Seeding of synthetic amyloid-β(1-42) monomers by amyloid-β(1-42) present in Alzheimer’s brains Öffentlichkeit

Abstract

As aggregates of the self-assembling amyloid-beta(1-42) peptide (Aβ42) become increasingly

popular targets in the search for Alzheimer’s disease (AD) therapeutics, it is especially critical to

further understand the aggregation mechanism and characterize the resulting three-dimensional

structures. Prior studies have semi-selectively extracted Aβ42 aggregates out of brain samples

from AD patients and characterized them with negative staining and cryo-EM. Helical Aβ42

fibrils can be identified, but the smaller oligomers that are believed to be the toxic agents remain

elusive. In this work, we aim to investigate the oligomerization and subsequent fibrillization of

Aβ42 in correlation to disease by releasing synthetic rhodamine-labeled Aβ42 (Rho-Aβ42)

monomers into AD brain extract. The solid-state monomers were dissolved into brain extract and

co-incubated over a 1-day period, theoretically allowing for co-aggregation to occur between

synthetic and natural Aβ42 where pre-existing Aβ42 fibrils serve as “seeds” for Rho-Aβ42

addition. Rho-Aβ42 was incubated in both “slow”-progressing and “rapid”-progressing AD

extract, along with a neutral salt buffer containing no brain matter. All samples were examined at

three time-points (t=0 hr, 3 hr, 24 hr) by negative stain transmission electron microscopy. We

found notable differences between the structures of Aβ42 fibrils formed in buffer and brain

extract conditions, emphasizing the need to consider the role of other brain components in

aggregation regardless of self-assembling properties. Subsequent studies will aim to track the

synthetic Aβ42 monomers during their incorporation into brain aggregates using fluorescence

microscopy, as they were synthesized with N-terminal Rhodamine B tags.

Table of Contents

Introduction………………………………………………………………………………………..1

Background………………………………………………………………………………………...5

Methods…………………………………………………………………………………………....10

Results……………………………………………………………………………………………...12

Discussion………………………………………………………………………………………....18

References………………………………………………………………………………………..24

About this Honors Thesis

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School	Emory College
Department	Chemistry
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Chemistry, Biochemistry
Stichwort	Alzheimer's disease Amyloid-beta
Committee Chair / Thesis Advisor	Lynn, David, Emory University
Committee Members	Liu, Fang, Emory University Wen, Zhexing, Emory University

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