Simple, Single-Shot Phosphoproteomic Analysis of Heat-Stable Tau Identifies Age-Related Changes in pS235- and pS396-Tau Levels in Non-human Primates

Abstract

Age is the most significant risk factor for Alzheimer’s disease (AD), and understanding its role in specific aspects of AD pathology will be critical for therapeutic development. Neurofibrillary tangles composed of hyperphosphorylated tau are a quintessential hallmark of AD. To study age-related changes in tau phosphorylation, we developed a simple, antibody-free approach for single shot analysis of tau phosphorylation across the entire protein by liquid-chromatography tandem mass spectrometry. This methodology is species independent; thus, while initially developed in a rodent model, we utilized this technique to analyze 36 phosphorylation sites on rhesus monkey tau from the prefrontal cortex (PFC), a region vulnerable to AD-linked degeneration. Data are available via ProteomeXchange with identifier PXD027971. We identified novel, age-related changes in tau phosphorylation in the rhesus monkey PFC and analyzed patterns of phosphorylation change across domains of the protein. We confirmed a significant increase and positive correlation with age of phosphorylated serine 235 tau and phosphorylated serine 396 tau levels in an expanded cohort of 14 monkeys. Histology showed robust labeling for tau phosphorylated at these sites in vulnerable layer III pyramidal cells in the PFC. The results presented in this study suggest an important role of the natural aging process in tau phosphorylation in rhesus monkey.

Going beyond established model systems of Alzheimer’s disease: companion animals provide novel insights into the neurobiology of aging

“…However, this depends on the age of the individual. Specifically, rhesus macaques have an age-related increase in tau phosphorylation (pTau) 166 . Further aggregation of this pTau into NFTs has been observed in particularly aged rhesus macaques, as was the case for a 38-year-old individual who developed NFTs in their entorhinal cortex 147 .…”

PET Imaging in Animal Models of Alzheimer’s Disease

“…Non-human primates such as rhesus macaques and marmosets are not known to develop AD but do accumulate Aβ deposits and show tauopathy in their aged brains ( Paspalas et al, 2018 ; Haque and Levey, 2019 ; Arnsten et al, 2021b ; Datta et al, 2021 ; Leslie et al, 2021 ). Intracranial injection of Aβ 42 and thiorphan, an inhibitor of neprilysin that is responsible for Aβ clearance, has been employed to generate an AD model in middle-aged (16–17 years) rhesus monkeys ( Li et al, 2010 ).…”