An online nano-LC-ESI-FTICR-MS method for comprehensive characterization of endogenous fragments from amyloid β and amyloid precursor protein in human and cat cerebrospinal fluid

• Published in: Journal of mass spectrometry. 2012-05, Vol.47 (5), p.591-603
• Main Authors: Brinkmalm, Gunnar, Portelius, Erik, Öhrfelt, Annika, Mattsson, Niklas, Persson, Rita, Gustavsson, Mikael K., Vite, Charles H., Gobom, Johan, Månsson, Jan-Eric, Nilsson, Jonas, Halim, Adnan, Larson, Göran, Rüetschi, Ulla, Zetterberg, Henrik, Blennow, Kaj, Brinkmalm, Ann
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino Acid Substitution; Amyloid beta-Peptides; Amyloid beta-Peptides - cerebrospinal fluid; Amyloid beta-Peptides - chemistry; Amyloid beta-Protein Precursor; Amyloid beta-Protein Precursor - cerebrospinal fluid; Amyloid beta-Protein Precursor - chemistry; amyloid β; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Cats; cerebrospinal fluid; Cerebrospinal fluid (biochemistry, cytology, circulation, manometry). Intracranial pressure determination; chemistry; Chromatography; Chromatography, Liquid - methods; Electrospray Ionization; endogenous peptides; Fundamental and applied biological sciences. Psychology; General aspects, investigation methods; Glycosylation; Humans; Immunoprecipitation; immunoprecipitation mass spectrometry; Investigative techniques, diagnostic techniques (general aspects); Liquid; Mass; Medical sciences; methods; Molecular Sequence Data; Neurologi; Neurology; Protein; Proteins; Sequence Alignment; Sequence Analysis; Sequence Analysis, Protein - methods; Spectrometry; Spectrometry, Mass, Electrospray Ionization - methods
• ISSN: 1076-5174; 1096-9888; 1096-9888
• DOI: 10.1002/jms.2987

Amyloid precursor protein (APP) is the precursor protein to amyloid β (Aβ), the main constituent of senile plaques in Alzheimer's disease (AD). Endogenous Aβ peptides reflect the APP processing, and greater knowledge of different APP degradation pathways is important to understand the mechanism underlying AD pathology. When one analyzes longer Aβ peptides by low‐energy collision‐induced dissociation tandem mass spectrometry (MS/MS), mainly long b‐fragments are observed, limiting the possibility to determine variations such as amino acid variants or post‐translational modifications (PTMs) within the N‐terminal half of the peptide. However, by using electron capture dissociation (ECD), we obtained a more comprehensive sequence coverage for several APP/Aβ peptide species, thus enabling a deeper characterization of possible variants and PTMs. Abnormal APP/Aβ processing has also been described in the lysosomal storage disease Niemann–Pick type C and the major large animal used for studying this disease is cat. By ECD MS/MS, a substitution of Asp7 → Glu in cat Aβ was identified. Further, sialylated core 1 like O‐glycans at Tyr10, recently discovered in human Aβ (a previously unknown glycosylation type), were identified also in cat cerebrospinal fluid (CSF). It is therefore likely that this unusual type of glycosylation is common for (at least) species belonging to the magnorder Boreoeutheria. We here describe a detailed characterization of endogenous APP/Aβ peptide species in CSF by using an online top‐down MS‐based method. Copyright © 2012 John Wiley & Sons, Ltd.