Direct analysis of tau from PSP brain identifies new phosphorylation sites and a major fragment of N-terminally cleaved tau containing four microtubule-binding repeats

• Published in: Journal of neurochemistry 2008-06, Vol.105 (6), p.2343-2352
• Main Authors: Wray, Selina, Saxton, Malcolm, Anderton, Brian H, Hanger, Diane P
• Format: Article
• Language: English
• Subjects: Adult and adolescent clinical studies; Alzheimer disease; Alzheimer's disease; Amino Acid Sequence; Binding sites; Biochemistry; Biological and medical sciences; Brain Chemistry - physiology; cleavage; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Humans; Medical sciences; Microtubules - chemistry; Microtubules - metabolism; Microtubules - pathology; Molecular Sequence Data; Neurology; Organic mental disorders. Neuropsychology; Peptide Fragments - isolation & purification; Peptide Fragments - metabolism; phosphorylation; Phosphorylation - physiology; progressive supranuclear palsy; Protein Binding; Protein Processing, Post-Translational; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Solubility; Spectrum analysis; Supranuclear Palsy, Progressive - metabolism; Supranuclear Palsy, Progressive - pathology; tau; tau Proteins - chemistry; tau Proteins - metabolism; Terminal Repeat Sequences - physiology
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2008.05321.x

Tangles containing hyperphosphorylated aggregates of insoluble tau are a pathological hallmark of progressive supranuclear palsy (PSP). Several phosphorylation sites on tau in PSP have been identified using phospho-specific antibodies, but no sites have been determined by direct sequencing due to the difficulty in enriching insoluble tau from PSP brain. We describe a new method to enrich insoluble PSP-tau and report eight phosphorylation sites [Ser46, Thr181, Ser202, Thr217, Thr231, Ser235, Ser396/Ser400 (one site) and Thr403/Ser404 (one site)] identified by mass spectrometry. We also describe a 35 kDa C-terminal tau fragment (tau35), lacking the N-terminus of tau but containing four microtubule-binding repeats (4R), that is present only in neurodegenerative disorders in which 4R tau is over-represented. Tau35 was readily detectable in PSP, corticobasal degeneration and 4R forms of fronto-temporal dementia with parkinsonism linked to chromosome 17, but was absent from control, Alzheimer's disease and Pick's disease brain. Our findings suggest the aggregatory characteristics of PSP-tau differ from those of insoluble tau in Alzheimer's disease brain and this might be related to the presence of a C-terminal cleavage product of tau.