Protein aggregation

Protein aggregation is a biological phenomenon in which mis-folded proteins aggregate (i.e., accumulate and clump together) either intra- or extracellularly. These protein aggregates are often toxic; protein aggregates have been implicated in a wide variety of disease known as amyloidoses, including ALS, Alzheimer's, Parkinson's and prion disease.

Introduction

After synthesis, proteins typically fold into a particular three-dimensional conformation: their native state. Only in their native state are they functional. This folding process is driven by the hydrophobic effect: a tendency for hydrophobic (i.e., “oil-ly”) portions of the protein to shield itself from the hydrophilic interior of the cell by burying into the interior of the protein. Thus, the exterior of a protein is typically hydrophilic, whereas the interior is typically hydrophobic.

However, newly synthesized proteins may not fold correctly, or properly folded proteins can spontaneously misfold. In these cases, if the cell does not assist the protein in re-folding, or degrade the unfolded protein, the unfolded protein may aggregate. In this process, exposed hydrophobic portions of the unfolded protein may interact with the exposed hydrophobic patches of other unfolded proteins, spontaneously leading to protein aggregation.