Ribosomal s6 kinase

In molecular biology, ribosomal s6 kinase (rsk) is a family of protein kinases involved in signal transduction. There are two subfamilies of rsk, p90^rsk, also known as MAPK-activated protein kinase-1 (MAPKAP-K1), and p70^rsk, also known as S6-H1 Kinase or simply S6 Kinase. There are three variants of p90^rsk in humans, rsk 1-3. Rsks are serine/threonine kinases and are activated by the MAPK/ERK pathway. There are two known mammalian homologues of S6 Kinase: S6K1 and S6K2.

ubstrates

Rsk is named for ribosomal protein s6, part of the mechanism of translation, but several other substrates have been identified, including other ribosomal proteins. Cytosolic substrates of p90^rsk include protein phosphatase 1; glycogen synthase kinase 3 (GSK3); L1 CAM, a neural cell adhesion molecule; Son of Sevenless, the Ras exchance factor; and Myt1, an inhibitor of cdc2.Morten Frödin and Steen Gammeltoft. 1999. Role and regulation of 90 kDa ribosomal S6 kinase (RSK) in signal transduction. "Molecular and Cellular Endocrinology" 151(1-2):Pages 65-77 (PMID 10411321 doi|10.1016/S0303-7207(99)00061-1 DOI)]

p90^rsk also regulates transcription factors including cAMP response element-binding protein (CREB); estrogen receptor-α (ERα); IκBα/NFκB; and c-Fos.

Genomics

p90 Rsk-1 is located at 1p. [ [http://www.ncbi.nlm.nih.gov/entrez/viewer.fcgi?val=NC_000001.9&from=26728836&to=26774107&dopt=gb GenBank] , [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=gene&cmd=Retrieve&dopt=full_report&list_uids=6195 Entrez Gene] ]

p90 Rsk-2 is located at Xp22.2 and contains 22 exons. Mutations in this gene have been associated with Coffin-Lowry syndrome, a disease characterised by severe psychomotor retardation and other developmental abnormalities. [OMIM|300075]

p90 Rsk-3 is located at 6q27. [Y Zhao, C Bjørbaek, S Weremowicz, C C Morton, and D E Moller. 1993. RSK3 encodes a novel pp90rsk isoform with a unique N-terminal sequence: growth factor-stimulated kinase function and nuclear translocation. Mol Cell Biol. 15(8):4353–4363.]

Proteomics

The main distinguishing feature between p90^rsk and p70^rsk is that the 90 kDa family contain two non-identical kinase domains, while the 70 kDa family contain only one kinase domain.

Research history

Rsk was first identified in "Xenopus laevis" eggs by Erikson and Maller in 1985. [Eleanor Erikson and James L. Maller. 1985. A Protein Kinase from Xenopus Eggs Specific for Ribosomal Protein S6. "PNAS" 82(3):742-746]

References

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