Beta Amyloid forms Plaques

From Proteopedia

Amyloid

Background

Amyloids are accumulated proteins that are folded up into a shape that allows for continual copies to be made of each protein. These proteins then create fibrils that is generated in the bone marrow and deposited throughout all organs and tissues. Numerous diseases can be credited to the over abundance of amyloid fibrils. Amyloids can be formed by many different proteins and polypeptides. Amyloids are formed by polymerization of monomeric peptides into fibers. It takes thousands and thousands to create a single fiber of amyloid. The formation relies on the sequance heavily, meaning any mutations can cause the assembly process to shut down.

When amyloids were first discovered, they were mistaken by the German scientist, Rudolf Virchow, to be starch. This was due to it's reaction with iodine staining of the time. It was in 1859 that the scientific community found that they were not starch, fatty acid deposits, or carbohydrate deposits; but instead albumoid proteinaceous material, which means it is made of a protein created by abumins.

Structure

The structure of the fibers typically form quaternary beta-sheet structures. The quaternary structure creates a larger group of polypeptides and proteins, which is stabilized by hydrogen bonds, disulfide-bridges, and salt-bridges.

Function

Amyloids have numerous functions for all organisms:

-Spider silk is formed by amyloids

-Increase cell adhesion on the top of Fungi to have stronger bonding

-Peptides and proteins are stored in the endocrine system of humans as amyloids

-Malaria uses amyloids as a coat protein

-Gas vesicles (that aid in buoyancy) of aquatic archaea and eubacteria

Disease

Amyloids are attributed to multiple diseases, such as:

Amyloidosis- this is where the amyloids build up more often in the liver, kidney, heart, spleen, nervous system, and the digestive tract. It cannot be cured but it can be managed so that the build up does not get high enough to cause organ failure. This occurs in most organisms (dogs, cats, humans, etc.).

Alzheimer's- some studies showed that Alzheimer's disease was connected to a build up of beta-amyloid, which causes the cell-to-cell signalling to be blocked in the brain. The same beta-amyloid can cause immune system activation, causing inflammation and deletion of any cell that was disabled by the beta-amyloid.

Structural highlights

Quaternary beta sheet structure, that can be easily copied and multiplied.

References

1. "Protein Structure." Particle Sciences - Technical Brief: 2009: Volume 8. http://www.particlesciences.com/news/technical-briefs/2009/protein-structure.html

2. Toyama, B. H., & Weissman, J. S. (2011). Amyloid Structure: Conformational Diversity and Consequences. Annual Review of Biochemistry, 80, 10.1146/annurev–biochem–090908–120656. http://doi.org/10.1146/annurev-biochem-090908-120656

3. "Amyloidosis." Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/amyloidosis/symptoms-causes/syc-20353178

4. "AMYLOIDOSIS: A CONVOLUTED STORY-Historical Review." British Journal of Haematology, 2001, Vol 114, pages 529-538. https://onlinelibrary.wiley.com/doi/epdf/10.1046/j.1365-2141.2001.02999.x

5. Maji, S. K., Perrin, M. H., Sawaya, M. R., Jessberger, S., Vadodaria, K., Rissman, R. A., … Riek, R. (2009). Functional Amyloids as Natural Storage of Peptide Hormones in Pituitary Secretory Granules. Science (New York, N.Y.), 325(5938), 328–332. http://doi.org/10.1126/science.1173155

6. Bayro, M. J., Daviso, E., Belenky, M., Griffin, R. G., & Herzfeld, J. (2012). An Amyloid Organelle, Solid-state NMR Evidence for Cross-β Assembly of Gas Vesicles. The Journal of Biological Chemistry, 287(5), 3479–3484. http://doi.org/10.1074/jbc.M111.313049

7. "More About Plaques." Alzheimer's Association. https://www.alz.org/braintour/plaques.asp