GSBS Dissertations and Theses

ORCID ID

0000-0003-0524-3338

Approval Date

9-8-2017

Document Type

Doctoral Dissertation

Academic Program

Biochemistry and Molecular Pharmacology

Department

Department of Neurology

First Thesis Advisor

Dr. Daryl A. Bosco

Keywords

amyotrophic lateral sclerosis, profilin 1, protein stability, X-ray crystallography, protein misfolding, actin dynamics, cell biology, neurodegeneration

Abstract

Mutations in profilin 1 (PFN1) cause amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease that targets motor neurons. PFN1 is a 15 kDa protein that is best known for its role in actin dynamics. However, little is known about the pathological mechanisms of PFN1 in ALS. In this dissertation, it is demonstrated that certain familial ALS-linked mutations severely destabilize the native conformation of PFN1 in vitro and cause accelerated turnover of the PFN1 protein in neuronal cells. This mutation-induced destabilization can account for the high propensity of ALS-linked variants to aggregate and also provides rationale for their reported functional defects in cell-based assays. The source of this destabilization is illuminated by the crystal structures of several PFN1 proteins, revealing an expanded cavity near the protein core of one ALS variant and predicting a non-surface exposed cavity in another. Functional biochemical experiments point to abnormalities in actin filament nucleation and elongation caused by PFN1 mutants. In HeLa cells, PFN1 is essential for the generation of actin-rich filopodia and expression of mutant PFN1 alters filopodia density further supporting a pathogenesis mechanism involving actin cytoskeleton. Taken together, this dissertation infers that the pathogenesis of ALS due to mutations in PFN1 can be mediated at least by two possibly related mechanisms, a destabilization of the native PFN1 structure and an impact on the actin assembly processes.

DOI

10.13028/M2TT2M

Rights and Permissions

Copyright is held by the author, with all rights reserved.

Available for download on Sunday, October 20, 2019

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