Direct Membrane Association Drives Mitochondrial Fission by the Parkinson Disease-associated Protein α-Synuclein

Abstract

The protein ␣-synuclein has a central role in Parkinson disease, but the mechanism by which it contributes to neural degeneration remains unknown. We now show that the expression of ␣-synuclein in mammalian cells, including neurons in vitro and in vivo, causes the fragmentation of mitochondria. The effect is specific for synuclein, with more fragmentation by ␣-than ␤-or ␥-isoforms, and it is not accompanied by changes in the morphology of other organelles or in mitochondrial membrane potential. However, mitochondrial fragmentation is eventually followed by a decline in respiration and neuronal death. The fragmentation does not require the mitochondrial fission protein Drp1 and involves a direct interaction of synuclein with mitochondrial membranes. In vitro, synuclein fragments artificial membranes containing the mitochondrial lipid cardiolipin, and this effect is specific for the small oligomeric forms of synuclein. ␣-Synuclein thus exerts a primary and direct effect on the morphology of an organelle long implicated in the pathogenesis of Parkinson disease.Many observations have implicated mitochondria in the pathogenesis of PD.2 Mitochondria from the substantia nigra of affected patients show a selective reduction in the activity of respiratory chain complex I (1). Somatic mutations also accumulate with age and PD in the mitochondrial DNA of substantia nigra neurons (2). In addition, the neurotoxins MPTP and rotenone, which produce models of PD, both act by disrupting mitochondrial function. Genetic evidence further supports a primary role for mitochondria in the pathogenesis of PD. Mutations in parkin and the mitochondrial kinase PINK1 both cause autosomal recessive PD (3), and these genes appear required for the normal clearance of defective mitochondria by autophagy (4). However, the molecular mechanisms responsible for mitochondrial dysfunction in the much more common sporadic forms of PD have remained unclear. Several observations suggest a central role for the protein ␣-synuclein in the pathogenesis of sporadic PD. Point mutations in synuclein produce a rare autosomal dominant form of PD (5-7), indicating a causative role for the protein. ␣-Synuclein also accumulates in the Lewy bodies and dystrophic neurites of essentially all patients with idiopathic PD (8), implicating the protein in sporadic as well as familial forms of the disease. Furthermore, duplication and particularly triplication of the SNCA (␣-synuclein) gene cause a severe, highly penetrant form of PD (9, 10), indicating a dose-dependent pathogenic role for the wild type protein when overexpressed and suggesting that the accumulation of synuclein in sporadic PD is the primary pathogenic event. However, the mechanism by which ␣-synuclein causes PD remains poorly understood. Expressed in yeast and Drosophila, human ␣-synuclein produces severe toxicity (11-14), but these model organisms lack endogenous synuclein, and the overexpression of wild type synuclein in mammalian systems causes remarkably little if any consistent toxicity (15-18).Althou...

Remodeling of Lipid Vesicles into Cylindrical Micelles by α-Synuclein in an Extended α-Helical Conformation

“…Overexpression of ␣S causes disruption of endoplasmic reticulum-Golgi trafficking (14), fragmentation of the Golgi apparatus (24,25), and distortion of mitochondrial membranes (26), causing them to fission (27). Taken together, these reports suggest that ␣S interacts widely with multiple organelles, but in all cases, these interactions involve membranes.…”

The Role of Mitochondrially Derived ATP in Synaptic Vesicle Recycling

“…AT1.03 YEMK and AT R122K/R126K fluorescence resonance energy transfer (FRET) sensors (which use a variant of CFP 5 (mseCFP) as the donor fluorophore and YFP (circularly permuted monomeric Venus) as the acceptor fluorophore, surrounding an ATP-binding protein) were the kind gifts from Hiromi Imamura (Kyoto University) and Hiroyuki Noji (Osaka University) (10). VGLUT1-pHluorin, mCherry-synaptophysin, mitoGFP, and the direct CFP-YFP fusion have been described (9,(11)(12)(13). Mito-FarRed (TagRFP657 fused to the mitochondrial targeting sequence, cytochrome c oxidase subunit VIII) and mTagBFP (used to make mito-mTagBFP) were kind gifts from Vladislav Verkhusha (Albert Einstein College of Medicine) (14,15), and Cre recombinase (Cre) was from Addgene.…”

Regulation and Quantification of Cellular Mitochondrial Morphology and Content

“…Another protein involved in Parkinson's disease, α-synuclein, also appears to play a role in mitochondrial quality control. However, the nature of this involvement is currently not fully understood [121][122][123]. Obviously, mitochondrial biogenesis and degradation by mitophagy act antagonistically, but at the same time complementary; and together they determine net mitochondrial content and mitochondrial quality.…”