Author/Editor     Stokin, Gorazd B; Almenar-Queralt, Angels; Gunawardena, Shermali; Rodrigues, Elizabeth M; Falzone, Tomas; Kim, Jungsu; Lillo, Conception; Mount, Stephanie L; Roberts, Elizabeth A; McGowan, Eileen
Title     Amyloid precursor protein-induced axonopathies are independent of amyloid-beta peptides
Type     članek
Source     Hum Mol Genet
Vol. and No.     Letnik 17, št. 22
Publication year     2008
Volume     str. 3474-86
Language     eng
Abstract     Overexpression of amyloid precursor protein (APP), as well as mutations in the APP and presenilin genes, causes rare forms of Alzheimer's disease (AD). These genetic changes have been proposed to cause AD by elevating levels of amyloid-beta peptides (Abeta), which are thought to be neurotoxic. Since overexpression of APP also causes defects in axonal transport, we tested whether defects in axonal transport were the result of Abeta poisoning of the axonal transport machinery. Because directly varying APP levels also alters APP domains in addition to Abeta, we perturbed Abeta generation selectively by combining APP transgenes in Drosophila and mice with presenilin-1 (PS1) transgenes harboring mutations that cause familial AD (FAD). We found that combining FAD mutant PS1 with FAD mutant APP increased Abeta42/Abeta40 ratios and enhanced amyloid deposition as previously reported. Surprisingly, however, this combination suppressed rather than increased APP-induced axonal transport defects in both Drosophila and mice. In addition, neuronal apoptosis induced by expression of FAD mutant human APP in Drosophila was suppressed by co-expressing FAD mutant PS1. We also observed that directly elevating Abeta with fusions to the Familial British and Danish Dementia-related BRI protein did not enhance axonal transport phenotypes in APP transgenic mice. Finally, we observed that perturbing Abeta ratios in the mouse by combining FAD mutant PS1 with FAD mutant APP did not enhance APP-induced behavioral defects. A potential mechanism to explain these findings was suggested by direct analysis of axonal transport in the mouse, which revealed that axonal transport or entry of APP into axons is reduced by FAD mutant PS1. Thus, we suggest that APP-induced axonal defects are not caused by Abeta.
Descriptors     AXONAL TRANSPORT
AMYLOID BETA-PROTEIN
AMYLOID BETA-PROTEIN PRECURSOR
ANALYSIS OF VARIANCE
ANIMALS
AXONS
BEHAVIOR, ANIMAL
DROSOPHILA
FEAR
IMMUNOHISTOCHEMISTRY
MICE
MICE, TRANSGENIC
MICROSCOPY, ELECTRON
TRANSGENES