Arun Upadhyay, United States of America
Northwestern University, Feinberg School of Medicine Department of NeurologyAuthor Of 1 Presentation
PULSE-CHASE PROTEOMICS OF APP KNOCK-IN MOUSE MODELS OF AMYLOID PATHOLOGY REVEALS SYNAPTIC DYSFUNCTION ORIGINATES IN PRESYNAPTIC TERMINALS
Abstract
Aims
Alzheimer’s disease (AD) is pathologically characterized by the presence of protein deposits in amyloid plaques and neurofibrillary tangles. However, an understanding of the mechanisms responsible for impaired protein degradation in AD is lacking. Our goal is to identify proteins with impaired turnover during the early stage of Aβ42 accumulation in vivo and determine how this process may contribute to AD etiology.
Methods
We performed 15N stable isotope metabolic pulse-chase labeling with liquid chromatography tandem-mass spectrometry (MS)- based proteomic analysis of App knock in mice. We monitored protein turnover in multiple brain regions across different stages of Aβ proteotoxicity in AppNL/NL, AppNL-F/NL-F, AppNL-G-F/NL-G-F models at six and 12 months of age. We also used immunohistochemistry, thioflavin, immunohistochemistry, electron microscopy, electrophysiology, and multi-isotope imaging MS, full methods can be found our upcoming Cell Systems publication.
Results
We discovered that the axon terminal represents the predominant cellular compartment with hampered proteostasis, as presynaptic proteins have impaired turnover just as Aβ42 accumulation becomes detectable. These proteins have elevated levels - not due to compensatory increases in mRNA abundance. Multiple synaptic vesicle (SV) associated proteins accumulated in both amyloid plaque-dependent and -independent manners. Aβ and APP interact with SV proteins, and Aβ42 impedes SV fusion. The SV pool is enlarged, and short-term potentiation is elevated before hippocampal synapse density is reduced or synaptic transmission becomes impaired.
Conclusions
Axon terminals are among the earliest and most vulnerable cellular compartments affected by AD-like pathology and may play a pioneering role in the establishment of synaptotoxicity and cognitive impairment in AD.