Jihong Wang

Prion diseases are neurodegenerative disorders characterized by the accumulation of a disease-associated prion protein and apoptotic neuronal death. Previous studies indicated that the ubiquitous expression of c-Abl tyrosine kinase transduces a variety of extrinsic and intrinsic cellular signals. In this study, we demonstrated that a synthetic neurotoxic prion fragment (PrP106-126) activated c-Abl tyrosine kinase, which in turn triggered the upregulation of MST1 and BIM, suggesting the activation of the c-Abl-BIM signaling pathway. The peptide fragment was found to result in cell death via mitochondrial dysfunction in neuron cultures. Knockdown of c-Abl using small interfering RNA protected neuronal cells from PrP106-126-induced mitochondrial dysfunction, production of reactive oxygen species, and apoptotic events inducing translocation of Bax to the mitochondria, cytochrome c release into the cytosol, and activation of caspase-9 and caspase-3. Blocking the c-Abl tyrosine kinase also prevented neuronal cells from PrP106-126-induced apoptotic morphological changes. This is the first study reporting that c-Abl tyrosine kinase as a novel upstream activator of MST1 and BIM plays an important role in prion-induced neuron apoptosis via mitochondrial dysfunction. Our findings suggest that c-Abl tyrosine kinase is a potential therapeutic target for prion disease.

Prion diseases are neurodegenerative disorders characterized by the accumulation of an abnormal disease-associated prion protein, PrPSc. In prion-infected brains, activated microglia are often present in the vicinity of PrPSc aggregates, and microglial activation is thought to play a key role in the pathogenesis of prion diseases. Although interleukin (IL)-1β release by prion-induced microglia has been widely reported, the mechanism by which primed microglia become activated and secrete IL-1β in prion diseases has not yet been elucidated. In this study, we investigated the role of the NACHT, LRR and PYD domains-containing protein (NALP)3 inflammasome in IL-1β release from lipopolysaccharide (LPS)-primed microglia after exposure to a synthetic neurotoxic prion fragment (PrP106-126).