RPS6KA3 (Ribosomal Protein S6 Kinase A3), also known as RSK2, is a serine/threonine kinase involved in cell growth, proliferation, and survival. It is activated by the MAPK/ERK signaling pathway and phosphorylates various substrates, including ribosomal protein S6, CREB, and histone H3. Mutations in RPS6KA3 are associated with Coffin-Lowry Syndrome, a rare X-linked intellectual disability disorder characterized by skeletal abnormalities, hearing loss, and developmental delays. Its role in diverse cellular processes makes it a subject of ongoing research in cancer and neurological disorders.