Pyroglutamate Amyloid β (Aβ) Aggravates Behavioral Deficits in Transgenic Amyloid Mouse Model for Alzheimer Disease

Pyroglutamate-modified A beta peptides at amino acid position three (A beta(pE3-42)) are gaining considerable attention as potential key players in the pathogenesis of Alzheimer disease (AD). A beta(pE3-42) is abundant in AD brain and has a high aggregation propensity, stability and cellular toxicity. The aim of the present work was to study the direct effect of elevated A beta(pE3-42) levels on ongoing AD pathology using transgenic mouse models. To this end, we generated a novel mouse model (TBA42) that produces A beta(pE3-42). TBA42 mice showed age-dependent behavioral deficits and A beta(pE3-42) accumulation. The A beta profile of an established AD mouse model, 5XFAD, was characterized using immunoprecipitation followed by mass spectrometry. Brains from 5XFAD mice demonstrated a heterogeneous mixture of full-length, N-terminal truncated, and modified A beta peptides: A beta(1-42), A beta(1-40), A beta(pE3-40), A beta(pE3-42), A beta(3-42), A beta(4-42), and A beta(5-42). 5XFAD and TBA42 mice were then crossed to generate transgenic FAD42 mice. At 6 months of age, FAD42 mice showed an aggravated behavioral phenotype compared with single transgenic 5XFAD or TBA42 mice. ELISA and plaque load measurements revealed that A beta(pE3) levels were elevated in FAD42 mice. No change in A beta(x-42) or other A beta isoforms was discovered by ELISA and mass spectrometry. These observations argue for a seeding effect of A beta(pE-42) in FAD42 mice.