Synaptic Adhesion Molecule Pcdh-{gamma}C5 Mediates Synaptic Dysfunction in Alzheimer's Disease

Synaptic dysfunction and neuronal excitatory/inhibitory imbalance have been implicated in Alzheimer's disease (AD) pathogenesis. Although intensive studies have been focused on the excitatory synaptic system, much less is known concerning the mechanisms mediating inhibitory synaptic dysfunction in AD. We reported previously that protocadherin-C5 (Pcdh-C5), a member of clustered Pcdh- subfamily of cadherin-type synaptic adhesion proteins, functions to promote GABAergic synaptic transmission. We reveal here that Pcdh-C5 is enriched in vesicular GABA transporter-positive synaptic puncta and its expression levels are increased in neuronal hyperexcitation conditions, upon β-amyloid (Aβ) treatment, and in amyloid precursor protein (APP)/presenilin-1 (PS1)-transgenic mice of both sexes. This is associated with elevated levels of GABAergic proteins and enhanced synaptic inhibition. Genetic knock-down experiments showed that Pcdh-C5 modulates spontaneous synaptic currents and Aβ-induced synaptic alterations directly. Our results support a model in which Pcdh-C5 senses neuronal hyperexcitation to augment GABAergic inhibition. This adaptive mechanism may be dysregulated under chronic excitation conditions such as AD, leading to aberrant Pcdh-C5 expression and associated synaptic dysfunction.

SIGNIFICANCE STATEMENT Synaptic dysfunction is causal for Alzheimer's disease (AD). Here, we reveal a novel pathway that contributes GABAergic synaptic dysfunction in AD mediated by protocadherin-C5. Our study not only identifies a new mechanism mediating excitatory/inhibitory balance in AD, but may also offer a new target for potential therapeutic intervention.

from #ORL-AlexandrosSfakianakis via ola Kala on Inoreader http://ift.tt/2xhsGuF