Tau/DDX6 interaction increases microRNA activity

Tauopathies, such as Alzheimer's disease, are characterized by intracellular aggregates of insoluble Tau proteins. Originally described as a microtubule binding protein, recent studies demonstrated additional physiological roles for Tau. The fact that a single protein can regulate multiple cellular functions has posed challenge in terms of understanding mechanistic cues behind the pathology. Here, we used tandem-affinity purification methodology coupled to mass spectrometry to identify novel interaction partners. We found that Tau interacts with DDX6, a DEAD box RNA helicase involved in translation repression and mRNA decay as well as in the miRNA pathway. Our results demonstrate that Tau increases the silencing activity of the miRNA let-7a, miR-21 and miR-124 through DDX6. Importantly, Tau mutations (P301S, P301L) found in the inherited tauopathies, frontotemporal dementia and parkinsonism linked to chromosome 17, disrupt Tau/DDX6 interaction and impair gene silencing by let-7a. Altogether, these data demonstrated a new unexpected role for Tau in regulating miRNA activity.