Proline-rich Akt substrate of 40-kDa contains a nuclear export signal

• Published in: Cellular signalling 2013-09, Vol.25 (9), p.1762-1768
• Main Authors: Wiza, Claudia, Nascimento, Emmani B.M., Linssen, Margot M.L., Carlotti, Françoise, Herzfeld de Wiza, Daniella, van der Zon, Gerard C.M., Maassen, J. Antonie, Diamant, Michaela, Guigas, Bruno, Ouwens, D. Margriet
• Format: Article
• Language: English
• Subjects: Activation; Adaptor Proteins, Signal Transducing - analysis; Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - metabolism; Akt; Animals; Cell Nucleus - metabolism; Cell- och molekylärbiologi; Control; Exports; Humans; Inhibitors; Insulin; Insulin - metabolism; Insulin action; International trade; Kinases; Medicin och hälsovetenskap; Medicinsk genetik; Medicinska och farmaceutiska grundvetenskaper; Membrane Proteins; Mice; Mutation; NIH 3T3 Cells; Nuclear export signal; Nuclear Export Signals; PRAS40; Proline - metabolism; Proteins; Proto-Oncogene Proteins c-akt - metabolism; Rats; Saccharomyces cerevisiae Proteins; Subcellular localization
• ISSN: 0898-6568; 1873-3913; 1873-3913
• DOI: 10.1016/j.cellsig.2013.05.022

The proline-rich Akt substrate of 40-kDa (PRAS40) has been linked to the regulation of the activity of the mammalian target of rapamycin complex 1 as well as insulin action. Despite these cytosolic functions, PRAS40 was originally identified as nuclear phosphoprotein in Hela cells. This study aimed to detail mechanisms and consequences of the nucleocytosolic trafficking of PRAS40. Sequence analysis identified a potential leucine-rich nuclear export signal (NES) within PRAS40. Incubation of A14 fibroblasts overexpressing human PRAS40 (hPRAS40) resulted in nuclear accumulation of the protein. Furthermore, mutation of the NES mimicked the effects of leptomycin B, a specific inhibitor of nuclear export, on the subcellular localization of hPRAS40. Finally, A14 cells expressing the NES-mutant showed impaired activation of components of the Akt-pathway as well as of the mTORC1 substrate p70 S6 kinase after insulin stimulation. This impaired insulin signaling could be ascribed to reduced protein levels of insulin receptor substrate 1 in cells expressing mutant NES. In conclusion, PRAS40 contains a functional nuclear export signal. Furthermore, enforced nuclear accumulation of PRAS40 impairs insulin action, thereby substantiating the function of this protein in the regulation of insulin sensitivity. [Display omitted] •PRAS40 contains a nuclear export signal.•Enforced nuclear accumulation of PRAS40 impairs insulin action.•PRAS40 regulates insulin action by affecting IRS1 protein levels.