Amyloids: the good, the bad and the ugly
Amyloids – insoluble fibrous protein aggregates that share specific structural traits – are well known for their involvement in diseases such as Alzheimer’s, Parkinson’s, prions diseases and even diabetes 2 and some cancers. As evil as they seem, however, they also have a kinder side. Stavros Hamodrakas, head of the Biophysics and Bioinformatics laboratory at the Faculty of Biology, University of Athens (Greece), talked today at the PRBB about functional, non-pathogenic amyloids.
He actually was the first person to propose that the silk moth eggshell (or chorion) was a natural, protective amyloid. The chorion is a multi-layered structure that protects the egg from desiccation and infections and which provides thermal insulation.
Hamodrakas reviewed in this talk his research over the last 30 years on this field. Since those first days, many more examples of protective amyloids have been found, from bacteria to human – including the covers of the eggs of many species such as fish, mouse and humans. Skipping through all the details, the conclusion was that tandem hexapeptide repeats present in the aminoacid sequence of the central domain of chorion proteins is what dictates the folding and self-assembly of those amyloid-like protein. One peculiarity he mentioned was the fact that all the proteins that form amyloids are very different amongst them at the sequence level. However, the structure – the focus of Hamodrakas’ research – has similarities.
The audience was very involved in the talk, and an interesting debate originated afterwards around the question: why are some amyloids functional, protective either, and others pathological? One of the potential answers is the fact that all protective amyloids are extracellular, so they don’t affect the functioning of the cell. And even thought they were synthesized within the cell, they were ‘protected’ within vesicles until they were secreted.
There’s still a lot to learn about protective amyloids, and the more we know about them, the better we can understand the pathological ones.
Report by Maruxa Martinez, Scientific Editor at the PRBB