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|Title:||Identification of cAMP-Dependent Kinase as a Third in Vivo Ribosomal Protein S6 Kinase in Pancreatic β-Cells|
|Authors:||Moore, Claire E. J.|
Herbert, Terence P.
|Citation:||Journal of Molecular Biology, 2009, 389 (3), pp. 480-494|
|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.|
|Rights:||This is the author’s final draft of the paper published as Journal of Molecular Biology, 2009, 389 (3), pp. 480-494. The final published version is available at http://www.sciencedirect.com/science/journal/00222836, Doi: 10.1016/j.jmb.2009.04.020|
|Appears in Collections:||Published Articles, Dept. of Cell Physiology and Pharmacology|
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