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Analyzing microglial-associated Aβ in Alzheimer's disease transgenic mice with a novel mid-domain Aβ-antibody
Kristi Henjum1,2, Vibeke Årskog1, Charlotte B Jendresen1
1Department of Pharmacology, University of Oslo and Oslo University Hospital, Blindern, P.O. 1057, 0316, Oslo, Norway.
Abstract:
The mechanisms of amyloid-β (Aβ)-degradation and clearance in Alzheimer's disease (AD) pathogenesis have been relatively little studied. Short Aβ-fragments form by enzymatic cleavage and alternate amyloid-beta precursor protein (APP)-processing. Here we characterized a novel polyclonal Aβ-antibody raised against an Aβ mid-domain and used it to investigate microglial Aβ-uptake in situ by microscopy at the light- and ultrastructural levels. The rabbit Aβ-mid-domain antibody (ab338), raised against the mid-domain amino acids 21-34 (Aβ21-34), was characterized with biochemical and histological techniques. To identify the epitope in Aβ recognized by ab338, solid phase and solution binding data were compared with peptide folding scores as calculated with the Tango software. The ab338 antibody displayed high average affinity (KD: 6.2 × 10-10 M) and showed preference for C-terminal truncated Aβ-peptides ending at amino acid 34 and Aβ-mid domain peptides with high scores of β-turn structure. In transgenic APP-mouse brain, ab338 labelled amyloid plaques and detected Aβ-fragments in microglia at the ultra- and light microscopic levels. This reinforces a role of microglia/macrophages in Aβ-clearance in vivo. The ab338 antibody might be a valuable tool to study Aβ-clearance by microglial uptake and Aβ-mid-domain peptides generated by enzymatic degradation and alternate production.
Insights
Researchers developed a new antibody to study how microglia clear amyloid-beta (Aβ) fragments in Alzheimer's disease (AD). This antibody helps visualize Aβ uptake by microglia, reinforcing their role in clearing toxic protein aggregates in the brain.
Area of Science:
- Neuroscience
- Immunology
- Biochemistry
Background:
- Alzheimer's disease (AD) pathogenesis involves amyloid-beta (Aβ) accumulation.
- Mechanisms of Aβ degradation and clearance, particularly by microglia, are not well understood.
- Short Aβ fragments arise from enzymatic cleavage and alternative amyloid-beta precursor protein (APP) processing.
Purpose of the Study:
- To characterize a novel polyclonal antibody targeting the Aβ mid-domain (ab338).
- To investigate microglial Aβ uptake in situ using light and ultrastructural microscopy.
- To explore the role of ab338 in studying Aβ clearance and mid-domain peptide generation.
Main Methods:
- Characterization of the ab338 antibody using biochemical and histological techniques.
- Epitope mapping of ab338 by comparing binding data with peptide folding scores (Tango software).
- Microscopic analysis (light and ultra-) of ab338 binding in transgenic APP-mouse brains to visualize Aβ in microglia.
Main Results:
- The ab338 antibody demonstrated high affinity (KD: 6.2 × 10-10 M) for Aβ mid-domain peptides, especially those with β-turn structures.
- ab338 specifically recognized C-terminal truncated Aβ peptides ending at amino acid 34.
- In APP-mouse brains, ab338 labeled amyloid plaques and detected Aβ fragments within microglia, confirming microglial uptake.
Conclusions:
- The ab338 antibody is a valuable tool for studying Aβ clearance mechanisms, particularly microglial Aβ uptake.
- Findings reinforce the significant role of microglia/macrophages in in vivo Aβ clearance.
- The antibody can aid in investigating Aβ mid-domain peptides generated through degradation and alternative processing pathways.
