Degradation of wild‐type alpha‐synuclein by a molecular chaperone leads to reduced aggregate formation

Alpha-synuclein, a presynaptic protein, was found to be the major component in the Lewy bodies (LB) in an age-related neurodegenerative disease, Parkinson's disease (PD). Even though the function of alpha-synuclein is not completely understood, it has been demonstrated to spontaneously aggregate into amyloid fibrils. With the aim of inhibiting aggregate formation, a molecular chaperone protein, Hsp104p, was investigated since it rescues cells from stress by resolubilizing denatured proteins from insoluble aggregates, in vivo as well as in vitro. Here, in order to examine whether Hsp104p functions as a regulator of aggregate formation for alpha-synuclein, we expressed the His-tagged wild-type (wt) synuclein and the glutathione-S-transferase (GST)-tagged Hsp104p in bacterial systems. Using thioflavin-T fluorescence assays, significant protection against fibril formation was observed with wt Hsp104p regardless of the presence of ATP, but not with mutant Hsp104p. To a lesser extent, the dissociation effect of wild-type Hsp104p was observed only in the presence of ATP. Interaction between Hsp104p and synuclein was also investigated using a GST pull-down experiment. Interestingly, Hsp104p degraded alpha-synuclein in a concentration-dependent manner with the synergistic assistance of ATP. These results suggest that Hsp104p could be developed as a therapeutic candidate in the treatment of protein aggregation-related neurodegenerative disease.