JNK1(MAPK8) is a member of the MAP kinase family. JNK1 is activated by threonine and tyrosine phosphorylation by either of two dual specificity kinases, MAP2K4 and MAP2K7.

JNK2 (p54a, SAPK1a), along with JNK1 and JNK3, is thought to play an important role in nuclear signal transduction through its environmental stress activation and subsequent phosphorylation of the nuclear transcription factor p53.

JNK3 is a neuron-specific form of c-Jun N-terminal kinases. Through its phosphorylation and nuclear localization, this kinase plays regulatory roles in the signaling pathways of neuronal apoptosis.

The JNK pathway is critically involved in diabetes and levels are abnormally elevated in obesity.