Reelin signaling antagonizes β-amyloid at the synapse

Abnormal processing of the amyloid precursor protein (APP) and β-amyloid (Aβ) plaque accumulation are defining features of Alzheimer disease (AD), a genetically complex neurodegenerative disease that is characterized by progressive synapse loss and neuronal cell death. Aβ induces synaptic dysfunction in part by altering the endocytosis and trafficking of AMPA and NMDA receptors. Reelin is a neuromodulator that increases glutamatergic neurotransmission by signaling through the postsynaptic ApoE receptors Apoer2 and Vldlr and thereby potently enhances synaptic plasticity. Here we show that Reelin can prevent the suppression of long-term potentiation and NMDA receptors, which is induced by levels of Aβ comparable to those present in an AD-afflicted brain. This reversal is dependent upon the activation of Src family tyrosine kinases. At high concentrations of Aβ peptides, Reelin can no longer overcome the Aβ induced functional suppression and this coincides with a complete blockade of the Reelin-dependent phosphorylation of NR2 subunits. We propose a model in which Aβ, Reelin, and ApoE receptors modulate neurotransmission and thus synaptic stability as opposing regulators of synaptic gain control.