Ubiquitin is conjugated with amino-terminally processed tau in paired helical filaments.
We have investigated ubiquitinated paired helical filaments, which produce a proteinaceous smear in SDS-polyacrylamide gel electrophoresis and immunoblotting. The smear consisted largely of the carboxy-terminal portion of tau and ubiquitin. The ubiquitin-targeted protein was identified as tau in paired helical filaments, and the conjugation sites were localized to the microtubule-binding region. Most ubiquitin in paired helical filaments occurred as a monoubiquitinated form, and only a small proportion of ubiquitin formed multiubiquitin chains. There was a ubiquitin-negative smear, in which tau was much less processed in the amino-terminal portion. This strongly suggests that the amino-terminal processing of tau in paired helical filaments precedes its ubiquitination.
Morishima-Kawashima
M
M
Department of Neuropathology, Faculty of Medicine, University of Tokyo, Japan.
Hasegawa
M
M
Takio
K
K
Suzuki
M
M
Titani
K
K
Ihara
Y
Y
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases; D006801:Humans; D013058:Mass Spectrometry; D008870:Microtubules / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016874:Neurofibrillary Tangles / Q000378:metabolism; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism*; D010449:Peptide Mapping; D011485:Protein Binding; D014452:Ubiquitins / Q000302:isolation & purification / Q000378:metabolism*; D016875:tau Proteins / Q000302:isolation & purification / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D010446:Peptide Fragments; D014452:Ubiquitins; D016875:tau Proteins; D010450:Endopeptidases