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Protein kinase B beta/Akt2 plays a specific role in muscle differentiation

Item Type:Article
Title:Protein kinase B beta/Akt2 plays a specific role in muscle differentiation
Creators Name:Vandromme, M. and Rochat, A. and Meier, R. and Carnac, G. and Besser, D. and Hemmings, B.A. and Fernandez, A. and Lamb, N.J.
Abstract:Insulin-like growth factors positively regulate muscle differentiation through activation of the phosphatidylinositol 3-kinase/protein kinase B (PKB/Akt) signaling pathway. Here, we compare the role of the two closely related alpha (Akt1) and beta (Akt2) isoforms of PKB in muscle differentiation. During differentiation of C2.7 or L6D2 myoblasts, PKBbeta was up-regulated whereas expression of PKBalpha was unaltered. Although the two isoforms were found active in both myoblasts and myotubes, cell fractionation experiments indicated that they displayed distinct subcellular localizations in differentiated cells with only PKBbeta localized in the nuclei. In a transactivation assay, PKBbeta (either wild-type or constitutively active) was more efficient than PKBalpha in activating muscle-specific gene expression. Moreover, microinjection of specific antibodies to PKBbeta inhibited differentiation of muscle cells, whereas control or anti-PKBalpha antibodies did not. On the other hand, microinjection of the anti-PKBalpha antibodies caused a block in cell cycle progression in both non muscle and muscle cells, whereas anti-PKBbeta antibodies had no effect. Taken together, these results show that PKBbeta plays a crucial role in the commitment of myoblasts to differentiation that cannot be substituted by PKBalpha.
Keywords:Cell Differentiation, Enzymologic Gene Expression Regulation, Microinjections, Muscles, Protein-Serine-Threonine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-akt, Transcriptional Activation
Source:Journal of Biological Chemistry
ISSN:0021-9258
Publisher:American Society for Biochemistry and Molecular Biology (U.S.A.)
Volume:276
Number:11
Page Range:8173-8179
Date:16 March 2001
Official Publication:https://doi.org/10.1074/jbc.M005587200
PubMed:View item in PubMed

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