Component of a protein kinase signal transduction cascade. Regulates the JNK and ERK5 pathways by phosphorylating and activating MAP2K5 and MAP2K7 (By similarity). Plays a role in caveolae kiss-and-run dynamics. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by phosphorylation on Thr-524. Interacts with PKN2; the interaction activates PKN2 kinase activity in a MAP3K2-independent kinase activity (By similarity). Self-associates. Binds both upstream activators and downstream substrates in multimolecular complexes. Interacts (via the kinase catalytic domain) with STK38. Interacts with XIAP/BIRC4. Upon EGF stimulation, translocates into the nucleus. Autophosphorylated. Ubiquitination by XIAP/BIRC4 does not lead to proteasomal degradation. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. MAP kinase kinase kinase subfamily.