RSK3 also known as ribosomal protein S6 kinase alpha-2 is encoded by the RPS6KA2 gene. RSK3 is a member of the RSK (ribosomal S6 kinase) family of serine and threonine kinases and contains 2 non-identical kinase catalytic domains and phosphorylates various substrates, including members of the mitogen-activated kinase (MAPK) signalling pathway. The activity of this protein has been implicated in controlling cell growth and differentiation.