Hsp60, amateur chaperone in amyloid-beta fibrillogenesis.

BACKGROUND: Molecular chaperones are a very special class of proteins that play essential roles in many cellular processes like folding, targeting and transport of proteins. Moreover, recent evidence indicates that chaperones can act as potentially strong suppressor agents in Alzheimer's disease (AD). Indeed, in vitro experiments demonstrate that several chaperones are able to significantly slow down or suppress aggregation of A\u3b2 peptide and in vivo studies reveal that treatment with specific chaperones or their overexpression can ameliorate some distinct pathological signs characterizing AD. METHODS: Here we investigate using a biophysical approach (fluorescence, circular dichroism (CD), transmission electron (TEM) and atomic force (AFM) microscopy, size exclusion chromatography (SEC)) the effect of the human chaperonin Hsp60 on A\u3b2 fibrillogenesis. RESULTS: We found that Hsp60 powerfully inhibits A\u3b2 amyloid aggregation, by closing molecular pathways leading to peptide fibrillogenesis. CONCLUSIONS: We observe that Hsp60 inhibits A\u3b2 aggregation through a more complex mechanism than a simple folding chaperone action. The action is specifically directed toward the early oligomeric species behaving as aggregation seeds for on-pathway amyloid fibrillogenesis. GENERAL SIGNIFICANCE: Understanding the specificity of the molecular interactions of Hsp60 with amyloid A\u3b2 peptide allowed us to emphasize the important aspects to be taken into consideration when considering the recent promising therapeutic strategies for neurodegeneration. Copyright \ua9 2016 Elsevier B.V. All rights reserved