Background information
The transcription factor NFkB is retained in the cytoplasm in an inactive form by the inhibitory protein IkB. Activation of NFkB requires that IkB be phosphorylated on specific serine residues, which results in the targeted degradation of IkB (1). IkB kinase alpha (IKK alpha), previously designated CHUK (2), interacts with IkB-alpha and specifically phosphorylates IkB-alpha on the sites that trigger its degradation, serines 32 and 36 (3). IKKalpha appears to be critical for NFkB activation in response to proinflammatory cytokines (4). Phosphorylation of the IkB by IKK alpha is stimulated by the NFkB inducing kinase (NIK), which itself is a central regulator for NFkB activation in response to TNF and IL-1 (5). The functional IKK complex contains three subunits, IKK alpha, IKK beta and IKK gamma (also designated NEMO), and each appears to make essential contributions to IkB phosphorylation (6). IKAP (IKK-complex-associated protein) is a protein that acts as a scaffold, interacting with NIK, IKK alpha and IKK beta and assembling them into an active kinase complex (7,8)
