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