Extracellular signal-regulated kinase (ERK) is a protein that plays a crucial role in transmitting signals from the cell surface to the nucleus. It is part of the mitogen-activated protein kinase (MAPK) pathway, which helps regulate various cellular processes, including growth, differentiation, and survival. ERK is activated by various external signals, such as growth factors, and helps cells respond appropriately to their environment. Once activated, ERK moves into the nucleus, where it can influence gene expression by phosphorylating specific transcription factors. This process is essential for many physiological functions, including development and tissue repair. Dysregulation of ERK signaling is associated with several diseases, including cancer.