John C. Chatham, Ph.D., Professor, and Adam R. Wende, Ph.D., Associate Professor, in the Division of Molecular and Cellular Pathology, have been awarded a two-year, R21 grant from the National Heart, Lung and Blood Institute (NHLBI) to study the role of protein O-linked N-Acetylglucosamine in regulating cardiac physiology.
All proteins are modified in different ways and alter cell function. The most common modification is phosphorylation. The modification the team studies, O-linked N-Acetylglucosamine – O-GlcNAc for short – is a little different in that it is based on the metabolism of glucose. It was identified in the mid-1980s but research on it has been slow to evolve.
The team responded to a program announcement from NHLBI that focused on studying the normal or healthy functioning of human cells and organs critical to the heart and lung, and studies that may reveal the basis of resilience. “The opportunity was high-risk and high-reward,” Chatham says.
Dr. John Chatham, Professor, Molecular and Cellular Pathology
"What I liked about it was the goal was not to understand disease—they’re asking basic questions about how things function," he says. "In the last five-plus years I've been growing more interested in the basic, ‘why?’ One area of specific interest highlighted in the program announcement was on fundamental knowledge of the glycome—sugars on proteins—and the role of post-translational modification of proteins in regulating cellular function. Our study is focused on a tiny piece of glycobiology, but it fit very well into the ask."
Wende says this funding opportunity was disease-agnostic and being able to focus on fundamental biology was a large part of its appeal.
"So many grants focus on disease,” he says. "But these proteins and these modifications are in place for a reason, and the disease happens when they don’t work, so we want to understand how and why they function. The modification of the proteins is ubiquitous—it takes places in the brain, heart, liver, you name it. A broader perspective is that what we learn about in the heart might work in other areas."
Chatham has been working in this particular area of research since the early 2000s. In May of 2015 he was awarded one of the first UAB School of Medicine AMC21 Reload Multi-investigator Grants, one of four funded of 45 grant proposals received. The title of that project was, "Protein O-GlcNAcylation: Central Mediator of Metabolic Induced Cardiovascular Complications."
Wende’s research in this area began about 2009, the year before he met Dr. Chatham. Wende says, “One of the reasons I came to UAB to start my faculty career was to be able to collaborate with Chatham on this topic.”
Dr. Adam Wende, Associate Professor, Molecular & Cellular Pathology
“The fact that this protein modification, O-GlcNAc, is related to glucose has generated interest especially related to diabetes and diabetic complications linked to the heart,” Chatham says. “We don’t really know what it does in terms of regulating the normal function of the heart.”
“What makes this study important and exciting is that in the disease state it has been assumed by many researchers that too much of this modification can lead to pathologies,” Wende says. "But we also know it’s part of the normal cell biology. Hyperglycemia in diabetes may lead to higher GlcNAc and disease but some of Dr. Chatham’s work has shown that, through fasting, GlcNAc levels are even more elevated."
The study's first aim looks at how fasting affects this protein modification, and the enzymes, OGT and OGA that regulate it, in the mouse heart. During time periods of fasting they plan to use immunohistochemistry to see where in cardiomyocytes the changes are occurring. They will also examine how the response of the heart to fasting is changed in mouse models from the Wende Lab, where hearts have been genetically modified to increase or decrease this modification.
In the second aim they will look at the spatial and temporal changes in O-GlcNAc, OGT and OGA in response to different stimuli such as insulin and stresses such as glucose deprivation. They will use fluorescently labeled OTG and OGA labeled with different fluorophores.
“When we stimulate the cells, we will be able to see where they go, and this has not been explored in cardiomyocytes before,” Chatham says.
Certain animal studies target ways to reduce this modification as a potential therapeutic in diabetes —suggesting reducing it would be beneficial. "If we really don’t know what it’s doing under normal conditions, or what would be the consequences of just decreasing it—it may not necessarily be a good thing. Not knowing the fundamental biology, it could be damaging--we just don’t understand it yet," Chatham explains.
Their goal is to use this study to generate preliminary data that can be used to support the submission of a five-year R01 within the next two years.
Chatham and Wende along with Jianhua Zhang, Ph.D., Professor, Division of Molecular and Cellular Pathology, have recently published a comprehensive review of O-GlcNAc biology in physiology and pathophysiology in Physiological Reviews.