Bioscience, Biotechnology, and Biochemistry
Online ISSN : 1347-6947
Print ISSN : 0916-8451
Biochemistry & Molecular Biology Regular Papers
Hamartin-Hsp70 Interaction Is Necessary for Akt-Dependent Tuberin Phosphorylation during Heat Shock
Hirohumi INOUEMoussa NDONGTsukasa SUZUKIMachiko KAZAMITakumi UYAMAKen-Ichi KOBAYASHITadahiro TADOKOROYuji YAMAMOTO
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Supplementary material

2009 Volume 73 Issue 11 Pages 2488-2493

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Abstract

Hamartin and tuberin interact directly to regulate cell growth negatively. In this study, far-western blotting revealed that hamartin binds directly Heat shock protein 70 (Hsp70), even in the absence of tuberin. While the hamartin-tuberin complex acts as a sensor for a variety of types of stress, it is unclear how the complex is regulated under stress conditions. We found that the hamartin-Hsp70 interaction is stabilized during heat shock. On the other hand, tuberin underwent degradation through phosphorylation in an Akt-dependent manner. Furthermore, we found that when Hsp70 expression was inhibited by N-formyl-3,4-methylenedioxy-benzylidene-γ-butyrolactam (KNK437), Akt phosphorylation on site Ser308 diminished and tuberin was not phosphorylated at Thr1462 during heat shock. We conclude that both hamartin and Hsp70 increase in response to heat shock, whereas tuberin is phosphorylated and thereafter degraded via the PI3K/Akt pathway. Through this pathway, hamartin-Hsp70 plays a crucial role as a scaffolding protein that transfers the Akt signal to tuberin.

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© 2009 by Japan Society for Bioscience, Biotechnology, and Agrochemistry
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