Interaction between huntingtin exon 1 and HEAT repeat structure probed by chimeric model proteins

Area of Science:

• Neuroscience
• Molecular Biology
• Protein Biochemistry

Background:

• Huntington disease (HD) is linked to aggregated huntingtin (HTT) protein with expanded polyglutamine (polyQ) repeats in exon 1.
• The large size of HTT hinders structural studies, leading to focus on the exon 1 region.
• The HTT C-terminus contains HEAT repeats crucial for cellular functions.

Purpose of the Study:

• To investigate the interaction between the HTT exon 1 region and its HEAT repeat structure.
• To understand how this interaction influences protein stability, flexibility, and fibril formation in the context of HD.

Main Methods:

• Construction of chimeric proteins combining HTT exon 1 and the HEAT repeat protein PR65/A.
• Analysis of the impact of HTT exon 1 on HEAT repeat structure and flexibility.
• Assessment of amyloid fibril formation in chimeric proteins with varying polyQ lengths.

Main Results:

• HTT exon 1 slightly destabilizes and increases the conformational flexibility of the downstream HEAT repeat structure.
• PolyQ length (wild-type vs. pathological) did not alter the interaction between HTT exon 1 and HEAT repeats.
• C-terminal fusion of HEAT repeats modulated the fibril architecture and formation kinetics of pathological HTT exon 1.

Conclusions:

• The interaction between HTT exon 1 and HEAT repeats is compatible with both normal HTT function and HD pathogenesis.
• This study offers a model for further research into HTT structure-function relationships and HD mechanisms.