Serine/threonine kinase which acts as a component of the MAP kinase signal transduction pathway (, ). Once activated, acts as an upstream activator of the p38 MAPK signal transduction cascade through the phosphorylation and activation of several MAP kinase kinases (, ). May function in a signal transduction pathway that is activated by various cell stresses and leads to apoptosis . Involved in phosphorylation of WNK4 in response to osmotic stress or hypotonic low-chloride stimulation via the p38 MAPK signal transduction cascade .
Isoform 2 and isoform 3 are widely expressed. Isoform 2 highest levels are observed in fetal brain, and isoform 3 highest levels in pancreas, peripheral blood leukocytes, fetal brain and spleen.