Triggers of full-length tau aggregation: a role for partially folded intermediates.
Alzheimer's disease is characterized in part by the accumulation of full-length tau proteins into intracellular filamentous inclusions. To clarify the events that trigger lesion formation, the aggregation of recombinant full-length four-repeat tau (htau40) was examined in vitro under near-physiological conditions using transmission electron microscopy and spectroscopy methods. In the absence of exogenous inducers, tau protein behaved as an assembly-incompetent monomer with little tertiary structure. The addition of anionic inducers led to fibrillization with nucleation-dependent kinetics. On the basis of circular dichroism spectroscopy and reactivity with thioflavin S and 8-anilino-1-naphthalenesulfonic acid fluorescent probes, the inducer stabilized a monomeric species with the folding characteristics of a premolten globule state. Planar aromatic dyes capable of binding the intermediate state with high affinity were also capable of triggering fibrillization in the absence of other inducers. Dye-mediated aggregation was characterized by concentration-dependent decreases in lag time, indicating increased nucleation rates, and submicromolar critical concentrations, indicating a final equilibrium that favored the filamentous state. The data suggest that the rate-limiting barrier for filament formation from full-length tau is conformational and that the aggregation reaction is triggered by environmental conditions that stabilize assembly-competent conformations.
Chirita
Carmen N
CN
Biophysics Program, The Ohio State University, Columbus, Ohio 43210, USA.
Congdon
Erin E
EE
Yin
Haishan
H
Kuret
Jeff
J
D000544:Alzheimer Disease / Q000209:etiology / Q000378:metabolism; D000817:Anilino Naphthalenesulfonates; D002942:Circular Dichroism; D005456:Fluorescent Dyes; D006801:Humans; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000737:chemistry* / Q000648:ultrastructure; D008854:Microscopy, Electron; D046912:Multiprotein Complexes; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000648:ultrastructure; D013050:Spectrometry, Fluorescence; D016875:tau Proteins
D000817:Anilino Naphthalenesulfonates; D005456:Fluorescent Dyes; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D011994:Recombinant Proteins; C027132:1-anilino-8-naphthalenesulfonate; C054369:MAPT protein, human; D016875:tau Proteins