2026 Symposium | Katherine Matthew | “Identifying Intracellular Creatine Sensing Sites and Mechanisms”
ABSTRACT
Creatine plays an important role in energy homeostasis in the cell and is obtained through both diet and endogenous synthesis. The endogenous synthesis of creatine involves a two-step enzymatic reaction. The first enzyme, L-arginine:glycine amidinotransferase (AGAT), uses arginine and glycine to synthesize guanidinoacetate (GAA). Then the second enzyme, guanidinoacetate methyltransferase, methylates GAA to form creatine. However, some people are born with impaired ability to synthesize or transport creatine leading to creatine deficiency syndromes (CDS). Creatine regulates its own synthesis in a negative feedback loop by downregulating AGAT expression; however, the exact mechanism of this regulation is unknown. Our lab had previously identified a portion of the N-terminus of AGAT (nAGp) which is sufficient for creatine-mediated downregulation and that this process likely occurs via ribosomal stalling. This led to our hypothesis that creatine binds the nascent nAGp in the ribosomal exit tunnel, causing translation to halt and the translation complex to disassociate. To investigate this hypothesis, I wanted to test whether the nAGp or the ribosome could interact with creatine on their own. I started by testing whether nAGp interacts with creatine without other factors using nuclear magnetic resonance spectroscopy. Using this technique, I determined that the nAGp does not interact with creatine without other factors present. The next step in this project is to investigate whether the ribosome can interact with creatine without other factors present. This work will help narrow down the mechanism of creatine-mediated AGAT downregulation which will ultimately help develop new treatment strategies for CDS patients.