RGG peptide induces the disassembly of disease-relevant FUS and TDP43 condensates

Dynamic membraneless ribonucleoprotein (RNP) condensates regulate different processes within a cell. The assembly and disassembly of these structures are intricately regulated to maintain cellular homeostasis. Dysregulation of these structures has been implicated in various neurodegenerative disorders like Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD). Identifying molecules that can disassemble these toxic assemblies is a promising approach to abrogate the associated disease phenotypes augmented by these condensates but is still poorly explored. In this study, we have identified a role for low-complexity peptide rich in arginine and glycine as a disassembly factor for mutant FUS and TDP43 condensates. Deletion of RGG-motif-containing yeast protein Sbp1 reduces the disassembly of FUS and TDP43 condensates and increases toxicity. Consistent with that, the expression of Sbp1 in human cells reduced the cytoplasmic condensates of FUS and TDP43 mutants (FUS-P525L and TDP43 lacking nuclear localization signal-ΔNLS) and increased nuclear localization of the FUS-P525L in an RGG-motif dependent manner. In accordance with the yeast data, we observed that the viability of cells expressing FUS-P525L improved upon the expression of Sbp1. In-cell sedimentation assay revealed that purified Sbp1 could partition FUS-P525L, but not the TDP43-ΔNLS mutant, from enriched insoluble condensates to soluble fraction. In-vitro sedimentation assay using a two-component purified system confirmed that partitioning of FUS, but not TDP43, increased to the soluble fraction in an RGG-motif-dependent manner. Finally, incubating the cells expressing FUS-P525L and TDP43-ΔNLS mutant with RGG-peptide resulted in a reduction of condensate size within the cells, suggesting the sufficiency of RGG peptides. Overall, our results identify a role of RGG-peptide in disassembling mutant FUS and TDP43 condensates implicated in ALS, projecting their possible therapeutic role in treating ALS.