RPS6KA4 encodes a member of the RSK (ribosomal S6 kinase) family of serine/threonine kinases. This kinase contains 2 non-identical kinase catalytic domains and phosphorylates various substrates, including CREB1 and c-fos. Alternate transcriptional splice variants of this gene have been observed but have not been thoroughly characterized. [provided by RefSeq].
p90 ribosomal S6 kinases (RSKs) are a family of protein serine/threonine kinases that regulate diverse
cellular processes such as cell growth, motility, survival and proliferation. There are four isoforms of
this enzyme; RSK1-4, which are directly activated by ERK1/2 in response to growth factors, many polypeptide hormones, neurotransmitters and chemokines. p90 RSKs phosphorylate numerous cytosolic and nuclear targets and act as downstream effectors of the ERK/MAPK signaling cascade. They are expressed ubiquitously in human tissues and exist in multiple subcellular compartments. Abberant activation of p90 RSKs has been linked to many human diseases, including breast and prostate cancers.