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Qin CX, Sleaby R, Davidoff AJ, Bell JR, De Blasio MJ, Delbridge LM, Chatham JC, Ritchie RH. Insights into the role of maladaptive hexosamine biosynthesis and O-GlcNAcylation in development of diabetic cardiac complications. Pharmacol Res 2016; 116:45-56. [PMID: 27988387 DOI: 10.1016/j.phrs.2016.12.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 10/28/2016] [Accepted: 12/13/2016] [Indexed: 12/21/2022]
Abstract
Diabetes mellitus significantly increases the risk of heart failure, independent of coronary artery disease. The mechanisms implicated in the development of diabetic heart disease, commonly termed diabetic cardiomyopathy, are complex, but much of the impact of diabetes on the heart can be attributed to impaired glucose handling. It has been shown that the maladaptive nutrient-sensing hexosamine biosynthesis pathway (HBP) contributes to diabetic complications in many non-cardiac tissues. Glucose metabolism by the HBP leads to enzymatically-regulated, O-linked attachment of a sugar moiety molecule, β-N-acetylglucosamine (O-GlcNAc), to proteins, affecting their biological activity (similar to phosphorylation). In normal physiology, transient activation of HBP/O-GlcNAc mechanisms is an adaptive, protective means to enhance cell survival; interventions that acutely suppress this pathway decrease tolerance to stress. Conversely, chronic dysregulation of HBP/O-GlcNAc mechanisms has been shown to be detrimental in certain pathological settings, including diabetes and cancer. Most of our understanding of the impact of sustained maladaptive HBP and O-GlcNAc protein modifications has been derived from adipose tissue, skeletal muscle and other non-cardiac tissues, as a contributing mechanism to insulin resistance and progression of diabetic complications. However, the long-term consequences of persistent activation of cardiac HBP and O-GlcNAc are not well-understood; therefore, the goal of this timely review is to highlight current understanding of the role of the HBP pathway in development of diabetic cardiomyopathy.
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Affiliation(s)
- Cheng Xue Qin
- Heart Failure Pharmacology, Baker IDI Heart & Diabetes Institute, Melbourne VIC 3004, Australia; Department of Pharmacology, University of Melbourne, VIC 3010, Australia
| | - Rochelle Sleaby
- Heart Failure Pharmacology, Baker IDI Heart & Diabetes Institute, Melbourne VIC 3004, Australia; Department of Physiology, University of Melbourne, VIC 3010, Australia
| | - Amy J Davidoff
- University of New England, Biddeford, ME, 04072, United States
| | - James R Bell
- Department of Physiology, University of Melbourne, VIC 3010, Australia
| | - Miles J De Blasio
- Heart Failure Pharmacology, Baker IDI Heart & Diabetes Institute, Melbourne VIC 3004, Australia; School of BioSciences, University of Melbourne, VIC 3010, Australia
| | | | - John C Chatham
- University of Alabama at Birmingham, Birmingham, AL, 35233, United States
| | - Rebecca H Ritchie
- Heart Failure Pharmacology, Baker IDI Heart & Diabetes Institute, Melbourne VIC 3004, Australia; Department of Pharmacology, University of Melbourne, VIC 3010, Australia; Department of Medicine, Monash University, Clayton 3800, VIC, Australia.
