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 (betaA), 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 betaA suggested presence of stable intravesicular conjugates.

Brain cathepsin B but not metalloendopeptidases degrade rAPP751 with production of amyloidogenic fragments. Comparison with synthetic peptides emulating beta- and gamma-secretase sites.

Lysosomal cathepsin B but not L degraded rAPP751 to yield C-terminal 19-25 kDa fragments containing beta A4, reinforcing the view that acidic proteases participate in endosomal-lysosomal processing to yield amyloidogenic fragments in situ. This mechanism is consistent with fragmentation of endogenous APPs within clathrin-coated vesicles (CVs) by vesicular hydrolases, with the appearance of C-terminal amyloidogenic fragments following incubation at pH 6.5.

In vitro analysis of ion channels in periaxolemmal-myelin and white matter clathrin coated vesicles: modulation by calcium and GTP gamma S.

This study reports the analysis of K+ channel activity in bovine periaxolemmal-myelin and white matter-derived clathrin-coated vesicles. Channel activity was evaluated by the fusion of membrane vesicles with phospholipid bilayers formed across a patch-clamp pipette. In periaxolemmal myelin spontaneous K+ channels were observed with amplitudes of 25-30, 45-55, and 80-100 pS, all of which exhibited mean open-times of 1-2 msec.

Amyloid precursor protein is enriched in axolemma and periaxolemmal-myelin and associated clathrin-coated vesicles.

The amyloid precursor protein (APP) is widely distributed within the CNS, where it is expressed in both neurons and glia. We have isolated axolemma and periaxolemmal-myelin from rat brain and have determined by Western blot that APPs, Mr 100-110 kDa, are major constituents of these membrane. Isolation of axolemma, periaxolemmal-myelin, and compact myelin show that while APP represents 1 and 0.