I-κB kinase (IKK-β) induces Hes1 expression, modulates dendritic morphology and neuronal survival, and it counteracts amyloid beta (Aβ) activity. (A) The efficiency of transfecting 7 days in vitro (DIV) cultured neurons (300,000 cells) with a vector expressing Flag-tagged IKKβ was 20-25%. After 16 h, the cells were lysed and Hes1 expression was quantified by real time PCR, and transfection of IKKβ increased Hes-1 mRNA levels by 35%. (B) Hippocampal neurons were cultured for 7 DIV (40,000 cells/cm2), treated with Aβ (5 μM), and/or co-transfected with enhanced fluorescent green protein (EGFP) and FLAG-tagged IKK-β for 16 h. Transfection with IKKβ increased the length (left panel) but decreased the number (right panel) of primary dendrites, and blocked the effect of Aβ on dendrite morphology. (C) 7 DIV hippocampal neurons (30,000 cells/cm2) were cultured for 7 days and then treated with Aβ (5 μM). Two days later, the neurons were co-transfected with EGFP, FLAG-tagged IKKβ and/or HA-tagged IKKα and the number of live cells was determined on the following day. IKKβ transfection rescued about 50% of neurons from Aβ-induced death (left panel), whereas this rescue was more modest when neurons were transfected with IKKα rather than IKKβ (right panel). *P < 0.05, **P < 0.01, and ***P < 0.001.