We have discovered that the predicted inactive pseudokinase selenoprotein O (SelO) adopts an atypical protein kinase fold, yet transfers AMP instead of phosphate to protein substrates in a post translational modification known as AMPylation. Our results illustrate the catalytic versatility of the protein kinase superfamily and suggest that AMPylation may be a more widespread post translational modification than previously appreciated. SelO localizes to the mitochondria, AMPylates proteins involved in cellular metabolism and redox biology, and appears to regulate an ancient and highly conserved cellular antioxidant signaling pathway. In higher eukaryotes, SelO contains the 21st genetically encoded amino acid, selenocysteine, which we propose functions as a redox sensor to regulate SelO activity in response to oxidative stress. Although reactive oxygen species are an obligatory part of human biology, elevated levels are characteristic of many disease states. For example, elevated reactive oxygen species can lead to DNA damage, which can initiate oncogenic transformation leading to cancer. Furthermore, alterations in redox homeostasis are implicated in the pathology of conditions such as stroke, heart attack, and peripheral vascular disease, all of which are major contributors to morbidity and mortality in United States. Therefore, a mechanistic understanding of the pathways that protect cells from oxidative stress could have major impacts on human health and disease. The major goal of this proposal is to determine the molecular mechanisms by which SelO-dependent AMPylation of mitochondrial proteins protects cells from oxidative stress and regulates redox homeostasis. As part of this work, we will determine the functional consequences of SelO-catalyzed AMPylation of a subset of substrates as well as the structural basis for the redox-dependent regulation of SelO activity. We anticipate that the results obtained herein will have the potential to define new paradigms of cellular regulation and redox signaling and could lead to innovative diagnostic tools or novel approaches for the treatment of human diseases.

Public Health Relevance

This project is focused on a SelO, a recently discovered pseudokinase with a unique catalytic activity, and its role in cellular antioxidant signaling. Redox homeostasis plays an essential role in many disease states and discovering new pathways involved in its regulation could have profound effects not only on our basic understanding of redox biology but also for patients with human diseases. !

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM135189-02
Application #
10092201
Study Section
Molecular and Integrative Signal Transduction Study Section (MIST)
Program Officer
Barski, Oleg
Project Start
2020-02-01
Project End
2024-01-31
Budget Start
2021-02-01
Budget End
2022-01-31
Support Year
2
Fiscal Year
2021
Total Cost
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Biochemistry
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390