The functional analysis of the CHMP2B missense mutation associated with neurodegenerative diseases in the endo-lysosomal pathway

Endosomal sorting complexes required for transport (ESCRTs) regulate a key sorting step of protein trafficking between endosomal compartments in lysosomal degradation. Interestingly, mutations in charged multivesicular body protein 2B (CHMP2B), which is a core subunit of ESCRT-III, have been identified in some neurodegenerative diseases. However, the cellular pathogenesis resulting from CHMP2B missense mutations is unclear. Furthermore, little is known about their functional analysis in post-mitotic neurons. In order to examine their cellular pathogenesis, we analyzed their effects in the endo-lysosomal pathway in post-mitotic neurons. Interestingly, of the missense mutant proteins, CHMP2BT104N mostly accumulated in the Rab5- and Rab7-positive endosomes and caused delayed degradation of EGFR as compared to CHMP2BWT. Furthermore, CHMP2BT104N showed less association with Vps4 ATPase and was avidly associated with Snf7-2, a core component of ESCRT-III, suggesting that it may cause defects in the process of dissociation from ESCRT. Of the missense variants, CHMP2BT104N caused prominent accumulation of autophagosomes. However, neuronal cell survival was not dramatically affected by expression of CHMP2BT104N. These findings suggested that, from among the various missense mutants, CHMP2BT104N was associated with relatively mild cellular pathogenesis in post-mitotic neurons. This study provided a better understanding of the cellular pathogenesis of neurodegenerative diseases associated with various missense mutations of CHMP2B as well as endocytic defects.

► Functional identification of CHMP2BT104N as a potential pathogenic mutation. ► CHMP2BT104N accumulated in Rab5 or Rab7 positive endosomes. ► CHMP2BT104N expression delayed EGFR degradation. ► CHMP2BT104N was abnormally associated with VPS4 and Snf7-2. ► Provide a possible pathogenic mechanism of CHMP2BT104N in post-mitotic neurons.