Occurrence of Total and Proteinase K-Resistant Alpha-Synuclein in Glioblastoma Cells Depends on mTOR Activity

• Published in: Cancers 2022-03, Vol.14 (6), p.1382
• Main Authors: Ryskalin, Larisa, Ferese, Rosangela, Morucci, Gabriele, Biagioni, Francesca, Busceti, Carla L, Michetti, Fabrizio, Lenzi, Paola, Frati, Alessandro, Fornai, Francesco
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Astrocytes; Autophagy; Brain tumors; Cytosol; Endopeptidase K; Experiments; Genes; Glioblastoma; Glioblastoma cells; Glioblastoma multiforme; Immunohistochemistry; Laboratories; Light; Microscopy; Morphology; Neurodegenerative diseases; Phenotypes; Polymerase chain reaction; Protein interaction; Proteinase; Proteins; Rapamycin; Stoichiometry; Synuclein; TOR protein; Vacuoles; Western blotting
• ISSN: 2072-6694; 2072-6694
• DOI: 10.3390/cancers14061382

Alpha-synuclein (α-syn) is a protein considered to be detrimental in a number of degenerative disorders (synucleinopathies) of which α-syn aggregates are considered a pathological hallmark. The clearance of α-syn strongly depends on autophagy, which can be stimulated by inhibiting the mechanistic target of rapamycin (mTOR). Thus, the overexpression of mTOR and severe autophagy suppression may produce α-syn accumulation, including the proteinase K-resistant protein isoform. Glioblastoma multiforme (GBM) is a lethal brain tumor that features mTOR overexpression and severe autophagy inhibition. Cell pathology in GBM is reminiscent of a fast, progressive degenerative disorder. Therefore, the present work questions whether, as is analogous to neurons during degenerative disorders, an overexpression of α-syn occurs within GBM cells. A high amount of α-syn was documented in GBM cells via real-time PCR (RT-PCR), Western blotting, immunohistochemistry, immuno-fluorescence, and ultrastructural stoichiometry, compared with the amount of β- and γ-synucleins and compared with the amount of α-syn counted within astrocytes. The present study indicates that (i) α-syn is overexpressed in GBM cells, (ii) α-syn expression includes a proteinase-K resistant isoform, (iii) α-syn is dispersed from autophagy-like vacuoles to the cytosol, (iv) α-syn overexpression and cytosol dispersion are mitigated by rapamycin, and (v) the α-syn-related GBM-like phenotype is mitigated by silencing the SNCA gene.