AAV‐mediated expression of wild‐type and ALS‐linked mutant VAPB selectively triggers death of motoneurons through a Ca²⁺‐dependent ER‐associated pathway

Abstract

J. Neurochem. (2010) 114 , 795–809. Abstract A dominant mutation in the gene coding for the vesicle‐associated membrane protein‐associated protein B (VAPB) was associated with amyotrophic lateral sclerosis, a fatal paralytic disorder characterized by the selective loss of motoneurons in the brain and spinal cord. Adeno‐associated viral vectors that we show to transduce up to 90% of motoneurons in vitro were used to model VAPB‐associated neurodegenerative process. We observed that Adeno‐associated viral‐mediated over‐expression of both wild‐type and mutated form of human VAPB selectively induces death of primary motoneurons, albeit with different kinetics. We provide evidence that ER stress and impaired homeostatic regulation of calcium (Ca 2+ ) are implicated in the death process. Finally, we found that completion of the motoneuron death program triggered by the over‐expression of wild‐type and mutant VAPB implicates calpains, caspase 12 and 3. Our viral‐based in vitro model, which recapitulates the selective vulnerability of motoneurons to the presence of mutant VAPB and also to VAPB gene dosage effect, identifies aberrant Ca 2+ signals and ER‐derived death pathways as important events in the motoneuron degenerative process.