Composition of white matter bovine brain coated vesicles: Evidence that several components influence beta-amyloid peptide to form oligomers and aggregates in vitro

Clathrin coated vesicles (CVs) purified from white matter of human or bovine brain contain amyloid precursor protein (APP), several C-terminal fragments encompassing the beta-amyloid domain (beta A), the alpha-secretase 11-12 kDa intermediate, ApoE and tau. The convergence of these components implicates CVs as potential sites for their interaction, yielding products linked to fibrillogenesis in Alzheimer's disease (AD). Analysis of components co-reactive with both anti-ApoE and beta A suggested presence of stable intravesicular conjugates, To evaluate these interactions in vitro, mixtures containing beta A(1-40), ApoE4 or E3 isoforms with and without lipid added as dymyristoyl phosphatidylcholine liposomes were co-incubated from 5 h to 7 days at 37 degrees C and analyzed on Western blots using a panel of antibodies recognizing beta A and ApoE. Data showed ApoE4 plus lipid induced beta A to form oligomers, conjugates and high M(r) aggregates. The rates of formation for these products varied significantly with the ApoE isoform. E3 formed conjugates more rapidly, but these levels were exceeded by those of E4 at 7 days. ApoE4 plus lipid facilitated more rapid formation of higher M(r) PA aggregates which appeared in parallel with beta A oligomers containing up to seven molecules of beta A. Data suggest that the native ApoE, as found in CVs which contain lipid, can be an effective agent for promoting formation of beta A oligomers or other complexes that may be linked to formation of abnormal deposits in AD. (C) 1997 Elsevier Science B.V.