α‐secretase mediated conversion of the amyloid precursor protein derived membrane stub C99 to C83 limits Aβ generation

S Jäger, S Leuchtenberger, A Martin… - Journal of …, 2009 - Wiley Online Library
S Jäger, S Leuchtenberger, A Martin, E Czirr, J Wesselowski, M Dieckmann, E Waldron…
Journal of neurochemistry, 2009Wiley Online Library
The Swedish mutation within the amyloid precursor protein (APP) causes early‐onset
Alzheimer's disease due to increased cleavage of APP by BACE1. While β‐secretase
shedding of Swedish APP (APPswe) largely results from an activity localized in the late
secretory pathway, cleavage of wild‐type APP occurs mainly in endocytic compartments.
However, we show that liberation of Aβ from APPswe is still dependent on functional
internalization from the cell surface. Inspite the unchanged overall β‐secretase cleaved …
Abstract
The Swedish mutation within the amyloid precursor protein (APP) causes early‐onset Alzheimer’s disease due to increased cleavage of APP by BACE1. While β‐secretase shedding of Swedish APP (APPswe) largely results from an activity localized in the late secretory pathway, cleavage of wild‐type APP occurs mainly in endocytic compartments. However, we show that liberation of Aβ from APPswe is still dependent on functional internalization from the cell surface. Inspite the unchanged overall β‐secretase cleaved soluble APP released from APPswe secretion, mutations of the APPswe internalization motif strongly reduced C99 levels and substantially decreased Aβ secretion. We point out that α‐secretase activity‐mediated conversion of C99 to C83 is the main cause of this Aβ reduction. Furthermore, we demonstrate that α‐secretase cleavage of C99 even contributes to the reduction of Aβ secretion of internalization deficient wild‐type APP. Therefore, inhibition of α‐secretase cleavage increased Aβ secretion through diminished conversion of C99 to C83 in APP695, APP695swe or C99 expressing cells.
Wiley Online Library