RPS6KA2 (RSK3) is a serine-threonine kinase that is part of the ribosomal S6 kinase family and the subfamily of insulin⁄mitogen-stimulated kinases. It is thought that RPS6KA2 is a signal-transducing intermediate in the cellular response to several growth factors. It is found in many tissues, but in higher levels in lung and skeletal muscle.