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National Biomedical Center
for Advanced Electron Spin Resonance Technology

Our research is supported by a grant from the National Institute of General Medical Sciences (NIGMS), part of the National Institutes of Health.

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Signature of an Aggregation-Prone Conformation of Tau Elucidated by Pulse Dipolar ESR

The self-assembly of the microtubule associated tau protein into fibrillar cell inclusions is linked to a number of devastating neurodegenerative disorders collectively known as tauopathies. The mechanism by which tau self-assembles into pathological entities is a matter of much debate, largely due to the lack of direct experimental insights into the earliest stages of aggregation. We made pulsed Dipolar ESR measurements of two key fibril-forming regions of tau, PHF6 and PHF6*,during the course of the aggregation. By monitoring the end-to-end distance distribution of these segments as a function of aggregation time, we showed that the PHF6(*) regions dramatically extend to distances commensurate with extended β-strand structures within the earliest stages of aggregation, well before fibril formation. Combined with simulations, our experiments show that the extended β-strand conformational state of PHF6(*) is readily populated under aggregating conditions, constituting a defining signature of aggregation-prone tau, and as such, a possible target for therapeutic interventions.

Funding:R21EB022731 (to SH), NSF MCB 1158577 (to JS), P41GM103521 (to JHF).

Publication: Eschmann NA, Georgieva ER, Ganguly P, Borbat PP,. Rappaport MD, Akdogan Y, Freed JH,. Shea J-E, and Han S. Sci. Rep. 7, 44739 (2017); PMCID: PMC5356194.

A (a) 12-mer peptide R2/12 (G273C/L284C) and a 14-mer peptide R2/14 (G272C/S285C), and (b) Δtau187, truncated from the full length, 441 residue tau between residues 255-441. Δtau187 includes all four microtubule binding repeats (MTBRs) to the C-terminus. Two Δtau187 constructs were made with double cysteine mutations in order to measure distances across both PHF6 regions, including Δtau187 G272C/S285C and Δtau187 G303C/S316C.

DEER time domain signal and corresponding distance distribution of Δtau187 G272C/S285C and G303C/S316C in addition to time-course of populations S and S* as a function of aggregation time for all double mutants.
Neil Eschmann (Department of Chemistry & Biochemistry, University of California, Santa Barbara)
Elka R. Georgieva (Department of Physiology & Biophysics, Weill-Cornell Medical College, New York City)
Pritam Ganguly (Department of Chemistry & Biochemistry, University of California, Santa Barbara) Peter P Borbat (ACERT) Maxime D. Rappaport, Yasar Akdogan (Department of Chemistry & Biochemistry, University of California, Santa Barbara) Jack H. Freed (ACERT) Joan-Emma Shea, and Songi Han (Department of Chemistry & Biochemistry, University of California, Santa Barbara)
June, 2017