Truncation mutation of CHMP2B disrupts late endosome function but reduces TDP-43 aggregation through HSP70 upregulation

TAR DNA-binding protein 43 (TDP-43)-positive cytoplasmic aggregation is a pathological hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). This aggregation contributes substantially to the neurodegeneration of ALS and FTLD. The endosome, a key component of membrane trafficking in eukaryotic cells and is involved in the autophagy-lysosome pathway. Endosome-related genes such as CHMP2B, Alsin, and TMEM106B, are either causative or act as genetic modifiers in ALS and FTLD. However, the association between endosomal functions and TDP-43 aggregations remain poorly understood. The C-terminal truncation mutation CHMP2B, which causes frontotemporal dementia associated with chromosome 3 (FTD3), disrupts late endosome (LE)-lysosomes fusion. Nevertheless, FTD3 does not induce TDP-43 pathology. In this study, we showed that CHMP2B mutation-induced LE dysfunction promotes TDP-43 aggregate degradation through enhanced recruitment to juxtanuclear quality control compartments. Transcriptomic analysis revealed that CHMP2Bintron5 overexpression upregulates HSP70 expression. New insights into the connection between CMHP2B and HSP70 as well as the role of HSP70-mediated membrane trafficking in TDP-43 aggregation, offer a valuable understanding of the disease mechanism of ALS and FTLD.