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Publication Abstract from PubMed

Microtubule-associated protein tau becomes abnormally phosphorylated in Alzheimer's disease and other tauopathies and forms aggregates of paired helical filaments (PHF-tau). AT8 is a PHF-tau specific monoclonal antibody that is a commonly used marker of neuropathology because of its recognition of abnormally phosphorylated tau. Previous reports described the AT8 epitope to include pS202/pT205. Our studies support and extend previous findings by also identifying pS208 as part of the binding epitope. We characterized the phosphoepitope of AT8 through both peptide binding studies and co-structures with phosphopeptides. From the co-crystal structure of AT8 Fab with the di-phosphorylated (pS202/pT205) peptide it appeared that an additional phosphorylation at S208 would also be accommodated by AT8. Phosphopeptide binding studies showed that AT8 bound to the triply phosphorylated tau peptide (pS202/pT205/pS208) 30-fold stronger than to the pS202/pT205 peptide, supporting the role of pS208 in AT8 recognition. We also show that the binding kinetics of the triply phosphorylated peptide pS202/pT205/pS208 was remarkably similar to that of PHF-tau. The co-structure of AT8 Fab with a pS202/pT205/pS208 peptide shows that the interaction interface involves all six CDRs and tau residues 202-209. All three phosphorylation sites are recognized by AT8, with pT205 acting as the anchor. Crystallization of the Fab/peptide complex under acidic conditions shows that CDR-L2 is prone to unfolding and precludes peptide binding, and may suggest a general instability in the antibody. This article is protected by copyright. All rights reserved.

Epitope mapping and structural basis for the recognition of phosphorylated tau by the anti-tau antibody AT8.,Malia TJ, Teplyakov A, Ernst R, Wu SJ, Lacy ER, Liu X, Vandermeeren M, Mercken M, Luo J, Sweet RW, Gilliland GL Proteins. 2016 Jan 21. doi: 10.1002/prot.24988. PMID:26800003^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.