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J Proteome Res. 2016 Feb 5;15(2):667-76. doi: 10.1021/acs.jproteome.5b01001. Epub 2016 Jan 19.

Tau Protein Quantification in Human Cerebrospinal Fluid by Targeted Mass Spectrometry at High Sequence Coverage Provides Insights into Its Primary Structure Heterogeneity.

Author information

1
CEA, iBiTec-S , Service de Pharmacologie et d'Immunoanalyse, Laboratoire d'Etude du Métabolisme des Médicaments, Gif-sur-Yvette 91191, France.
2
CHU Montpellier, IRMB, hôpital St Eloi, Laboratoire de Biochimie Protéomique Clinique et CCBHM , INSERM-UM1 U1040, Montpellier F-34000 France.
3
Inserm, UMR-S 1172, Alzheimer & Tauopathies, Centre de Recherche Jean-Pierre Aubert, Lille, Univ. Lille, Faculté de Médecine, Lille F-59045, France.
4
Centre Mémoire Ressources Recherche, CHU Montpellier, hôpital Gui de Chauliac, Montpellier. Université Montpellier I , Montpellier F-34000 France.

Abstract

Tau protein plays a major role in neurodegenerative disorders, appears to be a central biomarker of neuronal injury in cerebrospinal fluid (CSF), and is a promising target for Alzheimer's disease immunotherapies. To quantify tau at high sensitivity and gain insights into its naturally occurring structural variations in human CSF, we coupled absolute quantification using protein standard with the multiplex detection capability of targeted high-resolution mass spectrometry (MS) on a Quadrupole-Orbitrap instrument. Using recombinant tau we developed a step-by-step workflow optimization including an extraction protocol that avoided affinity reagents and achieved the monitoring of 22 tau peptides uniformly distributed along the tau sequence. The lower limits of quantification ranged (LLOQ) from 150 to 1500 pg/mL depending on the peptide. Applied to endogenous CSF tau, up to 19 peptides were detected. Interestingly, there were significant differences in the abundance of peptides depending on their position in the sequence, with peptides from the tau mid-domain appearing significantly more abundant than peptides from the N- and C-terminus domains. This MS-based strategy provided results complementary to those of previous ELISA or Western Blot studies of CSF tau and could be applied to tau monitoring in human CSF cohorts.

KEYWORDS:

alternative splicing-dependent peptides; cerebrospinal fluid; microtubule-associated tau protein; parallel reaction monitoring; protein absolute quantification; protein fragments; protein precipitation; solid-phase extraction

PMID:
26742856
DOI:
10.1021/acs.jproteome.5b01001
[Indexed for MEDLINE]

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