Lab Members

Coordinates ongoing lab efforts

Elevated O-GlcNAcylation promotes an enhanced immune response: When the SARs-CoV-2 virus emerged in late 2019, the world was faced with a challenge of simultaneously treating, fighting and understanding a novel pathogen. While little was initially known about the biology of this novel virus, it became immediately clear that patients with certain underlying diseases, like cancer, cardiovascular disease, and diabetes were at increased risk of developing severe COVID-19. This observation underscored the role a patient’s immune response played in disease risk. One common feature of these underlying diseases is that elevated O-GlcNAcylation has been described in all. Thus, I hypothesized that chronic hyper-O-GlcNAcylation, as seen in diseases like diabetes, predisposes patients to an altered immune response to pathogens. To test this hypothesize I study a mouse in which the O-GlcNAcase (OGA), the enzyme that removes O-GlcNAc has been deleted within the immune system. Thus, these mice have elevated O-GlcNAcylation in their immune cells. I have found that elevated O-GlcNAcylation limits nitric oxide production and promotes deregulation of specific pro-inflammatory cytokines. Additionally, along with Kaylee Philbrick (Post Bac), we seek to define how elevated O-GlcNAc impacts T cell activation and differentiation.

Current project: Development of next generation artificial bioorthogonal precursors to study levels and interaction partners of GlcNAc-containing glycoconjugates.

Description: Changes in GlcNAc-containing glycoconjugates are associated with a variety of human diseases, such as cancer, diabetes, and neurodegenerative diseases, however the mechanistic details linking altered glycosylation to disease pathology remain poorly understood. Recent efforts in the development of methods to study biomolecules in their native environment have unlocked the door of bioorthogonal chemistry. Functional group modifications around the sugar hydroxyl groups are tolerated by the biosynthetic pathways and transform them into the corresponding sugar-nucleotide donors. Our work is on the development of accessible and effective methods to monitor the levels and interaction partners of GlcNAc-containing glycoconjugates. N-Acetylglucosamine (GlcNAc) represents a critical link between cellular metabolism and glycoconjugates, such as O-GlcNAc and N-linked glycans, which regulate an important and ubiquitous cell signaling paradigm, as well as substrate function, localization, and stability. Our goal is to design and synthesis of easy-to-use bioorthogonal tools that can be used by any biomedical researcher to track levels and interaction partners of GlcNAc-containing glycoconjugates, and then to use them to understand their roles in human health and diseases. Our work prioritizes approaches that are simple to implement and makes use of “off-the shelf” reagents and procedures to develop and engineer bioorthogonal next-generation artificial metabolic reporters capable of specifically labeling GlcNAc-containing glycoconjugates and then applying them to pathogenic disease (metabolic dysfunction, neurodegeneration, and cancer) treatment.

Cells are able to catabolize a variety of nutrient fuels to generate energy, with carbohydrate and fatty acid oxidation being dominant drivers of ATP production in many cells outside the brain. This type of fuel flexibility is important for constitutively active tissues (e.g. the heart) or regulators of systemic metabolism (e.g. liver, adipose) to maintain optimal function despite natural fluctuations in the circulating nutrient supply. In addition, however, cells can shift their overall fuel preference in response to persistent conditions such as high fat diet, chronic stress or exercise training. Little is known about the mechanisms that drive this type of fuel shifting but fuel inflexibility has been implicated in the pathology of multiple diseases including cardiomyopathy, diabetes and non-alcoholic fatty liver disease (NAFLD). One candidate mechanism is through protein O-GlcNAcylation, which is dynamically responsive to acute nutrient levels, interactive with energy and metabolic signaling, but at a timescale that typically outlasts its triggering conditions. Mice with a genetically driven partial deletion of the O-GlcNAc removal enzyme O-GlcNAcase (OGA) demonstrate a persistent whole-body fuel shift away from fatty acid oxidation while pharmacological OGA depression delays the natural transition from carbohydrate to fatty acid fuel preference in mice moving from their fed active state to their resting and fasting state. These published data suggest that removal of O-GlcNAcylation from some protein targets may be required for the efficient utilization of fatty acid oxidation in metabolically flexible cell types. My research in the Hanover lab aims to investigate this supposition across three mechanistic hypotheses.

1. The O-GlcNAc status of transcription factors/co-factors guide their targeting or activity at the promoters of genes that encode for lipid oxidation proteins.
2. O-GlcNAc status influences the activity or stability of proteins that control the availability of fatty acids for oxidation.
3. Protein O-GlcNAcylation, whether through transcriptional or direct action, manipulates carnitine homeostasis, which is critical for the mitochondrial uptake of fatty acids.

A key question of interest is whether a non-dominant splice isoform of OGA (sOGA), which has been localized at both the lipid droplet membrane and in mitochondria, might play a particularly active or lipid-sensitive role in any of these hypothesized mechanisms.

