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This Article Full Text Full Text (PDF) All Versions of this Article: 291/5/E1031    most recent 00204.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Sakamoto, K. Articles by Goodyear, L. J. Search for Related Content PubMed PubMed Citation Articles by Sakamoto, K. Articles by Goodyear, L. J.

Role of Akt2 in contraction-stimulated cell signaling and glucose uptake in skeletal muscle

The Research Division, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts

Submitted 27 April 2006 ; accepted in final form 7 June 2006

The serine/threonine kinase Akt/PKB plays diverse roles in cells, and genetic studies have indicated distinct roles for the three Akt isoforms expressed in mammalian cells and tissues. Akt2 is a key signaling intermediate for insulin-stimulated glucose uptake and glycogen synthesis in skeletal muscle. Akt2 has also been shown to be activated by exercise and muscle contraction in both rodents and humans. In this study, we used Akt2 knockout mice to explore the role of Akt2 in exercise-stimulated glucose uptake and glycogen synthesis as well as intracellular signaling pathways that regulate glycogen metabolism in skeletal muscle. We found that Akt2 deficiency does not affect basal or exercise-stimulated glucose uptake or intracellular glycogen content in the soleus muscle. In addition, lack of Akt2 did not result in alterations in basal Akt Thr³⁰⁸ or basal and contraction-stimulated glycogen synthase kinase-3 (GSK-3) Ser⁹ phosphorylation, glycogen synthase phosphorylation, or glycogen synthase activity. In contrast, in situ contraction failed to elicit normal increases in Akt T-loop Thr³⁰⁸ phosphorylation and GSK-3 Ser²¹ phosphorylation in tibialis anterior muscles from Akt2-deficient animals. Our data establish a key role for Akt2 in the regulation of GSK-3 Ser²¹ phosphorylation with contraction and add genetic evidence to support the separation of the intracellular pathways regulated by insulin and exercise that converge on glucose uptake and glycogen synthesis in skeletal muscle.

exercise; glycogen; glycogen synthase kinase-3

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