RESUMO
Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder affecting over 1% of the 65 + age population. Saposin C, a lysosomal protein required for the normal activity of glucocerebrosidase (GCase), may serve as a disease modifier in PD. Saposin C is cleaved from its precursor, Prosaposin (PSAP), which is secreted as an uncleaved protein and exerts neuroprotective effects. In this study, we aim to elucidate the neuroprotective roles of PSAP and saposin C in PD by evaluating their effects on α-synuclein accumulation in human neuroblastoma cells. Stable overexpression of PSAP reduced monomeric α-synuclein levels in SH-SY5Y cells, while PSAP knockdown by small interfering RNA led to the opposite effect, and those effects were independent of GCase activity. Autophagy flux was decreased by stable PSAP overexpression. Furthermore, a flow-through assay revealed that recombinant saposin C was able to detach α-synuclein from artificial glucosylceramide-enriched lipid membranes at the lysosomal pH. Taken together, our findings provide further evidence that PSAP and saposin C as key proteins involved in α-synuclein clearance by dislodging it from lipid membranes.
Assuntos
Neuroblastoma , alfa-Sinucleína , Humanos , alfa-Sinucleína/genética , Saposinas/genética , Glucosilceramidas/farmacologiaRESUMO
Mutations in the glucocerebrosidase gene are a common genetic risk factor for developing Parkinson's disease. The reasons why glucocerebrosidase mutations cause an increased life-time risk of developing Parkinson's disease are not fully understood. Here, we aimed to verify whether glucocerebrosidase activity has an effect on total α-synuclein levels. We use SH-SY5Y and primary cortical cells and expose them to either Conduritol-ß-epoxide or siRNA targeting GBA 1. Unexpectedly, RNA interference towards GBA 1 and catalytic inhibition produce different effects on α-synuclein levels in cellular models.