SNCA and multiple system atrophy: To this end, we generated stable HEK293 cells expressing wild-type α-synuclein fused to the promiscuous mutant Escherichia coli biotin ligase (BirA*), in order to label interacting proteins within ~10 nm radius of α-synuclein aggregation induced with the addition of de novo-generated, pooled PD-amplified fibrils or pooled MSA-amplified fibrils (Fig. 5a).