Small-molecule drug screening identifies drug Ro 31-8220 that reduces toxic phosphorylated tau in Drosophila melanogaster

The intraneuronal aggregates of hyperphosphorylated and misfolded tau (neurofibrillary tangles, NFTs) cause a stereotypical spatiotemporal Alzheimer's disease (AD) progression that correlates with the severity of the associated cognitive decline. Kinase activity contributes to the balance between neuron survival and cell death. Hyperactivation of kinases including the conventional protein kinase C (PKC) is a defective molecular event accompanying associative memory loss, tau phosphorylation, and progression of AD or related neurodegenerative diseases. Here, we investigated the ability of small therapeutic compounds (a custom library) to improve tau-induced rough-eye phenotype in a Drosophila melanogaster model of frontotemporal dementia. We also assessed the tau phosphorylation in vivo and selected hit compounds. Among the potential hits, we investigated Ro 31-8220, described earlier as a potent PKCα inhibitor. Ro 31-8220 robustly improved the rough-eye phenotype, reduced phosphorylated tau species in vitro and in vivo, reversed tau-induced memory impairment, and improved the fly motor functions. In a human neuroblastoma cell line, Ro 31-8220 reduced the PKC activity and the tau phosphorylation pattern, but we also have to acknowledge the compound's wide range of biological activity. Nevertheless, Ro 31-8220 is a novel therapeutic mitigator of tau-induced neurotoxocity.