RPS6KA3 protein S6 kinase, 90kDa, polypeptide 3, also s RPS6KA3, is an enzyme that in humans is encoded by the RPS6KA3 gene.FunctionThis gene encodes a member of the RSK family of serine/threonine kinases. This kinase contains 2 non-identical kinase catalytic domains and phosphorylates various substrates, including members of the mitogen-activated kinase signalling pathway. The activity of this protein has been implicated in controlling cell growth and differentiation.Clinical significanceMutations in this gene have been associated with Coffin–Lowry syndrome.InteractionsRPS6KA3 has been shown to interact with CREB-binding protein, MAPK1 and PEA15.