Serine/threonine kinase that may play a role in the response to environmental stress and cytokines such as TNF-alpha. Appears to act upstream of the JUN N-terminal pathway. Phosphorylates SMAD1 on Thr-322.
The existence of an at least trimolecular complex consisting of nik, tak1, and ikk2, although the precise sequence of activation as well as the possible location of the kinases within the signalosome remains to be elucidated.