Structural and Quantitative Comparison of Cerebrospinal Fluid Glycoproteins in Alzheimer’s Disease Patients and Healthy Individuals
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Glycoproteins in cerebrospinal fluid (CSF) are altered in Alzheimer’s Disease (AD) patients compared to control individuals. We have utilized albumin depletion prior to 2D gel electrophoresis to enhance glycoprotein concentration for image analysis as well as structural glycoprotein determination without glycan release using mass spectrometry (MS). The benefits of a direct glycoprotein analysis approach include minimal sample manipulation and retention of structural details. A quantitative comparison of gel-separated glycoprotein isoforms from twelve AD patients and twelve control subjects was performed with glycoprotein-specific and total protein stains. We have also compared glycoforms in pooled CSF obtained from AD patients and control subjects with mass spectrometry. One isoform of α1-antitrypsin showed decreased glycosylation in AD patients while another glycosylated isoform of an unassigned protein was up-regulated. Protein expression levels of α1-antitrypsin were decreased, while the protein levels of apolipoprotein E and clusterin were increased in AD. No specific glycoform could be specifically assigned to AD.
KeywordsProteomics Glycoproteomics Glycoprotein N-linked Glycosylation Glycoform Isoform CSF Cerebrospinal fluid Alzheimer’s Disease α1-antitrypsin Apolipoprotein E Clusterin Haptoglobin α-1-β-glycoprotein Zinc-α-2-glycoprotein 2D gel electrophoresis 2D-GE Albumin depletion Image analysis Mass spectrometry FT-ICR MS Linear ion trap
The authors thank Dr. Hasse Karlsson, Inst Biomedicine, Goteborg University, for the nano-LC setup and good advice on mass spectrometry and data assignment. This work was supported by DMR 0084173, Swedish Research Council and Wilhelm och Martina Lundgrens stiftelse. The purchase of the LTQ-FT-ICR mass spectrometer was made possible through a grant from Knut and Alice Wallenberg Foundation (C. L. Nilsson and R. A. Zubarev).
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