title: Fibrillization of human tau is accelerated by exposure to lead via interaction with His-330 and His-362.
abstract: BACKGROUND
  Neurofibrillary tangles, mainly consisted of bundles of filaments formed by the microtubule-associated protein Tau, are a hallmark of Alzheimer disease. Lead is a potent neurotoxin for human being especially for the developing children, and Pb(2+) at high concentrations is found in the brains of patients with Alzheimer disease. However, it has not been reported so far whether Pb(2+) plays a role in the pathology of Alzheimer disease through interaction with human Tau protein and thereby mediates Tau filament formation. In this study, we have investigated the effect of Pb(2+) on fibril formation of recombinant human Tau fragment Tau(244-372) and its mutants at physiological pH.
  
  
  RESULTS
  As revealed by thioflavin T and 8-anilino-1-naphthalene sulfonic acid fluorescence, the addition of 5-40 µM Pb(2+) significantly accelerates the exposure of hydrophobic region and filament formation of wild-type Tau(244-372) on the investigated time scale. As evidenced by circular dichroism and Fourier transform infrared spectroscopy, fibrils formed by wild-type Tau(244-372) in the presence of 5-40 µM Pb(2+) contain more β-sheet structure than the same amount of fibrils formed by the protein in the absence of Pb(2+). However, unlike wild-type Tau(244-372), the presence of 5-40 µM Pb(2+) has no obvious effects on fibrillization kinetics of single mutants H330A and H362A and double mutant H330A/H362A, and fibrils formed by such mutants in the absence and in the presence of Pb(2+) contain similar amounts of β-sheet structure. The results from isothermal titration calorimetry show that one Pb(2+) binds to one Tau monomer via interaction with His-330 and His-362, with sub-micromolar affinity.
  
  
  CONCLUSIONS
  We demonstrate for the first time that the fibrillization of human Tau protein is accelerated by exposure to lead via interaction with His-330 and His-362. Our results suggest the possible involvement of Pb(2+) in the pathogenesis of Alzheimer disease and provide critical insights into the mechanism of lead toxicity.
authors.affiliation: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Hai-Li
authors.initials: HL
authors.lastname: Zhu
authors.forename: Sheng-Rong
authors.initials: SR
authors.lastname: Meng
authors.forename: Jun-Bao
authors.initials: JB
authors.lastname: Fan
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
authors.forename: Yi
authors.initials: Y
authors.lastname: Liang
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D002151:Calorimetry / Q000379:methods; D002942:Circular Dichroism / Q000379:methods; D018076:DNA, Complementary / Q000378:metabolism; D006493:Heparin / Q000737:chemistry; D006639:Histidine / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007854:Lead / Q000737:chemistry* / Q000633:toxicity; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009154:Mutation; D009498:Neurotoxins / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013696:Temperature; D013816:Thermodynamics; D016875:tau Proteins / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; C054369:MAPT protein, human; D009498:Neurotoxins; D011994:Recombinant Proteins; D016875:tau Proteins; D007854:Lead; D006639:Histidine; D006493:Heparin