Lauren Ball, PhD
Director, Mass Spectrometry Facility
2003 Ph.D., Medical University of South Carolina
Office: CRI 311
Role of O-GlcNAc Glycosylation in the Regulation of Insulin/IGF-1 Receptor Signal Transduction Pathways
The O-linked glycosylation of serine and threonine residues by a single monosaccharide, beta-N-acetylglucosamine (O-GlcNAc), is a dynamic and reversible posttranslational modification occurring on nuclear and cytoplasmic proteins. This modification regulates protein function in a manner analogous to S/T phosphorylation and furthermore may compete with S/T phosphorylation. The enzymes catalyzing the incorporation and removal of GlcNAc from proteins, O-GlcNAc transferase and O-GlcNAcase, respectively, are located in the nucleus and cytoplasm and are ubiquitously distributed in tissues. Many proteins are O-GlcNAc modified including transcription factors, oncogenes, tumor suppressors, heat shock proteins, nuclear pore proteins, and intracellular signaling molecules. Global protein O-GlcNAc modification increases with nutrient excess, cellular stress, and hormonal stimulation and dysregulation of this modification has been implicated in diabetes, cancer, and neurodegenerative disease.
The sugar donor for O-GlcNAc modification, UDP-GlcNAc, is generated by the metabolism of glucose through the hexosamine biosynthetic pathway. Under normal conditions 2-3% of the glucose entering the cell is committed to this pathway. However, in states of nutrient excess, such as type II diabetes, UDP-GlcNAc levels and the extent of protein O-GlcNAc modification rise. Thus, hyperglycemia-induced O-GlcNAc modification has been proposed to contribute to the microvascular complications (nephropathy, neuropathy, and retinopathy) associated with diabetes and may exacerbate diabetic periodontal disease.
We are interested in the role of O-GlcNAc modification of insulin receptor substrate proteins in the regulation of insulin receptor and insulin-like growth factor (IGF-1) receptor signaling pathways. Insulin receptor substrate-1 (IRS-1), a central molecule in the insulin/IGF-1 receptor pathways, mediates many of the metabolic and mitogenic effects of insulin and IGF-1. The phenotypic characteristics of transgenic animals deficient in IRS-1 reflect defects in both the insulin and IGF-1 receptor signaling pathways. These animals exhibit retarded growth, impaired endothelial-dependent vascular relaxation, peripheral insulin resistance of skeletal muscle and adipose tissue, and a decreased capacity for bone healing. A human polymorphism of IRS-1 has been linked to insulin resistance, endothelial dysfunction, and an increased risk for breast, prostate, and colorectal cancers. Following insulin or IGF-1 receptor stimulation, IRS-1 is phosphorylated by the receptor tyrosine kinases within distinct protein interaction motifs. These motifs provide a platform for interaction of IRS-1 with a number of downstream effectors including PI3Kinase, Grb2, and SHP-2. These interactions are further modulated by S/T kinases which are involved in positive or negative feedback regulation at the level of IRS-1. We are currently investigating the influence of O-GlcNAc modification on the phosphorylation state and the interactions of IRS-1 with binding partners.
In the laboratory, we use tandem mass spectrometry to identify the exact sites of protein O-GlcNAc modification and phosphorylation. Mass spectrometry provides a powerful tool for the identification and quantification of posttranslational modifications and the discovery of unanticipated protein-protein interactions. We are interested in developing proteomic methods to facilitate the isolation and identification of O-GlcNAcylated proteins to further examine the role of this modification in the regulation of protein function and its contribution to the development or progression of human disease. Elucidation of the mechanisms by which O-GlcNAc modification regulates signal transduction pathways may reveal novel targets of therapeutic intervention applicable to many human diseases.
