Quintana, G

Abstract Description Background ISG15 is induced in neurons by demyelination and elevated in MS patient cortical neurons. Our hypothesis is that ISGylation contributes to neuron loss in MS by impairing ubiquitin-dependent protein and mitochondrial turnover. Methods ISGylation was induced by IFNg treatment. Protein turnover: cortical neurons were transduced with AAV1.TRE.mCherry-DD to drive Tet-ON expression of the mCherry tagged with a degradation domain (DD). Following induction DD-mCherry is rapidly degraded allowing measurement of proteasome activity. Mitophagy: cortical neurons were transduced with AAV1.Syn.GFP-mCherry-FIS1 which targets mitochondria. Upon entry into the lysosome, GFP is rapidly quenched allowing quantification of mitophagy (non-colocalizing mCherry signal). C57BL/6 and ISG15 KO mice were subjected to a cuprizone diet, immunofluorescence and confocal imaging to assess neuronal density changes in the cortex over time. Results In WT but not ISG15 deficient neurons IFNg treatment delayed DD-mCherry degradation. Using the mito-QC reporter, elevated mitochondrial content and mitophagy levels were observed in ISG15 KO cortical neurons. Neuron density was preserved in ISG15 KO compared to WT. Conclusion IFNg-induced ISG15 impairs protein and mitochondrial turnover in neurons, and ISG15 deficiency protects neurons during demyelination. Future work will test how neuronal ISG15 impacts c-Gas STING pathway activation and ferroptosis in neurons during neurodegeneration. Funding Sources Generous donation from Don and Fran Herdrich. Topic Categories Neuroimmunology (NEUR)