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Natasha Zachara Portrait

Natasha Zachara
Associate Professor of Biological Chemistry
Johns Hopkins University School of Medicine

Department of Biological Chemistry
725. N. Wolfe Street, WBSB 408
Baltimore, MD21205
Office Phone: 410-955-7049
Lab Phone: 410-502-3210
Fax: 410-955-5759
Lab Web Site

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The role of nucleocytoplasmic glycosylation, O-GlcNAc, in cell survival and the celluar stress response.

Hundreds, if not thousands, of key cellular proteins in the nucleus, mitochondria and cytoplasm of metazoans are modified by O-linked β-N-acetylglucosamine (O-GlcNAc). Deletion of the UDP-GlcNAc: polypeptide O-β-N-acetyl-glucosaminyltransferase (OGT), the enzyme that adds O-GlcNAc, is lethal in animals and single cells highlighting the importance of this simple post-translational modification. O-GlcNAc is thought to act as a modulator of protein function, in a manner analogous to protein phosphorylation; the addition of O-GlcNAc to the protein backbone is dynamic, responding to morphogens, the cell cycle, changes in glucose metabolism, and cellular injury. O-GlcNAc occurs at sites on the protein backbone that are similar to those modified by protein kinases; and is reciprocal with phosphorylation on some well studied proteins, including RNA Pol II, estrogen receptor-β, SV-40 large T-antigen, endothelial nitric oxide synthase, and the c-Myc proto-oncogene product. These data suggest that one mechanism by which O-GlcNAc modulates cellular function is by competing with phosphorylation. A clear role for O-GlcNAc in cellular regulation has not emerged, although modulation of O-GlcNAc levels are implicated in the etiology of Type II Diabetes, cancer, and neurodegenerative diseases.

In response to multiple forms of cellular stress, levels of the O-GlcNAc protein modification are elevated rapidly and dynamically on myriad nuclear, mitocohdrial and cytoplasmic proteins. Several studies demonstrate that elevation of O-GlcNAc prior to heat stress, oxidative stress, hypoxia, trauma hemorrhage, and ischemia reperfusion injury is protective, suggesting that increased O-GlcNAc in response to stress is a survival response of cells injury. However, the mechanisms by which O-GlcNAc regulates protein function leading to cell survival have not been defined. Our long-term goal is to determine how stress-induced changes in the O-GlcNAc protein modification lead to increased cell/tissue survival in response to injury, in order to develop novel strategies for the treatment of numerous diseases, including ischemia reperfusion injury. Current research in the lab focus's on: 1) Characterizing the molecular mechanisms by which O-GlcNAc regulates heat shock protein expression; 2) The development of novel cells lines and tools for studying the O-GlcNAc modification; 3) Identifying proteins that are O-GlcNAc modified in response to different forms of cellular injury; 4) Understanding the signal transduction pathways that regulate O-GlcNAc modification in response to cellular injury; 5) Determining how O-GlcNAc regulates other stress-induced signaling pathways such as protein-phosphorylation. Together these studies will define a molecular road map from which we, and others, can determine the mechanism(s) by which O-GlcNAc promotes cell survival in diverse models, highlighting new targets for the development of alternative strategies that enhance stress-tolerance and promotes survival relevant models such as ischemic reperfusion injury. In addition, these studies will form a foundation for determining how dysregulation of the “O-GlcNAc-mediated stress response” contributes to pathologies such as type II diabetes and aging.

