\u3b1-synucleinopathies are a subset of progressive neurodegenerative disorders that share
several features and, above all, \u3b1-synuclein (\u3b1-syn) accumulation. Lewy bodies and neurites are
typical of Parkinson\u2019s disease (PD) and dementia with Lewy bodies, while Multiple System
Atrophy is characterized by the presence of glial cytoplasmic inclusions. Several mechanisms are
involved in the pathogenesis of these diseases, ranging from genetic factors, environment, cellular
disfunctions to \u3b1-syn misfolding. An increasing number of studies reported that \u3b1-syn is subjected
to post-translational modifications within Lewy bodies. Among them, C-terminal truncation seems
to increase its aggregation propensity.
Hemoglobin (Hb) genes expression was recently demonstrated in the central nervous system
and evidences suggest a putative role as oxygen reservoir and in mitochondrial respiration.
Dysregulation of Hb expression has been associated to several neurodegenerative disorders and,
in particular, to PD. Previous data from the laboratory of Prof. Gustincich showed that Hb alters mitochondrial
genes expression1, confers dopaminergic (DA) cells\u2019 susceptibility to MPP+ and rotenone in vitro
and impairs performance associated to motor learning in vivo2. Interestingly, the presence of Hb -
\u3b1-syn complexes in the brain of aging cynomolgus monkeys has recently been demonstrated3.
In this study, we aimed to unveil the interplay between Hb and \u3b1-syn and its contribution to
synucleinopathies. To this purpose, we took advantage of MN9D-Nurr1Tet-On dopaminergic
neuroblastoma cell lines (iMN9D) stably transfected with \u3b1 and \u3b2 chains of Hb1 and \u3b1-syn
preformed fibrils (PFFs) as a model of \u3b1-syn pathogenicity. We first demonstrate that iMN9D cells internalize PFFs and are therefore a suitable system
to study \u3b1-syn pathogenicity. Then, we show that PFFs treatment is toxic to cells and leads to the
accumulation of \u3b1-syn C-terminal truncated species (DC-\u3b1-syn) triggered in the presence of Hb.
Given the relevance of C-terminal cleavage products in terms of \u3b1-syn aggregation and toxicity,
we investigate the intracellular proteases likely involved in \u3b1-syn truncation. Among them, we
provide evidence that, in our model, calpains are involved in \u3b1-syn truncation.
In conclusion, taken together, these findings strongly support Hb implication in \u3b1-syn
processing and, therefore it exerts a significant role in the pathogenesis of \u3b1-synucleinopathies