Identification of a Potent Tau-Aggregate Clearing Compound Using Chemoproteomic-Integrated Phenotypic Screening (Enrichment)

Tauopathies are characterized by the formation of tau protein-based neurofibrillary tangles which impede neuronal function and contribute to the pathology of highly prevalent neurodegenerative disorders such as Alzheimer’s and Pick’s diseases. Despite the impact of these diseases, the underlying biology is poorly understood. Current therapeutic efforts to reduce and remove tau aggregates target a variety of cellular mechanisms including altering tau phosphorylation through kinase inhibition, stimulating autophagy and upregulating protein quality control mechanisms such as the endoplasmic reticulum associated protein degradation pathway (ERAD), however these efforts have not thus far resulted in effective therapeutic interventions. Here, we sought to identify new targets and mechanisms that might be exploited to address tauopathies, through a chemoproteomic-integrated phenotypic screen using a cellular model of tau-aggregate clearance. An optimized analogue derived from this effort induced tau aggregate clearance in both SH-SY5Y and iPSC-derived human neuron models of hTauP301L aggregation at nanomolar concentrations and led to the activation of the ERAD pathway. Chemoproteomic studies revealed interactions with several resident endoplasmic reticulum proteins containing thioredoxin domains whose activities are involved in the ERAD pathway and protein quality control. Genetic knockdown of one of these targets, protein disulfide isomerase 1 (P4HB), was found to recapitulate the tau aggregate-clearance phenotype, indicating that modulation of this protein may be of therapeutic benefit for tauopathies.