Identification of N-linked glycans as specific mediators of neuronal uptake of acetylated α-Synuclein

Cell-to-cell transmission of toxic forms of alpha-Synuclein (alpha S) is thought to underlie disease progression in Parkinson disease. alpha S in humans is constitutively N-terminally acetylated (alpha S-acetyl), although the impact of this modification is relatively unexplored. Here, we report that alpha S-acetyl is more effective at inducing intracellular aggregation in primary neurons than unmodified alpha S (alpha S-un). We identify complex N-linked glycans as binding partners for alpha S-acetyl and demonstrate that cellular internalization of alpha S-acetyl is reduced significantly upon cleavage of extracellular N-linked glycans, but not other carbohydrates. We verify binding of alpha S-acetyl to N-linked glycans in vitro, using both isolated glycans and cell-derived proteoliposomes. Finally, we identify neurexin 1 beta, a neuronal glycoprotein, as capable of driving glycan-dependent uptake of alpha S-acetyl. Importantly, our results are specific to alpha S-acetyl because alpha S-un does not demonstrate sensitivity for N-linked glycans in any of our assays. Our study identifies extracellular N-linked glycans-and the glycoprotein neurexin 1 beta specifically-as key modulators of neuronal uptake of alpha S-acetyl, drawing attention to the potential therapeutic value of alpha S-acetyl-glycan interactions.