The α-synuclein protein has been strongly correlated with Parkinson's disease (PD) and is a major component of the hallmark Lewy body aggregates associated with PD. Two different mutations in the α-synuclein gene as well as increased gene dosage of wild-type α-synuclein all associate with early onset cases of PD; and transgenic animal models overexpressing α-synuclein develop PD symptoms. α-Synuclein, a natively unfolded protein, can adopt a number of different folded conformations including a β-sheet form that facilitates formation of numerous aggregated morphologies, including long fibrils, spherical and linear protofibrils, and smaller aggregates or oligomers. The roles of the various morphologies of α-synuclein in the progression of PD are not known, and different species have been shown to be toxic. Here we show that single chain antibody fragments (scFv's) isolated from naïve phage display antibody libraries can be used to control the aggregation of α-synuclein. We isolated an scFv with nanomolar affinity for monomeric α-synuclein (KD = 2.5 × 10-8 M). When co-incubated with monomeric α-synuclein, the scFv decreased not only the rate of aggregation of α-synuclein, but also inhibited the formation of oligomeric and protofibrillar structures. The scFv binds the carboxyl terminal region of α-synuclein, suggesting that perturbation of this region can influence folding and aggregation of α-synuclein in vitro along with the previously identified hydrophobic core region of α-synuclein (residues 61-95, particularly residues 71-82). Since the scFv has been isolated from an antibody library based on human gene sequences, such scFv's can have potential therapeutic value in controlling aggregation of α-synuclein in vivo when expressed intracellularly as intrabodies in dopaminergic neurons.
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