Senthilvelrajan Kaniyappan1, Ram Reddy Chandupatla2, Eva-Maria Mandelkow3, Eckhard Mandelkow4. 1. DZNE, German Center for Neurodegenerative Diseases, Bonn, Germany; MPI for Metabolism Research, Hamburg, Germany. Electronic address: Senthil.Kaniyappan@dzne.de. 2. DZNE, German Center for Neurodegenerative Diseases, Bonn, Germany; MPI for Metabolism Research, Hamburg, Germany. 3. DZNE, German Center for Neurodegenerative Diseases, Bonn, Germany; MPI for Metabolism Research, Hamburg, Germany; CAESAR Research Center, Bonn, Germany. 4. DZNE, German Center for Neurodegenerative Diseases, Bonn, Germany; MPI for Metabolism Research, Hamburg, Germany; CAESAR Research Center, Bonn, Germany. Electronic address: Mandelkow@dzne.de.
Abstract
INTRODUCTION: Tau-mediated toxicity in Alzheimer's disease is thought to operate through low-n oligomers, rather than filamentous aggregates. However, the nature of oligomers and pathways of toxicity are poorly understood. Therefore, we investigated structural and functional aspects of highly purified oligomers of a pro-aggregant tau species. METHODS: Purified oligomers of the tau repeat domain were characterized by biophysical and structural methods. Functional aspects were investigated by cellular assays ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay of cell viability, lactate dehydrogenase release assay [for cell toxicity], reactive oxygen species production, and calcium assay), combined with analysis of neuronal dendritic spines exposed to oligomers. RESULTS: Purified low-n oligomers are roughly globular, with sizes around 1.6 to 5.4 nm, exhibit an altered conformation, but do not have substantial β-structure. Treatment of primary neurons with oligomers impairs spine morphology and density, accompanied by increased reactive oxygen species and intracellular calcium, but without affecting cell viability (by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay of cell viability and lactate dehydrogenase release assay [for cell toxicity]). DISCUSSION: Tau oligomers are toxic to synapses but not lethal to cells.
INTRODUCTION: Tau-mediated toxicity in Alzheimer's disease is thought to operate through low-n oligomers, rather than filamentous aggregates. However, the nature of oligomers and pathways of toxicity are poorly understood. Therefore, we investigated structural and functional aspects of highly purified oligomers of a pro-aggregant tau species. METHODS: Purified oligomers of the tau repeat domain were characterized by biophysical and structural methods. Functional aspects were investigated by cellular assays ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay of cell viability, lactate dehydrogenase release assay [for cell toxicity], reactive oxygen species production, and calcium assay), combined with analysis of neuronal dendritic spines exposed to oligomers. RESULTS: Purified low-n oligomers are roughly globular, with sizes around 1.6 to 5.4 nm, exhibit an altered conformation, but do not have substantial β-structure. Treatment of primary neurons with oligomers impairs spine morphology and density, accompanied by increased reactive oxygen species and intracellular calcium, but without affecting cell viability (by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay of cell viability and lactate dehydrogenase release assay [for cell toxicity]). DISCUSSION: Tau oligomers are toxic to synapses but not lethal to cells.
Authors: Negin Holland; P Simon Jones; George Savulich; Julie K Wiggins; Young T Hong; Tim D Fryer; Roido Manavaki; Selena Milicevic Sephton; Istvan Boros; Maura Malpetti; Frank H Hezemans; Franklin I Aigbirhio; Jonathan P Coles; John O'Brien; James B Rowe Journal: Mov Disord Date: 2020-07-11 Impact factor: 9.698