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Int J Biol Sci 2010; 6(6):599-612. doi:10.7150/ijbs.6.599

Research Paper

Aberrant Cytoplasm Localization and Protein Stability of SIRT1 is Regulated by PI3K/IGF-1R Signaling in Human Cancer Cells

Vanessa Byles, Laura K. Chmilewski, Joyce Wang, Lijia Zhu, Lora W. Forman, Douglas V. Faller, Yan Dai

Cancer Research Center and Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA.


SIRT1, an NAD-dependent histone/protein deacetylase, has classically been thought of as a nuclear protein. In this study, we demonstrate that SIRT1 is mainly localized in the nucleus of normal cells, but is predominantly localized in the cytoplasm of the cancer / transformed cells we tested. We found this predominant cytoplasmic localization of SIRT1 is regulated by elevated mitotic activity and PI3K/IGF-1R signaling in cancer cells. We show that aberrant cytoplasmic localization of SIRT1 is due to increased protein stability and is regulated by PI3K/IGF-1R signaling. In addition, we determined that SIRT1 is required for PI3K-mediated cancer cell growth. Our study represents the first identification that aberrant cytoplasm localization is one of the specific alternations to SIRT1 that occur in cancer cells, and PI3K/IGF-1R signaling plays an important role in the regulation of cytoplasmic SIRT1 stability. Our findings suggest that the over-expressed cytoplasmic SIRT1 in cancer cells may greatly contribute to its cancer-specific function by working downstream of the PI3K/IGF-1R signaling pathway.

Keywords: SIRT1, cytoplasm localization, protein stability, cancer cells, PI3K/IGF-1R

This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) License. See for full terms and conditions.
How to cite this article:
Byles V, Chmilewski LK, Wang J, Zhu L, Forman LW, Faller DV, Dai Y. Aberrant Cytoplasm Localization and Protein Stability of SIRT1 is Regulated by PI3K/IGF-1R Signaling in Human Cancer Cells. Int J Biol Sci 2010; 6(6):599-612. doi:10.7150/ijbs.6.599. Available from