a-Synucelin membrane association induces a mitochondrial fragmentation phenotype in a human Parkinson Disease models.

TMM SAEZ; G SEVLEVER; M ALLOATTI; LE CROMBERG; VM POZO DEVOTO; MG OTERO; TL FALZONE

San Diego

Congreso; 46th Annual Meeting of the Society for Neuroscience.; 2016

Society for Neuroscience.

Although initially α-Synuclein (α-Syn) studies associated to PD have focused on its role on aggregation and toxicity and away from the mitochondria, recently, growing interest is dedicated to the possible role that α-Syn exerts over the mitochondrial quality control. Biophysical properties of WT α-Syn or the dominant mutations A30P and A53T α-Syn suggest differential lipid binding affinities, which can give a hint on α-Syn interaction mechanism with mitochondria. To test whether α-Syn drives a mitochondrial phenotype we developed different human PD neuronal models derived from hESC or genetically modified hIPSC to analyze the effect of WT, A30P and A53T α-Syn on mitochondrial axonal transport, membrane potential and morphology. Initially, by live imaging of fluorescent mitochondria in axons we analyzed whether WT α-Syn or PD related mutants impairs the axonal transport of mitochondria. Significant defects in mitochondrial flux were observed for A53T α-Syn overexpression and milder defects for WT and A30P. Interestingly, a significant reduction in mitochondrial size plus an increase in axonal mitochondrial density was observed upon A53T α-Syn overexpression. These defects correlated with a high to low ratio of α-Syn localization within the mitochondrial fraction for A53T, WT and A30P, respectively. Therefore, we designed a mitochondrial targeting system based on FKBP-FRB dimerization that delivers α-Syn to the outer mitochondrial membrane (OMM) to test whether α-Syn interaction with the mitochondrial membrane in human neurons mediates the morphology effect. Surprisingly, we found that WT α-Syn delivery to the OMM reduced the size of the mitochondria to similar levels than A53T α-Syn, while A30P induced no effect. These results provide direct evidence of membrane interaction derived effect of α-Syn on mitochondrial size. Finally, CRISP-r/CAS9 genome edition in hIPSC were generated to test whether the N-terminal domain of α-Syn mediates fragmentation. Human neurons derived from CRISP modified IPSC revealed the opposite to fragmentation with abnormal elongated and ramified axonal mitochondria. Interestingly, the mitochondrial enlarged phenotype was lost after A53T α-Syn overexpression in this neurons. All together, our findings identify a new and relevant neuronal physiological role for α-Syn in the maintenance of mitochondrial morphology that when impaired by α-Syn overexpression or mutations can lead to abnormal fragmentation phenotypes observed as a common feature of PD.