Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular Biophysics and Biochemistry

First Advisor

Koleske, Anthony

Abstract

The Trio family of proteins consists of Trio, Kalirin, UNC-73 (in Caenorhabditis elegans) and dTrio (in Drosophila). Trio proteins are key regulators of cell morphogenesis and migration, tissue organization, and secretion and protein trafficking in many biological contexts. Recent discoveries have linked Trio and Kalirin to human disease, including neurological disorders and cancer. The genes for Trio family proteins encode a series of large multidomain proteins with up to three catalytic activities and multiple scaffolding and protein-protein interaction domains. As such, Trio family proteins engage a wide array of cell surface receptors, substrates, and interaction partners to coordinate changes in cytoskeletal regulatory and protein trafficking pathways. In Chapter 1, I provide a comprehensive review of the specific mechanisms by which Trio family proteins carry out their functions in cells, highlight the biological and cellular contexts in which they occur, and relate how alterations in these functions contribute to human disease. This sets up the context for a major goal of my thesis, which was to elucidate a regulatory mechanism of Trio catalytic activity and understand how disease associated mutations disrupt this regulation. In Chapter 2, I describe my co-first author work, which uncovered a mode of Trio regulation. The Trio spectrin repeats (SRs) are adjacent to the Trio GEF1 domain and disease-associated mutations to the SRs have been shown to impact Trio GEF1 activity. I provide evidence that the Trio SRs autoinhibit Trio GEF1 activity via intramolecular interactions, and this is relieved by disease-associated mutations. In Chapter 3, I discuss unpublished work to understand how Trio is regulated in a cellular context. I cover my work to generate a Trio knockout fibroblast cell line and discover activators of the autoinhibited Trio GEF1 activity. This preliminary work is supported by Chapter 4, in which I describe the most pressing future experiments and approaches I recommend to follow up my thesis work. Together, the work described in this thesis provides insight into a novel mechanism of Trio regulation and sets up a framework for many exciting future discoveries.

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