ABSTRACT / PROJECT SUMMARY
Alzheimer’s Disease (AD) is associated with a progressive loss of dendritic spines, microscopic dendritic
structures that serve as the sites of synaptic communication and are essential for the storage of memory. Levels
of the RhoGEF Ephexin5, a regulator of dendritic spine density, appear to be key in facilitating AD-induced
dendritic spine loss. Much about the substrate specificity of Ephexin5 and the regulation of Ephexin5 activity
remain unknown. The goal of this project is to determine the mechanisms by which Ephexin5 signaling
occurs in normal physiology and disease. It is my hypothesis that E5 undergoes a phosphorylation-
dependent shift in substrate specificity from RhoA to Rac1/Cdc42, relevant to its role in regulating spine plasticity
and contributing to the physiology of AD. Using 2-photon fluorescence lifetime imaging coupled with genetically
encoded FRET biosensors, I will optically probe the activity of GTPases in live tissue. I will define the substrate
specificity of neuronal E5 under normal physiological contexts, and in a model of AD-induced cellular damage.
Using mass spectrometry, I will determine if phosphorylation of Ephexin5 changes during neuronal signaling or
in an AD-like cellular state, and using phosphomutant analysis I will examine how phosphorylation influences E5
substrate specificity. My results will further the knowledge of the molecular mechanisms of learning and memory
and have the potential to identify novel therapeutic targets for AD.
Training for this project will take place at UC Davis, with the support of my mentor and Sponsor, Karen Zito, an
expert in the live-imaging of synapses, and Co-sponsor James Trimmer, and expert in neuronal protein structure
and function. I will acquire key technical skills in advanced live-cell imaging and mass spectrometry, which will
aid in the completion of this research project. Additionally I will hone skills of mentorship, management,
communication, and writing.
