Amyloid ß / PKC-dependent alterations in NMDA receptor composition are detected in early stages of Alzheimer´s disease.

ABSTRACT

Amyloid beta (Aß)-mediated synapse dysfunction is an early event in Alzheimer's disease (AD) pathogenesis and previous studies suggest that NMDA receptor (NMDAR) dysregulation may contribute to these pathological effects. Although Aß peptides impair NMDAR expression and activity, the mechanisms mediating these alterations in the early stages of AD are unclear. Here, we observed that NMDAR subunit NR2B and PSD-95 levels were aberrantly upregulated and correlated with Aß42 load in human postsynaptic fractions of the prefrontal cortex in early stages of AD patients, as well as in the hippocampus of 3xTg-AD mice. Importantly, NR2B and PSD95 dysregulation was revealed by an increased expression of both proteins in Aß-injected mouse hippocampi. In cultured neurons, Aß oligomers increased the NR2B-containing NMDAR density in neuronal membranes and the NMDA-induced intracellular Ca2+ increase, in addition to colocalization in dendrites of NR2B subunit and PSD95. Mechanistically, Aß oligomers required integrin ß1 to promote synaptic location and function of NR2B-containing NMDARs and PSD95 by phosphorylation through classic PKCs. These results provide evidence that Aß oligomers modify the contribution of NR2B to NMDAR composition and function in the early stages of AD through an integrin ß1 and PKC-dependent pathway. These data reveal a novel role of Aß oligomers in synaptic dysfunction that may be relevant to early-stage AD pathogenesis.