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Author Notes:

Correspondence: Nicholas T Seyfried; nseyfri@emory.edu and James J Lah; jlah@emory.edu

Authors' Contributions: LED, DMD and NTS performed the experiments.

EBD, DMD and NTS analyzed and compiled data.

LED and EBD prepared the manuscript with input upon revision from all authors.

Reagents and resources were provided by AIL, JJL and NTS, who also collaboratively designed the experiments.

All authors read and approved the final manuscript.

Acknowledgments: We thank members of the Lah/Levey and Seyfried laboratories for constructive discussion regarding this manuscript.

We also thank Bob Karaffa (Emory University Flow Cytometry Core Facility) for helpful technical advice.

Acknowledgement is made to the patient participants selected from the Clinical Research in Neurology (CRIN) database at the Emory Alzheimer's Disease Research Center (ADRC).

Disclosures: The authors declare that they have no competing interests.

Subjects:

Research Funding:

This work was supported by the National Institutes of Health through the Emory Alzheimer's Disease Center grant (P50AG025688), the Emory Neuroscience NINDS Proteomics Core Facilities (P30NS055077), and NIH training grants (T32 T32NS007480 to LED and F32 AG038259-01A2 to EBD).

Keywords:

  • blood biomarkers
  • platelet activation
  • mass spectrometry
  • membrane proteomics
  • glycoprotein
  • matrix metalloprotease inhibitor
  • amyloidogenic protein
  • alpha granule secretion
  • coagulation

Exploring the potential of the platelet membrane proteome as a source of peripheral biomarkers for Alzheimer's disease

Tools:

Journal Title:

Alzheimer's Research and Therapy

Volume:

Volume 5, Number 3

Publisher:

, Pages 32-32

Type of Work:

Article | Final Publisher PDF

Abstract:

Introduction Peripheral biomarkers to diagnose Alzheimer's disease (AD) have not been established. Given parallels between neuron and platelet biology, we hypothesized platelet membrane-associated protein changes may differentiate patients clinically defined with probable AD from noncognitive impaired controls. Methods Purified platelets, confirmed by flow cytometry were obtained from individuals before fractionation by ultracentrifugation. Following a comparison of individual membrane fractions by SDS-PAGE for general proteome uniformity, equal protein weight from the membrane fractions for five representative samples from AD and five samples from controls were pooled. AD and control protein pools were further divided into molecular weight regions by one-dimensional SDS-PAGE, prior to digestion in gel. Tryptic peptides were analyzed by reverse-phase liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Ionized peptide intensities were averaged for each identified protein in the two pools, thereby measuring relative protein abundance between the two membrane protein pools. Log2-transformed ratio (AD/control) of protein abundances fit a normal distribution, thereby permitting determination of significantly changed protein abundances in the AD pool. Results We report a comparative analysis of the membrane-enriched platelet proteome between patients with mild to moderate AD and cognitively normal, healthy subjects. A total of 144 proteins were determined significantly altered in the platelet membrane proteome from patients with probable AD. In particular, secretory (alpha) granule proteins were dramatically reduced in AD. Of these, we confirmed significant reduction of thrombospondin-1 (THBS1) in the AD platelet membrane proteome by immunoblotting. There was a high protein-protein connectivity of proteins in other pathways implicated by proteomic changes to the proteins that define secretory granules. Conclusions Depletion of secretory granule proteins is consistent with a preponderance of post-activated platelets in circulation in AD. Significantly changed pathways implicate additional AD-related defects in platelet glycoprotein synthesis, lipid homeostasis, amyloidogenic proteins, and regulators of protease activity, many of which may be useful plasma membrane-expressed markers for AD. This study highlights the utility of LC-MS/MS to quantify human platelet membrane proteins and suggests that platelets may serve as a source of blood-based biomarkers in neurodegenerative disease.

Copyright information:

© 2013 Donovan et al.; licensee BioMed Central Ltd.

This is an Open Access work distributed under the terms of the Creative Commons Attribution 2.0 Generic License (http://creativecommons.org/licenses/by/2.0/).

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