The etiology of Parkinson's disease (PD) converges on a common pathogenic pathway of mitochondrial defects in which α-Synuclein (αSyn) is thought to play a role. However, the mechanisms by which αSyn and its disease-associated allelic variants cause mitochondrial dysfunction remain unknown. Here, we analyzed mitochondrial axonal transport and morphology in human-derived neurons overexpressing wild-type (WT) αSyn or the mutated variants A30P or A53T, which are known to have differential lipid affinities. A53T αSyn was enriched in mitochondrial fractions, inducing significant mitochondrial transport defects and fragmentation, while milder defects were elicited by WT and A30P. We found that αSyn-mediated mitochondrial fragmentation was linked to expression levels in WT and A53T variants. Targeted delivery of WT and A53T αSyn to the outer mitochondrial membrane further increased fragmentation, whereas A30P did not. Genomic editing to disrupt the N-terminal domain of αSyn, which is important for membrane association, resulted in mitochondrial elongation without changes in fusion-fission protein levels, suggesting that αSyn plays a direct physiological role in mitochondrial size maintenance. Thus, we demonstrate that the association of αSyn with the mitochondria, which is modulated by protein mutation and dosage, influences mitochondrial transport and morphology, highlighting its relevance in a common pathway impaired in PD.

Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia Montañeses 2325 Buenos Aires C1428AQK Argentina

Instituto de Biología Celular y Neurociencias IBCN Facultad de Medicina Universidad de Buenos Aires Paraguay 2155 Buenos Aires CP1121 Argentina

Instituto de Biología Celular y Neurociencias IBCN St Anne's University Hospital CZ 65691 Brno Czech Republic

Instituto de Biología Celular y Neurociencias IBCN Vuelta de obligado 2490 Buenos Aires CP 1428 Argentina

Instituto de Investigación en Biomedicina de Buenos Aires CONICET Partner Institute of the Max Planck Society Buenos Aires Argentina

International Clinical Research Center St Anne's University Hospital CZ 65691 Brno Czech Republic

Laboratorio de Plasticidad Neuronal Fundación Instituto Leloir Av Patricias Argentinas 435 Buenos Aires CP C1405BWE Argentina