NMDA receptor subunit composition determines beta-amyloid-induced neurodegeneration and synaptic loss.

ABSTRACT: Aggregates of amyloid-beta (A?) and tau are hallmarks of Alzheimer's disease (AD) leading to neurodegeneration and synaptic loss. While increasing evidence suggests that inhibition of N-methyl-D-aspartate receptors (NMDARs) may mitigate certain aspects of AD neuropathology, the precise role of different NMDAR subtypes for A?- and tau-mediated toxicity remains to be elucidated. Using mouse organotypic hippocampal slice cultures from arcA? transgenic mice combined with Sindbis virus-mediated expression of human wild-type tau protein (hTau), we show that A? caused dendritic spine loss independently of tau. However, the presence of hTau was required for A?-induced cell death accompanied by increased hTau phosphorylation. Inhibition of NR2B-containing NMDARs abolished A?-induced hTau phosphorylation and toxicity by preventing GSK-3? activation but did not affect dendritic spine loss. Inversely, NR2A-containing NMDAR inhibition as well as NR2A-subunit knockout diminished dendritic spine loss but not the A? effect on hTau. Activation of extrasynaptic NMDARs in primary neurons caused degeneration of hTau-expressing neurons, which could be prevented by NR2B-NMDAR inhibition but not by NR2A knockout. Furthermore, caspase-3 activity was increased in arcA? transgenic cultures. Activity was reduced by NR2A knockout but not by NR2B inhibition. Accordingly, caspase-3 inhibition abolished spine loss but not hTau-dependent toxicity in arcA? transgenic slice cultures. Our data show that A? induces dendritic spine loss via a pathway involving NR2A-containing NMDARs and active caspase-3 whereas activation of eSyn NR2B-containing NMDARs is required for hTau-dependent neurodegeneration, independent of caspase-3.

SUBMITTER: Tackenberg C 

PROVIDER: S-EPMC3641351 | biostudies-literature | 2013 Apr

REPOSITORIES: biostudies-literature