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2
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Groves JA, Lee A, Yildirir G, Zachara NE. Dynamic O-GlcNAcylation and its roles in the cellular stress response and homeostasis. Cell Stress Chaperones 2013; 18:535-58. [PMID: 23620203 PMCID: PMC3745259 DOI: 10.1007/s12192-013-0426-y] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 03/29/2013] [Accepted: 04/01/2013] [Indexed: 12/15/2022] Open
Abstract
O-linked N-acetyl-β-D-glucosamine (O-GlcNAc) is a ubiquitous and dynamic post-translational modification known to modify over 3,000 nuclear, cytoplasmic, and mitochondrial eukaryotic proteins. Addition of O-GlcNAc to proteins is catalyzed by the O-GlcNAc transferase and is removed by a neutral-N-acetyl-β-glucosaminidase (O-GlcNAcase). O-GlcNAc is thought to regulate proteins in a manner analogous to protein phosphorylation, and the cycling of this carbohydrate modification regulates many cellular functions such as the cellular stress response. Diverse forms of cellular stress and tissue injury result in enhanced O-GlcNAc modification, or O-GlcNAcylation, of numerous intracellular proteins. Stress-induced O-GlcNAcylation appears to promote cell/tissue survival by regulating a multitude of biological processes including: the phosphoinositide 3-kinase/Akt pathway, heat shock protein expression, calcium homeostasis, levels of reactive oxygen species, ER stress, protein stability, mitochondrial dynamics, and inflammation. Here, we will discuss the regulation of these processes by O-GlcNAc and the impact of such regulation on survival in models of ischemia reperfusion injury and trauma hemorrhage. We will also discuss the misregulation of O-GlcNAc in diseases commonly associated with the stress response, namely Alzheimer's and Parkinson's diseases. Finally, we will highlight recent advancements in the tools and technologies used to study the O-GlcNAc modification.
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Affiliation(s)
- Jennifer A. Groves
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, 725 N. Wolfe St, Baltimore, MD 21205-2185 USA
| | - Albert Lee
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, 725 N. Wolfe St, Baltimore, MD 21205-2185 USA
| | - Gokben Yildirir
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, 725 N. Wolfe St, Baltimore, MD 21205-2185 USA
| | - Natasha E. Zachara
- The Department of Biological Chemistry, The Johns Hopkins University School of Medicine, 725 N. Wolfe St, Baltimore, MD 21205-2185 USA
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3
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Kim EJ. Chemical arsenal for the study of O-GlcNAc. Molecules 2011; 16:1987-2022. [PMID: 21358590 PMCID: PMC6259741 DOI: 10.3390/molecules16031987] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 02/03/2011] [Accepted: 02/15/2011] [Indexed: 12/24/2022] Open
Abstract
The concepts of both protein glycosylation and cellular signaling have been influenced by O-linked-β-N-acetylglucosamine (O-GlcNAc) modification (O-GlcNAcylation) on the hydroxyl group of serine or threonine residues. Unlike conventional protein glycosylation, O-GlcNAcylation is localized in the nucleocytoplasm and its cycling is a dynamic process that operates in a highly regulated manner in response to various cellular stimuli. These characteristics render O-GlcNAcylation similar to phosphorylation, which has long been considered a major regulatory mechanism in cellular processes. Various efficient chemical approaches and novel mass spectrometric (MS) techniques have uncovered numerous O-GlcNAcylated proteins that are involved in the regulation of many important cellular events. These discoveries imply that O-GlcNAcylation is another major regulator of cellular signaling. However, in contrast to phosphorylation, which is regulated by hundreds of kinases and phosphatases, dynamic O-GlcNAc cycling is catalyzed by only two enzymes: uridine diphospho-N-acetyl-glucosamine:polypeptide β-N-acetylglucosaminyl transferase (OGT) and β-D-N-acetylglucosaminidase (OGA). Many useful chemical tools have recently been used to greatly expand our understanding of the extensive crosstalk between O-GlcNAcylation and phosphorylation and hence of cellular signaling. This review article describes the various useful chemical tools that have been developed and discusses the considerable advances made in the O-GlcNAc field.
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Affiliation(s)
- Eun J Kim
- Department of Science Education-Chemistry Major, Daegu University, Gyeongbuk 712-714, Korea.
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4
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Abstract
Glycosylation is one of the most common and complex forms of posttranslational modifications of proteins in eukaryotes. Seven different protein-carbohydrate linkages have been characterized on nuclear and cytoplasmic glycoproteins, the most widespread of which is the modification of Ser/Thr residues with monosaccharides of O-linked beta-N-acetylglucosamine (O-GlcNAc). O-GlcNAc modification is concentrated in nuclear proteins. O-GlcNAc is thought to regulate protein function in a manner analogous to phosphorylation; and is implicated in the regulation of transcription, the proteasome, insulin and MAP kinase signaling, the cell cycle, and the cellular stress response. In this chapter we focus on methods for the detection of O-GlcNAc-modified proteins and discuss general techniques for the detection and subsequent analysis of other protein-carbohydrate conjugates.
