Molecular determinants of α-synuclein toxicity and aggregation revealed by deep mutagenesis

The abundant neuronal protein α-synuclein is a key driver of Parkinson's and related diseases. α-Synuclein adopts a wide variety of different conformational states, but it is often unclear which of these species is responsible for its various behaviors, complicating efforts to combat pathologic misfolding of α-synuclein. Whereas conventional approaches struggle to provide direct, high-resolution insight into these structure-activity relationships, deep mutational scanning (DMS) has recently emerged as a powerful approach to probe the structural basis of protein activity and identify the molecular determinants of pathology. In the present review, we highlight insights from recent DMS studies of α-synuclein, which have implicated membrane binding as an important contribution to its toxicity and aggregation. Further, experiments in different cell types reveal distinct determinants of aggregation, highlighting the role of the cellular environment in shaping the conformational landscape of α-synuclein. We therefore expect that DMS will fill an important gap in the characterization of protein structure-activity relationships, particularly for conformationally dynamic proteins, including those implicated in misfolding diseases.