Mechanistic insights on HDAC6 ZnF UBP-Tau interaction through biophysical and computational approaches

Histone deacetylase 6 is a unique cytoplasmic deacetylase implicated in cellular functions such as microtubule dynamics, protein quality control, ubiquitin-mediated degradation and neurodegenerative disorders. The ZnF UBP (zinc finger ubiquitin binding protein) domain of HDAC6 is known to be directly modulate several cellular processes linked to neurodegeneration such as sequestering polyubiquitinated aggregates and regulating protein aggregate clearance mechanisms in neurons. Microtubule associated protein Tau (MAP Tau) undergoes aggregation in neurodegenerative conditions like Alzheimer's disease (AD) and several other tauopathies. Tau is a natively disordered protein which is functionally regulated by wide array of post-translational modifications (PTMs) as well as by interacting with several proteins. This methodological study aims to understand the molecular interaction between HDAC6 ZnF UBP domain and Tau protein in order to elucidate the role of HDAC6 ZnF UBP domain in Tau aggregation and stability. We employed an integrated biochemical, biophysical and computational workflow to characterize the interaction between HDAC6 ZnF UBP and Tau. NMR spectroscopy, isothermal titration calorimetry and pull-down assay with purified HDAC6 ZnF UBP and Tau proteins demonstrated direct interaction between the two, with interaction associated structural perturbations and favourable binding kinetics as observed in NMR and ITC respectively. Computational analyses further suggest the formation of Tau-HDAC6 ZnF UBP complex and provided underlying molecular interactions involved in the binding of these two proteins. The findings in this study helps to advance the current understanding of regulatory role of HDAC6 specifically in Tau biology and further provides a useful framework for investigating the modulation of aggregation prone proteins via protein-protein interaction in neurodegenerative diseases.