• Rohit Duggaraju

Prions - A Unique Pathogen

Thumbnail by Robina Weermeijer, Unsplash Media


Some perilous, insidious neurodegenerative disorders are caused by interesting pathogens called prions. These infectious agents are separate from viral, bacterial, or fungal agents. Prions are transmissible, like viral infections, but can be much more harmful. These prion diseases have been categorized into a group called transmissible spongiform encephalopathies, or TSEs. They are responsible for many rare conditions such as Creutzfeldt–Jakob disease, CJD, vCGD, Kuru, and more. But what are prions? How do they work? And most importantly, are there possible cures to prion diseases?


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What are prions?

Prions, the smallest pathogens in the world, are actually misfolded, malfunctioning proteins. They are able to transmit their misfolded properties onto other proteins, causing a loss of function and disorders. They seem to be specifically harmful to proteins called prion proteins, which are mostly found in the brain. These prion proteins have an unknown function, but when they are misfolded by the prions, it causes degenerative disorders such as CJD. Prions have no genetic material, and are incredibly small. Over the past few years, there has been incredibly strong evidence to back up these hypotheses; however, prions are still not very understood and there is a lot of research happening right now.

Prions are also present in animal brains, causing mass diseases such as mad cow disease and more. Scientists believe that prion diseases can be transmitted through bodily fluids, feces, environmental contamination, and more.


How do prions pass on their properties to other prion proteins?

There is still much current research on this topic, but there have been many findings. During conformational remodeling events of prion proteins, where they are changed, misfolded prions are able to use themselves as a template to misfold a healthy prion protein. This starts a chain reaction that leads to degeneration of brain matter.


Understanding Protein Function

Proteins are genes being physically expressed. Proteins create traits, functions, and serve thousands of crucial functions in the body. All enzymes that catalyze reactions in our bodies are proteins. However, proteins need a very specific set of conditions to function properly. When in an abnormal pH, salinity level, temperature, or another condition, proteins begin to denature. Denaturation is when a protein is altered in shape and loses its function. When this happens, the purposes that the denatured protein served will no longer happen, causing damage to systems.

Denaturation can also be caused by direct changes in protein structure. For example, if any level of protein structure (amino acid sequence, etc) is changed, the function will also be changed/lost. To fully understand this, we must look at the four levels of protein structure.


Picture from Unsplash, Wix Media

The primary structure of a protein is its amino acid sequence. Remember, proteins are simply polypeptides, or polymers, of amino acid monomers bonded by polypeptide bonds. For example, a protein can have a sequence of amino acids that is leucine-threonine-valine (proteins are much longer than this, but this example is hypothetical). If this primary structure was changed to leucine-valine-threonine, the protein would function completely differently.

The secondary structure of a protein is the arrangements of amino acid sequences. This is almost like the 2D structure of a protein. For example, common secondary protein structures are beta pleated sheets and alpha helixes.

The tertiary structure of a protein is the 3D structure of protein, or how the different 2D arrangements are folded. Proteins fold in a very specific way, and if they are folded in a different way they are denatured.

The quaternary structure of a protein is how the protein interacts with other polypeptides. there are some proteins that are combinations of multiple proteins or polypeptide amino acid chains. If these interactions are changed, the protein function as a whole changes too.


When prion proteins are misfolded, this changes the tertiary structure of prion proteins, causing a completely different function.


Are there cures to prion diseases?

As of right now, there are no cures to prion diseases. However, they are being researched incredibly heavily right now. There is medication such as prion antibodies and so-called anti-prions that inhibit the replication of misfolded prion proteins, but they only slow the progress of the disease. These diseases are generally almost always fatal. There are ways to kill or destroy abnormal prions, by denaturing them to a point where they cannot function anymore. However, this still damages brain matter. Nonfunctional prions and misfolded prions still harm the brain, but nonfunctional prions cannot multiply. These are the only ways to slow the progress of diseases such as CJD right now.

In conclusion, prions are barely understood, small pathogens that already exist inside our brains, that when structurally changed can cause terrible and brutal brain disease.


Picture from Unsplash, Wix Media, by Robina Weermeijer

Bibliography

https://www.cdc.gov/prions/index.html

https://www.hopkinsmedicine.org/health/conditions-and-diseases/prion-diseases

https://www.scientificamerican.com/article/what-is-a-prion-specifica/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4106303/


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