Serine threonine-protein kinase involved in various processes such as neuronal proliferation, differentiation, migration and programmed cell death. Extracellular stimuli such as proinflammatory cytokines or physical stress stimulate the stress-activated protein kinase c-Jun N-terminal kinase (SAP JNK) signaling pathway. In this cascade, two dual specificity kinases MAP2K4 MKK4 and MAP2K7 MKK7 phosphorylate and activate MAPK1 JNK3. In turn, MAPK1 JNK3 phosphorylates a number of transcription factors, primarily components of AP-1 such as JUN and ATF2 and thus regulates AP-1 transcriptional activity. Plays regulatory roles in the signaling pathways during neuronal apoptosis. Phosphorylates the neuronal microtubule regulator STMN2. Acts in the regulation of the beta-amyloid precursor protein APP signaling during neuronal differentiation by phosphorylating APP. Participates also in neurite growth in spiral ganglion neurons.