Membrane binding, internalization, and sorting of alpha-synuclein in the cell

MASARACCHIA, CATERINA; HNIDA, MARILENA; GERHARDT, ELLEN; LOPES DA FONSECA, TOMÁS; VILLAR-PIQUE, ANNA; BRANCO, TIAGO; STAHLBERG, MARKUS A.; DEAN, CAMIN; FERNÁNDEZ, CLAUDIO O.; MILOSEVIC, IRA; OUTEIRO, TIAGO F.

Acta Neuropathologica Communications

BMC Springer

Año: 2018 vol. 6

Alpha-synuclein (aSyn) plays a crucial role in Parkinson?s disease (PD) and other synucleinopathies, since it misfoldsand accumulates in typical proteinaceous inclusions. While the function of aSyn is thought to be related to vesiclebinding and trafficking, the precise molecular mechanisms linking aSyn with synucleinopathies are still obscure.aSyn can spread in a prion-like manner between interconnected neurons, contributing to the propagation of thepathology and to the progressive nature of synucleinopathies. Here, we investigated the interaction of aSyn withmembranes and trafficking machinery pathways using cellular models of PD that are amenable to detailedmolecular analyses. We found that different species of aSyn can enter cells and form high molecular weight species,and that membrane binding properties are important for the internalization of aSyn. Once internalized, aSynaccumulates in intracellular inclusions. Interestingly, we found that internalization is blocked in the presence ofdynamin inhibitors (blocked membrane scission), suggesting the involvement of the endocytic pathway in theinternalization of aSyn. By screening a pool of small Rab-GTPase proteins (Rabs) which regulate membranetrafficking, we found that internalized aSyn partially colocalized with Rab5A and Rab7. Initially, aSyn accumulated inRab4A-labelled vesicles and, at later stages, it reached the autophagy-lysosomal pathway (ALP) where it getsdegraded. In total, our study emphasizes the importance of membrane binding, not only as part of the normalfunction but also as an important step in the internalization and subsequent accumulation of aSyn. Importantly, weidentified a fundamental role for Rab proteins in the modulation of aSyn processing, clearance and spreading,suggesting that targeting Rab proteins may hold important therapeutic value in PD and other synucleinopathies.