Cysteine-Independent Inhibition of Alzheimer's Disease-like Paired Helical Filament Assembly by Leuco-Methylthioninium (LMT). Issue 21 (19th October 2018)

• Record Type: Journal Article
• Authors: Al-Hilaly, Youssra K.; Pollack, Saskia J.; Rickard, Janet E.; Simpson, Michael; Raulin, Ana-Caroline; Baddeley, Thomas; Schellenberger, Pascale; Storey, John M.D.; Harrington, Charles R.; Wischik, Claude M.; Serpell, Louise C.
• Is Part Of: Journal of molecular biology. Volume 430:Issue 21(2018)
• Page Start: 4119
• Page End: 4131
• Publication Date: 2018-10-19
• Subjects: tau protein -- methylthioninium -- hydromethylthionine -- neurofibrillary tangles -- circular dichroism; AD Alzheimer's disease -- CD circular dichroism -- LMT leuco-methylthioninium -- LMTM leuco-methylthioninium bis(hydromethanesulfonate) -- MT methylthioninium -- MTC Methylthioninium chloride -- PBS phosphate-buffered saline -- PHFs paired helical filaments -- TEM transmission electron microscopy; Molecular biology -- Periodicals; Biology -- Periodicals; Biochemistry -- Periodicals; Bacteriology -- Periodicals; Molecular Biology -- Periodicals; Biochemistry -- Periodicals; Biologie moléculaire -- Périodiques; Biologie -- Périodiques; Biochimie -- Périodiques; Moleculaire biologie; Biochemistry; Biology; Molecular biology; Periodicals; 572.805
• DOI: 10.1016/j.jmb.2018.08.010
• Languages: English
• ISSNs: 0022-2836

Abstract

Abstract: Alzheimer's disease is a tauopathy characterized by pathological fibrillization 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 Alzheimer's disease in a stable reduced form as leuco-MT. It has been hypothesized 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-PAGE, 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 leuco-MT form of the molecule and that its mechanism of action is cysteine independent. Graphical Abstract: Highlights: Paired helical filaments (PHF) composed of tau form in Alzheimer's disease. PHF formation is a target for treatment. Methylthioninium (MT) inhibits spontaneous assembly of a core tau unit into PHFs. MT acts optimally in the reduced form as leuco-MT and not via cysteine oxidation. Leuco-MT is effective at much lower doses than the oxidized form of MT in clinical trials.