Multiple γ-secretase product peptides are coordinately increased in concentration in the cerebrospinal fluid of a subpopulation of sporadic Alzheimer’s disease subjects
1 Laboratory of Neuroscience, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
2 Department of Biological Regulation, School of Health Science, Faculty of Medicine, Tottori University, Yonago, Japan
3 Department of Molecular Neuroscience, Brain Research Institute, Niigata University, Niigata, Japan
4 Department of Neurology, Alzheimer's Disease Research Center, Washington University, School of Medicine, St. Louis, MO, USA
5 Centre of Excellence for Alzheimer’s Disease Research and Care, School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
6 McCusker Foundation for Alzheimer's Disease Research, Hollywood Private Hospital, Nedlands, WA, Australia
7 Neurology, Mount Sinai School of Medicine, Alzheimer’s Disease Research Center, New York, NY, USA
8 Psychiatry, Mount Sinai School of Medicine, Alzheimer’s Disease Research Center, New York, NY, USA
9 James J. Peters Veterans Administration Medical Center, Bronx, NY, USA
Molecular Neurodegeneration 2012, 7:16 doi:10.1186/1750-1326-7-16Published: 25 April 2012
Alcadeinα (Alcα) is a neuronal membrane protein that colocalizes with the Alzheimer's amyloid-β precursor protein (APP). Successive cleavage of APP by β- and γ-secretases generates the aggregatable amyloid-β peptide (Aβ), while cleavage of APP or Alcα by α- and γ-secretases generates non-aggregatable p3 or p3-Alcα peptides. Aβ and p3-Alcα can be recovered from human cerebrospinal fluid (CSF). We have previously reported alternative processing of APP and Alcα in the CSF of some patients with sporadic mild cognitive impairment (MCI) and AD (SAD).
Using the sandwich enzyme-linked immunosorbent assay (ELISA) system that detects total p3-Alcα, we determined levels of total p3-Alcα in CSF from subjects in one of four diagnostic categories (elderly controls, MCI, SAD, or other neurological disease) derived from three independent cohorts. Levels of Aβ40 correlated with levels of total p3-Alcα in all cohorts.
We confirm that Aβ40 is the most abundant Aβ species, and we propose a model in which CSF p3-Alcα can serve as a either (1) a nonaggregatable surrogate marker for γ-secretase activity; (2) as a marker for clearance of transmembrane domain peptides derived from integral protein catabolism; or (3) both. We propose the specification of an MCI/SAD endophenotype characterized by co-elevation of levels of both CSF p3-Alcα and Aβ40, and we propose that subjects in this category might be especially responsive to therapeutics aimed at modulation of γ-secretase function and/or transmembrane domain peptide clearance. These peptides may also be used to monitor the efficacy of therapeutics that target these steps in Aβ metabolis