c-Jun N-terminal kinase (JNK) is a type of protein kinase that plays a crucial role in cellular signaling. It is part of the mitogen-activated protein kinase (MAPK) pathway, which helps cells respond to various stressors, such as inflammation and oxidative stress. JNK is involved in regulating processes like cell growth, differentiation, and apoptosis (programmed cell death). JNK is activated by various stimuli, including cytokines and environmental stress. Once activated, it phosphorylates specific target proteins, influencing gene expression and cellular responses. Dysregulation of JNK activity has been linked to several diseases, including cancer and neurodegenerative disorders, highlighting its importance in maintaining cellular health.