Serine/threonine-protein kinase involved in different processes such as membrane blebbing and apoptotic bodies formation DNA damage response and MAPK14/p38 MAPK stress-activated MAPK cascade. Phosphorylates itself, MBP, activated MAPK8, MAP2K3, MAP2K6 and tubulins. Activates the MAPK14/p38 MAPK signaling pathway through the specific activation and phosphorylation of the upstream MAP2K3 and MAP2K6 kinases. In response to DNA damage, involved in the G2/M transition DNA damage checkpoint by activating the p38/MAPK14 stress-activated MAPK cascade, probably by mediating phosphorylation of upstream MAP2K3 and MAP2K6 kinases. May affect microtubule organization and stability. May play a role in the osmotic stress-MAPK8 pathway. Prevents MAP3K7-mediated activation of CHUK, and thus NF-kappa-B activation. Isoform 2, but not isoform 1, is required for PCDH8 endocytosis. Following homophilic interactions between PCDH8 extracellular domains, isoform 2 phosphorylates and activates MAPK14/p38 MAPK which in turn phosphorylates isoform 2. This process leads to PCDH8 endocytosis and CDH2 cointernalization. Both isoforms are involved in MAPK14/p38 MAPK activation (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with MAP2K3 and MAP2K6 (By similarity). Self-associates. Interacts with tubulins. Interacts with MAP3K7 and interfers with MAP3K7-binding to CHUK and thus prevents NF-kappa-B activation (By similarity). Isoform 2 interacts with PCDH8; this complex may also include CDH2 (By similarity). Found to be perinuclear and localized to vesicular compartment. In dendrites, colocalizes with PCDH8. Autophosphorylated. Phosphorylated by ATM (By similarity). Phosphorylated on Ser-1037 by MAPK14. This phosphorylation is required PCDH8 for endocytosis (By similarity). Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. STE20 subfamily. Contaminating sequence. Sequence of unknown origin in the N- and C-terminal parts. Extended N-terminus.