Targeting the ensemble of heterogeneous tau oligomers in cells: A novel small molecule screening platform for tauopathies

Chih Hung Lo, Colin Kin Wye Lim, Zhipeng Ding, Sanjula P. Wickramasinghe, Anthony R. Braun, Karen H. Ashe, Elizabeth Rhoades, David D. Thomas, Jonathan N. Sachs

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Objective: Understanding the heterogeneous pathology in Alzheimer's disease and related tauopathies is one of the most urgent and fundamental challenges facing the discovery of novel disease-modifying therapies. Through monitoring ensembles of toxic and nontoxic tau oligomers spontaneously formed in cells, our biosensor technology can identify tool compounds that modulate tau oligomer structure and toxicity, providing much needed insight into the nature and properties of toxic tau oligomers. Background: Tauopathies are a group of neurodegenerative disorders characterized by pathologic aggregation of the microtubule binding protein tau. Recent studies suggest that tau oligomers are the primary toxic species in tauopathies. New/Updated Hypothesis: We hypothesize that tau biosensors capable of monitoring tau oligomer conformation are able to identify tool compounds that modulate the structure and conformation of these tau assemblies, providing key insight into the unique structural fingerprints of toxic tau oligomers. These fingerprints will provide gravely needed biomarker profiles to improve staging of early tauopathy pathology and generate lead compounds for potential new therapeutics. Our time-resolved fluorescence resonance energy transfer biosensors provide us an exquisitely sensitive technique to monitor minute structural changes in monomer and oligomer conformation. In this proof-of-concept study, we identified a novel tool compound, MK-886, which directly binds tau, perturbs the conformation of toxic tau oligomers, and rescues tau-induced cytotoxicity. Furthermore, we show that MK-886 alters the conformation of tau monomer at the proline-rich and microtubule binding regions, stabilizing an on-pathway oligomer. Major Challenges for the Hypothesis: Our approach monitors changes in the ensemble of assemblies that are spontaneously formed in cells but does not specifically isolate or enrich unique toxic tau species. However, time-resolved fluorescence resonance energy transfer does not provide high-resolution, atomic scale information, requiring additional experimental techniques to resolve the structural features stabilized by different tool compounds. Linkage to Other Major Theories: Our biosensor technology is broadly applicable to other areas of tauopathy therapeutic development. These biosensors can be readily modified for different isoforms of tau, specific post-translational modifications, and familial Alzheimer's disease–associated mutations. We are eager to explore tau interactions with chaperone proteins, monitor cross-reactivity with other intrinsically disordered proteins, and target seeded oligomer pathology.

Original languageEnglish (US)
Pages (from-to)1489-1502
Number of pages14
JournalAlzheimer's and Dementia
Volume15
Issue number11
DOIs
StatePublished - Nov 2019

Bibliographical note

Funding Information:
The authors thank Nagamani Vunnam, Malaney C. Young, and Breeanne M. Brand from the Sachs Group; Tory Schaaf, Samantha Yuen, Andrew Thompson, and Razvan Cornea from the Thomas Group; and Benjamin Grant from Fluorescence Innovations, for technical support and discussions. The authors also thank Dr David Odde from the University of Minnesota for discussions. Compound dispensing and surface plasmon resonance (SPR) (S10 Shared Instrument Grant 1S10OD021539-01 funded by the Office of Research Infrastructure Programs (ORIP)/NIH at the UMN Institute of Therapeutic Drug Discovery and Development (ITDD) High-Throughput Screening Laboratory, and spectroscopy at the UMN Biophysical Technology Center. This research uses technology patented by the University of Minnesota, with an exclusive commercial license to Photonic Pharma LLC. The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: this study was supported by U.S. NIH grants to J.N.S. ( R01AG053951 ) and D.D.T. ( R37AG026160 ). C.H.L. was supported by a Doctoral Dissertation Fellowship from the University of Minnesota .

Funding Information:
The authors thank Nagamani Vunnam, Malaney C. Young, and Breeanne M. Brand from the Sachs Group; Tory Schaaf, Samantha Yuen, Andrew Thompson, and Razvan Cornea from the Thomas Group; and Benjamin Grant from Fluorescence Innovations, for technical support and discussions. The authors also thank Dr David Odde from the University of Minnesota for discussions. Compound dispensing and surface plasmon resonance (SPR) (S10 Shared Instrument Grant 1S10OD021539-01 funded by the Office of Research Infrastructure Programs (ORIP)/NIH at the UMN Institute of Therapeutic Drug Discovery and Development (ITDD) High-Throughput Screening Laboratory, and spectroscopy at the UMN Biophysical Technology Center. This research uses technology patented by the University of Minnesota, with an exclusive commercial license to Photonic Pharma LLC. The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: this study was supported by U.S. NIH grants to J.N.S. (R01AG053951) and D.D.T. (R37AG026160). C.H.L. was supported by a Doctoral Dissertation Fellowship from the University of Minnesota. Author contributions: C.H.L. designed and conducted all the experiments. C.K.W.L. and Z.D. contributed to protein purification and assisted with cell-based assays and biochemical experiments. S.W. and E.R. performed and analyzed the single-molecule fluorescence resonance energy transfer (FRET) experiment. D.D.T. provided expertise on FRET and high-throughput screening, and provided comments and edits to the manuscript. A.R.B. and K.H.A. provided comments and edits to the manuscript. C.H.L and J.N.S. wrote the manuscript.

Keywords

  • Conformational ensembles
  • Fibrillation kinetics
  • Heterogeneous tau oligomers
  • Small-molecule inhibitors
  • Tau oligomerization
  • Time-resolved FRET

Fingerprint Dive into the research topics of 'Targeting the ensemble of heterogeneous tau oligomers in cells: A novel small molecule screening platform for tauopathies'. Together they form a unique fingerprint.

Cite this