Quantification of Tau Protein Lysine Methylation in Aging and Alzheimer’s Disease

Article type: Research Article

Authors: Huseby, Carol J.^{a; 1} | Hoffman, Claire N.^{b; 1} | Cooper, Grace L.^b | Cocuron, Jean-Christophe^c | Alonso, Ana P.^c | Thomas, Stefani N.^d | Yang, Austin J.^d | Kuret, Jeff^{a; b; e; *}

Affiliations: [a] Interdisciplinary Biophysics Graduate Program, Ohio State University, Columbus, OH, USA | [b] Ohio State Biochemistry Program, Ohio State University, Columbus, OH, USA | [c] BioDiscovery Institute, University of North Texas, Denton, TX, USA | [d] Department of Anatomy and Neurobiology; Molecular & Structural Biology Program, Greenebaum Cancer Center, University of Maryland, Baltimore, MD, USA | [e] Department of Biological Chemistry & Pharmacology, Ohio State University, Columbus, OH, USA

Correspondence: [*] Correspondence to: Jeff Kuret, PhD, Department of Biological Chemistry & Pharmacology, Ohio State University, 1060 Carmack Rd, Columbus, Ohio, 43210, USA. Tel.: +1 614 688 5899; E-mail: kuret.3@osu.edu.

Note: [1] These authors contributed equally to this work.

Abstract: Tau is a microtubule-associated protein that normally interacts in monomeric form with the neuronal cytoskeleton. In Alzheimer’s disease, however, it aggregates to form the structural component of neurofibrillary lesions. The transformation is controlled in part by age- and disease-associated post-translational modifications. Recently we reported that tau isolated from cognitively normal human brain was methylated on lysine residues, and that high-stoichiometry methylation depressed tau aggregation propensity in vitro. However, whether methylation stoichiometry reached levels needed to influence aggregation propensity in human brain was unknown. Here we address this problem using liquid chromatography–tandem mass spectrometry approaches and human-derived tau samples. Results revealed that lysine methylation was present in soluble tau isolated from cognitively normal elderly cases at multiple sites that only partially overlapped with the distributions reported for cognitively normal middle aged and AD cohorts, and that the quality of methylation shifted from predominantly dimethyl-lysine to monomethyl-lysine with aging and disease. However, bulk mol methylation/mol tau stoichiometries never exceeded 1 mol methyl group/mol tau protein. We conclude that lysine methylation is a physiological post-translational modification of tau protein that changes qualitatively with aging and disease, and that pharmacological elevation of tau methylation may provide a means for protecting against pathological tau aggregation.

Keywords: Aging, Alzheimer’s disease, mass spectrometry, methylation, phosphorylation, post-translational modification, tau protein

DOI: 10.3233/JAD-190604

Journal: Journal of Alzheimer's Disease, vol. 71, no. 3, pp. 979-991, 2019