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Thellung S, Scoti B, Corsaro A, Villa V, Nizzari M, Gagliani MC, Porcile C, Russo C, Pagano A, Tacchetti C, Cortese K, Florio T. Pharmacological activation of autophagy favors the clearing of intracellular aggregates of misfolded prion protein peptide to prevent neuronal death. Cell Death Dis 2018; 9:166. [PMID: 29416016 PMCID: PMC5833808 DOI: 10.1038/s41419-017-0252-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 12/13/2017] [Accepted: 12/19/2017] [Indexed: 12/22/2022]
Abstract
According to the “gain-of-toxicity mechanism”, neuronal loss during cerebral proteinopathies is caused by accumulation of aggregation-prone conformers of misfolded cellular proteins, although it is still debated which aggregation state actually corresponds to the neurotoxic entity. Autophagy, originally described as a variant of programmed cell death, is now emerging as a crucial mechanism for cell survival in response to a variety of cell stressors, including nutrient deprivation, damage of cytoplasmic organelles, or accumulation of misfolded proteins. Impairment of autophagic flux in neurons often associates with neurodegeneration during cerebral amyloidosis, suggesting a role in clearing neurons from aggregation-prone misfolded proteins. Thus, autophagy may represent a target for innovative therapies. In this work, we show that alterations of autophagy progression occur in neurons following in vitro exposure to the amyloidogenic and neurotoxic prion protein-derived peptide PrP90-231. We report that the increase of autophagic flux represents a strategy adopted by neurons to survive the intracellular accumulation of misfolded PrP90-231. In particular, PrP90-231 internalization in A1 murine mesencephalic neurons occurs in acidic structures, showing electron microscopy hallmarks of autophagosomes and autophagolysosomes. However, these structures do not undergo resolution and accumulate in cytosol, suggesting that, in the presence of PrP90-231, autophagy is activated but its progression is impaired; the inability to clear PrP90-231 via autophagy induces cytotoxicity, causing impairment of lysosomal integrity and cytosolic diffusion of hydrolytic enzymes. Conversely, the induction of autophagy by pharmacological blockade of mTOR kinase or trophic factor deprivation restored autophagy resolution, reducing intracellular PrP90-231 accumulation and neuronal death. Taken together, these data indicate that PrP90-231 internalization induces an autophagic defensive response in A1 neurons, although incomplete and insufficient to grant survival; the pharmacological enhancement of this process exerts neuroprotection favoring the clearing of the internalized peptide and could represents a promising neuroprotective tool for neurodegenerative proteinopathies.
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Affiliation(s)
- Stefano Thellung
- Section of Pharmacology, Department of Internal Medicine (DiMI), and Centre of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy
| | - Beatrice Scoti
- Section of Pharmacology, Department of Internal Medicine (DiMI), and Centre of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy
| | - Alessandro Corsaro
- Section of Pharmacology, Department of Internal Medicine (DiMI), and Centre of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy
| | - Valentina Villa
- Section of Pharmacology, Department of Internal Medicine (DiMI), and Centre of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy
| | - Mario Nizzari
- Section of Pharmacology, Department of Internal Medicine (DiMI), and Centre of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy
| | - Maria Cristina Gagliani
- Section of Human Anatomy, Department of Experimental Medicine (DIMES), School of Medicine, University of Genova, Genova, Italy
| | - Carola Porcile
- Department of Health Sciences, University of Molise, Campobasso, Italy
| | - Claudio Russo
- Department of Health Sciences, University of Molise, Campobasso, Italy
| | - Aldo Pagano
- Section of Human Anatomy, Department of Experimental Medicine (DIMES), School of Medicine, University of Genova, Genova, Italy.,Ospedale Policlinico San Martino, IRCCS per l'Oncologia, Genova, Italy
| | - Carlo Tacchetti
- Centro Imaging Sperimentale, IRCCS Istituto Scientifico San Raffaele, Milano, Italy.,Vita-Salute San Raffaele University, Milano, Italy
| | - Katia Cortese
- Section of Human Anatomy, Department of Experimental Medicine (DIMES), School of Medicine, University of Genova, Genova, Italy
| | - Tullio Florio
- Section of Pharmacology, Department of Internal Medicine (DiMI), and Centre of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy.
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