Aggregation and membrane activity of mutant A30P alpha-synuclein on mitochondrial membranes.

The A30P point mutation in the α-synuclein (α-syn) protein is linked to a familial form of Parkinson's disease (PD), the most common motor neurodegenerative disorder. The association of α-syn with lipids in cellular membranes plays a key role in modulating the aggregation behavior of the protein, as well as its toxicity. Here, we studied the impact of the A30P mutation on the interaction of α-syn with mitochondrial membranes, since the interplay between α-syn aggregation and mitochondrial dysfunction is central for the pathogenic process in PD, but still not completely understood. Experiments using model vesicles with membranes enriched in the mitochondrial signature phospholipid cardiolipin (CL) demonstrated that these membranes markedly accelerate and promote the aggregation of A30P α-syn, with respect to the wild-type protein. In turn, A30P caused enhanced changes in membrane fluidity and permeabilization of CL-containing membranes. Moreover, utilizing single-channel planar bilayer measurements, A30P α-syn was shown to increase the membrane conductance in mito-mimetic bilayers, possibly by membrane thinning and incorporation of ion-conducting pores. The incubation of A30P α-syn with isolated mitochondria caused mitochondrial swelling, efflux of cytochrome c and lowered the mitochondrial membrane potential, all key indicators of mitochondrial membrane damage. Collectively, our results demonstrate that the A30P mutation aggravates the deleterious liaison between α-syn and CL-rich membranes, providing a mechanistic basis for mitochondrial dysfunction associated with this α-syn variant.