Title
Cysteine-Independent Inhibition of Alzheimer’s Disease-like Paired Helical Filament Assembly by Leuco-Methylthioninium (LMT)
Author
Youssra K. Al-Hilaly, Saskia J. Pollack, Janet E. Rickard, Michael Simpson, Ana-C Raulin, Thomas Baddeley, Pascale Schellenberger, John M. D. Storey, Charles R. Harrington, Claude M.Wischik, Louise C.Serpell
Year
2018
Journal
Journal of Molecular Biology
Abstract
Alzheimer's disease (AD) is a tauopathy characterised by pathological fibrillisation of tau protein to form the paired helical filaments (PHFs) which constitute neurofibrillary tangles. The methylthioninium (MT) moiety reverses the proteolytic stability of the PHF core and is in clinical development for treatment of AD in a stable reduced form as leuco-MT (LMT). It has been hypothesised that MT acts via oxidation of cysteine residues which is incompatible with activity in the predominantly reducing environment of living cells. We have shown recently that the PHF-core tau unit assembles spontaneously in vitro to form PHF-like filaments. Here we describe studies using circular dichroism, SDS-polyacrylamide gel electrophoresis, transmission electron microscopy and site-directed mutagenesis to elucidate the mechanism of action of the MT moiety. We show that MT inhibitory activity is optimal in reducing conditions, that the active moiety is the reduced LMT form of the molecule, and that its mechanism of action is cysteine-independent.
Instrument
J-715
Keywords
Circular dichroism, Higher order structure, Ligand binding, Secondary structure, Chemical stability, Aggregation, Biochemistry