Transthyretin's Regulatory Role in Beta-Amyloid Aggregation and Toxicity Alzheimer's disease (AD) has been linked to deposition of beta-amyloid (A?) as amyloid plaques in the brain. Transgenic mice expressing the human A? precursor protein (APP) produce high levels of A? and develop amyloid plaques, but they do not suffer the extensive neuronal cell death that is characteristic of AD. Recent studies have uncovered a possible explanation: these transgenic mice greatly increase the synthesis of the transport protein transthyretin (TTR), and TTR appears to protect the mice from the neurotoxic effects of A?. The long-term goals of this project are to answer three questions that arise from these intriguing results: (1) how does TTR exert its protective activity? (2) why does this natural protective activity fail in AD? (3) can it be restored? Our hypothesis is that subtle changes in TTR tertiary and/or quaternary structure strongly modulate TTR- A? interactions.
In specific aim 1, several TTR mutants that differ in their tertiary and/or quaternary structure and stability will be produced and characterized. Each mutant will be screened for its ability to interfere with A? aggregation, and to inhibit A? toxicity in an in vitro cell culture model. The data will be analyzed to identify correlations between TTR structure and stability with its ability to alter A? aggregation and toxicity.
In specific aim 2, a detailed examination of the interaction between TTR (both wildtype and selected mutants) and A? will be undertaken. Biophysical and biochemical tools such as circular dichroism, fluorescence, static and dynamic light scattering, crosslinking, and kinetic modeling will be employed. From these data will emerge molecular-level mechanistic insights into the nature of TTR-A? association and the means by which TTR affects A? aggregation kinetics. The goal of specific aim 3 is to identify small ligands that stabilize TTR and determine their influence on TTR's ability to modulate A? aggregation and toxicity.
In aim 4, TTR (wildtype and mutants) along with TTR-binding ligands will be tested for protection against A? toxicity in ex vivo and in vivo mouse models. This will be achieved by using a newly developed assay in which stereotactic injection of A? into mouse brain leads to loss of CA1 and dentate gyrus neurons, and by infection of astrocytes with adenovirus-TTR constructs. The project spans from characterization of the structure and stability of TTR (and mutants), through in vitro assessment of TTR's effect on A? aggregation and toxicity, to in vivo evaluation of TTR efficacy at preventing neuronal cell death. These studies will provide a sound and rational basis for developing novel pharmacological approaches to preventing AD by enhancement of the natural defenses provided by TTR.

Public Health Relevance

Alzheimer's disease has been linked to deposition of beta-amyloid plaques in the brain and subsequent death of neurons. Previous studies with transgenic mice suggest that a normal protein, transthyretin, may provide some protection against the neuronal cell death caused by beta-amyloid. This investigation will provide a sound and rational basis for developing novel pharmacological approaches to preventing Alzheimer's disease by enhancement of the natural defenses provided by transthyretin.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
1R01AG033493-01
Application #
7614921
Study Section
Special Emphasis Panel (ZRG1-MDCN-C (02))
Program Officer
Refolo, Lorenzo
Project Start
2009-08-01
Project End
2011-07-31
Budget Start
2009-08-01
Budget End
2010-07-31
Support Year
1
Fiscal Year
2009
Total Cost
$412,697
Indirect Cost
Name
University of Wisconsin Madison
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
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Lu, Xiaomeng; Murphy, Regina M (2018) Nanoparticle Tracking for Protein Aggregation Research. Methods Mol Biol 1777:145-158
Pate, Kayla M; Murphy, Regina M (2017) Cerebrospinal Fluid Proteins as Regulators of Beta-amyloid Aggregation and Toxicity. Isr J Chem 57:602-612
Lu, Xiaomeng; Brickson, Claire R; Murphy, Regina M (2016) TANGO-Inspired Design of Anti-Amyloid Cyclic Peptides. ACS Chem Neurosci 7:1264-74
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Cho, Patricia Y; Joshi, Gururaj; Boersma, Melissa D et al. (2015) A Cyclic Peptide Mimic of the ?-Amyloid Binding Domain on Transthyretin. ACS Chem Neurosci 6:778-89
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Yang, Dennis T; Joshi, Gururaj; Cho, Patricia Y et al. (2013) Transthyretin as both a sensor and a scavenger of ?-amyloid oligomers. Biochemistry 52:2849-61

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