| IKKi The transcription factor NFiB is retained in the cytoplasm in an inactive form by the inhibitory protein IiB. Activation of NFiB requires that IiB be phosphorylated on specific serines residues, which results in targeted degradation of IiB. IiB kinase i (IKKi), previously designated CHUK, interacts with IiB-i and specifically phosphorylates IiB-i on the sites that trigger its degradation, serines 32 and 36. IKKi appears to be critical for NFiB activation in response to proinflammatory cytokines. Phosphorylation of IiB by IKKi is stimulated by the NFiB inducing kinase (NIK), which itself is a central regulator for NFiB activation in response to TNF and IL-1. The functional IKK complex contains three subunits, IKKi , IKKi and IKKi (also designated NEMO), and each appear to make essential contributions to IiB phosphorylation. |
