Hsp20, a novel α‐crystallin, prevents Aβ fibril formation and toxicity

Abstract

Abstract␤-Amyloid (A␤) is a major protein component of senile plaques in Alzheimer's disease, and is neurotoxic when aggregated. The size of aggregated A␤ responsible for the observed neurotoxicity and the mechanism of aggregation are still under investigation; however, prevention of A␤ aggregation still holds promise as a means to reduce A␤ neurotoxicity. In research presented here, we show that Hsp20, a novel ␣-crystallin isolated from the bovine erythrocyte parasite Babesia bovis, was able to prevent aggregation of denatured alcohol dehydrogenase when the two proteins are present at near equimolar levels. We then examined the ability of Hsp20 produced as two different fusion proteins to prevent A␤ amyloid formation as indicated by Congo Red binding; we found that not only was Hsp20 able to dramatically reduce Congo Red binding, but it was able to do so at molar ratios of Hsp20 to A␤ of 1 to 1000. Electron microscopy confirmed that Hsp20 does prevent A␤ fibril formation. Hsp20 was also able to significantly reduce A␤ toxicity to both SH-SY5Y and PC12 neuronal cells at similar molar ratios. At high concentrations of Hsp20, the protein no longer displays its aggregation inhibition and toxicity attenuation properties. Size exclusion chromatography indicated that Hsp20 was active at low concentrations in which dimer was present. Loss of activity at high concentrations was associated with the presence of higher oligomers of Hsp20. This work could contribute to the development of a novel aggregation inhibitor for prevention of A␤ toxicity.

Reversal of amyloid-induced heart disease in desmin-related cardiomyopathy

“…In contrast with these data, a number of in vitro studies showed that overexpression of heat-shock protein family members significantly attenuated A␤-, PQ-, and ␣-synucleinmediated toxicity (3), indicating that chaperone expression was cytoprotective against neurodegeneration. In fact, a number of genetic studies in animal models of human disease indicate that molecular chaperones are potent suppressors of neurodegeneration (36)(37)(38). The mechanism or mechanisms have not been defined, but a reasonable hypothesis is that the chaperone might decrease initial formation of the soluble but misfolded protein supramolecular structures that go on to develop amyloid-like characteristics.…”

Heat Shock Proteins 70 and 90 Inhibit Early Stages of Amyloid β-(1–42) Aggregation in Vitro

“…Similarly, addition of Hsp70 and its cochaperone partner, Hsp40, to Huntingtin, an aggregationprone protein that causes Huntington disease, blocks oligomer formation (43,51). In addition to these findings, other chaperones, such as Hsp20 (52) and Hsp104 (53), have been shown to limit amyloid formation in vitro. Together, the combination of genetic and biochemical evidence provides compelling support for a direct role of chaperones in these diseases.…”

A study of aqueous humour proteins in patients of primary open angle glaucoma

“…Unlike the high molecular weight Hsps, which are involved in protein folding in vivo, under normal conditions, sHsps play an important role in protecting organism from stress. Such small heat shock proteins are reported to share an evolutionarily conserved sequence of 80-100 amino acids, located in the C-terminal region, called the alpha-crystallin [28]. Tamm et al [20] have demonstrated that both monkey and human TM cell cultures stressed by heat shock, exhibited a significant increase in alpha B-crystallin mRNA.…”