Recent Publications | Additional Publications
1. Pehar M, Ball LE, Sharma DR, Harlan BA, Comte-Walters S, Neely BA, Vargas MR. Changes in Protein Expression and Lysine Acetylation Induced by Decreased Glutathione Levels in Astrocytes. Mol Cell Proteomics. 2016 Feb; 15(2):493-505. doi: 10.1074/mcp.M115.049288. PMID:26486419.
2. Williams GR, Bethard JR, Berkaw MN, Nagel AK, Luttrell LM, Ball LE. Exploring G protein-coupled receptor signaling networks using SILAC-based phosphoproteomics. Methods. 2015 Jul 6. pii: S1046-2023(15)30010-4. doi: 10.1016/j.ymeth.2015.06.022. PMID:26160508
3. Uys JD, McGuier NS, Gass JT, Griffin WC 3rd, Ball LE, Mulholland PJ. Chronic intermittent ethanol exposure and withdrawal leads to adaptations in nucleus accumbens core postsynaptic density proteome and dendritic spines. Addict Biol. 2015 Mar 17. doi: 10.1111/adb.12238.
4. Nagel AK, Ball LE. Intracellular protein O-GlcNAc modification integrates nutrient status with transcriptional and metabolic regulation. Adv Cancer Res. 2015;126:137-66. doi: 10.1016/bs.acr.2014.12.003.
5. Nagel AK, Ball LE. O-GlcNAc modification of the runt-related transcription factor 2 (Runx2) links osteogenesis and nutrient metabolism in bone marrow mesenchymal stem cells. Mol Cell Proteomics. 2014 Dec;13(12):3381-95. doi: 10.1074/mcp.M114.040691.
6. Nagel AK, Ball LE. O-GlcNAc transferase and O-GlcNAcase: achieving target substrate specificity. Amino Acids. 2014 Oct;46(10):2305-16. doi: 10.1007/s00726-014-1827-7.
7. Leymarie N, Griffin PJ, Jonscher K, Kolarich D, Orlando R, McComb M, Zaia J, Aguilan J, Alley WR, Altmann F, Ball LE, Basumallick L, Bazemore-Walker CR, Behnken H, Blank MA, Brown KJ, Bunz SC, Cairo CW, Cipollo JF, Daneshfar R, Desaire H, Drake RR, Go EP, Goldman R, Gruber C, Halim A, Hathout Y, Hensbergen PJ, Horn DM, Hurum D, Jabs W, Larson G, Ly M, Mann BF, Marx K, Mechref Y, Meyer B, Möginger U, Neusüss C, Nilsson J, Novotny MV, Nyalwidhe JO, Packer NH, Pompach P, Reiz B, Resemann A, Rohrer JS, Ruthenbeck A, Sanda M, Schulz JM, Schweiger-Hufnagel U, Sihlbom C, Song E, Staples GO, Suckau D, Tang H, Thaysen-Andersen M, Viner RI, An Y, Valmu L, Wada Y, Watson M, Windwarder M, Whittal R, Wuhrer M, Zhu Y, Zou C. Interlaboratory Study on Differential Analysis of Protein Glycosylation by Mass Spectrometry: the ABRF Glycoprotein Research Multi-Institutional Study 2012. Mol Cell Proteomics. 2013 Jun 18. PMID:23764502
8. Nagel AK, Schilling M, Comte-Walters S, Berkaw MN, Ball LE. Identification of O-linked N-acetylglucosamine (O-GlcNAc)-modified osteoblast proteins by electron transfer dissociation tandem mass spectrometry reveals proteins critical for bone formation. Mol Cell Proteomics. 2013 Apr;12(4):945-55. doi: 10.1074/mcp.M112.026633. Epub 2013 Feb 26. PMID:23443134
9. Darley-Usmar VM, Ball LE, Chatham JC. Protein O-linked β-N-acetylglucosamine: a novel effector of cardiomyocyte metabolism and function. J Mol Cell Cardiol. 2012 Mar;52(3):538-49. doi: 10.1016/j.yjmcc.2011.08.009. Epub 2011 Aug 22. Review. PMID:21878340