Despite
Alzheimer's disease (AD) being the most common
neurodegenerative disorder worldwide, no FDA-approved disease-modifying treatments have been approved for this condition since 2003. Neuronal-type alpha7
nicotinic acetylcholine receptors (α7nAChRs) play an essential role in cognitive functions, binding with extracellular β-
amyloid (Aβ plaques) and inhibiting Aβ-induced neurotoxicity. α7nAChRs are impaired early in the course of AD; drugs targeting α7nAChRs are being hotly pursued as a treatment of AD.
Encenicline, a partial selective agonist of α7nAChR and modulator of
acetylcholine, failed in phase III trials because of gastrointestinal side effects. We, therefore, evaluated the efficacy of
galantamine, a positive allosteric modulator at α7nAChRs and an
acetylcholinesterase inhibitor, that has been used since 2000 as first-line treatment of mild-to-moderate
dementia. This study highlights an important new benefit with
galantamine. We found that
galantamine inhibits Aβ1-42-induced apoptosis by activating the JNK signaling pathway, thus enhancing α7nAChR expression, and also inhibits the Akt pathway, which further increases autophagosome biogenesis and autophagy. These effects can be reproduced by α7nAChR overexpression in the absence of
galantamine. Importantly, the α7
subunit protein sequence of α7nAChRs contains 3 LC3-interacting regions; our immunoprecipitation data show that α7 binds with the autophagosomal marker
protein LC3. This is the first report to provide evidence showing that the
cell surface receptor α7nAChR acts as a cargo carrier for LC3 binding for Aβ1-42 sequestration to autophagosomes, suggesting a novel mechanism for the neuroprotective efficacy of
galantamine in AD.