Change in the Oligomeric State of ?-Synuclein Variants in Living Cells

: The accumulation of beta-sheet-rich alpha-synuclein (alpha-Syn) protein in human brain cells is a pathological hallmark of Parkinson's disease (PD). Moreover, it has been reported that familial PD mutations (A30P, E46K, H50Q, G51D, and A53T) accumulate at an accelerated rate both in vivo and in vitro. In addition, accumulations of various Cterminal alpha-Syn truncations, such as C-terminal-truncated N103 alpha synuclein (N103), were found in an aggregated form in the brain tissue of PD patients. Fluorescent protein-tagged wild-type alpha-Syn, A30P, E46K, H50Q, G51D, A53T, and N103 were transfected into HEK293T and SHSY5Y cells, and their diffusion behaviors were investigated with a custom-built fluorescence microscope system. Based on our experimental results, the oligomerization of alpha-Syn is a time-dependent process in both HEK293T and SHSY5Y cells, and the oligomer state approaches a plateau after 48 h of transfection. The change in the oligomeric state of E46K, H50Q, and G51D exhibited a similar trend to the wild type at a lower concentration but became intense at a higher concentration. A53T and N103 possess smaller diffusion coefficients than wild-type alpha-synuclein and other family PD mutations, indicating that these two mutants could form higher oligomeric states or stronger interactions in HEK293T and SHSY5Y cells. In contrast, the smallest oligomer and the lowest intracellular interaction among all investigated alpha-Syn variants were found for A30P. These phenomena indicated the presence of different pathogeneses among familial PD mutants and C-terminal alpha-Syn truncations.

Automated summary

This study demonstrates that the abnormal accumulation of alpha-Syn protein in human brain cells is a pathological feature of Parkinson's disease. There are differences in oligomer formation and intracellular interactions between familial Parkinson's disease mutants and C-terminal alpha-Syn truncations.