Trehalose Effect on the Aggregation of Model Proteins into Amyloid Fibrils.

Eleonora Mari,Caterina Ricci,Maria Grazia Ortore,Francesco Spinozzi,Paolo Mariani,Silvia Pieraccini

doi:10.3390/life10050060

Eleonora Mari, Caterina Ricci + Show 4 more

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https://doi.org/10.3390/life10050060

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Journal: Life	Publication Date: May 13, 2020
Citations: 18	License type: CC BY 4.0

Affiliation: Marche Polytechnic University, University of Bologna

Abstract

Protein aggregation into amyloid fibrils is a phenomenon that attracts attention from a wide and composite part of the scientific community. Indeed, the presence of mature fibrils is associated with several neurodegenerative diseases, and in addition these supramolecular aggregates are considered promising self-assembling nanomaterials. In this framework, investigation on the effect of cosolutes on protein propensity to aggregate into fibrils is receiving growing interest, and new insights on this aspect might represent valuable steps towards comprehension of highly complex biological processes. In this work we studied the influence exerted by the osmolyte trehalose on fibrillation of two model proteins, that is, lysozyme and insulin, investigated during concomitant variation of the solution ionic strength due to NaCl. In order to monitor both secondary structures and the overall tridimensional conformations, we have performed UV spectroscopy measurements with Congo Red, Circular Dichroism, and synchrotron Small Angle X-ray Scattering. For both proteins we describe the effect of trehalose in changing the fibrillation pattern and, as main result, we observe that ionic strength in solution is a key factor in determining trehalose efficiency in slowing down or blocking protein fibrillation. Ionic strength reveals to be a competitive element with respect to trehalose, being able to counteract its inhibiting effects toward amyloidogenesis. Reported data highlight the importance of combining studies carried out on cosolutes with valuation of other physiological parameters that may affect the aggregation process. Also, the obtained experimental results allow to hypothesize a plausible mechanism adopted by the osmolyte to preserve protein surface and prevent protein fibrillation.

Highlights

A polypeptide chain in the folding process can achieve ordered or disordered structure, depending on the amino acid sequence, and on the physical and chemical features of the environment in which the protein is expressed
In the light of renewed studies on trehalose behavior in water [35,36], or of trehalose preferential exclusion from protein hydration shell [37], we report on trehalose effect on amyloid fibrillation of two model proteins explored as a function of ionic strength
The influence of trehalose on lysozyme aggregation has been investigated analyzing the concomitant effectiveness of increasing ionic strength on the protein conformational evolution in time

Summary

Introduction

A polypeptide chain in the folding process can achieve ordered or disordered structure, depending on the amino acid sequence, and on the physical and chemical features of the environment in which the protein is expressed. In non-pathological conditions, numerous stabilizing forces contribute to maintaining the correct folding of the protein On this issue, hydrophobic interactions play a very important role: non-polar amino acids tend to minimize exposure to a polar solvent, such as water, locating themselves within the protein structure, while polar and charged amino acids are exposed to the surface of the protein, establishing close interactions with the solvent [1]. Hydrophobic interactions play a very important role: non-polar amino acids tend to minimize exposure to a polar solvent, such as water, locating themselves within the protein structure, while polar and charged amino acids are exposed to the surface of the protein, establishing close interactions with the solvent [1] In stressful situations, such as extreme variations in temperature and pH, increased ionic strength or mechanical agitation, every protein can lose its native conformation, experiencing the possibility of rearranging into a different conformation or aggregating with other proteins in solution [2,3,4,5]. The protein is allowed to establish protein-protein rather than protein-solvent interactions, with consequent modifications in aggregation and precipitation [6]

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