TAK1 (or MAP3K7) was shown to participate in regulation of transcription by transforming growth factor beta (TGF beta). TAK1 is stimulated in response to TGF beta and bone morphogenetic protein. These results suggest that TAK1 functions as a mediator in the signaling pathway of TGF beta superfamily members. TAB1 and TAB2 are TAK1 binding proteins that may function as activators of the TAK1 (TGF b activated kinase 1) MAPKKK in TGF b signal transduction. TAB1 induced TAK1 activation promoted the dissociation of active forms of IKKa and IKK b from active TAK1, whereas the IKK mutants remained to interact with active TAK1. TNF a activated endogenous TAK1, and the kinase negative TAK1 acted as a dominant negative inhibitor against TNF a induced NFkB activation. TAK1 was suggested to act as a regulatory kinase of IKKs.
