Date of Award

1-1-2015

Document Type

Masters Thesis

Degree Name

M.S.

Organizational Unit

Chemistry and Biochemistry

First Advisor

Martin Margittai, Ph.D.

Second Advisor

Bryan J. Cowen

Third Advisor

Michelle Knowles

Fourth Advisor

Bri

Fifth Advisor

Scott Nichols

Keywords

Acrylodan, Biological sciences, HSP104, Heat shock protein 104, Molecular chaperones, Pure sciences, Tau

Abstract

The accumulation of microtubule-associated protein tau into fibrillar aggregates is the hallmark of Alzheimer’s disease and other neurodegenerative disorders, collectively referred to as tauopathies. Fibrils can propagate from one cell to the next and spread throughout the brain. However, a study shows that only small aggregates can be taken up by cultured neuronal cells. The mechanisms that lead to the breakage of fibrils into smaller fragments remain unknown. In yeast, the AAA+ chaperone HSP104 processes the reactivation of protein aggregates and is responsible for fragmentation of fibrils. This study focused on investigating the effects of molecular chaperones on tau fibrils and using HSP104 as a model system to test whether we can monitor fibril fracturing.

The assays used to detect the chaperone’s actions on tau utilized acrylodan fluorescence, thioflavin T fluorescence, and sedimentation. Tau fibrils were either formed with a cofactor, heparin, to accelerate assembly or without a cofactor. In the process of investigating the effects of HSP104 on tau fibrils, this study established an assay to determine the effects of breakage on the seeding properties of tau fibrils. Our findings demonstrated that the sonication of tau fibrils produces smaller fragments (seeds) that accelerate the conversion of monomeric tau into fibrils. The use of this assay with HSP104 provided evidence that HSP104 inhibits the elongation of tau fibrils. Indeed, HSP104 inhibits the aggregation of soluble tau into aggregates. However, tau fibril breakage and dissociation were not observed with HSP104, either alone or in combination with co-chaperones (HSP70 and HSP40). Our findings provide insights into the seeding properties of tau fibrils, and suggest that fragmentation is a critical part of tau assembly. This knowledge should be valuable for understanding tau fibril aggregation and propagation in the brain, which is necessary to identify new treatments for neurodegenerative diseases.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Rights Holder

Ahmed Omran

Provenance

Received from ProQuest

File Format

application/pdf

Language

en

File Size

91 p.

Discipline

Biochemistry, Neurosciences, Chemistry

Download



Share

COinS