Ugalde, Cathryn L ORCID: 0000-0001-8663-6437, Annesley, Sarah J, Gordon, Shane E ORCID: 0000-0003-3964-8317, Mroczek, Katelyn, Perugini, Matthew A ORCID: 0000-0001-8052-5584, Lawson, Victoria A ORCID: 0000-0002-7362-7176, Fisher, Paul R, Finkelstein, David I ORCID: 0000-0002-8167-4917 and Hill, Andrew F ORCID: 0000-0001-5581-2354 (2020) Misfolded α-synuclein causes hyperactive respiration without functional deficit in live neuroblastoma cells. Disease Models and Mechanisms, 13 (1). ISSN 1754-8403

Abstract

The misfolding and aggregation of the largely disordered protein, α-synuclein, is a central pathogenic event that occurs in the synucleinopathies, a group of neurodegenerative disorders that includes Parkinson's disease. While there is a clear link between protein misfolding and neuronal vulnerability, the precise pathogenic mechanisms employed by disease-associated α-synuclein are unresolved. Here, we studied the pathogenicity of misfolded α-synuclein produced using the protein misfolding cyclic amplification (PMCA) assay. To do this, previous publishedmethodswere adapted to allow PMCA-induced protein fibrillization to occur under non-toxic conditions. Insight into potential intracellular targets of misfolded α-synuclein was obtained using an unbiased lipid screen of 15 biologically relevant lipids that identified cardiolipin (CA) as a potential binding partner for PMCA-generated misfolded α-synuclein. To investigate whether such an interaction can impact the properties of α-synuclein misfolding, protein fibrillization was carried out in the presence of the lipid. We show that CA both accelerates the rate ofα-synuclein fibrillization and produces species that harbourenhanced resistance to proteolysis. Because CA is virtually exclusively expressed in the inner mitochondrial membrane, we then assessed the ability of these misfolded species to alter mitochondrial respiration in live nontransgenic SH-SY5Y neuroblastoma cells. Extensive analysis revealed that misfoldedα-synucleincauses hyperactive mitochondrial respiration without causing any functional deficit.These datagive strong support for the mitochondrion as a target for misfolded α-synuclein and reveal persistent, hyperactive respiration as a potential upstream pathogenic event associated with the synucleinopathies.

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