Alternative Processing of gamma-Secretase Substrates in Common Forms of Mild Cognitive Impairment and Alzheimer's Disease: Evidence for gamma-Secretase Dysfunction

作者：Hata Saori; Fujishige Sayaka; Araki Yoichi; Taniguchi Miyako; Urakami Katsuya; Peskind Elaine; Akatsu Hiroyasu; Araseki Masahiko; Yamamoto Kazuo; Martins Ralph N; Maeda Masahiro; Nishimura Masaki; Levey Allan; Chung Kathryn A; Montine Thomas; Leverenz James; Fagan Anne; Goate Alison; Bateman Randall; Holtzman David M; Yamamoto Tohru; Nakaya Tadashi; Gandy Sam; Suzuki Toshiharu^*

来源：Annals of Neurology, 2011, 69(6): 1026-1031.

DOI：10.1002/ana.22343

Objective: The most common pathogenesis for familial Alzheimer's disease (FAD) involves misprocessing (or alternative processing) of the amyloid precursor protein (APP) by gamma-secretase due to mutations of the presenilin 1 (PS1) gene. This misprocessing/alternative processing leads to an increase in the ratio of the level of a minor gamma-secretase reaction product (A beta 42) to that of the major reaction product (A beta 40). Although no PS1 mutations are present, altered A beta 42/40 ratios are also observed in sporadic Alzheimer's disease (SAD), and these altered ratios apparently reflect deposition of A beta 42 as amyloid.
Methods: Using immunoprecipitation-mass spectrometry with quantitative accuracy, we analyzed in the cerebrospinal fluid (CSF) of various clinical populations the peptide products generated by processing of not only APP but also an unrelated protein, alcadein (Alc). Alc undergoes metabolism by the identical APP alpha-secretases and gamma-secretases, yielding a fragment that we have named p3-Alca because of the parallel genesis of p3-Alc(alpha) peptides and the p3 fragment of APP. As with A beta, both major and minor p3-Alc(alpha)s are generated. We studied the alternative processing of p3-Alc(alpha) in various clinical populations.
Results: We previously reported that changes in the A beta 42/40 ratio showed covariance in a linear relationship with the levels of p3-Alc(alpha) [minor/major] ratio in media conditioned by cells expressing FAD-linked PS1 mutants. Here we studied the speciation of p3-Alc(alpha) in the CSF from 3 groups of human subjects (n 158): elderly nondemented control subjects; mild cognitive impairment (MCI) subjects with a clinical dementia rating (CDR) of 0.5; SAD subjects with CDR of 1.0; and other neurological disease (OND) control subjects. The CSF minor p3-Alc(alpha) variant, p3-Alc(alpha)38, was elevated (p < 0.05) in MCI subjects or SAD subjects, depending upon whether the data were pooled and analyzed as a single cohort or analyzed individually as 3 separate cohorts.
Interpretation: These results suggest that some SAD may involve alternative processing of multiple c-secretase substrates, raising the possibility that the molecular pathogenesis of SAD might involve gamma-secretase dysfunction. ANN NEUROL 2011;69:1026-1031

• 出版日期2011-6