Identification of novel N-terminal fragments of amyloid precursor protein in cerebrospinal fluid

• Published in: Experimental neurology Vol. 223; no. 2; pp. 351 - 358
• Main Authors: Portelius, Erik, Brinkmalm, Gunnar, Tran, AiJun, Andreasson, Ulf, Zetterberg, Henrik, Westman-Brinkmalm, Ann, Blennow, Kaj, Öhrfelt, Annika
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.2010
• Subjects: Aged; Alzheimer Disease - cerebrospinal fluid; Alzheimer's disease; Amyloid beta-Protein Precursor - cerebrospinal fluid; Amyloid beta-Protein Precursor - chemistry; Amyloid beta-Protein Precursor - isolation & purification; Amyloid precursor protein; Blotting, Western; Cerebrospinal fluid; Female; Humans; Immunoprecipitation; Male; Mass spectrometry; Molecular Weight; Peptide Fragments - cerebrospinal fluid; Peptide Fragments - chemistry; Pilot Projects; Protein Structure, Tertiary; Psychiatry; Psykiatri; Solubility; Spectrometry, Mass, Electrospray Ionization; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Immunoprecipitation; Cerebrospinal fluid; Alzheimer's disease; Mass spectrometry; Amyloid precursor protein
• ISSN: 0014-4886; 1090-2430; 1090-2430
• DOI: 10.1016/j.expneurol.2009.06.011

Alzheimer's disease (AD) is a progressive neurodegenerative disorder of the central nervous system. Two pathological hallmarks in the brain of AD patients are neurofibrillary tangles and senile plaques. The plaques consist mainly of β-amyloid (Aβ) peptides that are produced from the amyloid precursor protein (APP), by sequential cleavage by β- and γ-secretase. Most previous studies have been focused on the C-terminal fragments of APP, where the Aβ sequence is localized. The purpose of this study was to search for N-terminal fragments of APP in cerebrospinal fluid (CSF) using mass spectrometry (MS). By using immunoprecipitation (IP) combined with matrix-assisted laser desorption/ionization time-of-flight MS as well as nanoflow liquid chromatography coupled to high resolution tandem MS we were able to detect and identify six novel N-terminal APP fragments [APP (18–119), APP (18–121), APP (18–122), APP (18–123), APP (18–124) and APP (18–126)], having molecular masses of approximately 12 kDa. The presence of these APP derivatives in CSF was also verified by Western blot analysis. Two pilot studies using either IP-MS or Western blot analysis indicated slightly elevated levels of N-terminal APP fragments in CSF from AD patients compared with controls, which are in need of replications in independent and larger patient materials.