Inhibitors of Amyloid Beta Oligomerization and Toxicity

Author

• Maria C. Zabala Rodriguez, University of Central FloridaFollow

Keywords

Amyloid Beta, Alzheimer's disease, oligomers, protein disulfide isomerase, oligomer reversal, amyloid toxcity

Abstract

Neurotoxic aggregates of amyloid beta (Aβ) peptide contribute to the etiology of Alzheimer's disease (AD). Aβ_1-42 forms oligomeric structures that undergo further aggregation into protofibrils and fibrils. Oligomeric Aβ_1-42 is more toxic than monomers or mature fibrils. In this work, we used two distinct approaches to inhibit Aβ_1-42 oligomerization and toxicity. First, seven distinct but overlapping Aβ fragments were used to identify their individual aggregation propensities and their effects on Aβ_1-42 oligomerization and cytotoxicity. Studies on suppression of Aβ_1-42 cytotoxicity by peptides, including those derived from Aβ_1-42, have been conducted before, but peptides encompassing the whole Aβ_1-42 sequence have not been systematically analyzed. Aβ_1-42 was allowed to aggregate and form oligomeric assemblies in aqueous buffer for 4 h in the absence or presence of 2-fold molar excess of an Aβ fragment. Cytotoxicity analysis then recorded the impact of each fragment on Aβ_1-42 cytotoxicity as well as the toxicity of the fragments themselves. An enzyme-linked immunosorbent assay that detects oligomeric Aβwas used to determine the effect of each fragment on Aβ_1-42 oligomerization after 4 h of aggregation. Four fragments of Aβ_1-42 inhibited the toxicity of oligomeric Aβ_1-42 to various degrees, while two others conferred no cellular protection against Aβ_1-42 toxicity. Interestingly, one fragment enhanced Aβ_1-42 toxicity after 4 h of aggregation. Three of the four fragments that blocked Aβ_1-42 toxicity partially disrupted oligomer formation, showing correlation between the inhibition of Aβ_1-42 aggregation and the inhibition of cellular toxicity. Second, we examined whether protein disulfide isomerase (PDI), a chaperone mainly found in the endoplasmic reticulum, could reverse the oligomeric state of aggregated Aβ_1-42 and thus its toxicity. Previous work has demonstrated that PDI inhibits Aβ_1-42 aggregation at sub-stoichiometric concentrations. To assess PDI's effect on Aβ_1-42 toxicity, Aβ_1-42 was allowed to aggregate for 2 h before the addition of PDI at a 1:10 molar ratio of PDI to Aβ_1-42 and then allowed to aggregate for another 2 h. MTS cytotoxicity assays using PC-12 cells showed that adding PDI 2 h after the start of aggregation improves cell survival. Through a differential centrifugation assay followed by Western blot, we qualitatively illustrated that PDI can reverse a 2 h aggregate of Aβ_1-42 to the monomeric state. Overall, in this project we have learned that inhibiting the oligomeric assembly of Aβ_1-42 directly decreases the effect of Aβ_1-42 toxicity. Inhibition of Aβ_1-42 toxicity was seen with both fragments derived from Aβ_1-42 and PDI, shedding light into two novel approaches as possible therapeutics for AD.

Completion Date

2024

Semester

Spring

Committee Chair

Teter, Ken; Tatulian, Suren

Degree

Master of Science (M.S.)

College

College of Medicine

Department

Burnett School of Biomedical Sciences

Degree Program

Biotechnology

Format

application/pdf

Identifier

DP0028375

URL

https://purls.library.ucf.edu/go/DP0028375

Language

English

Rights

In copyright

Release Date

May 2029

Length of Campus-only Access

5 years

Access Status

Masters Thesis (Campus-only Access)

Campus Location

Orlando (Main) Campus

STARS Citation

Zabala Rodriguez, Maria C., "Inhibitors of Amyloid Beta Oligomerization and Toxicity" (2024). Graduate Thesis and Dissertation 2023-2024. 206.
https://stars.library.ucf.edu/etd2023/206

Accessibility Status

Meets minimum standards for ETDs/HUTs