GSE96096
Neuroserpin polymers cause oxidative stress in a neuronal model of the dementia FENIB
The serpinopathies are human pathologies caused by mutations that promote polymerisation and intracellular deposition of proteins of the serpin superfamily, leading to a poorly understood cell toxicity. The dementia familial encephalopathy with neuroserpin inclusion bodies (FENIB) is caused by polymerisation of the neuronal serpin neuroserpin (NS) within the endoplasmic reticulum (ER) of neurons. We have generated transgenic neural progenitor cell (NPC) cultures from mouse embryonic cerebral cortex, stably expressing the control protein GFP (green fluorescent protein), or human wild type, G392E or deltaNS. We have characterised these cells in the proliferative state and after differentiation to neurons. Our results show that G392E NS formed polymers that were mostly retained within the ER, while wild type NS was correctly secreted as a monomeric protein into the culture medium. DeltaNS was absent at steady state due to its rapid degradation, but it was easily detected upon proteasomal block. Looking at their intracellular distribution, wild type NS was found in partial co-localisation with ER and Golgi markers, while G392E NS was localised within the ER only. Furthermore, polymers of NS were detected by ELISA and immunofluorescence in neurons expressing the mutant but not the wild type protein. We used our model system to investigate which cellular pathways were activated by intracellular polymers of G392E NS by performing RNA sequencing of differentiated cells expressing G392E NS or the negative control protein GFP, and identified 747 genes with a significant upregulation (623) or downregulation (124) in G392E NS-expressing cells. We focused our attention on genes involved in the defence against oxidative stress that were up-regulated in cells expressing G392E NS. Inhibition of these defences by specific pharmacological reagents uncovered the damaging effects of NS polymers. Our results support a role for oxidative stress in the cellular toxicity underlying the neurodegenerative dementia FENIB. Overall design: mRNA profiles of neural progenitor cells stably overexpressing GFP or G392E neuroserpin were generated by deep sequencing, in triplicate, using Illumina HiSeq2000.