Aβ-42 sidechain deamidation at Q15 or N27 modulates protein aggregation and alters microglial cytokines and CD68
Abstract:
The progressive aggregation of amyloid beta (Aβ) monomers into oligomers is a critical factor in Alzheimer's disease (AD) pathogenesis. Although mutated forms of Aβ have been shown to display altered aggregation dynamics, the specific effects of deamidated Aβ on microglial function remain understudied. Our research group previously found that the deamidated variant Aβ-42-N27D modified Aβ aggregation, reduced neurotoxicity, and reduced microglial reactivity, but the impact of Aβ-42 side chain deamidation in general on such parameters remained unclear. Here, we expanded on our prior work by investigating how two site-specific Aβ-42 mutations (Q15E & N27D), where neutral amide side chains are replaced with negatively charged carboxylic acids, affect aggregation and microglial immune response using a mouse microglial cell line. Size exclusion chromatography revealed that Aβ-42-Q15E and Aβ-42-N27D exhibit distinct aggregation profiles compared to Aβ-42 wild type (WT). Multiplexed analysis of 8 cytokines secreted into the culture medium revealed that Aβ-42-Q15E and Aβ-42-N27D decrease the expression of inflammatory cytokines such as IL-6, IP-10, and MIP-1α relative to Aβ-42-WT. Immunocytochemistry revealed that Aβ-42-Q15E and Aβ-42-N27D decrease CD68 expression relative to Aβ-42-WT. These findings demonstrate that deamidation significantly alters Aβ-42 aggregation and microglial activation, suggesting structural modifications to Aβ-42 modulate inflammatory signaling in AD. This work provides a foundation for future studies on Aβ-42 post-translational modifications as potential therapeutic targets in AD.S.
Insights
Deamidation of amyloid beta (Aβ) alters its aggregation and reduces microglial activation, impacting Alzheimer's disease (AD) inflammation. This suggests Aβ post-translational modifications are key therapeutic targets for AD.
Area of Science:
- Neuroscience
- Biochemistry
- Immunology
Background:
- Amyloid beta (Aβ) aggregation into oligomers is central to Alzheimer's disease (AD) pathogenesis.
- Deamidated Aβ variants show altered aggregation and reduced neurotoxicity, but their impact on microglial function needs further study.
- Previous work indicated Aβ-42-N27D modified aggregation and reduced microglial reactivity, yet the general effect of Aβ-42 side chain deamidation remained unclear.
Purpose of the Study:
- To investigate the effects of site-specific Aβ-42 deamidation mutations (Q15E & N27D) on Aβ aggregation.
- To determine how these deamidated Aβ-42 variants influence microglial immune response and inflammatory cytokine secretion.
- To explore the potential of Aβ-42 post-translational modifications as therapeutic targets in AD.
Main Methods:
- Utilized size exclusion chromatography to analyze aggregation profiles of Aβ-42-Q15E and Aβ-42-N27D compared to wild-type (WT).
- Performed multiplexed cytokine analysis to quantify 8 secreted cytokines from microglial cell cultures.
- Employed immunocytochemistry to assess CD68 expression in microglial cells.
Main Results:
- Aβ-42-Q15E and Aβ-42-N27D exhibited distinct aggregation profiles compared to Aβ-42-WT.
- Both deamidated variants significantly decreased the secretion of inflammatory cytokines (IL-6, IP-10, MIP-1α) relative to Aβ-42-WT.
- Aβ-42-Q15E and Aβ-42-N27D reduced CD68 expression in microglial cells compared to Aβ-42-WT.
Conclusions:
- Deamidation of Aβ-42 significantly alters its aggregation dynamics.
- Aβ-42 deamidation modulates microglial activation and inflammatory signaling pathways relevant to AD.
- Structural modifications of Aβ-42, including deamidation, represent promising avenues for developing novel AD therapeutics.
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