Elizabeth A. Sweeny, PhD

Dr. Sweeny received her PhD in Biochemistry and Molecular Biophysics at the University of Pennsylvania. Her graduate work was focused on enzymology and stress responses, using biophysical and biochemical techniques to study the structure and mechanism of a yeast disaggregase Hsp104. She then spent a year doing postdoctoral research at the MIT-Broad Synthetic Biology Foundry working on a project involving the transfer of a refactored nitrogen fixation gene cluster from bacteria into the mitochondria of yeast. Afterwards she moved to the Lerner Research Institute at the Cleveland Clinic, where her research focused on the regulation of heme proteins and heme homeostasis in the cell. Dr. Sweeny started her lab at MCW in August 2021. The lab is currently focused on 1) investigating the crosstalk between heme proteins and the actin cytoskeleton, mitochondria, RNA processing proteins, and cellular stress response systems and 2) using patient derived tissues and cells to investigate the role these factors play in cardiovascular health and disease, with a specific focus on the role of NOX5 in the development and progress of atrial fibrillation.

Heme proteins play essential roles in several critical cellular processes, including gas exchange, catalysis, electron transfer reactions, transcriptional control, and initiation and propagation of signaling cascades. Consequently, dysfunction of heme proteins contributes to many human diseases including pulmonary and cardiovascular disorders. In many of these diseases it is unclear how pathogenic changes begin or the cascade of events that ultimately cause disease. This is particularly true for atrial fibrillation (AF). The main risk factor for AF development is aging, and AF therapies are mostly focused on treatment rather than prevention. In large part this is due to our incomplete understanding of the factors that drive AF initiation and progression. Therefore, a more comprehensive understanding of the basic biology behind normal cardiac function and the molecular mechanisms behind pathological cascades will allow for the development of novel therapeutics that could prevent in addition to treat AF and other cardiovascular disorders.

We are particularly interested in a transmembrane heme containing signaling enzyme NADPH oxidase 5 (NOX5). NOX5 is activated by increases in intracellular calcium to produce a superoxide burst. While its physiological roles are still being uncovered, it’s been shown to be critical for monocyte differentiation into dendritic cells, differentiation and maturation of oligodendrocytes, sperm motility and viability, and vascular contraction. Additionally, it’s been implicated in cancers, diabetes, and cardiovascular disorders. Using a protocol to study heme insertion and subsequent activity of NOX5 we found that changes in intracellular heme levels, nitric oxide, and Hsp90 binding dynamically regulate NOX5 activity through controlling its heme saturation and oligomerization.

NOX5 in atrial fibrillation.
AF is characterized by rapid, irregular heartbeats and increases the risk for stroke, myocardial infarction, heart failure and death. Recently, NOX5 was identified as a regulator of vascular contraction, linking calcium and redox signaling, and a number of known NOX5 regulators including peptide hormones, kinases and intracellular Ca2+, have been shown to be dysregulated in AF. In preliminary studies we’ve found that NOX5 protein is found in tissue from the Left Atrial Appendage (LAA) from patients in sinus rhythm as well as patients in AF. We have also been able to study NOX5 activity in induced pluripotent stem cell (iPSC) derived cardiomyocytes (CMs) and found that treatment with AngII and ET-1 increase superoxide production and that increased intracellular heme levels increases it further. Overall we are interested in understanding how NOX5 and changes in its expression and activity play a role in normal cardiomyocyte biology as well as the pathogenesis of atrial fibrillation. By coupling biochemistry, cell biology, and studies in patient derived cells and tissues, we can manipulate the system (pacing stress, changes in heme and NO exposure to iPSC-CMs) and study the downstream effects - alterations in NOX5 PTMs, protein partners, activity, expression, localization, and the global effects of these changes. Then using patient derived tissue we can test our hypotheses generated from the iPSC-CM system.

NOX5 protein partners
We have used two methods to probe the interactomes of a number of heme proteins including NOX5. The NOX5 protein partners pulled out of these MS screens show a strong enrichment for mitochondrial proteins, proteins associated with the actin cytoskeleton, RNA regulating proteins, and cellular chaperones. We are interested in understanding how these interactions contribute to physiological and pathological cellular responses not only to increase our basic biological understanding of the cell, but also to provide a path to the development of new therapeutics and biomarkers for disease diagnosis and treatment. We use a variety of techniques to study the role of these interactions in cells and how they drive cellular responses using model cell systems (HEK293 with and without NOX5 expression) and iPSC derived cardiomyocytes.