Recent Publications

Zachara NE. (2012) The Roles of O-Linked β-N-Acetylglucosamine (O-GlcNAc) in Cardiac Physiology and Disease.  AJP Heart and Circulatory Physiology, 302(10):H1905-18.
PubMed Reference 

Zachara NE, Molina H, Wong K, Pandey A, Hart GW. (2011) The dynamic stress-induced O-GlcNAcome highlights functions for O-GlcNAc in DNA Repair and other cellular pathways. Amino Acids, 40(3):793-808.
PubMed Reference
Paruchuri VDP and Zachara NE. “Defining the Cardiac O-GlcNAcome, A Review of Approaches and Methasologies”, Special series: Integrating proteomics into cardiovascular disease in Circulation: Cardiovascular Genetics, 2011 Dec 1;4(6):710.
PubMed Reference
Zachara NE, Vosseller KL and Hart  GW. (2011) Detection and analysis of proteins modified by O-Linked N-acetylglucosamine. In Current Protocols in Protein Science, Johns Wiley and Sons Inc., New York, USA. Chapter 12, Unit 12.8.
PubMed Reference
Kazemi K, Chang H, Haserodt SK, McKen C, Zachara NE. (2010) O-GlcNAc Regulates Stress-Induced Heat Shock Protein Expression in a GSK-3β Dependent Manner. J. Biol. Chem. Dec 10;285(50):39096-107. Epub 2010 Oct 6.
PubMed Reference
Zachara NE. (2009). Detection and Analysis of Nuclearcytoplasmic Glycoproteins. In The Nucleus: Principles and Protocols, Meth Mol Biol. Hancock R (ed) Humana Press (Totowa, USA). Volume 464, pp. 227-254.
PubMed Reference
Zachara NE.  (2009) Detecting the “O-GlcNAc-ome”; Detection, Purification, and Analysis of O-GlcNAc Modified Proteins. In Glycomics, Meth Mol Biol. Packer N, Karlsson GN (eds) Humana Press (Totowa, USA). Volume 534, pp.251-79.
PubMed Reference
Ngoh GA, Facundo HT, Hamid T, Dillmann W, Zachara NE, Jones SP.  (2009). Unique Hexosaminidase Reduces Metabolic Survival Signal and Sensitizes Cardiac Myocytes to Hypoxia-Reoxygenation Injury. Circ. Res. 104(1):41-9.
PubMed Reference
Jones SP, Zachara NE, Teshima Y, Hart GW, Marban E.  (2008) Endogenously-recruitable cardioprotection by N-acetylglucosamine linkage to cellular proteins. Circulation, 117(9):1172-82.
PubMed Reference
Zachara NE. (2007) The sweet nature of cardioprotection. Amer J Phys (Heart and Circulatory Physiology; 293: H1324-H1326.
PubMed Reference
Zachara NE, Hart GW.  (2006) Cell Signaling, the Essential Role of O-GlcNAc! Biochim. Biophys. Acta, 1761: 599-617.
PubMed Reference
Slawson C, Zachara NE, Vissekker K, Cheung W, Lane MD, and Hart GW. (2005) Perturbations in O-GlcNAc protein modification cause severe defects in mitotic progression and cytokinesis. J. Biol. Chem., 280, 32944-32956.
PubMed Reference 
O'Donnell N, Zachara NE, Hart GW, and Marth JD.  (2004) OGT-dependent X-chromosome-linked intracellular protein glycosylation is essential for mammalian viability and cellular metabolism. Mol. Cell. Biol., 24, 1680-1690.
PubMed Reference
Zachara NE, O'Donnell O, Mercer JJ, Marth JD, and Hart GW (2004) Dynamic O-GlcNAc modification of nucleocytoplasmic proteins in response to stress. A survival response of mammalian cells. J. Biol. Chem., 279, 30133-30142.
PubMed Reference
Zachara NE and Hart GW.  (2004) O-GlcNAc a sensor of cellular state: The role of nucleocytoplasmic glycosylation in modulating cellular function in response to nutrition and stress. Biochim. Biophys. Acta., 1673, 13-28.
PubMed Reference
Zachara NE, Cheung WD, and Hart GW.  (2004) Nucleocytoplasmic glycosylation, O-GlcNAc: identification and site mapping. In Signal Transduction Protocols, Methods in Molecular Biology, R. Dickson and M. Mendenhall (eds), Humana Press, Totowa, USA. Volume 284, pp.175-194.
PubMed Reference


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