brain control of body fluid compartments

Mass spectrometry (MS) techniques enable a broad characterization throughout the protein, with high specificity and quantitative precision, which has been challenging using traditional immunochemistry tools. In this context, understanding the qualitative as well as quantitative aspects of tau phosphorylation at more than 80 potential phosphorylation sites is critical for dissecting changes in the landscape of tau phosphorylation during aggregation over the course of disease progression. Despite evidence that tau phosphorylation can induce its self-assembly, the exact mechanism or the critical phosphorylation sites are a matter of debate ( Alonso et al., 2001). Supporting this hypothesis, abnormally-phosphorylated tau (p-tau) has been detected in AD tau aggregates using phospho-specific antibodies ( Köpke et al., 1993 Braak and Braak, 1995 Augustinack et al., 2002). One of the main hypotheses regarding the origin of the pathogenesis of AD attributes abnormal tau phosphorylation patterns to its disassembly from microtubules and aggregation as paired helical filaments (PHF Iqbal et al., 2005 Wang and Mandelkow, 2016). However, to date, the biological and molecular pathways leading to the abnormal tau proteins observed in the different tauopathies are not well understood. Normally a soluble protein, there is a growing body of evidence associating insoluble tau accumulation in the brain with cognitive decline ( Villemagne et al., 2015 Schöll et al., 2016). Tau protein aggregation in the brain is one of the hallmarks of neurodegenerative diseases called tauopathies, including Alzheimer disease (AD), some frontotemporal dementia (FTD), progressive supranuclear palsy (PSP), Pick’s disease, and corticobasal degeneration (CBD). Targeted MS multiplexing ability and high-throughput capacity lets us envision the use of these new p-tau measurements as promising biomarkers for AD diagnosis and tracking therapeutic responses. These site-specific p-tau rates are independent of tau concentration and distinct of current CSF tau and p-tau assays measuring tau isoforms levels. Conversely, we found that S202 was hypophosphorylated in CSF and was not hyperphosphorylated in AD, demonstrating that p-tau isoforms could have different metabolisms depending on which sites are phosphorylated. This supports the hypothesis that tau hyperphosphorylation could be a physiological process amplified by AD pathology. In AD CSF, hyperphosphorylation on these sites was exacerbated, and phosphorylation on T153 and T175 specifically were detected. CSF tau proteins from non-AD participants were significantly hyperphosphorylated on T111, T205, S208, T217 and T231. Comparison of the p-tau rates from the brain and the CSF indicated that the abundance of phosphorylated sites varied in a site-specific manner. Notably, phosphorylation on T205 and S208, recognized by AT8 antibody defining Braak stages of brain tau aggregation, were not detected in normal brain soluble tau but were found in the CSF. Some phosphorylation sites increased in CSF, while others decreased compared to brain.

Brain soluble tau phosphorylation sites are localized on three domains including a proline-rich mid-domain, the C-terminus, and a cluster on the N-terminal projection domain not previously characterized.

We detected 29 distinct phosphorylated tau (p-tau) sites in full-length tau from soluble human brain lysate and 12 sites on truncated tau in CSF, mainly in the mid-domain. This method enables us to compare the abundance of phosphorylation sites in tau proteins in the brain and cerebrospinal fluid (CSF) in humans with and without AD. To investigate this further, we developed a highly sensitive and specific mass spectrometry (MS) method using parallel reaction monitoring (PRM) to identify tau phosphorylation sites. Though the mechanism of tau destabilization is not fully understood yet, tau protein has been found to be hyperphosphorylated in tau aggregates. Tau protein aggregation into neurofibrillary tangles in the central nervous system contributes to the etiology of certain neurodegenerative disorders, including Alzheimer’s disease (AD). and Joanne Knight Alzheimer’s Disease Research Center, Washington University School of Medicine, St.

2Hope Center for Neurological Disorders, Washington University School of Medicine, St.

1Department of Neurology, Washington University School of Medicine, St.

Barthélemy 1*, Nipun Mallipeddi 1, Paul Moiseyev 1, Chihiro Sato 1 and Randall J.

Brain control of body fluid compartments