Dynamic modification of nuclear and cytosolic proteins by O-linked N-Acetylglucosamine (O-GlcNAc) is as abundant as protein phosphorylation in all multi-cellular eukaryotes. Two- to five- percent of glucose is metabolized to the end product of the hexosamine biosynthetic pathway (HBP), leading to ~millimolar UDP-GlcNAc in cells. UDP-GlcNAc is the immediate donor for O-GlcNAcylation. O-GlcNAcylation often has an antagonistic, reciprocal (""""""""Yin-Yang"""""""") relationship with Ser/Thr phosphorylation. Many laboratories have documented a key role for HBP, and more particularly, O-GlcNAcylation as a mechanism underlying glucose toxicity and insulin resistance, the hallmark of type II diabetes. We propose to continue our studies of the roles of O-GlcNAcylation in insulin signaling and resistance by elucidating the mechanisms by which elevated O-GlcNAc blocks insulin signaling in adipocytes and hepatocytes. We will reveal the site-specific interplay between phosphorylation, and O-GlcNAc's, and elucidate specific roles of each post-translational modification in signaling and transcriptional regulation key to insulin action.
Specific Aims : 1) To continue to examine the Structural/Functional Significance of Protein Phosphatase 1 (PP1c) Interactions with O-GlcNAc Transferase (OGT). 2) To continue to elucidate the specific dynamic relationships between O-GlcNAcylation and O-Phosphorylation in the insulin signaling cascade, in order to explain O-GlcNAc's specific roles in hyperglycemic-induced insulin resistance. 3) To continue to examine the roles of O-GlcNAc in the functions/localization/stability and promoter activity of the insulin regulated FOXO1 transcription factor that plays a key role in regulating glucose production by the liver. These studies are revealing an unexpected paradigm for the regulation of signaling pathways by nutrients and by cellular stress. The ability of increased O-GlcNAcylation to block insulin signaling and the modification's sensitivity to stress and nutrients serves to unify current hypotheses of diabetes etiology at the molecular level. These studies will result in novel avenues for therapeutics.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK061671-07
Application #
7612133
Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
Program Officer
Sechi, Salvatore
Project Start
2002-05-01
Project End
2010-06-30
Budget Start
2009-05-01
Budget End
2010-06-30
Support Year
7
Fiscal Year
2009
Total Cost
$314,714
Indirect Cost
Name
Johns Hopkins University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218
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Ma, Junfeng; Hart, Gerald W (2017) Analysis of Protein O-GlcNAcylation by Mass Spectrometry. Curr Protoc Protein Sci 87:24.10.1-24.10.16
Ma, Junfeng; Banerjee, Partha; Whelan, Stephen A et al. (2016) Comparative Proteomics Reveals Dysregulated Mitochondrial O-GlcNAcylation in Diabetic Hearts. J Proteome Res 15:2254-64
Ma, Junfeng; Hart, Gerald W (2016) Mass Spectrometry-Based Quantitative O-GlcNAcomic Analysis. Methods Mol Biol 1410:91-103
Banerjee, Partha S; Lagerlöf, Olof; Hart, Gerald W (2016) Roles of O-GlcNAc in chronic diseases of aging. Mol Aspects Med 51:1-15
Hardivillé, Stéphan; Hart, Gerald W (2016) Nutrient regulation of gene expression by O-GlcNAcylation of chromatin. Curr Opin Chem Biol 33:88-94
Lagerlöf, Olof; Slocomb, Julia E; Hong, Ingie et al. (2016) The nutrient sensor OGT in PVN neurons regulates feeding. Science 351:1293-6
Ramirez-Correa, Genaro A; Ma, Junfeng; Slawson, Chad et al. (2015) Removal of Abnormal Myofilament O-GlcNAcylation Restores Ca2+ Sensitivity in Diabetic Cardiac Muscle. Diabetes 64:3573-87
Ma, Junfeng; Liu, Ting; Wei, An-Chi et al. (2015) O-GlcNAcomic Profiling Identifies Widespread O-Linked ?-N-Acetylglucosamine Modification (O-GlcNAcylation) in Oxidative Phosphorylation System Regulating Cardiac Mitochondrial Function. J Biol Chem 290:29141-53
Banerjee, Partha S; Ma, Junfeng; Hart, Gerald W (2015) Diabetes-associated dysregulation of O-GlcNAcylation in rat cardiac mitochondria. Proc Natl Acad Sci U S A 112:6050-5

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