Alzheimer's disease (AD) is a debilitating disorder first recognized over a century ago. Since then, AD has been extensively investigated; however, many questions remain concerning how molecular hallmarks translate to clinical symptoms. Pathologically, AD is characterized by the misfolding and aggregation of proteins, particularly amyloid beta 1-42 peptides (A?42) and hyperphosphorylated tau. Although A?42 accumulation is one of the earliest pathological events, how increased levels of A?42 induce toxicity in neurons and contribute to synaptic loss remains poorly understood. One hypothesis, as evidenced by the plaques and tangles found in AD patients' brains, is that A?42 impairs protein degradation either by directly interacting with proteins or by sequestering or hampering protein degradation machinery causing vulnerable proteins to persist in the brain. This project aims to determine the specific proteins that have decreased degradation dynamics in models of AD-like pathology. Proteins that persist for longer periods due to stunted degradation may potentially contribute to AD etiology through loss-of-function mechanisms or by disrupting protein homeostasis balance, both of which may lead to neuronal dysfunction. To investigate protein degradation dynamics in AD-like pathology, I am using pulse-chase metabolic labeling in an in vivo paradigm with the recently developed APP knock-in mice. I will then analyze the degradation rates of thousands of proteins using proteomic-based quantitative mass spectrometry. In these experiments, proteins are labeled with ?heavy? isotopes, then chased with ?light? isotopes. I subsequently measure degradation rates by monitoring the remaining ?heavy? proteins. Proteins with decreased degradation dynamics in the presence of A?42 may represent substrates of impaired protein degradation and may reveal critical components in early AD pathology. Based on preliminary data, proteins with the most severe degradation impairments were significantly enriched for proteins associated with the presynaptic active zone, especially synaptic vesicle proteins. These proteins had impaired degradation in the cortex and hippocampus, but not the cerebellum, a brain region where A?42 pathology is absent until late stages of the disease, further supporting an A?42 dependent effect. These findings indicate that synaptic vesicle proteins may represent pioneering protein networks that contribute to synaptic dysfunction in AD-like pathology. This project also aims to determine the molecular mechanisms underlying the degradation impairment in synaptic vesicle proteins by investigating the involvement of non-A?42 fragments of APP processing, as well as by investigating the role of tau. This proposal represents a unique approach that has the potential to identify novel proteins or protein pathways that contribute to AD etiology or early pathology, as well as determine potential mechanisms for how some proteins, which may play a critical role in early AD pathology, persist in the brain.

Public Health Relevance

Alzheimer's disease (AD) is the most prominent neurodegenerative disorder, affecting approximately 40 million people worldwide; and AD is projected to drastically increase in prevalence over the next few decades. The current proposal aims to understand the early molecular basis of AD by determining how amyloid beta affects protein degradation, especially at the synapse. These studies may reveal proteins or pathways that are critical to AD etiology or early pathology, and subsequently could be targeted to prevent or halt the progression of this debilitating disease.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Predoctoral Individual National Research Service Award (F31)
Project #
1F31AG059364-01A1
Application #
9681715
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Yang, Austin Jyan-Yu
Project Start
2018-12-01
Project End
2020-11-30
Budget Start
2018-12-01
Budget End
2019-11-30
Support Year
1
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Neurology
Type
Schools of Medicine
DUNS #
005436803
City
Chicago
State
IL
Country
United States
Zip Code
60611