Modulation of mitochondrial quality control through autophagic pathway in familial Alzheimer's disease

Autophagy is a highly conserved cellular catabolic process recognized as an essential pathway for the maintenance of cellular homeostasis. Growing evidence implicates autophagic dysfunction in the pathogenesis of several neurodegenerative disorders, including Alzheimer's disease (AD), thus its modulation might represent an interesting therapeutic tool. Searching for a compound that stimulates autophagic pathway, led us to identify the inhibitor of RPSA receptor, NSC47924. In this study, we show that, NSC47924 down-modulated Akt-mTOR-axis pathway, the master regulator of autophagy, which was abnormally hyperactivated in fibroblasts from genetic AD-affected patients. Consistently, by monitoring the conversion of LC3, we found that inhibition of RPSA enhanced and restored the compromised autophagic flux. Moreover, by qRT-PCR analysis we found that inhibitor treatment upregulated the expression of autophagy-linked genes. Importantly, AD-affected fibroblasts exhibited massive mitochondrial network fragmentation and mitophagy defects, which were restored through the stimulation of autophagy induced by RPSA inhibition. Consistent with an efficient elimination of dysfunctional mitochondria, we found that the turnover of both the mitophagy regulators PINK1 and Parkin and the autophagic receptors p62, NDP52, OPTN, was modulated, thus restoring a highly interconnected organelle's network. In addition, the improvement of mitochondrial morphology correlated with a functional recovery, as assessed by Seahorse analysis and mitochondrial ROS production evaluation. Collectively, our findings suggest that RPSA inhibition stimulates an autophagic pathway promoting the efficient removal of damaged mitochondria, favouring the recovery of cellular homeostasis, and counteracting crucial AD pathogenic mechanisms.