JNK (c-Jun N-terminal Kinase) is part of the MAPK (Mitogen-Activated Protein Kinase) family, comprising three major isoforms: JNK1, JNK2, and JNK3. These kinases, activated by stress signals such as UV radiation, heat shock, and inflammatory factors, phosphorylate and activate specific transcription factors like c-Jun, thereby regulating cell survival, proliferation, differentiation, and death. JNK is widely expressed in various cells and tissues, with JNK1 and JNK2 being ubiquitously present in multiple tissues, while JNK3 is primarily expressed in the brain. The activation and function of JNK are finely regulated, and its aberrant activation is associated with various diseases such as cancer, neurodegenerative disorders, and inflammatory responses.