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Oligoproline effects on polyglutamine conformation and aggregation

Anusri Bhattacharyya1, Ashwani K Thakur, Veronique M Chellgren

  • 1Graduate School of Medicine, University of Tennessee, 1924 Alcoa Highway, Knoxville, TN 37920, USA.

Journal of Molecular Biology
|December 3, 2005
PubMed

Insights

Adding a P10 sequence to polyglutamine (polyGln) significantly reduces amyloid aggregate formation in neurological disease models. This finding offers new insights into polyGln aggregation and potential therapeutic strategies for diseases like Huntington's disease.

Area of Science:

  • Neuroscience
  • Biochemistry
  • Molecular Biology

Background:

  • Nine neurological diseases are linked to expanded CAG repeats, causing polyglutamine (polyGln) expansion in proteins.
  • The protein context and sequence surrounding polyGln influence its aggregation and disease pathology.
  • Huntington's disease (HD) involves polyGln expansion in huntingtin protein, followed by an oligoproline region.

Purpose of the Study:

  • To investigate the effect of C-terminal oligoproline sequences on polyglutamine (polyGln) aggregation.
  • To determine the optimal length and placement of oligoproline sequences for suppressing polyGln aggregation.
  • To explore the mechanism by which oligoproline sequences modulate polyGln aggregation and its implications for neurological diseases.

Main Methods:

  • Synthesis of peptides containing polyglutamine (polyGln) sequences with varying C-terminal oligoproline extensions.
  • Analysis of amyloid-like aggregate formation using techniques to measure aggregation rate and stability.
  • Circular dichroism spectroscopy to assess changes in peptide secondary structure.
  • Testing the effect of C-terminal P10 sequence on Abeta fibril formation.

Main Results:

  • A C-terminal P10 sequence significantly decreased the rate and stability of polyGln amyloid-like aggregate formation.
  • The suppressive effect was maintained with P6 but lost with P3 oligoproline sequences.
  • Spacer sequences between polyGln and P10 did not abolish the effect, but N-terminal or tethered P10 sequences were ineffective.
  • P10 addition altered the circular dichroism spectra of polyGln peptides, suggesting stabilization of an aggregation-incompetent monomer conformation.
  • The P10 sequence's effect on aggregation was transportable, modulating Abeta fibril formation.

Conclusions:

  • C-terminal oligoproline sequences, particularly P10, can effectively suppress polyglutamine (polyGln) aggregation.
  • The structural context and placement of oligoproline sequences are critical for their inhibitory effect.
  • These findings suggest a potential therapeutic strategy for polyGln-repeat neurological diseases by modulating protein aggregation.

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