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5
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Butkinaree C, Park K, Hart GW. O-linked beta-N-acetylglucosamine (O-GlcNAc): Extensive crosstalk with phosphorylation to regulate signaling and transcription in response to nutrients and stress. BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1800:96-106. [PMID: 19647786 PMCID: PMC2815129 DOI: 10.1016/j.bbagen.2009.07.018] [Citation(s) in RCA: 339] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 07/14/2009] [Accepted: 07/18/2009] [Indexed: 02/03/2023]
Abstract
BACKGROUND Since its discovery in the early 1980s, O-linked-beta-N-acetylglucosamine (O-GlcNAc), a single sugar modification on the hydroxyl group of serine or threonine residues, has changed our views of protein glycosylation. While other forms of protein glycosylation modify proteins on the cell surface or within luminal compartments of the secretory machinery, O-GlcNAc modifies myriad nucleocytoplasmic proteins. GlcNAcylated proteins are involved in transcription, ubiquitination, cell cycle, and stress responses. GlcNAcylation is similar to protein phosphorylation in terms of stoichiometry, localization and cycling. To date, only two enzymes are known to regulate GlcNAcylation in mammals: O-GlcNAc transferase (OGT), which catalyzes the addition of O-GlcNAc, and beta-N-acetylglucosaminidase (O-GlcNAcase), a neutral hexosaminidase responsible for O-GlcNAc removal. OGT and O-GlcNAcase are regulated by RNA splicing, by nutrients, and by post-translational modifications. Their specificities are controlled by many transiently associated targeting subunits. As methods for detecting O-GlcNAc have improved our understanding of O-GlcNAc's functions has grown rapidly. SCOPE OF REVIEW In this review, the functions of GlcNAcylation in regulating cellular processes, its extensive crosstalk with protein phosphorylation, and regulation of OGT and O-GlcNAcase will be explored. MAJOR CONCLUSIONS GlcNAcylation rivals phosphorylation in terms of its abundance, protein distribution and its cycling on and off of proteins. GlcNAcylation has extensive crosstalk with phosphorylation to regulate signaling, transcription and the cytoskeleton in response to nutrients and stress. GENERAL SIGNIFICANCE Abnormal crosstalk between GlcNAcylation and phosphorylation underlies dysregulation in diabetes, including glucose toxicity, and defective GlcNAcylation is involved in neurodegenerative disease and cancer and most recently in AIDS.
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Affiliation(s)
- Chutikarn Butkinaree
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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6
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Dorfmueller HC, van Aalten DMF. Screening-based discovery of drug-like O-GlcNAcase inhibitor scaffolds. FEBS Lett 2009; 584:694-700. [PMID: 20026047 PMCID: PMC2828546 DOI: 10.1016/j.febslet.2009.12.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Revised: 12/01/2009] [Accepted: 12/13/2009] [Indexed: 11/26/2022]
Abstract
O-GlcNAcylation is an essential posttranslational modification in metazoa. Modulation of O-GlcNAc levels with small molecule inhibitors of O-GlcNAc hydrolase (OGA) is a useful strategy to probe the role of this modification in a range of cellular processes. Here we report the discovery of novel, low molecular weight and drug-like O-GlcNAcase inhibitor scaffolds by high-throughput screening. Kinetic and X-ray crystallographic analyses of the binding modes with human/bacterial O-GlcNAcases identify some of these as competitive inhibitors. Comparative kinetic experiments with the mechanistically related human lysosomal hexosaminidases reveal that three of the inhibitor scaffolds show selectivity towards human OGA. These scaffolds provide attractive starting points for the development of non-carbohydrate, drug-like OGA inhibitors.
