G3BP1 Maintains Lysosomal Homeostasis to Limit Tau Aggregate Accumulation

Abstract

Tau aggregation is a pathological hallmark of a group of neurodegenerative diseases collectively termed tauopathies. While impaired proteostasis is known to drive the accumulation of abnormal proteins, the molecular factors influencing Tau aggregate clearance remain incompletely understood. In this study, we employed a cell-based Tau reporter assay combined with a lentivirus-based pooled CRISPR-Cas9 loss-of-function library to identify genes that regulate Tau aggregation. Genome-wide screening revealed that candidate genes were significantly enriched in categories related to mRNA metabolic processes and autophagy. Among them, we focused on the RNA-binding protein G3BP1, which is functionally associated with both processes. Detailed analyses showed that G3BP1 deficiency promoted the accumulation of Tau aggregates without affecting stress granule formation or autophagic flux. Instead, G3BP1 dysfunction resulted in impaired lysosomal homeostasis, as evidenced by reduced lysosomal abundance and acidification. Furthermore, lysosomal damage induced by L-leucyl-L-leucine methyl ester (LLOMe) enhanced Tau aggregation, particularly in G3BP1-deficient cells. Conversely, pharmacological activation of TFEB by the curcumin analog C1 restored lysosomal function and suppressed Tau aggregate accumulation to wild-type levels. These findings highlight a role of G3BP1 in maintaining lysosomal homeostasis and promoting Tau clearance. Our results further suggest that therapeutic strategies aimed at enhancing lysosomal biogenesis, such as TFEB activation, may hold promise for the treatment of tauopathies.