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: 3.53). 05/2012; 7(5):e37427. DOI: 10.1371/journal.pone.0037427
Source: PubMed

ABSTRACT 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this mini-review, we will highlight work in the last 30 years that has clearly demonstrated that the O-GlcNAc modification is nutrient responsive and plays multiple roles in metabolic regulation of signaling and gene expression. Further, we will examine recent studies that have investigated the impact of O-GlcNAc in a variety of glucose- and insulin-responsive tissues and the roles attributed to O-GlcNAc in the induction of insulin resistance and glucose-toxicity, the hallmarks of type II diabetes mellitus. We will also summarize potential causal roles for the O-GlcNAc modification in complications associated with diabetes.
    Journal of Biological Chemistry 10/2014; DOI:10.1074/jbc.R114.591560 · 4.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Human embryonic stem cells (hESCs) have received considerable attention due to their therapeutic potential and their usefulness in understanding early development and cell fate commitment. In order to appreciate the unique properties of these pluripotent, self-renewing cells, we have performed an in-depth multidimensional fractionation followed by LC-MS/MS analysis of the hESCs harvested from defined media to elucidate expressed, phosphorylated, O-GlcNAc modified, and secreted proteins. From the triplicate analysis, we were able to assign more than 3000 proteins with less than 1% false-discovery rate. This analysis also allowed us to identify nearly 500 phosphorylation sites and 68 sites of O-GlcNAc modification with the same high confidence. Investigation of the phosphorylation sites allowed us to deduce the set of kinases that are likely active in these cells. We also identified more than 100 secreted proteins of hESCs that likely play a role in extracellular matrix formation and remodeling, as well as autocrine signaling for self-renewal and maintenance of the undifferentiated state. Finally, by performing in-depth analysis in triplicate, spectral counts were obtained for these proteins and post-translationally modified peptides, which will allow us to perform relative quantitative analysis between these cells and any derived cell type in the future.This article is protected by copyright. All rights reserved
    Proteomics 01/2015; 15(2-3). DOI:10.1002/pmic.201400132 · 3.97 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The liver is a vital organ responsible for maintaining nutrient homeostasis. After a meal, insulin stimulates glycogen and lipid synthesis in the liver; in the fasted state, glucagon induces gluconeogenesis and ketogenesis, which produce glucose and ketone bodies for other tissues to use as energy sources. These metabolic changes involve spatiotemporally co-ordinated signaling cascades. O-linked β-N-acetylglucosamine (O-GlcNAc) modification has been recognized as a nutrient sensor and regulatory molecular switch. This review highlights mechanistic insights into spatiotemporal regulation of liver metabolism by O-GlcNAc modification and discusses its pathophysiological implications in insulin resistance, non-alcoholic fatty liver disease, and fibrosis.
    Frontiers in Endocrinology 12/2014; 5:221. DOI:10.3389/fendo.2014.00221

Full-text (3 Sources)

Available from
May 22, 2014