Journal Article

The structured core domain of αB-crystallin can prevent amyloid fibrillation and associated toxicity

Baldwin, Andrew J., Cascio, Duilio, Eisenberg, David S., Ecroyd, Heath, Laganowsky, Arthur, Liu, Cong, Collier, Miranda P., Cox, Dezerae, Stroud, James, Benesch, Justin L. P., Carver, John A., Sawaya, Michael R., Robinson, Carol V., Hochberg, Georg K. A.

2014

Overview

We find that the core domain of the human molecular chaperone αB-crystallin can function effectively in preventing protein aggregation and amyloid toxicity. The core domain represents only half the total sequence of the protein, but it is one of the most potent known inhibitors of the aggregation of amyloid-β, a process implicated in Alzheimer’s disease. We have determined high-resolution structures of this core domain and investigated its biophysical properties in solution. We find that the excised domain efficiently prevents amyloid aggregation and thereby reduces the toxicity of the resulting aggregates to cells. The structures of these domains that we present should represent useful scaffolds for the design of novel amyloid inhibitors. Mammalian small heat-shock proteins (sHSPs) are molecular chaperones that form polydisperse and dynamic complexes with target proteins, serving as a first line of defense in preventing their aggregation into either amorphous deposits or amyloid fibrils. Their apparently broad target specificity makes sHSPs attractive for investigating ways to tackle disorders of protein aggregation. The two most abundant sHSPs in human tissue are αB-crystallin (ABC) and HSP27; here we present high-resolution structures of their core domains (cABC, cHSP27), each in complex with a segment of their respective C-terminal regions. We find that both truncated proteins dimerize, and although this interface is labile in the case of cABC, in cHSP27 the dimer can be cross-linked by an intermonomer disulfide linkage. Using cHSP27 as a template, we have designed an equivalently locked cABC to enable us to investigate the functional role played by oligomerization, disordered N and C termini, subunit exchange, and variable dimer interfaces in ABC. We have assayed the ability of the different forms of ABC to prevent protein aggregation in vitro. Remarkably, we find that cABC has chaperone activity comparable to that of the full-length protein, even when monomer dissociation is restricted through disulfide linkage. Furthermore, cABC is a potent inhibitor of amyloid fibril formation and, by slowing the rate of its aggregation, effectively reduces the toxicity of amyloid-β peptide to cells. Overall we present a small chaperone unit together with its atomic coordinates that potentially enables the rational design of more effective chaperones and amyloid inhibitors.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: alpha-Crystallin B Chain - chemistry / alpha-Crystallin B Chain - metabolism / Amino Acid Sequence / amyloid / Amyloid beta-Peptides - toxicity / Animals / Biological Sciences / crosslinking / Crystallization / Cysteine - metabolism / dissociation / heat shock proteins / HEK293 Cells / HeLa Cells / HSP27 Heat-Shock Proteins - chemistry / HSP27 Heat-Shock Proteins - metabolism / Humans / Magnetic Resonance Spectroscopy / Mammals / Molecular Sequence Data / oligomerization / PC12 Cells / PNAS Plus / PNAS Plus: Significance Statements / Protein Multimerization - drug effects / Protein Structure, Quaternary / Protein Structure, Tertiary / Rats / Structure-Activity Relationship / toxicity