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Monomeric Alpha-Synuclein Exerts a Physiological Role on Brain ATP Synthase.

ABSTRACT: Misfolded ?-synuclein is a key factor in the pathogenesis of Parkinson's disease (PD). However, knowledge about a physiological role for the native, unfolded ?-synuclein is limited. Using brains of mice lacking ?-, ?-, and ?-synuclein, we report that extracellular monomeric ?-synuclein enters neurons and localizes to mitochondria, interacts with ATP synthase subunit ?, and modulates ATP synthase function. Using a combination of biochemical, live-cell imaging and mitochondrial respiration analysis, we found that brain mitochondria of ?-, ?-, and ?-synuclein knock-out mice are uncoupled, as characterized by increased mitochondrial respiration and reduced mitochondrial membrane potential. Furthermore, synuclein deficiency results in reduced ATP synthase efficiency and lower ATP levels. Exogenous application of low unfolded ?-synuclein concentrations is able to increase the ATP synthase activity that rescues the mitochondrial phenotypes observed in synuclein deficiency. Overall, the data suggest that ?-synuclein is a previously unrecognized physiological regulator of mitochondrial bioenergetics through its ability to interact with ATP synthase and increase its efficiency. This may be of particular importance in times of stress or PD mutations leading to energy depletion and neuronal cell toxicity. SIGNIFICANCE STATEMENT:Misfolded ?-synuclein aggregations in the form of Lewy bodies have been shown to be a pathological hallmark in histological staining of Parkinson's disease (PD) patient brains. It is known that misfolded ?-synuclein is a key driver in PD pathogenesis, but the physiological role of unfolded monomeric ?-synuclein remains unclear. Using neuronal cocultures and isolated brain mitochondria of ?-, ?-, and ?-synuclein knock-out mice and monomeric ?-synuclein, this current study shows that ?-synuclein in its unfolded monomeric form improves ATP synthase efficiency and mitochondrial function. The ability of monomeric ?-synuclein to enhance ATP synthase efficiency under physiological conditions may be of importance when ?-synuclein undergoes the misfolding and aggregation reported in PD.

SUBMITTER: Ludtmann MH

PROVIDER: S-EPMC5059426 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Monomeric Alpha-Synuclein Exerts a Physiological Role on Brain ATP Synthase.

Ludtmann Marthe H R MH Angelova Plamena R PR Ninkina Natalia N NN Gandhi Sonia S Buchman Vladimir L VL Abramov Andrey Y AY

The Journal of neuroscience : the official journal of the Society for Neuroscience 20161001 41

Misfolded α-synuclein is a key factor in the pathogenesis of Parkinson's disease (PD). However, knowledge about a physiological role for the native, unfolded α-synuclein is limited. Using brains of mice lacking α-, β-, and γ-synuclein, we report that extracellular monomeric α-synuclein enters neurons and localizes to mitochondria, interacts with ATP synthase subunit α, and modulates ATP synthase function. Using a combination of biochemical, live-cell imaging and mitochondrial respiration analysi ...[more]

PMID: 27733604

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Project description:Human alpha-Synuclein (alphaSyn) is a natively unfolded protein whose aggregation into amyloid fibrils is involved in the pathology of Parkinson disease. A full comprehension of the structure and dynamics of early intermediates leading to the aggregated states is an unsolved problem of essential importance to researchers attempting to decipher the molecular mechanisms of alphaSyn aggregation and formation of fibrils. Traditional bulk techniques used so far to solve this problem point to a direct correlation between alphaSyn's unique conformational properties and its propensity to aggregate, but these techniques can only provide ensemble-averaged information for monomers and oligomers alike. They therefore cannot characterize the full complexity of the conformational equilibria that trigger the aggregation process. We applied atomic force microscopy-based single-molecule mechanical unfolding methodology to study the conformational equilibrium of human wild-type and mutant alphaSyn. The conformational heterogeneity of monomeric alphaSyn was characterized at the single-molecule level. Three main classes of conformations, including disordered and "beta-like" structures, were directly observed and quantified without any interference from oligomeric soluble forms. The relative abundance of the "beta-like" structures significantly increased in different conditions promoting the aggregation of alphaSyn: the presence of Cu2+, the pathogenic A30P mutation, and high ionic strength. This methodology can explore the full conformational space of a protein at the single-molecule level, detecting even poorly populated conformers and measuring their distribution in a variety of biologically important conditions. To the best of our knowledge, we present for the first time evidence of a conformational equilibrium that controls the population of a specific class of monomeric alphaSyn conformers, positively correlated with conditions known to promote the formation of aggregates. A new tool is thus made available to test directly the influence of mutations and pharmacological strategies on the conformational equilibrium of monomeric alphaSyn.

Dataset Information

Monomeric Alpha-Synuclein Exerts a Physiological Role on Brain ATP Synthase.

Publications

Monomeric Alpha-Synuclein Exerts a Physiological Role on Brain ATP Synthase.

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