A Quantitative LC-MS/MS Method for Distinguishing the Tau Protein Forms Phosphorylated and Nonphosphorylated at Serine-396

• DOI: 10.1021/jasms.2c00324
• Publication Date: 2023-01-31T14:28:18Z
• Authors: Anne-Marie Jacobsen; Nico C. van de Me...; Dorte K. Ditlevsen; Ketil Tvermosegaard; Frank Schalk; Wietske Lambert; Christoffer Bundg...; Jan T. Pedersen; Nina Rosenqvist
• Keywords: Tau protein; Tauopathy

Hyperphosphorylated tau protein is well-known to be involved in the formation of neurofibrillary tangles and progression age-related neurodegenerative diseases (tauopathies), including Alzheimer's Disease (AD). Tau phosphorylated at serine-396 (pS396-tau) often linked disease progression, we therefore developed an analytical method measure pS396-tau cerebrospinal fluid (CSF) humans animal models AD. In S396-region, multiple phosphorylation sites are present, causing structural complexity sensitivity challenges for conventional bottom-up mass spectrometry approaches. Here, present indirect LC-MS/MS quantification pS396-tau. We take advantage reproducible miscleavage caused by S396 being preceded a lysine (K395) proteolytic enzyme trypsin not cleaving when following amino acid phosphorylated. Therefore, treatment with discriminates between forms without can quantified as difference total S396-tau nonphosphorylated S396-tau. To qualify method, it was successfully applied human CSF from healthy controls patients Mild Cognitive Impairment addition, rTg4510 mice where clear dose dependent decrease observed intravenous administration monoclonal antibody (Lu AF87908, hC10.2) targeting epitope containing pS396. Finally, formal validation conducted. conclusion, this sensitive LC-MS/MS-based measurement allows quantitative translational biomarker applications tauopathies investigations potential drug induced effects.