Prion

Our bodies have tiny parts called proteins.

Most proteins have a good shape. Some proteins fold the wrong way. These are called prions.

A prion can touch a normal protein. Then, the normal protein changes shape too. This makes more prions. It is like a chain reaction.

These prions can hurt the brain. They can make animals and people very sick. This can happen to sheep or deer. It can even happen to cows.

Prions are hard to stop. They are very strong. We do not have a way to fix them yet. Scientists are still studying them.

Our bodies are full of proteins. Most proteins have a healthy shape.

A prion is a protein that has folded the wrong way. This is called a misfolded protein. Prions are different from germs like bacteria or viruses. They do not have DNA or RNA.

Prions work in a strange way. A prion can touch a normal protein. It causes that normal protein to change its shape too. This creates more misfolded proteins. This set of steps can lead to many more prions. This can happen through genetic changes or by touching a prion.

These proteins can cause serious diseases. These diseases affect the brain and other tissues. They are fatal, which means they cannot be cured. Prions cause scrapie in sheep. They cause chronic wasting disease in deer. They also cause mad cow disease in cattle. In humans, they can cause Creutzfeldt–Jakob disease. Prions are very tough. They can resist many ways to clean them. This makes them hard to stop.

Prions are tiny, misfolded proteins that cause serious diseases. Most proteins in our bodies have a specific shape that helps them work.

A prion is a protein that has folded into the wrong shape. Unlike bacteria or viruses, prions do not contain DNA or RNA. They are known as proteinaceous infectious particles. These proteins mainly affect the brain and other neural tissues. Because they damage cells, the diseases they cause are always fatal.

Prions work through a strange and steady process. They start with a normal protein called PrPC. When a prion, or PrPSc, meets a normal protein, it changes that protein's shape.

This new protein becomes a prion itself. These prions can then form long, stacked chains called amyloids. These amyloids build up in the body and cause cell death. The ends of these chains act like templates for more proteins to join. This allows the misfolded proteins to grow and spread quickly.

Scientists have worked hard to understand these particles. The term "prion" was coined in 1982 by Stanley B. Prusiner. He used it to describe how these proteins can infect others. Before this, people did not fully understand how a protein could act like a germ. Prusiner's work helped explain how a shape could be passed along. This discovery changed how we think about infectious diseases. It showed that something without DNA could still spread through a body.

There are many different prion diseases in animals and humans. In sheep, the disease is called scrapie. Deer can get a condition called chronic wasting disease. Cattle can suffer from bovine spongiform encephalopathy, often called mad cow disease. In humans, one common version is Creutzfeldt–Jakob disease, or CJD.

Scientists also found a prion form of alpha-synuclein in 2015. This was linked to a disease called multiple system atrophy. These diseases are very hard to treat because they progress steadily.

Prions are much tougher than many other tiny germs. They are resistant to many chemical and physical cleaning methods. This makes them very hard to get rid of in medical settings. This toughness can cause concerns about how they might spread through medical tools. You can think of them like a shape that refuses to change back. Once they take on their new, incorrect shape, they stay that way. This stability is what makes them such a unique scientific mystery.

A prion is a misfolded protein that causes serious disease. Most proteins in the body have a specific three-dimensional shape. This shape allows them to perform vital biological tasks. However, a prion is a version of a protein that has folded incorrectly.

This change in shape causes the protein to behave like an infectious agent. Unlike viruses, bacteria, or fungi, prions do not contain nucleic acids like DNA or RNA. They are known as proteinaceous infectious particles. Prions are responsible for fatal neurodegenerative diseases in many animals and humans. These diseases primarily attack the brain and other neural tissues.

To understand how prions work, we must look at the major prion protein, or PrP. Humans and other animals have a normal version of this protein called PrPC. PrPC is found on cell membranes, including in blood components like platelets. In humans, PrPC has 209 amino acids and a mainly alpha-helical structure. The infectious version of this protein is called PrPSc.

When PrPSc meets a normal PrPC protein, it forces the normal protein to change its shape. This process is called conformational change. The normal protein becomes a misfolded PrPSc protein. This new protein can then interact with even more PrPC proteins. This creates a chain reaction of misfolding.

Prions grow and spread through specific structural mechanisms. One theory is the heterodimer model, where one PrPSc molecule converts one PrPC molecule. However, scientists believe prions mostly exist as larger structures called fibrils.

These fibrils are long, stacked chains of proteins known as amyloids. The ends of these amyloid fibers act as templates. Free protein molecules attach to the ends and refold to match the fiber. This allows the fiber to grow longer. As these fibers grow and break, the number of infectious particles increases exponentially. This rapid growth explains how the disease spreads quickly through the body.

These misfolded proteins are incredibly stable. They are resistant to denaturation, which is the process of breaking down proteins. They can even resist proteases, which are the enzymes the body uses to digest proteins.

Because they are so tough, prions are difficult to destroy with chemical or physical cleaning. This stability raises serious concerns about iatrogenic spread. This is when a disease is spread through medical instruments during procedures. The accumulation of these amyloid aggregates in tissue eventually leads to cell death.

Scientists have identified many different prion diseases across species. In sheep, the condition is called scrapie. In deer, it is known as chronic wasting disease (CWD). Cattle can suffer from bovine spongiform encephalopathy (BSE), often called mad cow disease. In humans, one major form is Creutzfeldt–Jakob disease (CJD).

In 2015, researchers discovered that a prion form of alpha-synuclein is linked to multiple system atrophy (MSA). These diseases are progressive and have no known effective treatment. They are invariably fatal once they begin.

The history of prion science changed how we view infection. The term "prion" was coined in 1982 by Stanley B. Prusiner. He used it to describe these proteinaceous infectious particles. Before this discovery, it was not widely accepted that a protein alone could cause disease. Prusiner's work showed that a change in protein shape could be passed along. This challenged the idea that all infectious agents must contain genetic material. This discovery opened new ways to study how proteins function and fail.

While prions are famous for causing disease, the normal PrP protein has many important roles. Scientists are still investigating its exact functions. Research suggests PrP may help with cell-cell communication in the brain. It might also be involved in maintaining long-term memory. Some studies show PrP is necessary for the self-renewal of bone marrow in stem cells. It may even play a role in innate immunity against certain viruses. Understanding the normal protein is the key to understanding why the misfolded version is so destructive.