Assessment of Peptide Chemical Modifications on the Development of an Accurate and Precise Multiplex Selected Reaction Monitoring Assay for Apolipoprotein E Isoforms

Research output: Contribution to journalArticle

Abstract

Apolipoprotein E (ApoE) is a polymorphic protein that plays a major role in lipid metabolism in the central nervous system and periphery. It has three common allelic isoforms, ApoE2, ApoE3 and ApoE4, that differ in only one or two amino acids. ApoE isoforms have been associated with the occurence and progression of several pathological conditions, such as coronary atherosclerosis and Alzheimer's disease. The aim of this study was to develop a mass spectrometry (MS)-based assay for absolute quantification of ApoE isoforms in cerebrospinal fluid and plasma samples using isotope-labeled peptides. The assay included five tryptic peptides: CLAVYQAGAR (ApoE2), LGADMEDVCGR (ApoE2 and 3);. LAVYQAGAR (ApoE3 and 4), LGAD-MEDVR (ApoE4), and LGPLVEQGR (total ApoE). Both cerebrospinal fluid and plasma samples were assayed to validate the method. The digestion yield and the extension of chemical modifications in selected amino acid residues (methionine oxidation, glutamine deamidation, and cyclization of N-terminus carbamidomethylcysteine) were also studied. The ApoE phenotype was successfully assigned to all samples analyzed in a blinded manner. The method showed good linearity (R-2 > 0.99) and reproducibility (within laboratory imprecision <13%). The comparison of the MS-based assay with an ELISA for total ApoE concentration showed a moderate correlation (R-2 = 0.59). This MS-based assay can serve as an important tool in clinical studies aiming to elucidate the association between ApoE genotype, total ApoE, and ApoE isoform concentrations in various disorders related to ApoE polymorphisms.

Details

Authors
  • Eduardo Martinez-Morillo
  • Henrietta Nielsen
  • Ihor Batruch
  • Andrei P. Drabovich
  • Ilijana Begcevic
  • Mary F. Lopez
  • Lennart Minthon
  • Guojun Bu
  • Niklas Mattsson
  • Erik Portelius
  • Oskar Hansson
  • Eleftherios P. Diamandis
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Neurology

Keywords

  • apolipoprotein E, cerebrospinal fluid, chemical modification, isoform, peptide, plasma, selected reaction monitoring
Original languageEnglish
Pages (from-to)1077-1087
JournalJournal of Proteome Research
Volume13
Issue number2
Publication statusPublished - 2014
Publication categoryResearch
Peer-reviewedYes