Simple, single-shot phosphoproteomic analysis of heat-stable tau

We developed a simple, antibody-free approach for single shot analysis of tau phosphorylation across the entire protein by liquid-chromatography tandem mass spectrometry (LC-MS/MS) to study age-related changes in tau phosphorylation. 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 degeneration. 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 serine235 tau and phosphorylated serine396 tau levels in an expanded cohort of 14 monkeys.