Extracellular Signal-Regulated Kinase (ERK) is a protein kinase 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 is activated by various growth factors and hormones. Once activated, ERK influences several cellular processes, including growth, differentiation, and survival. ERK is typically activated through a cascade involving Ras, a small GTPase, and MEK, another kinase. This activation leads to the phosphorylation of target proteins, which can alter gene expression and cellular behavior. Dysregulation of ERK signaling is associated with various diseases, including cancer.