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Affiliation(s)
- Helge C Dorfmueller
- Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, Scotland, UK
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7
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Macauley MS, Vocadlo DJ. Increasing O-GlcNAc levels: An overview of small-molecule inhibitors of O-GlcNAcase. Biochim Biophys Acta Gen Subj 2009; 1800:107-21. [PMID: 19664691 DOI: 10.1016/j.bbagen.2009.07.028] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 07/17/2009] [Accepted: 07/28/2009] [Indexed: 11/25/2022]
Abstract
The O-GlcNAc modification is found on many nucleocytoplasmic proteins. The dynamic nature of O-GlcNAc, which in some ways is reminiscent of phosphorylation, has enabled investigators to modulate the stoichiometry of O-GlcNAc on proteins in order to study its function. Although several genetic and pharmacological methods for manipulating O-GlcNAc levels have been described, one of the most direct approaches of increasing global O-GlcNAc levels is by using small-molecule inhibitors of O-GlcNAcase (OGA). As the interest in increasing O-GlcNAc levels has grown, so too has the number of OGA inhibitors. This review provides an overview of the available methods of increasing O-GlcNAc levels, with a special emphasis on inhibition of OGA by small molecules. Known inhibitors of OGA are discussed with particular attention on those most suitable for cell-based biological studies. Several examples in which OGA inhibitors have been used to study the functional role of the O-GlcNAc modification in biological systems are discussed, highlighting the pros and cons of different inhibitors.
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Affiliation(s)
- Matthew S Macauley
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
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8
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He Y, Martinez-Fleites C, Bubb A, Gloster TM, Davies GJ. Structural insight into the mechanism of streptozotocin inhibition of O-GlcNAcase. Carbohydr Res 2008; 344:627-31. [PMID: 19217614 DOI: 10.1016/j.carres.2008.12.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 12/02/2008] [Accepted: 12/03/2008] [Indexed: 10/21/2022]
Abstract
Despite decades of its use in diabetes research, the mechanism of cytotoxicity of streptozotocin (STZ) toward pancreatic beta-islet cells has remained a topic of discussion. Although STZ toxicity is likely a function of its capacity to promote DNA alkylation, it has been proposed that STZ induces pancreatic beta-cell death through O-GlcNAcase inhibition. In this report, we explore the binding mode of STZ to a close homolog of human O-GlcNAcase, BtGH84 from Bacteroides thetaiotaomicron. Our results show that STZ binds in the enzyme active site in its intact form, without the formation of a covalent adduct, consistent with solution studies on BtGH84 and human O-GlcNAcase, as well as with structural work on a homolog from Clostridium perfringens. The active site of the BtGH84 is considerably deformed upon STZ binding and as a result the catalytic machinery is expelled from the binding cavity.
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Affiliation(s)
- Yuan He
- Department of Chemistry, Structural Biology Laboratory, The University of York, Heslington, York, YO10 5YW, UK
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9
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Pathak S, Dorfmueller HC, Borodkin VS, van Aalten DMF. Chemical dissection of the link between streptozotocin, O-GlcNAc, and pancreatic cell death. ACTA ACUST UNITED AC 2008; 15:799-807. [PMID: 18721751 PMCID: PMC2568864 DOI: 10.1016/j.chembiol.2008.06.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2008] [Revised: 06/11/2008] [Accepted: 06/23/2008] [Indexed: 01/09/2023]
Abstract
Streptozotocin is a natural product that selectively kills insulin-secreting β cells, and is widely used to generate mouse models of diabetes or treat pancreatic tumors. Several studies suggest that streptozotocin toxicity stems from its N-nitrosourea moiety releasing nitric oxide and possessing DNA alkylating activity. However, it has also been proposed that streptozotocin induces apoptosis by inhibiting O-GlcNAcase, an enzyme that, together with O-GlcNAc transferase, is important for dynamic intracellular protein O-glycosylation. We have used galacto-streptozotocin to chemically dissect the link between O-GlcNAcase inhibition and apoptosis. Using X-ray crystallography, enzymology, and cell biological studies on an insulinoma cell line, we show that, whereas streptozotocin competitively inhibits O-GlcNAcase and induces apoptosis, its galacto-configured derivative no longer inhibits O-GlcNAcase, yet still induces apoptosis. This supports a general chemical poison mode of action for streptozotocin, suggesting the need for using more specific inhibitors to study protein O-GlcNAcylation.
