An Inducible Neural Stem Progenitor Cell Model for Testing Therapeutic Interventions Against Neurodegeneration FENIB.

Familial encephalopathy with neuroserpin inclusion bodies (FENIB) is a neurodegenerative pathology caused by accumulation of mutant neuroserpin (NS) polymers inside the endoplasmic reticulum (ER) of neurons, leading to cellular toxicity and neuronal death. To date, there is no cure for FENIB, and only palliative care is available for FENIB patients, underlining the urgency to develop therapeutic strategies. The purpose of this work was to create a cellular system designed for testing small molecules able to reduce the formation of NS polymers. Our results show the generation and characterisation of a novel cell culture model for FENIB based on neural stem progenitor cells (NPCs) with inducible expression of either wild type (WT) or G392E NS, a variant that causes severe FENIB. We also report the use of these novel cell lines to explore the effects of four different proteolysis targeting chimaera (PROTAC) compounds, small bivalent molecules engineered to bind to the E3 ubiquitin ligase cereblon, and to NS through a recruiting motif based on the small molecule embelin. This approach aims to enhance the degradation of mutant NS after retro-translocation to the cytosol by facilitating its targeting to the proteasome. Our results show little toxicity and no variation in NS levels with any of the compounds tested. In conclusion, this work sets the basis for future attempts to identify molecules able to prevent NS accumulation inside the ER of cultured cells.