title: Quantification of amyloid precursor protein isoforms using quantification concatamer internal standard.
abstract: It is likely that expression and/or post-translational generation of various protein isoforms can be indicative of initial pathological changes or pathology development. However, selective quantification of individual protein isoforms remains a challenge, because they simultaneously possess common and unique amino acid sequences. Quantification concatamer (QconCAT) internal standards were originally designed for a large-scale proteome quantification and are artificial proteins that are concatamers of tryptic peptides for several proteins. We developed a QconCAT for quantification of various isoforms of amyloid precursor protein (APP). APP-QconCAT includes tryptic peptides that are common for all isoforms of APP concatenated with those tryptic peptides that are unique for specific APP isoforms. Isotope-labeled APP-QconCAT was expressed, purified, characterized, and further used for quantification of total APP, APP695, and amyloid-β (Aβ) in the human frontal cortex from control and severe Alzheimer's disease donors. Potential biological implications of our quantitative measurements are discussed. It is also expected that using APP-QconCAT(s) will advance our understanding of biological mechanism by which various APP isoforms involved in the pathogenesis of Alzheimer's disease.
authors.affiliation: Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, United States.
authors.forename: Junjun
authors.initials: J
authors.lastname: Chen
authors.forename: Meiyao
authors.initials: M
authors.lastname: Wang
authors.forename: Illarion V
authors.initials: IV
authors.lastname: Turko
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism / Q000473:pathology; D000595:Amino Acid Sequence; D016564:Amyloid beta-Protein Precursor / Q000032:analysis* / Q000378:metabolism / Q000592:standards; D002247:Carbon Isotopes / Q000737:chemistry; D002540:Cerebral Cortex / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007553:Isotope Labeling; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes / Q000737:chemistry; D010455:Peptides / Q000032:analysis / Q000592:standards; D020033:Protein Isoforms / Q000032:analysis / Q000378:metabolism / Q000592:standards; D012015:Reference Standards; D053719:Tandem Mass Spectrometry / Q000592:standards; D014357:Trypsin / Q000378:metabolism
chemical_list: D016564:Amyloid beta-Protein Precursor; D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D010455:Peptides; D020033:Protein Isoforms; D014357:Trypsin