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Are there any proteins not found in the brain that are affected by prions?

Are there any proteins not found in the brain that are affected by prions?


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A prion is an abnormally folded protein that is capable of causing otherwise normal proteins to also misfold and become prions. They are responsible for causing diseases such as Kuru and Creutzfeldt-Jakob disease. These are both diseases of the brain. Are there any non-brain proteins that also have corresponding prions that can cause disease, or do prion diseases only affect the brain?


Yes, malformed prion proteins can affect tissues outside of the brain.

Via: https://www.merckmanuals.com/home/brain,-spinal-cord,-and-nerve-disorders/prion-diseases/overview-of-prion-diseases

Another familial prion disease has been recently discovered. It differs from other prion diseases because it causes diarrhea and affects nerves throughout the body years before symptoms of brain malfunction develop. It is described as prion disease associated with diarrhea and autonomic neuropathy.

Via: https://www.merckmanuals.com/home/brain,-spinal-cord,-and-nerve-disorders/prion-diseases/prion-disease-associated-with-diarrhea-and-autonomic-neuropathy

Symptoms begin when people are in their 30s. People have persistent watery diarrhea and bloating. They may lose weight. Because the nerves that control body processes are affected, people may not be able to pass urine (called urinary retention) or may lose control of their bladder (urinary incontinence). Their blood pressure may drop when they stand up, causing them to feel dizzy or light-headed (called orthostatic hypotension). People may lose sensation in their feet. Later, when people are in their 40s or 50s, mental function deteriorates, and seizures may occur.


Although it may hadn't be described, I think that nothing chemical or physical would be an impediment to affect other organs, so, said this, in my opinion they could exist.

I found this one affecting outside the brain https://www.nejm.org/doi/full/10.1056/NEJMoa1214747 , I hope that this it's useful to you.

Héctor.


Prion disease is caused when cellular prion protein (PrPc) is misfolded to form abnormal prion protein called scrapie prion protein (PrPSc). These newly formed abnormal prions can't be degraded by enzymes so they keep on accumulating and are responsible for stimulating other normal proteins to fold improperly and form protein aggregates. Accumulation of these amyloids cause diseases and these misfolded prions can't be converted back to normal prion protein.

Via: https://ghr.nlm.nih.gov/condition/prion-disease#genes

These prion proteins (PrPc) are present throughout our body but in lesser proportion as compared to brain cells and recent studies have shown the possibility of this protein aggregation the cause of diseases outside the brain,

Via: https://www.ncbi.nlm.nih.gov/pubmed/21481020

MAVS, RIP1, and RIP3 are other prion-like proteins which are found in other parts of the body. These are not responsible for causing any disease. These proteins aggregate into filamentous amyloid and lead to cell death to prevent the spreading of viral infection.

Via: https://www.nature.com/articles/s41418-018-0172-x


Prions

Christopher J. Burrell , . Frederick A. Murphy , in Fenner and White's Medical Virology (Fifth Edition) , 2017

Abstract

Prions cause major neurodegenerative diseases in humans. A common feature is the spongiform degeneration of the gray matter of the brain accompanied by astroglial hypertrophy and proliferation. Despite intensive efforts, a nucleic acid genome has not been found: prions are “infectious proteins.” Although reaching very high titers in infected brains, the incubation period may extend to many years. Prions are the result of specific conformational changes to the PrP protein. The emergence of bovine spongiform encephalitis in the UK in 1986 has resulted in transmission to humans of a disease termed new variant CJD as a result of contaminated meat entering the food chain.


Alzheimer's: Protein from outside the brain may be involved

A study in mice has discovered that amyloid beta, the protein that causes one of the hallmarks of Alzheimer’s disease in the brain, may also come from other parts of the body.

Share on Pinterest Scientists find that amyloid beta can permeate the blood-brain barrier to give rise to Alzheimer’s disease.

In the journal Molecular Psychiatry, researchers describe how they surgically attached mice to each other for several months to show that amyloid beta in the bloodstream can enter the brain and cause symptoms of Alzheimer’s disease.

If the study findings are true of humans, then the team hopes that they might lead to drugs that do not have to target the brain, which is difficult to reach and treat. It might be easier eliminate the protein before it reaches the brain — for example, by targeting the liver or kidneys instead.

