Mass spectrometry quantification of clusterin in the human brain
Mass spectrometry quantification of clusterin in the human brain
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Date
2012-08-20
Authors
Chen, Junjun
Wang, Meiyao
Turko, Illarion
Advisor
Citation
Chen, J., Wang, M. & Turko, I.V. Mass spectrometry quantification of clusterin in the human brain. Mol Neurodegeneration 7, 41 (2012).
DRUM DOI
Abstract
Background: The multifunctional glycoprotein clusterin has been associated with late-onset Alzheimer’s disease
(AD). Further investigation to define the role of clusterin in AD phenotypes would be aided by the development of
techniques to quantify level, potential post-translational modifications, and isoforms of clusterin. We have
developed a quantitative technique based on multiple reaction monitoring (MRM) mass spectrometry to measure
clusterin in human postmortem brain tissues.
Results: A stable isotope-labeled concatenated peptide (QconCAT) bearing selected peptides from clusterin was
expressed with an in vitro translation system and purified. This clusterin QconCAT was validated for use as an
internal standard for clusterin quantification using MRM mass spectrometry. Measurements were performed on the
human postmortem frontal and temporal cortex from control and severe AD cases. During brain tissues processing,
1% SDS was used in the homogenization buffer to preserve potential post-translational modifications of clusterin.
However, MRM quantifications in the brain did not suggest phosphorylation of Thr
393
, Ser
394
, and Ser
396
residues
reported for clusterin in serum. MRM quantifications in the frontal cortex demonstrated significantly higher
(P < 0.01) level of clusterin in severe AD group (39.1 ± 9.1 pmol/mg tissue protein) in comparison to control group
(25.4 ± 4.4 pmol/mg tissue protein). In the temporal cortex, the clusterin levels were not significantly different,
29.0 ± 7.9 pmol/mg tissue protein and 28.0 ± 8.4 pmol/mg tissue protein in control and severe AD groups,
respectively.
Conclusions: The proposed protocol is a universal quantitative technique to assess expression level of clusterin. It is
expected that application of this protocol to quantification of various clusterin isoforms and potential
post-translational modifications will be helpful in addressing the role of clusterin in AD.