Extensive Crosstalk between O-GlcNAcylation and Phosphorylation Regulates Akt Signaling

Division of Antitumor Pharmacology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
PLoS ONE (Impact Factor: 3.23). 05/2012; 7(5):e37427. DOI: 10.1371/journal.pone.0037427
Source: PubMed


O-linked N-acetylglucosamine glycosylations (O-GlcNAc) and O-linked phosphorylations (O-phosphate), as two important types of post-translational modifications, often occur on the same protein and bear a reciprocal relationship. In addition to the well documented phosphorylations that control Akt activity, Akt also undergoes O-GlcNAcylation, but the interplay between these two modifications and the biological significance remain unclear, largely due to the technique challenges. Here, we applied a two-step analytic approach composed of the O-GlcNAc immunoenrichment and subsequent O-phosphate immunodetection. Such an easy method enabled us to visualize endogenous glycosylated and phosphorylated Akt subpopulations in parallel and observed the inhibitory effect of Akt O-GlcNAcylations on its phosphorylation. Further studies utilizing mass spectrometry and mutagenesis approaches showed that O-GlcNAcylations at Thr 305 and Thr 312 inhibited Akt phosphorylation at Thr 308 via disrupting the interaction between Akt and PDK1. The impaired Akt activation in turn resulted in the compromised biological functions of Akt, as evidenced by suppressed cell proliferation and migration capabilities. Together, this study revealed an extensive crosstalk between O-GlcNAcylations and phosphorylations of Akt and demonstrated O-GlcNAcylation as a new regulatory modification for Akt signaling.

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    • "Subsequent study from Soesanto and colleagues reports that Akt itself can undergo O-GlcNAcylation [73]. Geng’s and Gong’s groups later demonstrated that O-GlcNAcylation of Akt inhibits its Thr 308 phosphorylation in various cell types [74, 75]. Geng’s group further mapped the O-GlcNAcylation sites of Akt and illustrated that O-GlcNAcylation occurs at Thr305 and Thr312. "
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    • "However, the relationship between O-GlcNAcylation and phosphorylation of Akt in cancer cells is not fully elucidated. Wang et al. showed that O-GlcNAcylations at Thr305 and Thr312 inhibited Akt phosphorylation at Thr308 via disrupting the interaction between Akt and PDK1 in MCF-7 cells (51). The impaired Akt activation affected functions of Akt, as evidenced by suppressed cell proliferation and migration capabilities. "
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