause apoptosis of WEHI-231 B cells.