Rapid cellular uptake of Alzheimer amyloid βA4 peptide by cultured human neuroblastoma cells

Abstract

Cerebral deposition of [~A4 (~-amyloid) peptide is a major pathological feature of AIzheimer's disease. Although the mechanism of [~A4 production from cells has been investigated extensively, so far little is known about the catabolism of the peptide. We report here that the human neuroblastoma cell line SH-SY5Y can rapidly clear [~A4 in the culture medium. The clearance was not due to the degradation by extraceilularly released protease, but rather due to intracellular degradation after cellular uptake. This clearance activity was specific to SH-SY5Y cells among several cell types examined. Some of the [~A4-derived peptides lacking the N-terminal part of the molecule were not catabolized, suggesting a specific interaction between the cells and ~A4. Although most of the peptide was degraded after uptake, small amounts of peptide was accumulated in insoluble fractions of the cells and remained stable for several days. These observations suggest that this uptake-degradation activity may contribute to AD pathogenesis in two different ways: either to prevent the amyloid deposition by reducing extracellular [~A4 concentrations, or to promote the deposition by producing insoluble seeds for amyloid formation.

Amyloid beta peptide directly inhibits PKC activation

“…These results indicate that treatment of Ah inhibited activation of PKCa and PKCq in the cell. We tested whether extracellular Ah entered the cell, as was previously reported (Bahr et al, 1998;Bi et al, 2002;Ida et al, 1996;Knauer et al, 1992;Nagele et al, 2002;Yang et al, 1995;Yazawa et al, 2001). Immunocytochemical and Western blot analyses confirmed localization of Ah 1 -42 peptides inside the cells that were treated with exogenous Ah 1 -42, but not in cells that were not treated with Ah 1 -42.…”

Endothelin-converting Enzymes Degrade Intracellular β-Amyloid Produced within the Endosomal/Lysosomal Pathway and Autophagosomes*

“…4 shows the results of 48 h of treatment with 5 nM A␤ and 100 M PA. Levels of eA␤ and iA␤ were measured soon after A␤ addition and again after 48 h. A␤ measurement after the 48-h incubation period showed a dramatic decrease in the level of exogenous A␤ in the presence or absence of PA, indicating internalization or nearly complete degradation by proteases insensitive to PA. Levels of iA␤ were measured to determine whether the peptide had been internalized and accumulated within the cell. There was no increase in iA␤ accumulation following treatment with 5 nM A␤, suggesting that if SH-SY5Y cells endocytose A␤ (34,35), any internalized peptide is degraded by non-PA sensitive proteases.…”

Expression of Transgenic APP mRNA Is the Key Determinant for Beta-Amyloid Deposition in PS2APP Transgenic Mice

“…Fifteen microgrammes of total protein extract was fractionated and subsequently transferred onto a nitrocellulose membrane (Amersham, Hybond) as already described using WO 2 primary antibody for the detection of APP [10] . Signals were quantified applying Syngene Genetools Software.…”