Osmolytes dynamically regulate mutant Huntingtin aggregation and CREB function in Huntington's disease cell models

Area of Science:

• Biochemistry
• Neuroscience
• Cell Biology

Background:

• Huntington's disease (HD) is linked to mutant Huntingtin (mHtt) aggregation.
• Intrinsically disordered proteins like mHtt are challenging to study.
• Osmolytes modulate protein folding and aggregation.

Purpose of the Study:

• To investigate the role of osmolytes in mHtt aggregation and pathogenicity.
• To explore the impact of mHtt aggregation on transcription factor function and cell survival.
• To test the hypothesis that soluble mHtt species drive neurodegeneration.

Main Methods:

• Utilized inducible PC12 and striatal neuron cell models of HD.
• Applied stabilizing polyol osmolytes and the destabilizing osmolyte urea.
• Assessed mHtt aggregation into inclusion bodies (IBs) via microscopy.
• Measured CREB transcription factor activity and cell survival under stress.
• Investigated the role of HSP70 and HSC70 chaperones.

Main Results:

• Stabilizing osmolytes induced mHtt aggregation into IBs, while urea did not.
• Osmolyte-induced IB formation correlated with improved cell survival under stress.
• Diffuse mHtt repressed CREB activity, which was mitigated by osmolytes or urea.
• HSP70/HSC70 knockdown did not affect osmolyte-induced aggregation.

Conclusions:

• Stabilizing polyol osmolytes promote mHtt aggregation, alleviating CREB dysfunction and enhancing cell survival.
• Osmolytes offer a novel approach to modulate mHtt aggregation and toxicity.
• Findings support the hypothesis that soluble, lower molecular weight mHtt species are pathogenic in HD.