Role of the protein domain Arg101-Arg103 in the JD aggregation pathway implicated in SCA3 Disease

Ataxin 3 (AT3) is a polyQ protein responsible for the neurodegenerative disease called Machado-Joseph disease (MJD), the most common form of Spinocerebellar Ataxias worldwide. Efforts have been made in the past to understand the mechanisms of AT3 aggregation and fibre formation, because of their implication in the MJD. However, The molecular mechanism underneath the Ataxin 3 misfolding process and the protein aggregation pathway has not yet been fully clarified. A computational study recently performed has identified residues Arg101-Arg103 as possible players in a first step of the N-terminal Josephin Domain (JD) dimerization driven by electrostatics interactions. The present project will focus on performing protein mutations at Arg101-Arg103 residues to experimentally demonstrate the role of this protein domain in the JD aggregation pathway. The identification of specific JD amyloidogenic regions might open new routes for the design of i) specific mutations able to reduce the amyloidogenic nature of the JD without interfering with the physiological function but also ii) novel rational drugs designed to drive the JD thermodynamic and kinetic stability toward specific non-amyloidogenic JD structures. The above-mentioned investigation may provide novel insights for a deeper understanding of molecular mechanisms behind JD and AT3 aggregation dynamics and kinetics, a key to successfully design novel strategies targeting MJD disease.