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α-Synuclein impairs ferritinophagy in the retinal pigment epithelium: Implications for retinal iron dyshomeostasis in Parkinson’s disease.
Sci Rep. 2017 Oct 9;7(1):12843. doi: 10.1038/s41598-017-12862-x
Baksi S, Singh N
Abstract:
Retinal degeneration is prominent in Parkinson's disease (PD), a neuromotor disorder associated with aggregation of α-synuclein (α-syn) in the substantia-nigra (SN). Although α-syn is expressed in the neuroretina, absence of prominent aggregates suggests altered function as the likely cause of retinal pathology. We demonstrate that α-syn impairs ferritinophagy, resulting in the accumulation of iron-rich ferritin in the outer retina in-vivo and retinal-pigment-epithelial (RPE) cells in-vitro. Over-expression of Rab1a restores ferritinophagy, suggesting that α-syn impairs lysosomal function by disrupting the trafficking of lysosomal hydrolases. Surprisingly, upregulation of ferritin in RPE cells by exogenous iron in-vitro stimulated the release of ferritin and α-syn in exosomes, suggesting that iron overload due to impaired ferritinophagy or other cause(s) is likely to initiate prion-like spread of α-syn and ferritin, creating retinal iron dyshomeostasis and associated cytotoxicity. Since over-expression of α-syn is a known cause of PD, these results explain the likely cause of PD-associated retinal degeneration.
PMID: 28993630
Free Full-Text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5634503/
Tags: alpha-synuclein, ferritin, iron, lysosomes, parkinson's, RPE cells