Nucleation mechanisms and morphologies in insulin amyloid fibril formation

TY - CHAP

T1 - Nucleation mechanisms and morphologies in insulin amyloid fibril formation

AU - Foderà, Vito

AU - Librizzi, F

AU - Vetri, V

AU - Militello, V

AU - Navarra, G

AU - Leone, M

PY - 2011

Y1 - 2011

N2 - Aggregation processes, and in general the physical and chemical instability of proteins, are at the moment a major problem related to different scientific fields, spanning from biochemistry and biophysics to pharmaceutical and medical sciences. In fact, increased knowledge on protein aggregation may clarify different aspects related to several degenerative pathologies like Alzheimer's and Parkinson's diseases and type-II diabetes. In this chapter, we present and discuss our experimental results on thermally induced aggregation of a model system protein, the hormone insulin. This molecule is largely used in protein-based drugs and exhibits a great propensity to form amyloid aggregates with mechanisms similar to those of other disease-related proteins. Therefore, insights on insulin stability in adverse conditions as well as on mechanisms of fibril formation have a double relevance. Using the scientific approach developed by our group in the last few years, we analyze the fibrillation kinetics of insulin as a function of the initial protein concentration paying particularly attention on the balance between different nucleation-elongation mechanisms and their effects on the final fibril morphologies. Using the fluorescence properties of amyloid sensitive dye Thioflavin T (ThT), static/dinamic light scattering and atomic force microscopy (AFM), the main role of secondary nucleation in determining the well-known exponential time course has been revealed. Specifically, the role of the early stable fibril surfaces and their ability in catalyzing the fibrillation reaction has been considered. Moreover, the fine investigation of the early stages of the process shows a pronounced stochasticity in the first aggregation events leading to an overall spatial heterogeneity in the formation of the early stable amyloid fibrils. These evidences are discussed and lead us to suggest a picture of interconnected events taking place at different stages in the process.

AB - Aggregation processes, and in general the physical and chemical instability of proteins, are at the moment a major problem related to different scientific fields, spanning from biochemistry and biophysics to pharmaceutical and medical sciences. In fact, increased knowledge on protein aggregation may clarify different aspects related to several degenerative pathologies like Alzheimer's and Parkinson's diseases and type-II diabetes. In this chapter, we present and discuss our experimental results on thermally induced aggregation of a model system protein, the hormone insulin. This molecule is largely used in protein-based drugs and exhibits a great propensity to form amyloid aggregates with mechanisms similar to those of other disease-related proteins. Therefore, insights on insulin stability in adverse conditions as well as on mechanisms of fibril formation have a double relevance. Using the scientific approach developed by our group in the last few years, we analyze the fibrillation kinetics of insulin as a function of the initial protein concentration paying particularly attention on the balance between different nucleation-elongation mechanisms and their effects on the final fibril morphologies. Using the fluorescence properties of amyloid sensitive dye Thioflavin T (ThT), static/dinamic light scattering and atomic force microscopy (AFM), the main role of secondary nucleation in determining the well-known exponential time course has been revealed. Specifically, the role of the early stable fibril surfaces and their ability in catalyzing the fibrillation reaction has been considered. Moreover, the fine investigation of the early stages of the process shows a pronounced stochasticity in the first aggregation events leading to an overall spatial heterogeneity in the formation of the early stable amyloid fibrils. These evidences are discussed and lead us to suggest a picture of interconnected events taking place at different stages in the process.

M3 - Book chapter

SP - 111

EP - 137

BT - Protein aggregation

PB - Nova Science Publishers

ER -