The modification of intracellular proteins by O-linked ?-N-acetylglucosamine (O-GlcNAc) has emerged as a novel regulator of cytoprotection. Numerous forms of cellular injury, including cardiac ischemic preconditioning (acute, prolonged, and remote), lead to elevated levels of O-GlcNAc in both in vivo and in vitro models. Elevating O-GlcNAcylation before, or immediately after, the induction of cellular injury is protective in models of ischemia reperfusion (I/R) injury, as well as heat stress, oxidative stress, endoplasmic reticulum stress, hypoxia, and trauma hemorrhage. Together, these data suggest that O-GlcNAc is a novel endogenous cardioprotective agent. To date, the majority of work studying the O-GlcNAc modification in models of I/R injury has focused on identifying the proteins and mechanisms by which O-GlcNAc mediates cardioprotection. However, understanding the regulation of the O-GlcNAc modification during injury is critical and is yet unstudied. The goal of this proposal is to map the regulatory networks of the enzymes that cycle the O-GlcNAc modification, the O- GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Specifically, we will complete the following aims:
Aim 1. Define the impact of protein-protein interactions on OGT and OGA activity and substrate targeting in the injured heart. Quantitative mass spectrometry will be used to identify protein-interactors of OGT and OGA. A combination of biochemical approaches will be used to interrogate the role of these effector- proteins on O-GlcNAc cycling in the ischemic heart.
Aim 2. Map the OGT and OGA covalent-regulatory networks in the injured heart. The O-GlcNAc modification sites, and other covalent-regulators, of OGT and OGA will be identified. The impact of O- GlcNAcylation on OGT/OGA function will be assessed in models of oxidative stress and I/R injury. Collectively, we anticipate that these studies will define the pathways that regulate OGT, OGA, and O- GlcNAcylation during I/R injury. This critical insight will provide a framework for investigating novel therapeutic targets for myocardial infarction and an understanding about how the O-GlcNAc-mediated stress response is dysregulated contributing to cardiovascular disease
Our goal is to determine how the two enzymes, the O-GlcNAc transferase and the O-GlcNAcase, which write and erase a cardioprotective modification, the sugar O-GlcNAc, are regulated in the heart in response injury (for example, heart attack). These studies will highlight targets for the development of novel therapeutics to reduce tissue damage and death, resulting from myocardial infarction, stroke, and trauma hemorrhage.
| Zachara, Natasha E (2018) Critical observations that shaped our understanding of the function(s) of intracellular glycosylation (O-GlcNAc). FEBS Lett 592:3950-3975 |
