Identification of cAMP-Dependent Kinase as a Third in Vivo Ribosomal Protein S6 Kinase in Pancreatic β-Cells

Claire E.J. Moore, Jianling Xie, Edith Gomez, Terence P. Herbert

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Ribosomal protein S6 (rpS6) is phosphorylated in vivo by isoforms of p70 S6 protein kinase and p90 ribosomal S6 kinase, and there is good evidence that it plays a positive role in controlling pancreatic β-cell size and function. In this report, we demonstrate in the pancreatic β-cell line MIN6 (mouse insulinoma cell line 6) and islets of Langerhans that agents which stimulate increases in cAMP, such as glucagon-like peptide-1 and forskolin, lead to the phosphorylation of rpS6 at Ser235/Ser236 independently of the activation of the currently known in vivo rpS6 kinases via a pathway that is sensitive to inhibitors of cAMP-dependent protein kinase [protein kinase A (PKA)]. This cAMP-dependent rpS6 kinase activity is also sensitive to PKI in vitro, and PKA exclusively phosphorylates recombinant rpS6 on Ser235/Ser236 in vitro. With these data taken together, we conclude that PKA can phosphorylate rpS6 exclusively at Ser235/Ser236 in vivo in pancreatic β-cells, thus providing a potentially important link between cAMP signalling and the regulation of protein synthesis. Lastly, we provide evidence that PKA is also likely to phosphorylate rpS6 on Ser235/Ser236 in vivo in a number of other mammalian cell types.

LanguageEnglish
Pages480-494
Number of pages15
JournalJournal of Molecular Biology
Volume389
Issue number3
DOIs
Publication statusPublished - 12 Jun 2009

Keywords

  • GLP1
  • PKA
  • S6K
  • mTORC1
  • rpS6

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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