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. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Moderately inhibited by staurosporine, a broad-range protein kinase inhibitor. Self-associates. Interacts with MAP2K3 and MAP2K6. 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. Found to be perinuclear and localized to vesicular compartment. In dendrites, colocalizes with PCDH8. Autophosphorylated. Phosphorylated by ATM (By similarity). Phosphorylated on Ser-1038 by MAPK14. This phosphorylation is required PCDH8 for endocytosis. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. STE20 subfamily.