Synuclein Proteins of the Pufferfish Fugu rubripes: Sequences and Functional Characterization

In humans, three genes encode the related a-, ß-, and ¿-synucleins, which function as lipid-binding proteins in vitro. They are being widely studied, mainly because of the central involvement of a-synuclein in a number of neurodegenerative diseases, including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. In these diseases, the normally soluble a-synuclein assembles into abnormal filaments. Here, we have identified and characterized the synuclein gene family from the pufferfish Fugu rubripes. It consists of four genes, which encode a-, ß-, ¿1-, and ¿2-synucleins. They range from 113 to 127 amino acids in length and share many of the characteristics of human synucleins, including the presence of imperfect amino-terminal repeats of 11 amino acids, a hydrophobic middle region, and a negatively charged carboxy-terminus. All four synucleins are expressed in the Fugu brain. Recombinant Fugu synucleins exhibited differential liposome binding, which was strongest for a-synuclein, followed by ß-, ¿2-, and ¿1-synucleins. In assembly experiments, Fugu a-, ¿1-, and ¿2-synucleins formed filaments more readily than human a-synuclein. Fugu ß-synuclein, by contrast, failed to assemble in bulk. Filament assembly of synucleins was directly proportional to their degree of hydrophobicity and their tendency to form ß-sheet structure, and correlated inversely with their net charge.