IκBα degradation and p52 production in P5 mutant. Graphs showing IκBα degradation (panel A) and p52 formation (panel B) after stimulation with CD40L of HEK-293 cells (HEK-293), a clone expressing control CD40 (HEK-C), and 3 clones showing decreasing expression of P5 mutant (HEK-P5 cl1, cl2, cl3). Stimulation induced IκBα degradation and p52 formation only in CD40 expressing cells depending on CD40 surface expression levels. The protein expression values were determined by densitometric analysis of immunoblots from 2 independent experiments and were expressed as percentages (means ± SD) of the values in nonstimulated cells (NS).