p90RSK, also known as RSK1 or RPS6KA1 (ribosomal protein S6 kinase alpha-1), belongs to the serine/threonine kinase family. It is a widely expressed kinase that is involved in regulating various cellular activities such as cell growth, proliferation, and survival. As a downstream effector molecule in the mitogen-activated protein kinase (MAPK) pathway, p90RSK plays a crucial role.