As co-senior researcher Weihong Song, a professor of psychiatry at the University of British Columbia in Canada, explains, “The blood-brain barrier weakens as we age. That might allow more amyloid beta to infiltrate the brain, supplementing what is produced by the brain itself and accelerating the deterioration.”

Alzheimer’s disease is the most common form of dementia, which is a brain-wasting disorder that progressively destroys people’s ability to reason, remember, communicate, and take care of themselves.

Although there is a type of Alzheimer’s that can strike younger people, it is more common in those aged 60 and older.

Of the 47 million people worldwide with dementia, approximately 65 percent are thought to have Alzheimer’s disease.

In the United States, there are around 5 million people living with Alzheimer’s disease, and this number is projected to reach 14 million by 2050.

The exact cause of Alzheimer’s is not yet clear. Experts generally believe that there are several causes and that they arise differently in different people.

A prominent hallmark of the disease is the presence in the brain of sticky, abnormal deposits of amyloid beta protein. As the deposits — also known as plaques — increase, they disrupt brain cells and their connections to each other, and eventually the brain cells die.

Amyloid beta comes from a larger protein that is found not only in the brain but also in other organs. It is also produced in blood platelets, muscles, and blood vessels.

In their study report, the researchers explain that because of the blood-brain barrier, there has been a general belief that the amyloid beta that causes the brain plaques found in Alzheimer’s disease originates only in the brain. This view, however, has never been tested.

For their study, the team engineered mice to carry a version of a human gene that produces high levels of amyloid beta and surgically attached them — in a method called “parabiosis” — to normal “wild-type” mice.

After a period of 12 months, the normal mice had developed Alzheimer’s disease, including the accumulation of plaques of amyloid beta between brain cells.

The team also found that some of the animals’ brain cells contained features similar to “tangles,” or twisted strands of protein, which are another hallmark of Alzheimer’s disease. These tangles also kill brain cells.

There were also other signs of Alzheimer’s disease, such as the degeneration of brain cells, small bleeds, and inflammation.

Also, after only 4 months of being joined to the mice carrying the mutated gene, the normal mice’s brains were already showing disruptions to the electrical signals that carry information between the cells.

Prof. Song says that the amyloid beta had traveled from the mice with the mutated gene through the bloodstream to the brains of the normal mice.

“ Alzheimer’s disease is clearly a disease of the brain, but we need to pay attention to the whole body to understand where it comes from, and how to stop it.”

Prof. Weihong Song


NIH Researchers Discover How Prion Protein Damages Brain Cells

Findings Could Advance Understanding of Mad Cow Disease, Related Disorders.

Scientists at the National Institutes of Health have gained a major insight into how the rogue protein responsible for mad cow disease and related neurological illnesses destroys healthy brain tissue.

"This advance sets the stage for future efforts to develop potential treatments for prion diseases or perhaps to prevent them from occurring." said Duane Alexander, M.D., Director of NIH’s Eunice Kennedy ShriverNational Institute of Child Health and Human Development (NICHD), where the study was conducted.

The researchers discovered that the protein responsible for these disorders, known as prion protein (PrP), can sometimes wind up in the wrong part of a cell. When this happens, PrP binds to Mahogunin, a protein believed to be essential to the survival of some brain cells. This binding deprives cells in parts of the brain of functional Mahogunin, causing them to die eventually. The scientists believe this sequence of events is an important contributor to the characteristic neurodegeneration of these diseases.

The findings were published in the current issue of the journal Cell. The study was conducted by Oishee Chakrabarti, Ph.D. and Ramanujan S. Hegde, M.D., Ph.D., of the NICHD Cell Biology and Metabolism Program.

Central to prion diseases like mad cow disease and to many other diseases is the phenomenon known as protein misfolding, Dr. Hegde explained. Proteins are made up of long chains of molecules known as amino acids. When proteins are created, they must be carefully folded into distinct configurations. The process of protein folding is analogous to origami, where a sheet of paper is folded into intricate shapes. Upon correct folding, proteins are transported to specific locations within cells where they can perform their various functions. However, the protein chains sometimes misfold. When this happens, the incorrectly folded protein takes the wrong shape, cannot function properly, and as a consequence, is sometimes relegated to a different part of the cell.

