Objective: Study the direct and indirect effects of iron overload on alpha synuclein homeostasis in a genetic model of hemochromatosis (HFE)

Background: Parkinson’s disease (PD) is characterized by the presence of alpha synuclein-containing Lewy bodies with selective vulnerability of particular neuronal populations, especially the dopaminergic neurons in the substantia nigra (SN). Increased levels of iron and ferritin in the SN also appear to be consistent features of the disease, but it remains unclear whether this accumulation is pathologic and if it relates to synuclein aggregation. Population genotype studies have returned conflicting results in regards to correlation between polymorphisms in iron metabolism genes (transferrin, transferrin receptor 1, HFE, frataxin, and lactoferrin) and PD. Nevertheless, a direct effect on synuclein can be postulated due to the known effect of metal ions on protein aggregation in vitro, the presence of a putative iron responsive element (IRE) in the 5’- untranslated region of the alpha synuclein messenger RNA, and the effects of iron on synuclein disposal via autophagy and proteasome activity.

Methods: Human neuroblastoma SH-SY5Y cell lines with stable transfection of two common HFE mutations (C282Y and H63D) were used to study alpha synuclein in iron-overloaded states. Total synuclein protein was assessed by Western analysis, while oligomers were studied using blue native PAGE. Autophagic flux was assessed via Western blot for LC3 and proteasome activity via effects on a artificial fluorescent/luminescent substrates. Transcripts were measured using RT-PCR

Results: Western blot analysis showed that H63D and C282Y HFE-expressing cells had higher levels of total alpha synuclein compared to wild type. Addition of the iron chelator deferoxamine had varying effects on the intracellular labile iron pool and alpha synuclein levels. The impact of the HFE mutants on transcription of alpha synuclein, autophagic flux and proteasome activity and ultimately the levels of higher molecular weight alpha synuclein oligomers was also assessed.

Conclusions: These findings support the concept that iron may play a synuclein-mediated role in PD neurodegeneration.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/alpha-synuclein-protein-homeostasis-and-oligomerization-in-iron-overloaded-cells-expressing-mutant-hfe/