Date of Award

Fall 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular Biophysics and Biochemistry

First Advisor

Koleske, Anthony

Abstract

The TRIO family of proteins, which includes Trio, Kalirin, UNC-73 (in Caenorhabditis elegans), and dTrio (in Drosophila), are key regulators of cell morphogenesis, migration, tissue organization, and neuronal development through their regulation of Rho GTPases. These proteins feature multiple catalytic and scaffolding domains that mediate GTPase activation and cellular localization. TRIO proteins are essential for processes like actin dynamics, cell migration, and synaptic function, and disruptions in their activity have been linked to neurodevelopmental and neuropsychiatric disorders. This study focuses on Trio, specifically its regulatory mechanisms and how disease-related mutations disrupt its catalytic activity, contributing to various human diseases.

In Chapter 1, I provide a review of the known mechanisms by which Trio carries out its functions in the brain and how disruptions contribute to human mental diseases. This sets up context for the primary goal of my thesis: elucidate auto-regulatory mechanisms by which Trio controls catalytic activity and how disease-related mutations disrupt this regulation.

In Chapter 2, I describe my first author work which discovered the αN-Linker region of GEF2 is critical for catalytic activity for RhoA, and this is decreased by the presence of the PH domain of GEF2. Variants near the αN-Linker region are associated with bipolar disorder, epilepsy and schizophrenia and are located in the unique β3-β4 loop of GEF2. I provide evidence that schizophrenia-associated variant GEF2 D2202G and epilepsy-associated variants GEF2 P2210L and GEF2 G2211E, release GEF2 autoinhibition by its PH2 domain. I also provide evidence that this activation led to reduced neuritogenesis in Nuero-2A (N2A) cells. This contrasts notably from the PH1 domain of TRIO, which enhances GEF1 exchange activity on Rac1.

In Chapter 3, I describe the primary future experiments and approaches I recommend to continue my thesis work. Deciphering the specific molecular alterations caused by different TRIO variants can potentially identify therapeutic targets that may lead to more effective treatments for conditions such as schizophrenia and epilepsy. This aspect adds a translational dimension to my research, aligning it with the broader goal of advancing new therapeutic approaches for Trio-related disorders.

Lastly, in Chapter 4 and Chapter 5, I describe unpublished work in projects aimed at 1) to understand the impacts of the PH domain on BRAG1 GEF activity on the Arf1 GTPase, and 2) to understand the relationship between actin filaments and NMDA receptors. Chapter 6 describes overall conclusions and closing statements.

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