Component of a protein kinase signal transduction cascade (PubMed:9808624). Activates the ERK and JNK kinase pathways by phosphorylation of MAP2K1 and MAP2K4 (PubMed:9808624). May phosphorylate the MAPK8/JNK1 kinase (PubMed:17761173). Activates CHUK and IKBKB, the central protein kinases of the NF-kappa-B pathway (PubMed:9808624). 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-1400 and Thr-1412 following oligomerization. Binds both upstream activators and downstream substrates in multimolecular complexes through its N-terminus (PubMed:9808624). Oligomerizes after binding MAP2K4 or TRAF2 (PubMed:9808624). Interacts with AXIN1 (PubMed:12223491, PubMed:15262978). Interacts (via the kinase catalytic domain) with STK38 (PubMed:17906693). Interacts with GRIPAP1 (PubMed:17761173). Autophosphorylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. MAP kinase kinase kinase subfamily.