Examining the Role of the AMP‐activated Protein Kinase in Stress‐Dependent O‐GlcNAc Signaling

Abstract

Acute enhancement of O‐linked‐beta‐N‐acetylglucosamine (O‐GlcNAc) modification on intracellular proteins activates an endogenous protective program in numerous models of injury, including cardiac ischemia reperfusion injury (IR/I). The O‐GlcNAc transferase (OGT) and the O‐GlcNAcase (OGA) enzymes are responsible for adding and removing the O‐GlcNAc moiety from proteins, respectively. This project aims to understand how cells regulate OGT and OGA in response to oxidative stress to promote cell survival and cardioprotection. AMP‐activated protein kinase (AMPK) integrates cellular stress signals with energy balance to affect cellular function, and thus plays a critical role in the cellular stress response. Our data and other studies suggest a complex interplay between OGT, OGA, AMPK, and downstream kinases that may impact stress‐induced O‐GlcNAcylation. These data include: 1) mTOR interacts with OGA in response to oxidative stress; 2) OGT and AMPK interact in response to oxidative stress, and AMPK is O‐ GlcNAc modified; and 3) ULK‐1 interacts with OGT in response to oxidative stress. To explore the significance of these interactions, we are taking two approaches. Firstly, we are examining stress‐induced glycosylation in AMPK knockout MEFs. Secondly, we are generating tagged constructs of OGT and AMPK to test the impact of the interaction between these enzymes on their function, as well as the impact of O‐GlcNAcylation on AMPK function. These experiments will further elucidate the molecular mechanisms by which OGT is regulated during injury.