Objective: Endosomal sorting required for transport (ESCRT) orchestrates endo-lysosomal soring of ubiquitinated proteins, multivesicular body formation. The aim of this study is to elucidate the mechanism by which ESCRT dysfunction leads to cellular toxicity and subsequent neurodegeneration.

Background: Defects in the ESCRT pathway have been implicated in several neurodegenerative diseases including AD, PD and ALS, but the underlying molecular mechanisms that link them to neurodegeneration remain unknown.

Methods: We specifically deleted the key molecule of ESCRT-0, hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), in neurons of the forebrain by crossing loxP-flanked Hrs mice with transgenic mice in which Cre expression in driven by calcium/calmodulin-dependent protein kinase Iiα promoter. In order to unveil the molecular processes responsible for executing Hrs-silencing-mediated neurotoxicity, Hrs-depleted PC12 cells were subjected to the PathScan® intracellular signaling array.

Results: The Hrsflox/flox; CaMKIIα-cre mice showed postnatal growth retardation and progressive locomotor decline. Histologically, the Hrsflox/flox; CaMKIIα-cre mice exhibited marked hippocampal neuronal loss accompanied by the accumulation of ubiquitinated proteins, including α-synuclein, TDP-43 and huntingtin as well as the autophagic substrate p62. Consistent with this, silencing of Hrs in PC12 cells not only led to α-synuclein accumulation in addition to impaired autophagic flux, but also suppressed cell viability through the induction of ER stress followed by the activation of JNK and RIPK1, a key regulator of necroptosis. Moreover, necrostatin-1, a specific inhibitor of RIPK1, and pan-caspase inhibitors partially reduced the neurotoxicity observed in the Hrs-silenced cells.

Conclusions: Altogether, we demonstrated that forebrain-specific ablation of ESCRT-0/Hrs induced hippocampal neuronal cell loss and locomotor dysfunction in mice. In particular, our work offers the novel insight that the loss of Hrs in neuronal cells impaired the late stage of autophagic flux as well as induced insoluble, ubiquitinated protein aggregates and ER stress-mediated apoptotic and necroptotic cell death.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/escrt-0-dysfunction-compromises-autophagic-degradation-of-protein-aggregates-and-facilitates-er-stress-mediated-neurodegeneration-via-apoptotic-and-necroptotic-pathways/