Targeting LAMP2 in human cerebrospinal fluid with a combination of immunopurification and high resolution parallel reaction monitoring mass spectrometry. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Sjödin, Simon; Öhrfelt, Annika; Brinkmalm, Gunnar; Zetterberg, Henrik; Blennow, Kaj; Brinkmalm, Ann
• Is Part Of: Clinical proteomics. Volume 13:Issue 1(2016)
• Page Start: 1
• Page End: 14
• Publication Date: 2016-12
• Subjects: Alzheimer's disease -- Neurodegenerative diseases -- Cerebrospinal fluid -- Biomarker -- LAMP2 -- Endo-lysosomal dysfunction -- Immunoprecipitation -- Parallel reaction monitoring; Proteomics -- Periodicals; Proteins -- Periodicals; Medical genetics -- Periodicals; 572.6
• DOI: 10.1186/s12014-016-9104-2
• Languages: English
• ISSNs: 1542-6416

Abstract

Abstract Background Alzheimer's disease is the most common form of dementia. An increasing body of evidence suggests that endo-lysosomal dysfunction is a pathogenic mechanism of Alzheimer's disease. Thus there is a potential for proteins involved in the normal function of endo-lysosomal vesicles to act as biomarkers of disease. Herein we focused on the lysosomal protein LAMP2 that is involved in chaperone mediated autophagy. Results Using a combination of immunoprecipitation, digestion and nano-liquid chromatography tandem mass spectrometry we targeted and identified six tryptic LAMP2 peptides in human cerebrospinal fluid. Employing the identified proteotypic tryptic peptides a hybrid immunoprecipitation high resolution parallel reaction monitoring mass spectrometric method was developed for the relative quantitation of LAMP2. The method was evaluated in a number of experiments which defined the overall methodological as well as the analytical micro-liquid chromatography mass spectrometric intra- and inter-day variability. We identified an overall methodological peptide dependent intra-day variability of 8–16 %. The inter-day experiments showed similar results. The analytical contribution to the variation was minor with a coefficient of variation of 0.5–2.1 %, depending on the peptide. Using the developed method, with defined and limited variability, we report increased cerebrospinal fluid levels of three LAMP2 peptides in Alzheimer's disease subjects (n = 14), as compared to non-Alzheimer's disease controls (n = 14). Conclusion Altered LAMP2 levels in cerebrospinal fluid may indicate endo-lysosomal dysfunction in Alzheimer's disease. However, further studies in larger cohorts comprised of well-defined patient materials are required. We here present a tool which can be used for exploring the relevance of the level of LAMP2 as a potential measure of lysosomal dysfunction in Alzheimer's disease or other neurodegenerative diseases.