Human Small Heat Shock Protein B8 Inhibits Protein Aggregation without Affecting the Native Folding Process

Abstract

Small Heat Shock Proteins (sHSPs) are key components of our Protein Quality Control system and are thought to act as reservoirs that neutralize irreversible protein aggregation. Yet, sHSPs can also act as sequestrases, promoting protein sequestration into aggregates, thus challenging our understanding of their exact mechanisms of action. Here, we employ optical tweezers to explore the mechanisms of action of the human small heat shock protein HSPB8 and its pathogenic mutant K141E, which is associated with neuromuscular disease. Through single-molecule manipulation experiments, we studied how HSPB8 and its K141E mutant affect the refolding and aggregation processes of the maltose binding protein. Our data show that HSPB8 selectively suppresses protein aggregation without affecting the native folding process. This anti-aggregation mechanism is distinct from previous models that rely on the stabilization of unfolded polypeptide chains or partially folded structures, as has been reported for other chaperones. Rather, it appears that HSPB8 selectively recognizes and binds to aggregated species formed at the early stages of aggregation, preventing them from growing into larger aggregated structures. Consistently, the K141E mutation specifically targets the affinity for aggregated structures without impacting native folding, and hence impairs its anti-aggregation activity.

Mechanistic Intimate Insights into the Role of Hydrogen Sulfide in Alzheimer’s Disease: A Recent Systematic Review

“…Furthermore, the RSS-induced m ifications in the Heat Shock Protein 90 (HSP90) chaperone system unveil another lay complexity, raising questions about protein quality control pathways. These observa underscore the need for an in-depth investigation into the multifaceted roles of RS neurodegenerative conditions [42].…”

The major inducible small heat shock protein HSP20-3 in the tardigrade Ramazzottius varieornatus forms filament-like structures and is an active chaperone

“…Comparison of the molecular adaptions across Eutardigrada ( Hypsibius exemplaris, R. varieornatus , Richtersius coronifer ) and Heterotardigrada 21 with two other related invertebrates, the arthropod, Drosophila melanogaster and the nematode, Caenorhabditis elegans and various vertebrates and yeast 7 established that proteins in addition to the tardigrade specific proteins (CAHS, MAHS, SAHS) are necessary for the unique molecular adaptions that supports cryptogenic responses to extreme stresses 7 , 21 . With this in mind, we investigated the small heat shock protein (sHSP) family present in R. varieornatus because sHSPs have properties in common with CAHS and SAHS proteins, such as their ability to prevent protein aggregation and precipitation 22 , 23 , 24 , 25 , form biomolecular condensates 26 , 27 , 28 and to be upregulated in response to cold and heat shock of R. varieornatus 29 , 30 .…”