JNK (c-Jun N-terminal Kinase), also referred to as Stress Activated Protein Kinase (SAPK), is one of the main mitogen-activated protein kinases (MAPKs) in mammals. JNK is expressed as ten different isoforms due to differential mRNA splicing. The predominant forms are JNK1 and JNK2. JNK is activated by a variety of cellular signals including growth factors, inflammatory cytokines, and environmental stress. The JNK/SAPK signaling pathway involves sequential activation of MAPK kinase kinase (MEKK1), MAPK kinase 4 (MKK4) or MKK7, SAPK/JNK, and c-Jun. Full activation of JNK requires phosphorylation of a threonine and a tyrosine residue in the motif Thr-Pro-Tyr. MKK7 and MKK4 phosphorylate JNK at threonine 183 and tyrosine 185, respectively. The JNK pathway functions to modulate cell cycle, apoptotic and transcriptional responses to stress.
Alternate names: JNK-46, JNK-55, JNK1/JNK2, MAPK8, MAPK9, PRKM8, PRKM9, SAPK1, c-Jun N-terminal kinase 1, c-Jun N-terminal kinase 2