In Cellulo Analysis of Huntingtin Inclusion Bodies by Cryogenic Nanoprobe SAXS

Huntington's disease (HD) is one of nine neurodegenerative disorders associated with an extension of polyglutamine (polyQ) in proteins. In HD, the polyQ tract in the huntingtin protein is extended beyond a threshold of 38 amino acids leading to the formation of amyloidal structures in the cytoplasm and nucleus. We investigated here the structure of Htt (Huntingtin) amyloid fibrils incellulo with nanoprobe small angle X-ray scattering. As these measurements were performed under cryogenic conditions, the information is obtained on the aggregates in their natural, hydrated environment without the need of staining and chemical fixation. We also could show the presence of oligomer structures not visible in fluorescence microscopy. Structural information on repetitive units inside of Htt inclusion bodies was determined from the SAXS data and compared to electron microscopy images. The results suggest that nanoprobe cryo-SAXS can serve as powerful tool to investigate the kinetics of amyloid aggregate formation inside cells and to understand how fibril formation can be influenced by drugs and other external stimuli.

Automated summary

Huntington's disease is a neurodegenerative disorder associated with the extension of polyglutamine in proteins, leading to the formation of amyloidal structures. By using nanoprobe small angle X-ray scattering in cellulo, the structure of Htt amyloid fibrils was investigated under cryogenic conditions, providing insights into aggregate formation without chemical fixation. It was also revealed that nanoprobe cryo-SAXS can serve as a powerful tool to study the kinetics of amyloid aggregate formation inside cells and understand how fibril formation can be influenced by drugs and external stimuli.