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P3‐155: The Amyloid precursor protein in synaptic plasticity: A matrix approach
Author(s) -
Brayne Carol,
Hunter Sally
Publication year - 2011
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2011.05.1595
Subject(s) - synaptic plasticity , neuroscience , amyloid precursor protein , presenilin , biology , metaplasticity , neurotransmission , amyloid (mycology) , synaptic scaling , alzheimer's disease , disease , biochemistry , medicine , receptor , botany , pathology
Background: The risk of Alzheimer’s disease (AD) increases with age. However, some elderly individuals escape cognitive impairment even into the 10 decade of life. Some of these oldest-old individuals are clinically classified as non-demented, yet, upon autopsy, are found to have high levels of amyloid-beta (As) plaques. Understanding how high-pathology non-demented individuals differ from those with AD will provide a unique perspective into disease mechanisms. Membrane rafts are domains rich in cholesterol and sphingolipid that contain a subset of proteins involved in As production. We are investigating membrane rafts from a unique cohort of 90-100 year-old AD cases, high As pathology non-demented individuals, and 90-100 and 65-75 year-old non-demented individuals free of As pathology. Methods: Fresh frozen cerebral cortex was homogenized and lysed in hypotonic buffer and membrane rich fractions were isolated by low and high speed centrifugations. Membranes were homogenized in 1% Triton X-100 at 4 C and fractionated by stepwise sucrose density centrifugation to enrich for lipid rafts. Purified rafts were characterized by immunoblotting utilizing antibodies against flotilin, APP, BACE-1, Abeta40 and 42, ApoE, and Tau. Results: Flotilin positive raft fractions from AD and non-demented oldest-old with high As pathology contained monomers, dimers and oligomers of As42 while those groups free of As pathology had no detectable As42. Densitometric quantification of As42 monomers revealed 30-fold more As42 in high amyloid plaque load groups regardless of cognitive conditions compared to pathology free groups. Rafts from all cohorts contained similar levels of APP, tau and ApoE. As40 was not detected in the raft fractions under investigation. Conclusions: Our results suggest that As is absent frommembrane rafts in individuals free of amyloid plaque pathology. In contrast, AD and non-demented high pathology oldestold individuals have abundant raft associated monomeric and oligomeric As42. It has been suggested that the progressive accumulation of membrane-bound As-related peptides may participate in the pathophysiology of AD. Transmembrane protein domains can generate thermodynamically stable dimeric and polymeric structures in situ by the close interaction of their hydrophobic domains in non-polar environments. Our studies demonstrate that membrane associated As appears not to be inextricably linked to overt Alzheimer’s dementia.