Component of a protein kinase signal transduction cascade (PubMed:14500727). Activates the ERK and JNK kinase pathways by phosphorylation of MAP2K1 and MAP2K4 (PubMed:14500727). May phosphorylate the MAPK8/JNK1 kinase (PubMed:17761173). Activates CHUK and IKBKB, the central protein kinases of the NF-kappa-B pathway (PubMed:14500727). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by autophosphorylation on Thr-1381 and Thr-1393 following oligomerization. Binds both upstream activators and downstream substrates in multimolecular complexes through its N-terminus. Oligomerizes after binding MAP4K2 or TRAF2. Interacts with AXIN1. Interacts (via the kinase catalytic domain) with STK38 (By similarity). Interacts with GRIPAP1 (By similarity). Highly expressed in the heart and spleen while a lower level expression is seen in the liver. Autophosphorylated. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. MAP kinase kinase kinase subfamily.