Structural insight into transmissive mutant huntingtin species by correlative light and electron microscopy and cryo-electron tomography

Xuyuan Kuang; Kyle Nunn; Jennifer Jiang; Paul Castellano; Uttara Hardikar; Arianna Horgan; Joyce Kong; Zhiqun Tan; Wei Dai

doi:10.1016/j.bbrc.2021.04.124

Structural insight into transmissive mutant huntingtin species by correlative light and electron microscopy and cryo-electron tomography

Biochem Biophys Res Commun. 2021 Jun 30:560:99-104. doi: 10.1016/j.bbrc.2021.04.124. Epub 2021 May 10.

Authors

Xuyuan Kuang¹, Kyle Nunn², Jennifer Jiang², Paul Castellano², Uttara Hardikar², Arianna Horgan³, Joyce Kong⁴, Zhiqun Tan⁵, Wei Dai⁶

Affiliations

¹ Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA; Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA; Department of Hyperbaric Oxygen, Xiangya Hospital, Central South University, Changsha, Hunan, 410008, China.
² Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA; Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA.
³ Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA; School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA.
⁴ Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA; Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA.
⁵ Department of Anatomy and Neurobiology, University of California Irvine School of Medicine, Irvine, CA, 29697, USA; Institute for Memory Impairment and Neurological Disorders, University of California-Irvine, Irvine, CA, 29697, USA. Electronic address: [email protected].
⁶ Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA; Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA. Electronic address: [email protected].

Abstract

Aggregates of mutant huntingtin (mHTT) containing an expanded polyglutamine (polyQ) tract are hallmarks of Huntington's Disease (HD). Studies have shown that mHTT can spread between cells, leading to the propagation of misfolded protein pathology. However, the structure of transmissive mHTT species, and the molecular mechanisms underlying their transmission remain unknown. Using correlative light and electron microscopy (CLEM) and cryo-electron tomography (cryo-ET), we identified two types of aggregation-prone granules in conditioned medium from PC12 cells expressing a mHTT N-terminal fragment: densities enclosed by extracellular vesicles (EVs), and uncoated, amorphous meshworks of heterogeneous oligomers that co-localize with clusters of EVs. In vitro assays confirmed that liposomes induce condensation of polyQ oligomers into higher-order assemblies, resembling the uncoated meshworks observed in PC12 conditioned medium. Our findings provide novel insights into formation and architecture of transmissive mHTT proteins, and highlight the potential role of EVs as both carriers and modulators of transmissive mHTT proteins.

Keywords: Cryo-electron tomography; Extracellular vesicles; Mutant huntingtin; Protein transmission.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animals
Culture Media, Conditioned
Electron Microscope Tomography
Huntingtin Protein / genetics*
Huntingtin Protein / ultrastructure*
Liposomes
Microscopy
Microscopy, Electron
Mutation
PC12 Cells
Protein Folding
Rats

Substances

Culture Media, Conditioned
Huntingtin Protein
Liposomes

Grants and funding

P01 NS092525/NS/NINDS NIH HHS/United States