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Affiliation(s)
- Shalini Pathak
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, Scotland
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10
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Akimoto Y, Hart GW, Wells L, Vosseller K, Yamamoto K, Munetomo E, Ohara-Imaizumi M, Nishiwaki C, Nagamatsu S, Hirano H, Kawakami H. Elevation of the post-translational modification of proteins by O-linked N-acetylglucosamine leads to deterioration of the glucose-stimulated insulin secretion in the pancreas of diabetic Goto-Kakizaki rats. Glycobiology 2006; 17:127-40. [PMID: 17095531 DOI: 10.1093/glycob/cwl067] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Many nuclear and cytoplasmic proteins are O-glycosylated on serine or threonine residues with the monosaccharide beta-N-acetylglucosamine, which is then termed O-linked N-acetylglucosamine (O-GlcNAc). It has been shown that abnormal O-GlcNAc modification (O-GlcNAcylation) of proteins is one of the causes of insulin resistance and diabetic complications. In this study, in order to examine the relationship between O-GlcNAcylation of proteins and glucose-stimulated insulin secretion in noninsulin-dependent type (type 2) diabetes, we investigated the level of O-GlcNAcylation of proteins, especially that of PDX-1, and the expression of O-GlcNAc transferase in Goto-Kakizaki (GK) rats, which are an animal model of type-2 diabetes. By immunoblot and immunohistochemical analyses, the expression of O-GlcNAc transferase protein and O-GlcNAc-modified proteins in whole pancreas and islets of Langerhans of 15-week-old diabetic GK rats and nondiabetic Wistar rats was examined. The expression of O-GlcNAc transferase at the protein level and O-GlcNAc transferase activity were increased significantly in the diabetic pancreas and islets. The diabetic pancreas and islets also showed an increase in total cellular O-GlcNAc-modified proteins. O-GlcNAcylation of PDX-1 was also increased. In the diabetic GK rats, significant increases in the immunoreactivities of both O-GlcNAc and O-GlcNAc transferase were observed. PUGNAc, an inhibitor of O-GlcNAcase, induced an elevation of O-GlcNAc level and a decrease of glucose-stimulated insulin secretion in isolated islets. These results indicate that elevation of the O-GlcNAcylation of proteins leads to deterioration of insulin secretion in the pancreas of diabetic GK rats, further providing evidence for the role of O-GlcNAc in the insulin secretion.
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Affiliation(s)
- Yoshihiro Akimoto
- Department of Anatomy, Kyorin University School of Medicine, Mitaka, Tokyo, Japan.
