Decrease in age-adjusted cerebrospinal fluid beta-secretase activity in Alzheimer's subjects.
OBJECTIVE
To develop a novel cerebrospinal fluid (CSF) beta-secretase-1 activity assay and evaluate beta-secretase-1 (BACE-1) activity as a potential biomarker in human Alzheimer's disease.


METHODS
The assay consisted of an enzymatic reaction of CSF samples with an optimized beta-secretase peptide substrate and the cleavage products were detected using a neo-epitope specific antibody.


RESULTS
The CSF BACE-1 activity assay described exhibits time, temperature, dose, and pH dependence, with sensitivity down to <1 pM of recombinant BACE-1 enzyme, and is completely blocked by BACE-1 inhibitors. The endogenous BACE-1 enzyme in CSF appears to exist as a c-terminally truncated protein, based on both western blotting and capture-based activity assays. In a small cohort of human subjects, an age-dependent increase in CSF BACE activity was observed (~1.0 pM/year, p<0.05). In Alzheimer's disease subjects, a significant decline in age-adjusted CSF BACE activity was observed compared to controls (56% in the log-transformed scale, p=0.02).


CONCLUSIONS
We have developed a robust assay to measure CSF BACE-1 activity which could serve as a potential biomarker in human Alzheimer's disease subjects.
Wu
Guoxin
G
Alzheimer's Research, Merck Research Laboratory, West Point, PA, USA.
Sankaranarayanan
Sethu
S
Tugusheva
Kate
K
Kahana
Jason
J
Seabrook
Guy
G
Shi
Xiao-Ping
XP
King
Elizabeth
E
Devanarayan
Viswanath
V
Cook
Jacquelynn J
JJ
Simon
Adam J
AJ
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000134:cerebrospinal fluid* / Q000201:enzymology*; D053829:Amyloid Precursor Protein Secretases / Q000134:cerebrospinal fluid*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000134:cerebrospinal fluid*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008253:Macaca mulatta; D008297:Male; D008875:Middle Aged; D010436:Pepstatins / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D012680:Sensitivity and Specificity
D010436:Pepstatins; D011480:Protease Inhibitors; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; C031375:pepstatin