Significance/Impact – Not only will these studies expand our understanding of protein O-GlcNAcylation as a context-dependent metabolic rheostat but they may shed light on the unknown function of OGA splice regulation, which has been putatively linked to the manifestation of clinical diabetes. Furthermore, insight into the mechanisms behind adaptive fuel preference may aid in the development of therapies to mimic the metabolic benefits of exercise and fasting or to mitigate conditions of toxic lipid accumulation.

Relevant Publications - Lockridge, A & Hanover, J. A Nexus of Lipid and O-GlcNAc Metabolism in Physiology and Disease. Frontiers in Endocrinology, section Molecular and Structural Endocrinology.  Front. Endocrinol. 30 August 2022. Doi: 10.3389/fendo.2022.943576

O-GlcNAc modulation impacts DNA damage repair machinery in highly replicative cells

Highly replicative cells accumulate DNA mutations leading to accumulation of point mutations and chromosome abnormalities. Using mouse embryonic stem cells, mouse embryonic fibroblasts and cancer cells, Dr. Cruz aims to understand how O-GlcNAc modulation impacts replication stress, DNA damage machinery and cell fate. Dr. Cruz’s work has focused on how O-GlcNAc acts in cell plasticity and differentiation with the goal of defining metabolic and molecular O-GlcNAc targets that are involved in the response to replicative stress.

O-GlcNAc Transferase (OGT) is a highly conserved enzyme that catalyzes the transfer of a GlcNAc sugar from UDP-GlcNAc to serine and threonine residues of its >1000 different intracellular substrates. This posttranslational modification is dynamic and can be removed by O-GlcNAcase (OGA). Disruption of the O-GlcNAc balance has been implicated in a wide variety of diseases; elevated O-GlcNAcylation has been observed in diabetes, cardiovascular disease, and cancer. These diseases are among the common conditions that put patients at increased risk of severe infectious disease, such as by COVID-19 infection, and it has been proposed that hyper-O-GlcNAcylation is partially responsible for this risk. This is supported by evidence that hyper-O-GlcNAcylation contributes to a pro-inflammatory phenotype in macrophages. While an increase in O-GlcNAcylation has been shown to be necessary for proper T-cell activation, it remains unclear if underlying hyper-O-GlcNAcylation impacts the T cell response. To better understand the impact of chronically elevated O-GlcNAc on T cell function, we activated CD4+ splenocytes harvested from mice in which OGA is specifically deleted in lymphocytes (Oga^CD2-Cre) in vitro via culturing with α-CD3/CD28. Using this system, we investigated the effect of Oga-mediated hyper-O-GlcNAcylation on immunoregulatory transcription factors and cytokines at the transcriptional and translational levels. This research will give us insights into how O-GlcNAc levels modulate the immune response and have further implications in understanding inflammatory and autoimmune diseases.

Conducted Research/Editing - Detoxication

Conducts research—Lectins and Carbohydates

Current Position: Senior researcher, Novartis, Inc.

Current Position: Professor, University of Tokyo.

Current Position: Director of Research, Glycobiology, Inc.

Current Position: Senior Researcher, University of Sienna.

Current Position: Professor, University of Texas, Galveston.

Current Position: Professor, Wright State University.

Current Position: Professor, Head of Innovation Field Virus-based Technologies, Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB.

Current Position: Research Associate Professor, Georgetown University.

Current Position: Research Associate Professor, University of Pennsylvania.

Current Position: Researcher, University of Sienna.

Current Position: Research, Merck Pharmaceuticals.

Current Position: Staff Physician, FDA

Current Position: Program Officer, NIAID.

Current Position: Staff, NCBI, National Library of Medicine.

Current Position: Director, Division of Informatics, University of Maryland.

Current Position: Associate Professor, Dept. of Biochemistry and Health Science, Changwon National University (DOK).

Current Position: Associate Professor, Dept. of Cytobiochemistry, University of Lodz.

Current Position: Associate Professor, Changwon National University (DOK).

Current Position: Director, Research and Development Team, Gyeonggi BioCenter, Gyeonggi Institute of Science and Technology Promotion

Current Position: Assistant Professor, Dept. of Science Education-Chemistry Major, Daegu University.

Current Position: Retired.

Current Position: Assistant Professor, Biology Dept., College of Holy Cross.

Current Position: Staff Scientist, FDA/CBER, Laboratory of Bacterial Polysaccharide

Current Position: Program Officer, NIGMS

Current Position: Ph.D, Candidate, Washington University in St. Louis

Current Position: Reviewer, FDA.

Current Position: Biologist, FDA.

Current Position: Assistant Professor, Medical College of Wisconsin.

Current Position: Medical Student, University of Connecticut Medical School.

Current Position: Lab Manager, Versiti Blood Center of Wisconsin.

Current Position: Medical Student, Columbia University Medical School.

Current Position: Scientist, Salubrious Biotherapeutics.

Current Position: Medical Student, Georgetown Medical School.

Current Position: Assistant Professor, Korean Food Research Institute