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11
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Macauley MS, Whitworth GE, Debowski AW, Chin D, Vocadlo DJ. O-GlcNAcase uses substrate-assisted catalysis: kinetic analysis and development of highly selective mechanism-inspired inhibitors. J Biol Chem 2005; 280:25313-22. [PMID: 15795231 DOI: 10.1074/jbc.m413819200] [Citation(s) in RCA: 297] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The post-translational modification of serine and threonine residues of nucleocytoplasmic proteins with 2-acetamido-2-deoxy-d-glucopyranose (GlcNAc) is a reversible process implicated in multiple cellular processes. The enzyme O-GlcNAcase catalyzes the cleavage of beta-O-linked GlcNAc (O-GlcNAc) from modified proteins and is a member of the family 84 glycoside hydrolases. The family 20 beta-hexosaminidases bear no apparent sequence similarity yet are functionally related to O-GlcNAcase because both enzymes cleave terminal GlcNAc residues from glycoconjugates. Lysosomal beta-hexosaminidase is known to use substrate-assisted catalysis involving the 2-acetamido group of the substrate; however, the catalytic mechanism of human O-GlcNAcase is unknown. By using a series of 4-methylumbelliferyl 2-deoxy-2-N-fluoroacetyl-beta-D-glucopyranoside substrates, Taft-like linear free energy analyses of these enzymes indicates that O-GlcNAcase uses a catalytic mechanism involving anchimeric assistance. Consistent with this proposal, 1,2-dideoxy-2'-methyl-alpha-D-glucopyranoso-[2,1-d]-Delta2'-thiazoline, an inhibitor that mimics the oxazoline intermediate proposed in the catalytic mechanism of family 20 glycoside hydrolases, is shown to act as a potent competitive inhibitor of both O-GlcNAcase (K(I) = 0.070 microm) and beta-hexosaminidase (K = 0.070 microm). A series of 1,2-dideoxy-2'-methyl-alpha-D-glucopyranoso-[2,1-d]-Delta2'-thiazoline analogues were prepared, and one inhibitor demonstrated a remarkable 1500-fold selectivity for O-GlcNAcase (K(I) = 0.230 microm) over beta-hexosaminidase (K(I) = 340 microm). These inhibitors are cell permeable and modulate the activity of O-GlcNAcase in tissue culture. Because both enzymes have vital roles in organismal health, these potent and selective inhibitors of O-GlcNAcase should prove useful in studying the role of this enzyme at the organismal level without generating a complex chemical phenotype stemming from concomitant inhibition of beta-hexosaminidase.
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Affiliation(s)
- Matthew S Macauley
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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12
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Kneass ZT, Marchase RB. Protein O-GlcNAc modulates motility-associated signaling intermediates in neutrophils. J Biol Chem 2005; 280:14579-85. [PMID: 15703172 DOI: 10.1074/jbc.m414066200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The modification of serine/threonine residues on cytoplasmic and nuclear proteins by N-acetylglucosamine (O-GlcNAc) is suggested to play a role in the regulation of a variety of signal transduction pathways. We have previously shown that glucosamine (GlcNH(2)), a metabolic precursor of O-GlcNAcylation, increases (2)O-GlcNAc and enhances motility in neutrophils. Here, we extend this correlation by showing that a mechanistically distinct means of increasing O-GlcNAc, achieved by inhibition of O-GlcNAc removal with O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc), increases basal cellular motility and directional migration induced by the chemoattractant formyl-methionine-leucine-phenylalanine (fMLP). Furthermore, we demonstrate that O-GlcNAc modulates the activities of signaling intermediates known to regulate neutrophil movement. GlcNH(2) and PUGNAc increase both the basal and fMLP-induced activity of a central mediator of cellular motility, the small GTPase Rac. Phosphoinositide 3-kinase, an important regulator of Rac activity and neutrophil motility, is shown to regulate the signaling pathway on which GlcNH(2) and PUGNAc act. Rac is an important upstream regulatory element in p38 and p44/42 mitogen-activated protein kinase (MAPK) signaling in neutrophils, and these MAPKs are implicated in chemotactic signal transduction. We show that GlcNH(2) and PUGNAc treatment increases p42/44 and p38 MAPK activities and that these increases are associated with activation of upstream MAPK kinases. These data indicate that O-GlcNAcylation is an important signaling element in neutrophils that modulates the activities of several critical signaling intermediates involved in the regulation of cellular movement.
