siRNA-mediated depletion of p23 in N2a cells affects APP metabolism. A and B, Lysates of N2a cells transfected with control non-specific (NS) or p23 siRNA were probed with antibodies specific for four p24 family members, three components of the γ-secretase, β-COP, and calnexin. Knockdown of p23 expression causes co-ordinate diminution the steady-state levels of p24, p25 and tp24. Also note the increased accumulation of immature and mature nicastrin in p23-depleted cells. C, Lysates of siRNA transfected N2aSwe cells were probed with antibodies specific for APP, calnexin, p115, and Grasp55. D, Secreted Aβ40 and Aβ42 in the media conditioned by N2aSwe were quantified using two-site ELISAs. The data represent mean ± SEM of three sets of transfections. * p < 0.05; ** p < 0.01. E, N2aSwe cells were labeled with [35S]met/cys for 15 min and APP FL were immunoprecipitated from cell lysates using Ab 369 (top); sAPP were immunoprecipitated using mAb P2-1 from media of cells labeled for 3 h (bottom).