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Distinct mechanisms for the activation of the RSK kinases/MAP2 kinase/pp90rsk and pp70-S6 kinase signaling systems are indicated by inhibition of protein synthesis.

Authors
Type
Published Article
Journal
Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research
1044-9523
Publisher
Philadelphia, PA : The Association
Publication Date
Volume
2
Issue
6
Pages
279–285
Identifiers
PMID: 1648378
Source
Medline

Abstract

Previous studies demonstrated that addition of protein synthesis inhibitors to quiescent cells resulted in the stimulation of S6 kinase activity. The present characterization of several growth factor- and oncogene-regulated protein-serine/threonine kinases demonstrated that pp70-S6 protein kinase and not pp90rsk, RSK kinase, or MAP2 kinase activities were rapidly stimulated. Dose-response experiments revealed a close correlation between the extent of protein synthesis inhibition and the level of activation of pp70-S6 kinase activity. Analysis of S6 phosphorylation suggests that activation of pp90rsk S6 phosphotransferase activity, whose Xenopus homologues appear to be responsible for S6 phosphorylation during oocyte maturation, may participate in, but is not essential for, the increase in S6 phosphorylation observed in growth-stimulated somatic animal cells. These studies provide additional evidence for the existence of two distinct, independently regulated protein phosphorylation cascades activated in the early G1 phase of the cell cycle.

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