Publication Details

Cappelli, S., Penco, A., Mannini, B., Cascella, R., Wilson, M. R., Ecroyd, H., Li, X., Buxbaum, J. N., Dobson, C. M., Cecchi, C., Relini, A. & Chiti, F. (2016). Effect of molecular chaperones on aberrant protein oligomers in vitro: super-versus sub-stoichiometric chaperone concentrations. Biological Chemistry: official scientific journal of the GBM, 397 (5), 401-415.


Living systems protect themselves from aberrant proteins by a network of chaperones. We have tested in vitro the effects of different concentrations, ranging from 0 to 16 μm, of two molecular chaperones, namely αB-crystallin and clusterin, and an engineered monomeric variant of transthyretin (M-TTR), on the morphology and cytotoxicity of preformed toxic oligomers of HypF-N, which represent a useful model of misfolded protein aggregates. Using atomic force microscopy imaging and static light scattering analysis, all were found to bind HypF-N oligomers and increase the size of the aggregates, to an extent that correlates with chaperone concentration. SDS-PAGE profiles have shown that the large aggregates were predominantly composed of the HypF-N protein. ANS fluorescence measurements show that the chaperone-induced clustering of HypF-N oligomers does not change the overall solvent exposure of hydrophobic residues on the surface of the oligomers. αB-crystallin, clusterin and M-TTR can diminish the cytotoxic effects of the HypF-N oligomers at all chaperone concentration, as demonstrated by MTT reduction and Ca2+ influx measurements. The observation that the protective effect is primarily at all concentrations of chaperones, both when the increase in HypF-N aggregate size is minimal and large, emphasizes the efficiency and versatility of these protein molecules.



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