Role of cytochrome c in α-synuclein radical formation: implications of α-synuclein in neuronal death in Maneb- and paraquat-induced model of Parkinson’s disease

Abstract

BackgroundThe pathological features of Parkinson’s disease (PD) include an abnormal accumulation of α-synuclein in the surviving dopaminergic neurons. Though PD is multifactorial, several epidemiological reports show an increased incidence of PD with co-exposure to pesticides such as Maneb and paraquat (MP). In pesticide-related PD, mitochondrial dysfunction and α-synuclein oligomers have been strongly implicated, but the link between the two has not yet been understood. Similarly, the biological effects of α-synuclein or its radical chemistry in PD is largely unknown. Mitochondrial dysfunction during PD pathogenesis leads to release of cytochrome c in the cytosol. Once in the cytosol, cytochrome c has one of two fates: It either binds to apaf1 and initiates apoptosis or can act as a peroxidase. We hypothesized that as a peroxidase, cytochrome c leaked out from mitochondria can form radicals on α-synuclein and initiate its oligomerization.MethodSamples from controls, and MP co-exposed wild-type and α-synuclein knockout mice were studied using immuno-spin trapping, confocal microscopy, immunohistochemistry, and microarray experiments.ResultsExperiments with MP co-exposed mice showed cytochrome c release in cytosol and its co-localization with α-synuclein. Subsequently, we used immuno-spin trapping method to detect the formation of α-synuclein radical in samples from an in vitro reaction mixture consisting of cytochrome c, α-synuclein, and hydrogen peroxide. These experiments indicated that cytochrome c plays a role in α-synuclein radical formation and oligomerization. Experiments with MP co-exposed α-synuclein knockout mice, in which cytochrome c-α synuclein co-localization and interaction cannot occur, mice showed diminished protein radical formation and neuronal death, compared to wild-type MP co-exposed mice. Microarray data from MP co-exposed wild-type and α-synuclein knockout mice further showed that the absence of α-synuclein per se or its co-localization with cytochrome c confers protection from MP co-exposure, as several important pathways were unaffected in α-synuclein knockout mice.ConclusionsAltogether, these results show that peroxidase activity of cytochrome c contributes to α-synuclein radical formation and oligomerization, and that α-synuclein, through its co-localization with cytochrome c or on its own, affects several biological pathways which contribute to increased neuronal death in an MP-induced model of PD.Electronic supplementary materialThe online version of this article (doi:10.1186/s13024-016-0135-y) contains supplementary material, which is available to authorized users.

Wheel and Deal in the Mitochondrial Inner Membranes: The Tale of Cytochromecand Cardiolipin

“…Oxidative Medicine and Cellular Longevity oxidation of CL (to which it is anchored) facilitating the release of Cc from the IMM and subsequent massive release into the cytosol at the onset of apoptosis [18,62]. Extramitochondrial Cc molecules interact with a variety of targets in the cytosol and nucleus, leading to a point of no return in the programmed cell death regulation [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77].…”

“…Additionally, tyrosine phosphorylation impairs the formation of radicals, preventing dimerization [191]. This fact may be critical in pathological processes such as Parkinson's disease [66]. Therefore, the PTM that affect these residues are key in regulating Cc activity.…”

“…For instance, oxidation of sulfite to its radical SO 3 -• is a key mechanism in sulfite toxicity [164]. Moreover, Cc mediates the formation of tyrosine radicals responsible for α-synuclein dimerization [66,165], which leads to the development of the Lewy body diseases.…”

“…Moreover, Cc has been implicated in the development of Parkinson's disease-as it colocalizes with α-synuclein in the Lewy bodies [214]. In fact, the peroxidase activity of Cc plays an important role in the aggregation of α-synuclein by tyrosine dimerization [66,174].…”

Identification of Hub Genes and Key Pathways of Paraquat Induced Human Embryonic Pulmonary Fibrosis by Bioinformatics Analysis and Vitro Experiments

“…Microarray technology help to determinate mRNA pro les related to human disease and provides a comprehensive, unbiased approach to systematically analyze disease processes, including pulmonary brosis (5). Moreover, some studies have declared that PQ intoxication may alterate at the genome level (5)(6)(7)(8). Accordingly, integrative analyses of genes and pathways associated with lung brosis may provide an insight into therapeutic targets and diagnostic biomarkers for PQ-induced pulmonary brosis.…”