Apolipoprotein E: isoform specific differences in tertiary structure and interaction with amyloid-β in human
Phillip B Jones1, Kenneth W Adams, Anete Rozkalne
1Harvard Medical School, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Charlestown, Massachusetts, United States of America.
Plos One
|February 8, 2011
Summary
Alzheimer's research reveals Apolipoprotein E4 (ApoE4) binds more amyloid-beta (Aβ) in plaques than ApoE3. This difference in ApoE isoforms may increase Alzheimer's disease risk.
Area of Science:
- Neuroscience
- Biochemistry
- Molecular Biology
Background:
- Alzheimer's disease (AD) is characterized by amyloid-beta (Aβ) plaques.
- Apolipoprotein E (ApoE) isoforms, particularly ApoE4, are major genetic risk factors for AD.
- Understanding isoform-specific ApoE interactions with Aβ is crucial for AD pathogenesis.
Purpose of the Study:
- To investigate isoform-specific differences in Aβ-ApoE interactions and ApoE conformation within human Alzheimer brain plaques.
- To quantify the binding affinity and distribution of ApoE3 and ApoE4 with Aβ in situ.
- To explore the structural basis for increased AD risk associated with the APOEε4 allele.
Main Methods:
- Utilized Fluorescence Lifetime Imaging Microscopy-Förster Resonance Energy Transfer (FLIM-FRET) for in situ protein interaction measurements.
- Applied traditional biochemical assays to complement in situ findings.
- Analyzed ApoE N-terminal fragments in brain plaques.
Main Results:
- ApoE3 exhibits closer interaction with Aβ compared to ApoE4.
- A higher proportion of Aβ within plaques is associated with ApoE4 than ApoE3.
- Increased levels of ApoE N-terminal fragments were observed in ApoE4 plaques, indicating higher susceptibility to cleavage.
- A small but significant isoform-specific difference in ApoE domain interaction was detected.
Conclusions:
- Isoform-specific differences in ApoE conformation influence Aβ deposition in Alzheimer's disease.
- ApoE4's increased susceptibility to cleavage at the hinge region leads to impaired Aβ clearance.
- These findings support a mechanism linking ApoE4's conformational and cleavage properties to increased AD risk.
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