Although further studies are required to elucidate the detailed mechanisms of α-syn fibrillation in vivo, our findings provide the concept of the UBQLN2 LLPS-catalyzed fibrillation of α-syn and demonstrate the effects of UBQLN2 LLPS modulation by an STI1 region-targeted compound in the context of neurodegenerative disease development. This evidence concerns the gene UBQLN2 and neurodegenerative disease.