Uncovering Chaperone Activity in Uncommon Places: Determining the Chaperone Activity of the N-terminal Sequence of HspB1 and Chaperone-Functionalized Nanoparticles

Abstract

The small heat shock proteins (sHsp), ubiquitous cellular homeostasis machinery, are oligomeric chaperone proteins. sHsps play an important role in maintaining cell function and survival under stress conditions such as high temperatures. By binding to non-native proteins in an ATP-independent manner, sHsps effectively prevent harmful aggregation of denatured proteins, promote proper protein folding, or facilitate protein degradation. Defects in sHsps can result in abnormal accumulation of proteins or aberrant protein folding, which leads to many pathologies such as cataracts, tumors and neurodegenerative diseases including Parkinson’s disease and Alzheimer’s disease.1 Structural studies have demonstrated that sHsps contain a highly conserved α-crystallin domain flanked by variable N-terminal and C-terminal regions (NTR and CTR, respectively). sHsps usually exist as large, polydisperse oligomers and therefore, due to their dynamic organization, the specific mechanism(s) of how sHsp bind to substrate and function are not well understood. Nonetheless, it is suggested that the variable NTR of the protein contributes to substrate binding and oligomerization.2,3 We have purified the NTR of HspB1 and determined it has chaperone activity for at least two model substrates. Furthermore, we have attached the NTR to gold nanoparticles, creating multivalent peptide-nanoparticle conjugates (artificial sHsps), which also demonstrate chaperone activity. Further experiments will include probing additional regions of HspB1 for chaperone activity and to determine the therapeutic potential of “artificial” sHsps.