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A Temporal Quantitative Profiling of Newly Synthesized Proteins during Abeta Accumulation

ABSTRACT: Accumulation of aggregated amyloid beta in the brain is believed to impair multiple cellular pathways and play a central role in Alzheimer disease pathology. But how this process is regulated remains unclear. In theory, measuring protein synthesis is the most direct way to evaluate a cell response to stimuli, but to date there have been few reliable methods to do this. To identify the protein regulatory network during the development of Abeta deposition in AD, we applied a new proteomic technique to quantitate newly synthesized protein (NSP) changes in the cerebral cortex and hippocampus of 2-, 5- and 9-month-old APP/PS1 AD transgenic mice. This bioorthogonal non-canonical amino acid tagging analysis combined PALM (Pulse Azidohomoalanine Labeling in Mammals) and HILAQ (Heavy Isotope Labeled AHA Quantitation) to reveal a comprehensive dataset of NSPs prior to and post Abeta deposition, including the identification of proteins not previously associated with AD, and demonstrated that the pattern of differentially expressed NSPs is age dependent. We also found dysregulated vesicle transportation networks including endosomal subunits, coat protein complex I (COPI) and mitochondrial respiratory chain throughout all time points and two brain regions. These results point to a pathological dysregulation of vesicle transportation that occurs prior to Abeta accumulation and the onset of AD symptoms, which may progressively impact the entire protein network and thereby drive neurodegeneration. This study illustrates key pathway regulation responses to the development of AD pathogenesis by directly measuring the changes in protein synthesis and provides unique insights into the mechanisms that underlie AD.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Mus Musculus (ncbitaxon:10090)

SUBMITTER: John R.Yates III

PROVIDER: MSV000086234 | MassIVE | Sat Oct 03 11:30:00 BST 2020

REPOSITORIES: MassIVE

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Project description:Extracellular senile plaques of amyloid beta (Abeta) are a pathological hallmark in brain of patients with Alzheimer`s Disease (AD). Abeta is generated by the amyloidogenic processing of the amyloid precursor protein (APP). Concomitant to Abeta load, AD brain is characterized by an increase in protein level and activity of the angiotensin-converting enzyme (ACE). ACE inhibitors are a widely used class of drugs with established benefits for patients with cardiovascular disease. However, the role of ACE and ACE inhibition in the development of Abeta plaques and the process of AD-related neurodegeneration is not clear since ACE was reported to degrade Abeta. To investigate the effect of ACE inhibition on AD-related pathomechanisms, we used Tg2576 mice with neuron-specific expression of APPSwe as AD model. From 12 months of age, substantial Abeta plaque load accumulates in the hippocampus of Tg2576 mice as a brain region, which is highly vulnerable to AD-related neurodegeneration. The effect of central ACE inhibition was studied by treatment of 12 month-old Tg2576 mice for six months with the brain penetrating ACE inhibitor captopril. At an age of 18 months, hippocampal gene expression profiling was performed of captopril-treated Tg2576 mice relative to untreated 18 month-old Tg2576 controls with high Abeta plaque load. As an additional control, we used 12 month-old Tg2576 mice with low Abeta plaque load. Whole genome microarray gene expression profiling revealed gene expression changes induced by the brain-penetrating ACE inhibitor captopril, which could reflect the neuro-regenerative potential of central ACE inhibition. Microarray gene expression profiling was performed of hippocampi isolated from aged, 18 month-old Tg2576 (APPSwe-transgenic) AD mice with high Abeta plaque load relative to age-matched Tg2576 mice, which were treated for 6 months with the centrally active ACE inhibitor captopril. Another study group consisted of 12 month-old Tg2576 mice with low Abeta plaque load. In total, three study groups were analyzed, i.e. (i) 18 month-old untreated Tg2576 mice with high Abeta plaque load, (ii) age-matched Tg2576 mice treated for 6 months with the brain-penetrating ACE inhibitor captopril (20 mg/kg body weight/day in drinking water), and (iii) untreated 12 month-old Tg2576 mice with low Abeta plaque load reflecting the time point when captopril treatment was initiated. Two biological replicates were made of each group, and total hippocampal RNA of four mice was pooled for one gene chip.

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A Temporal Quantitative Profiling of Newly Synthesized Proteins during Abeta Accumulation

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