Interaction between calpain-1 and HSP90: new insights into the regulation of localization and activity of the protease

PLoS One. 2015 Jan 9;10(1):e0116738. doi: 10.1371/journal.pone.0116738. eCollection 2015.

Abstract

Here we demonstrate that heat shock protein 90 (HSP90) interacts with calpain-1, but not with calpain-2, and forms a discrete complex in which the protease maintains its catalytic activity, although with a lower affinity for Ca2+. Equilibrium gel distribution experiments show that this complex is composed by an equal number of molecules of each protein partner. Moreover, in resting cells, cytosolic calpain-1 is completely associated with HSP90. Since calpain-1, in association with HSP90, retains its proteolytic activity, and the chaperone is displaced by calpastatin also in the absence of Ca2+, the catalytic cleft of the protease is not involved in this association. Thus, calpain-1 can form two distinct complexes depending on the availability of calpastatin in the cytosol. The occurrence of a complex between HSP90 and calpain-1, in which the protease is still activable, can prevent the complete inhibition of the protease even in the presence of high calpastatin levels. We also demonstrate that in basal cell conditions HSP90 and calpain-1, but not calpain-2, are inserted in the multi-protein N-Methyl-D-Aspartate receptor (NMDAR) complex. The amount of calpain-1 at the NMDAR cluster is not modified in conditions of increased [Ca2+]i, and this resident protease is involved in the processing of NMDAR components. Finally, the amount of calpain-1 associated with NMDAR cluster is independent from Ca2+-mediated translocation. Our findings show that HSP90 plays an important role in maintaining a given and proper amount of calpain-1 at the functional sites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / chemistry
  • Calcium / metabolism
  • Calcium-Binding Proteins / chemistry
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism
  • Calpain / chemistry
  • Calpain / metabolism*
  • Cell Line
  • HSP90 Heat-Shock Proteins / chemistry
  • HSP90 Heat-Shock Proteins / genetics
  • HSP90 Heat-Shock Proteins / metabolism*
  • Humans
  • Immunoprecipitation
  • Ions / chemistry
  • Male
  • Mice
  • Microscopy, Confocal
  • Peptide Hydrolases / metabolism
  • Protein Binding
  • Rats
  • Receptors, N-Methyl-D-Aspartate / chemistry
  • Receptors, N-Methyl-D-Aspartate / metabolism
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics

Substances

  • Calcium-Binding Proteins
  • HSP90 Heat-Shock Proteins
  • Ions
  • Receptors, N-Methyl-D-Aspartate
  • Recombinant Proteins
  • calpastatin
  • Peptide Hydrolases
  • Calpain
  • Calcium

Grants and funding

This work was supported by grants from the University of Genoa to MA (PRA Averna 2013). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.