In the case of prion diseases, the culprit protein that misfolds and causes brain cell damage is PrP. Normally, PrP is found on the surface of many cells in the body, including in the brain. However, the normal folding and distribution of PrP can go wrong. If a rogue misfolded version of PrP enters the body, it can sometimes bind to the normal PrP and "convert" it into the misfolded form.

This conversion process is what causes mad cow disease, also known as bovine spongiform encephalopathy. Feed prepared from cattle tissue containing an abnormally folded form of PrP can infect cows. In very rare instances, people eating meat from infected cows are thought to have contracted a similar illness called variant Creutzfeld Jacob disease (vCJD). In other human disorders, genetic errors cause other abnormal forms of PrP to be produced.

"The protein conversion process has been well studied," Dr. Hegde said. "But the focus of our laboratory has been on how — and why — abnormal forms of PrP cause cellular damage."

To investigate this problem, Dr. Hegde’s team has been studying exactly how, when, and where the cell produces abnormal forms of PrP. They had found that many of the abnormal forms of PrP were located in the wrong part of the cell. Rather than being on the cell’s surface, some PrP is exposed to the cytoplasm, the gelatinous interior of the cell. Moreover, several studies from Dr. Hegde’s group and others showed that when too much of a cell’s PrP is exposed to the cytoplasm in laboratory mice, they develop brain deterioration.

"The sum of these discoveries provided us with a key insight," Dr. Hegde said. "We realized that in at least some cases, PrP might be inflicting its damage by interfering with something in the cytoplasm."

In the current study, Drs. Chakrabarti and Hegde sought to determine what went wrong when PrP was inappropriately exposed to the cytoplasm. Their next clue came from a strain of mice with dark mahogany-colored fur. Although these mice develop normally at first, parts of their nervous systems deteriorate with age. Upon autopsy, their brains are riddled with tiny holes, and have the same spongy appearance as the brains of people and animals that died of prion diseases. The gene that is defective in this strain of mice is named Mahogunin.

"The similarity in brain pathology between the Mahogunin mutant mice and that seen in prion diseases suggested to us that there might be a connection," Dr. Hegde said.

To investigate this possible connection, the researchers first analyzed PrP and Mahogunin in cells growing in a laboratory dish. When the researchers introduced altered forms of PrP into the cytoplasm of cells, they saw that Mahogunin molecules in the cytoplasm bound to the PrP, forming clusters. This clustering led to damage in the cell that was very similar to the damage occurring when cells are deprived of Mahogunin.

The researchers found that this damage did not occur in the cell cultures if PrP was confined to the surface of the cell, if the cells were provided with additional Mahogunin, or if PrP was prevented from binding to Mahogunin.

The researchers then studied mice with a laboratory induced version of a human hereditary prion disorder called GSS, or Gerstmann-Straussler-Scheinker Syndrome. This extremely rare disease causes progressive neurological deterioration, typically leading to death between age 40 to 60. Dr. Hegde explained that some GSS mutations result in a form of PrP that comes in direct contact with the cytoplasm. In mice that contain one of these mutations, the researchers discovered that cells in parts of the brain were depleted of Mahogunin. The researchers did not see this depletion if PrP was engineered to avoid the cytoplasm.

The findings, Dr. Hedge said, strongly suggest that altered forms of PrP interfere with Mahogunin to cause some of the neurologic damage that occurs in prion diseases.

"PrP probably interferes with other proteins too," Dr. Hegde said. "But our findings strongly suggest that the loss of Mahogunin is an important factor."

An understanding of how PrP interacts with Mahogunin sets the stage for additional studies that may find ways to prevent PrP from entering the cytoplasm, or to replace Mahogunin that has been depleted.


Prion diseases: New clues in the structure of prion proteins

Photomicrograph of a neural tissue specimen, harvested from a scrapie affected mouse, revealing the presence of prion protein stained in red. Credit: National Institute ofAllergy and Infectious Diseases(NIAID)

Prion diseases are a group of rapidly progressive, fatal and infectious neurodegenerative disorders affecting both humans and animals. Bovine spongiform encephalopathy (BSE) or "mad cow" disease is one of the most famous since in 1996 scientists found that the agent responsible for the disease in cows is the same agent responsible for Creutzfeldt-Jakob Disease (vCJD), a disease affecting humans.

