Pyroglutamate-Modified Amyloid-β Protein Demonstrates Similar Properties in an Alzheimer's Disease Familial Mutant Knock-In Mouse and Alzheimer's Disease Brain

Abstract

Background: N-terminally truncated, pyroglutamate-modified amyloid-β (Aβ) peptides are major constituents of amyloid deposits in Alzheimer's disease (AD). Methods: Using a newly developed ELISA for Aβ modified at glutamate 3 with a pyroglutamate (pE3Aβ), brain pE3Aβ was characterized in human AD in an AD mouse model harboring double knock-in amyloid precursor protein (APP)-KM670/671NL and presenilin 1 (PS1)-P264L (APP/PS1-dKI) mutations, and in a second mouse model with transgenic overexpression of human APP695 with APP-KM670/671NL (Tg2576). Results: pE3Aβ increased in the AD brain versus age-matched controls, with pE3Aβ/total Aβ at 45 and 10%, respectively. Compared to controls, the AD brain demonstrated 8.5-fold increased pE3Aβ compared to non-pE3Aβ species, which increased 2.7-fold. In the APP/PS1-dKI brain, pE3Aβ/total Aβ increased from 7% at 3 months to 16 and 19% at 15 and 19 months, respectively. In Tg2576, pE3Aβ/total Aβ was only 1.5% at 19 months, suggesting that APP/PS1-dKI, despite less total Aβ compared to Tg2576 at comparable ages, more closely mimics AD brain pathology. Conclusion: This report supports a significant role for pE3Aβ in AD pathogenesis by confirming that pE3Aβ represents a large fraction of Aβ within the AD brain. Compared to the age-matched control brain, pE3Aβ increased to a greater extent compared to Aβ species without this N-terminal modification. Further, the APP/PS1-dKI model more closely resembles the AD brain in this regard, compared to the Tg2576 model.

A Sensitive Aβ Oligomer Assay Discriminates Alzheimer's and Aged Control Cerebrospinal Fluid

“…The Erenna platform is used in clinical settings (Tarawneh et al, 2012;Wang et al, 2012) to measure low abundance analytes in blood and CSF. Ongoing studies evaluating CSF from individuals sampled longitudinally will confirm whether oligomers correlate with crosssectional and progressing disease, as well as with variables such as age, sex, apoE genotype, and other demographic, biochemical, and cognitive measures.…”

“…A␤ monomer ELISAs were previously reported (Sankaranarayanan et al, 2009) using commercially available antibodies: 6E10 (A␤3-8), 12F4 (A␤42-selective), and G210 (A␤40-selective) (Covance). Total A␤ ELISA used comparable methods including capture with antibody 6E10, except the detecting antibody was 4G8 (A␤17-24; Covance; Wu et al, 2013).…”

“…The flow-based, A␤ oligomer sandwich ELISA was constructed using a paramagnetic microparticle, immunoassay platform (Erenna immunoassay system; Singulex; Todd et al, 2007). Microparticles (MPs) to capture A␤ oligomers were prepared by binding 12.5 g of biotinylated 19.3 per milligram of streptavidin-coated MPs.…”

“…Oligomeric A␤ seems to be the most toxic form and has been isolated from AD brain (Kuo et al, 1996;Gong, et al, 2003;Shankar et al, 2008;Tomic et al, 2009;Koffie et al, 2012). In model systems, oligomers are more toxic and correlate with cognitive impairments in AD mouse models (Lesné et al, 2006;Cheng et al, 2007;Hernandez et al, 2010), and humans (Tomic et al, 2009;Mc Donald et al, 2010).…”

“…Oligomeric A␤ seems to be the most toxic form and has been isolated from AD brain (Kuo et al, 1996;Gong, et al, 2003;Shankar et al, 2008;Tomic et al, 2009;Koffie et al, 2012). In model systems, oligomers are more toxic and correlate with cognitive impairments in AD mouse models (Lesné et al, 2006;Cheng et al, 2007;Hernandez et al, 2010), and humans (Tomic et al, 2009;Mc Donald et al, 2010). Therapies targeting A␤ oligomers directly, or targeting posttranslational modifications that predispose toward oligomer formation, have been advanced (Gong et al, 2003;Lesné et al, 2006;McLaurin et al, 2006;Townsend et al, 2006;Schilling et al, 2008;Lambert et al, 2009;Demattos et al, 2012;Nussbaum et al, 2012).…”