Structural disorder of monomeric α-synuclein persists in mammalian cells

Abstract

Intracellular aggregation of the human amyloid protein α-synuclein is causally linked to Parkinson's disease. While the isolated protein is intrinsically disordered, its native structure in mammalian cells is not known. Here we use nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy to derive atomic-resolution insights into the structure and dynamics of α-synuclein in different mammalian cell types. We show that the disordered nature of monomeric α-synuclein is stably preserved in non-neuronal and neuronal cells. Under physiological cell conditions, α-synuclein is amino-terminally acetylated and adopts conformations that are more compact than when in buffer, with residues of the aggregation-prone non-amyloid-β component (NAC) region shielded from exposure to the cytoplasm, which presumably counteracts spontaneous aggregation. These results establish that different types of crowded intracellular environments do not inherently promote α-synuclein oligomerization and, more generally, that intrinsic structural disorder is sustainable in mammalian cells.

Structural characterization of the interaction of α-synuclein nascent chains with the ribosomal surface and trigger factor

“…1E), this would indicate that there may be a specific affinity of the ribosome surface for aromatic residues. Interestingly, similar patterns of NMR line broadening have been observed for αSyn within bacterial (32) and mammalian cells (49), which suggests that there may be a common role for charged and aromatic residues in governing protein interactions both with the ribosome surface and with other components of the cellular milieu.…”

Potential Modes of Intercellular Alpha-Synuclein Transmission

“…Alpha synuclein (α-syn) is a 140 amino acid, soluble protein found predominantly within the central nervous system (CNS), and is enriched in the peripheral nervous system and circulating erythrocytes (Barbour et al, 2008;Theillet et al, 2016;Weinreb et al, 1996). The normal role of α-syn remains unclear, however high concentrations of the protein exist within neuronal presynaptic terminals, indicating potential function(s) in synaptic transmission (Cheng, Vivacqua and Yu, 2011).…”

“…Pathological α-syn displays many of these characteristics. The NAC region of α-syn contributes to stabilizing the β-sheet conformational change (Iwai, 2000;Theillet et al, 2016;Rodriguez et al, 2015). α-Syn fibrils have been shown to be insoluble, and persist in the extracellular environment, thus aiding transmissibility (Cookson, 2009).…”

Phosphorylation-induced unfolding regulates p19 INK4d during the human cell cycle

“…In-cell NMR allows the study of proteins and their post-translational modifications in cellular environments [12][13][14]. Alternatively, purified isotope-labeled proteins of interest may be added directly to unlabeled, native cell lysates to study how endogenous cellular proteins such as kinases, phosphatases or proteases act on them [15,16].…”