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.
- 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.
- O-GlcNAc status influences the activity or stability of proteins that control the availability of fatty acids for oxidation.
- 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.