SorCS1 inhibits amyloid-β binding to neurexin and rescues amyloid-β-induced synaptic pathology

Amyloid-{beta} oligomers (A{beta}Os), toxic peptide aggregates found in Alzheimers disease (AD), cause synapse pathology. A{beta}Os interact with Neurexins (NRXs), key synaptic organizers, and this interaction dampens normal trafficking and function of NRXs. Axonal trafficking of NRX is in part regulated by its interaction with SorCS1, a protein sorting receptor, but the impact of SorCS1 regulation of NRXs in A{beta} pathology was previously unstudied. Here, we show competitive interaction of SorCS1 and A{beta}Os with {beta}-NRXs and rescue effects of SorCS1 on A{beta}O-induced synaptic pathology. Like A{beta}Os, SorCS1 binds to NRX1{beta} through the histidine-rich-domain (HRD) of NRX1{beta}, and SorCS1 and A{beta}Os compete for NRX1{beta} binding. In cultured hippocampal neurons, SorCS1 colocalizes with NRX1{beta} on the axon surface, and axonal expression of SorCS1 rescues A{beta}O-induced impairment of NRX-mediated presynaptic organization and presynaptic vesicle recycling as well as A{beta}O-induced structural defects in excitatory synapses. Thus, we reveal a role of SorCS1 in the rescue of A{beta}O-induced NRX dysfunction and synaptic pathology, providing the basis for a novel potential therapeutic strategy for AD.