Multiple sites in αB-crystallin modulate its interactions with desmin filaments assembled in vitro

PLoS One. 2011;6(11):e25859. doi: 10.1371/journal.pone.0025859. Epub 2011 Nov 9.

Abstract

The β3- and β8-strands and C-terminal residues 155-165 of αB-crystallin were identified by pin arrays as interaction sites for various client proteins including the intermediate filament protein desmin. Here we present data using 5 well-characterised αB-crystallin protein constructs with substituted β3- and β8-strands and with the C-terminal residues 155-165 deleted to demonstrate the importance of these sequences to the interaction of αB-crystallin with desmin filaments. We used electron microscopy of negatively stained samples to visualize increased interactions followed by sedimentation assays to quantify our observations. A low-speed sedimentation assay measured the ability of αB-crystallin to prevent the self-association of desmin filaments. A high-speed sedimentation assay measured αB-crystallin cosedimentation with desmin filaments. Swapping the β8-strand of αB-crystallin or deleting residues 155-165 increased the cosedimentation of αB-crystallin with desmin filaments, but this coincided with increased filament-filament interactions. In contrast, substitution of the β3-strand with the equivalent αA-crystallin sequences improved the ability of αB-crystallin to prevent desmin filament-filament interactions with no significant change in its cosedimentation properties. These data suggest that all three sequences (β3-strand, β8-strand and C-terminal residues 155-165) contribute to the interaction of αB-crystallin with desmin filaments. The data also suggest that the cosedimentation of αB-crystallin with desmin filaments does not necessarily correlate with preventing desmin filament-filament interactions. This important observation is relevant not only to the formation of the protein aggregates that contain both desmin and αB-crystallin and typify desmin related myopathies, but also to the interaction of αB-crystallin with other filamentous protein polymers.

Publication types

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

MeSH terms

  • Binding Sites
  • Crystallins / chemistry
  • Crystallins / genetics
  • Crystallins / metabolism*
  • Crystallins / ultrastructure
  • Desmin / chemistry
  • Desmin / genetics
  • Desmin / metabolism*
  • Desmin / ultrastructure
  • Humans
  • Microscopy, Electron, Transmission
  • Mutagenesis, Site-Directed
  • Protein Binding

Substances

  • Crystallins
  • Desmin