α-Casein Inhibits Insulin Amyloid Formation by Preventing the Onset of Secondary Nucleation Processes.
α-Casein is known to inhibit the aggregation of several proteins, including the amyloid β-peptide, by mechanisms that are not yet completely clear. We studied its effects on insulin, a system extensively used to investigate the properties of amyloids, many of which are common to all proteins and peptides. In particular, as for other proteins, insulin aggregation is affected by secondary nucleation pathways. We found that α-casein strongly delays insulin amyloid formation, even at extremely low doses, when the aggregation process is characterized by secondary nucleation. At difference, it has a vanishing inhibitory effect on the initial oligomer formation, which is observed at high concentration and does not involve any secondary nucleation pathway. These results indicate that an efficient inhibition of amyloid formation can be achieved by chaperone-like systems, by sequestering the early aggregates, before they can trigger the exponential proliferation brought about by secondary nucleation mechanisms.
Institute of Biophysics, UOS Palermo, National Research Council, Via Ugo La Malfa 153, Palermo 90146, Italy.
Fabio
F
Librizzi
Institute of Biophysics, UOS Palermo, National Research Council, Via Ugo La Malfa 153, Palermo 90146, Italy.
Rita
R
Carrotta
Institute of Biophysics, UOS Palermo, National Research Council, Via Ugo La Malfa 153, Palermo 90146, Italy.
Dario
D
Spigolon
Institute of Biophysics, UOS Palermo, National Research Council, Via Ugo La Malfa 153, Palermo 90146, Italy.
Donatella
D
Bulone
Institute of Biophysics, UOS Palermo, National Research Council, Via Ugo La Malfa 153, Palermo 90146, Italy.
Pier Luigi
PL
San Biagio
atomic force microscopy; chaperones; circular dichroism; differential scanning calorimetry; thioflavin T