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Affiliation(s)
- Zachary T Kneass
- Department of Cell Biology, MCLM 690, University of Alabama, Birmingham, Alabama 35294, USA
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13
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Whelan SA, Hart GW. Proteomic approaches to analyze the dynamic relationships between nucleocytoplasmic protein glycosylation and phosphorylation. Circ Res 2003; 93:1047-58. [PMID: 14645135 DOI: 10.1161/01.res.0000103190.20260.37] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
O-linked beta-N-acetylglucosamine (O-GlcNAc) is both an abundant and dynamic posttranslational modification similar to phosphorylation that occurs on serine and threonine residues of cytosolic and nuclear proteins in all metazoans and cell types examined, including cardiovascular tissue. Since the discovery of O-GlcNAc more than 20 years ago, the elucidation of O-GlcNAc as a posttranslational modification has been slow, albeit similar to the rate of acceptance of phosphorylation, because of the lack of tools available for its study. Identifying O-GlcNAc posttranslational modifications on proteins is a major challenge to proteomics. The recent development of mild beta-elimination followed by Michael addition with dithiothreitol has significantly improved the site mapping of both O-GlcNAc and O-phosphate in functional proteomics. beta-Elimination followed by Michael addition with dithiothreitol facilitates the study of the labile O-GlcNAc modification in the etiology of disease states. We discuss how recent technological innovations will expand our present understanding of O-GlcNAc and what the implications are for diabetes and cardiovascular complications.
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Affiliation(s)
- Stephen A Whelan
- Johns Hopkins University School of Medicine, Department of Biological Chemistry, 725 N Wolfe St, Baltimore, Md, USA
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14
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Okuyama R, Fujiwara T, Ohsumi J. High glucose potentiates palmitate-induced NO-mediated cytotoxicity through generation of superoxide in clonal beta-cell HIT-T15. FEBS Lett 2003; 545:219-23. [PMID: 12804779 DOI: 10.1016/s0014-5793(03)00534-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Prolonged exposure to free fatty acids induces beta-cell cytotoxicity. We investigated whether this fatty-acid-induced cytotoxicity is affected by high glucose levels. In clonal beta-cell HIT-T15, palmitate-induced cytotoxicity was potentiated depending on elevated glucose concentrations due to increased apoptosis without cytotoxic effects of high glucose per se. This palmitate cytotoxicity was blocked by NO synthase inhibitors, and palmitate actually increased cellular NO production. The potentiation of palmitate cytotoxicity under high glucose was reversed by decreasing superoxide production, suggesting that superoxide overproduction under high glucose enhances NO-mediated cytotoxicity in beta-cells, which may explain the mechanism of synergistic deterioration of pancreatic beta-cells by free fatty acids and high glucose.
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Affiliation(s)
- Ryo Okuyama
- Pharmacology and Molecular Biology Research Laboratories, Sankyo Co. Ltd., 2-58 Hiromachi-1-chome, Shinagawa-ku, 140-8710, Tokyo, Japan.
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15
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Liu K, Paterson AJ, Konrad RJ, Parlow AF, Jimi S, Roh M, Chin E, Kudlow JE. Streptozotocin, an O-GlcNAcase inhibitor, blunts insulin and growth hormone secretion. Mol Cell Endocrinol 2002; 194:135-46. [PMID: 12242036 DOI: 10.1016/s0303-7207(02)00155-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Type 2 diabetes mellitus results from a complex interaction between nutritional excess and multiple genes. Whereas pancreatic beta-cells normally respond to glucose challenge by rapid insulin release (first phase insulin secretion), there is a loss of this acute response in virtually all of the type 2 diabetes patients with significant fasting hyperglycemia. Our previous studies demonstrated that irreversible intracellular accumulation of a glucose metabolite, protein O-linked N-acetylglucosamine modification (O-GlcNAc), is associated with pancreatic beta-cell apoptosis. In the present study, we show that streptozotocin (STZ), a non-competitive chemical blocker of O-GlcNAcase, induces an insulin secretory defect in isolated rat islet cells. In contrast, transgenic mice with down-regulated glucose to glucosamine metabolism in beta-cells exhibited an enhanced insulin secretion capacity. Interestingly, the STZ blockade of O-GlcNAcase activity is also associated with a growth hormone secretory defect and impairment of intracellular secretory vesicle trafficking. These results provide evidence for the roles of O-GlcNAc in the insulin secretion and possible involvement of O-GlcNAc in general glucose-regulated hormone secretion pathways.
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Affiliation(s)
- Kan Liu
- Department of Medicine/Endocrinology, Cell Biology, University of Alabama at Birmingham, 1808 7th Avenue South, Rm 756, Birmingham, AL 35294, USA
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