The role of protein kinase R in dystonia

Dystonia is a progressive neurological motor disease with few treatment options and no cure. This review synthesizes the results of recent studies that implicate protein kinase R in mediating the molecular mechanisms of dystonia pathogenesis. Mutations in the PKR gene EIF2AK2 and the PKR activator protein PACT are associated with early-onset generalized dystonia. Protein kinase R (PKR) is important for neuronal function. Genetic depletion or inhibition of PKR is associated with increased long-term potentiation and memory, while also causing neuronal hyper-excitability and seizures in mouse models. PKR also senses double stranded RNA within cells and activates the integrated stress response (ISR). The ISR is a conserved signaling pathway that hinges on controlled translational suppression to remodel gene expression during stress. When PKR is activated through binding double stranded RNA or the PKR activator protein PACT, PKR dimerizes, autophosphorylates, and phosphorylates the translation initiation factor eIF2. Translation suppression by p-eIF2 causes stress granule formation and the upregulation of stress-induced genes. The ISR is thought to drive cellular resilience during acute stress. However, chronic ISR activation is associated with neurological diseases, traumatic brain injury, and aging. Neurodevelopmental and neurodegenerative diseases are associated with mutations in other integrated stress response genes, suggesting a critical role for ISR regulation in neuronal health. A growing body of work suggests the ISR is also dysfunctional in dystonia. Future research investigating the molecular mechanisms of the ISR in dystonia will likely reveal therapeutic targets and treatment strategies for this currently incurable disease.