Identification of novel N-terminal fragments of amyloid precursor protein in cerebrospinal fluid.
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 beta-amyloid (Abeta) peptides that are produced from the amyloid precursor protein (APP), by sequential cleavage by beta- and gamma-secretase. Most previous studies have been focused on the C-terminal fragments of APP, where the Abeta 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.
Portelius
Erik
E
Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy, University of Gothenburg, S-431 80 Mölndal, Sweden. erik.portelius@neuro.gu.se
Brinkmalm
Gunnar
G
Tran
Aijun
A
Andreasson
Ulf
U
Zetterberg
Henrik
H
Westman-Brinkmalm
Ann
A
Blennow
Kaj
K
Ohrfelt
Annika
A
D000368:Aged; D000544:Alzheimer Disease / Q000134:cerebrospinal fluid*; D016564:Amyloid beta-Protein Precursor / Q000134:cerebrospinal fluid* / Q000737:chemistry* / Q000302:isolation & purification; D015153:Blotting, Western; D005260:Female; D006801:Humans; D047468:Immunoprecipitation; D008297:Male; D008970:Molecular Weight; D010446:Peptide Fragments / Q000134:cerebrospinal fluid* / Q000737:chemistry; D010865:Pilot Projects; D017434:Protein Structure, Tertiary; D012995:Solubility; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D016564:Amyloid beta-Protein Precursor; D010446:Peptide Fragments