On the Seeding and Oligomerization of pGlu-Amyloid Peptides (in vitro)

Abstract

Oligomerization of amyloid beta (Abeta) peptides is the decisive event in the development of Alzheimer's disease (AD), the most common neurogenerative disorder in developed countries. Recent evidence links this conformation-driven process to primary- and secondary-structure modifications of Abeta. The N and C terminus of deposited Abeta has been shown to possess conspicuous heterogeneity. While the C-terminally longer form of Abeta, i.e., Abeta (42), is considered more amyloidogenic, the role of the N-terminal modifications, e.g., truncation and glutamate cyclization accounting for the majority of the deposited peptides, is less understood. In the present study, we characterized the oligomerization and seeding capacity of pGlu-amyloid peptides using two unrelated techniques based on flow cytometry or flourescence dye binding. Under different conditions and irrespective of the C terminus of Abeta, i.e., Abeta40 or 42, pGlu-modified peptides displayed an up to 250-fold accelerated initial formation of aggregates compared to unmodified Abeta. The accelerated seed formation is accompanied by a change in the oligomerization kinetics because of N-terminal pGlu formation. Furthermore, the formation of mixed aggregates consisting of either pGlu-Abeta (3-42) or ADan or ABri and Abeta (1-42) was investigated by Abeta fluorescence labeling in flow cytometry. The results suggest that pGlu-modified peptides are potential seeding species of aggregate formation in vivo. The data presented here and the abundance of pGlu peptides in amyloidoses, such as FBD and AD, suggest pGlu-amyloid peptides as a species with biophysical characteristics that might be in particular crucial for the initiation of the disease.

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

“…N-terminal deletions generally enhance aggregation of ␤-amyloid peptides in vitro (53). Additionally, A␤ pE3 is known to have a high aggregation propensity (54,55), increased stability (56), enhanced toxicity compared with fulllength A␤ (57), and dramatically reduced solubility at physiological pH-conditions (58). Our findings go along with the A␤ pE3 seeding hypothesis (20,54,57).…”

Near-infrared fluorescence molecular imaging of amyloid beta species and monitoring therapy in animal models of Alzheimer’s disease

“…Studies showed that pyroglutamate Aβ [AβN3(pE)] contributed substantially to AD pathology because of its high neurotoxicity and abundance in AD brains (53,54). To investigate whether CRANAD-3 can interact with AβN3(pE), we performed fluorescence spectral testing similar to experiments with other Aβs.…”

Neuroprotective natural antibodies to assemblies of amyloidogenic peptides decrease with normal aging and advancing Alzheimer's disease

“…Pyroglutamate variant A␤3(pE)-42 and to a lesser extent A␤11(pE)-42 are a predominant A␤ species in AD plaques (2-4, 10, 52), and together with other N-and C-terminally truncated A␤ species, they are also formed in plaque-free brains of healthy individuals aged at least 70 years (6). Moreover, because A␤3(pE)-42 forms aggregation seeds 250-fold faster than unmodified A␤ (53) it may trigger antibody responses at very low concentrations long before pathological changes are observed in the brain. Indeed, human plasma in general showed high reactivity against pyroglutamate-modified peptides such as A␤3(pE)-42, A␤11(pE)-42, but only low reactivity against unmodified A␤11-42 ( Fig.…”