title: Characteristics of TBS-extractable hyperphosphorylated tau species: aggregation intermediates in rTg4510 mouse brain.
abstract: Conditional overexpression of four-repeat human tau containing the P301L missense mutation in the rTg4510 mouse model of tauopathy leads to progressive accumulation of neurofibrillary tangles and hyperphosphorylated, sarkosyl-insoluble tau species, which are biochemically comparable to abnormal tau characteristic of hereditary tauopathies termed FTDP-17. To fully understand the impact of tau species at different stages of self-assembly on neurodegeneration, we fractionated rTg4510 brain representing several stages of tauopathy to obtain TBS-extractable (S1), high salt/sarkosyl-extractable (S3), and sarkosyl-insoluble (P3) fractions. Under reducing condition, the S1 fraction was demonstrated by western blotting to contain both 50-60 kDa normally-sized and 64 kDa tau. Both are thermo-stable, but the 64 kDa tau showed a higher degree of phosphorylation. Under non-reducing condition, nearly all TBS-extractable 64 kDa tau were detected as ∼130 kDa species consistent with the size of dimer. Quantitative analysis showed ∼80 times more 64 kDa tau in S1 than P3 fraction. Immunoelectron microscopy revealed tau-positive granules/short filaments in S1 fraction. These structures displayed MC1 immunoreactivities indicative of conformational/pathological change of tau. MC1 immunoreactivity was detected by dot blotting in samples from 2.5 month-old mice, whereas Ab39 immunoreactivity indicative of late stages of tau assembly was detected only in P3 fraction. Quantitative analysis also demonstrated a significant inverse correlation between brain weight and 64 kDa tau, but the level of TBS-extractable 64 kDa tau reflects neurodegeneration better than that of sarkosyl-insoluble 64 kDa tau. Together, the findings suggest that TBS-extractable 64 kDa tau production is a potential target for therapeutic intervention of tauopathies.
authors.affiliation: Center for Translational Research in Neurodegenerative Disease and Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA. nsahara@ufl.edu
authors.forename: Naruhiko
authors.initials: N
authors.lastname: Sahara
authors.forename: Michael
authors.initials: M
authors.lastname: DeTure
authors.forename: Yan
authors.initials: Y
authors.lastname: Ren
authors.forename: Abdul-Shukkur
authors.initials: AS
authors.lastname: Ebrahim
authors.forename: Dongcheul
authors.initials: D
authors.lastname: Kang
authors.forename: Joshua
authors.initials: J
authors.lastname: Knight
authors.forename: Christiane
authors.initials: C
authors.lastname: Volbracht
authors.forename: Jan Torleif
authors.initials: JT
authors.lastname: Pedersen
authors.forename: Dennis W
authors.initials: DW
authors.lastname: Dickson
authors.forename: Shu-Hui
authors.initials: SH
authors.lastname: Yen
authors.forename: Jada
authors.initials: J
authors.lastname: Lewis
mesh_terms: D000818:Animals; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000378:metabolism* / Q000473:pathology*; D001923:Brain Chemistry / Q000502:physiology; D005591:Chemical Fractionation / Q000379:methods; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation / Q000502:physiology; D014325:Tromethamine / Q000737:chemistry*; D016875:tau Proteins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D016875:tau Proteins; D014325:Tromethamine