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Alzheimer disease-specific conformation of hyperphosphorylated paired helical filament-tau is polyubiquitinated through Lys-48, Lys-11, and Lys-6 ubiquitin conjugation
被引:234
作者:
Cripps, D
Thomas, SN
Jeng, Y
Yang, F
Davies, P
Yang, AJ
机构:
[1] Univ So Calif, Sch Pharm, Dept Pharmaceut Sci, Los Angeles, CA 90089 USA
[2] Yeshiva Univ Albert Einstein Coll Med, Dept Pathol, Bronx, NY 10461 USA
[3] Yeshiva Univ Albert Einstein Coll Med, Dept Neurosci, Bronx, NY 10461 USA
[4] Micro Tech Sci Inc, Vista, CA 92081 USA
关键词:
D O I:
10.1074/jbc.M512786200
中图分类号:
Q5 [生物化学];
Q7 [分子生物学];
学科分类号:
071010 ;
081704 ;
摘要:
One of the key pathological hallmarks of Alzheimer disease (AD) is the accumulation of paired helical filaments (PHFs) of hyperphosphorylated microtubule-associated protein Tau. Tandem mass spectrometry was employed to examine PHF-Tau post-translational modifications, in particular protein phosphorylation and ubiquitination, to shed light on their role in the early stages of Alzheimer disease. PHF-Tau from Alzheimer disease brain was affinity-purified by MC1 monoclonal antibody to isolate a soluble fraction of PHF-Tau in a conformation unique to human AD brain. A large number of phosphorylation sites were identified by employing a data-dependent neutral loss algorithm to trigger MS3 scans of phosphopeptides. It was found that soluble PHF-Tau is ubiquitinated at its microtubule-binding domain at residues Lys-254, Lys-311, and Lys-353, suggesting that ubiquitination of PHF-Tau may be an earlier pathological event than previously thought and that ubiquitination could play a regulatory role in modulating the integrity of microtubules during the course of AD. Tandem mass spectrometry data for ubiquitin itself indicate that PHF-Tau is modified by three polyubiquitin linkages, at Lys-6, Lys-11, and Lys-48. Relative quantitative analysis indicates that Lys-48-linked polyubiquitination is the primary form of polyubiquitination with a minor portion of ubiquitin linked at Lys-6 and Lys-11. Because modification by Lys-48-linked polyubiquitin chains is known to serve as the essential means of targeting proteins for degradation by the ubiquitin-proteasome system, and it has been reported that modification at Lys-6 inhibits ubiquitin-dependent protein degradation, a failure of the ubiquitin-proteasome system could play a role in initiating the formation of degradation-resistant PHF tangles.
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页码:10825 / 10838
页数:14
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