A new study carried out by Scuola Internazionale Superiore di Studi Avanzati (SISSA) in collaboration with other institutions including Genos Glycoscience Research Laboratory from Zagreb, Croatia, and Elettra Sincrotrone Trieste, provides important information on the differences in structures of the prions, proteins responsible for diseases that at the state of the art are incurable.

One of the main unanswered problems revolving around prion diseases is the existence of strains, leading to a wide range of disorders with different symptoms, incubation time, histopathology, etc. "For a better understanding of the mechanism of the diseases and the existence of strains, resolving the structure of the prion protein is necessary" neuroscientist Natali Nakic, first author of the paper "Site-specific analysis of N-glycans from different sheep prion strains," just published in PLOS Pathogens, says. The prion protein is a glycoprotein, meaning polysaccharides called glycans encompass a large part of the protein structure. The new study is the first one of its kind as it focuses on comparing glycan structures from different strains.

Professor Giuseppe Legname, co-author of the paper, is the Director of SISSA Prion Biology Laboratory and has been collaborating with Elettra Sincrotrone Trieste since 2006. "Carbohydrate of the glycoproteins were sequenced for the first time thanks to the collaboration with Genos Glycoscience Research Laboratory, using a highly sensitive technique called Liquid chromatography/mass spectrometry," he says. "It has long been questioned whether the diversity in prion strains may depend on the glycans that compose them as well as on protein folding. Our results led us to an answer for the first time."

"In this study, glycans from two different sheep prion strains were compared," Natali Naki adds. "After an extensive analysis, no major differences in glycan structures were found between the two strains, suggesting that glycans may not be responsible for the biochemical and neuropathological differences." A remarkable goal as it represents another step toward the fully understanding of prion glycoproteins and the cellular mechanism of prion diseases.


Prion diseases are confirmed by taking a sample of brain tissue during a biopsy or after death. Healthcare providers, however, can do a number of tests before to help diagnose prion diseases such as CJD, or to rule out other diseases with similar symptoms. Prion diseases should be considered in all people with rapidly progressive dementia.

  • MRI (magnetic resonance imaging) scans of the brain
  • Samples of fluid from the spinal cord (spinal tap, also called lumbar puncture)
  • Electroencephalogram, which analyzes brain waves this painless test requires placing electrodes on the scalp
  • Blood tests
  • Neurologic and visual exams to check for nerve damage and vision loss

US confirms first case of mad cow in 6 years

He and his team started with the brains of 14 people who had died with MSA. It can only be definitively diagnosed by examining the brain after death, and is marked by the inappropriate buildup of a protein called alpha synuclein.

Prions from their brains infected cells in lab dishes, changing their function, and caused symptoms resembling Parkinson’s in mice, they reported in the Proceedings of the National Academies of Science.

They examined the brains of the mice and found a buildup of alpha-synuclein.

“Now we’ve conclusively shown that a new type of prion causes MSA,” said Kurt Giles, a neurology expert at UCSF who worked on the study.

This doesn’t necessarily mean that MSA is transmissible in the same way that CJD and BSE can be, outside experts cautioned.

“It is important to state that this study does not demonstrate human-to-human transmission. In fact, it suggests MSA does not transmit easily,” Dr. Valerie Sim, a prion expert at the University of Alberta in Canada, said in a statement.

Cattle got BSE from eating sheep infected with scrapie, a similar brain condition. People can get vCJD from eating infected beef but it is extremely rare – just over 200 cases worldwide have been reported since the first case in the mid-1990s. Cannibals who eat human brains get a similar disease called kuru, and deer and elk are vulnerable to a condition called chronic wasting disease.

“It is important to state that this study does not demonstrate human-to-human transmission."

Knowing there’s another disease spread by prions is worrying because it is extremely difficult to destroy the mutant prions. Standard disinfection does not remove them, and people have been infected with CJD from contaminated surgical instruments.

“You can’t kill a protein,” Giles said. “And it can stick tightly to stainless steel, even when the surgical instrument is cleaned.”

Some experimental therapies for Parkinson’s involve implanting cells or electrodes into the brain, and because MSA can be confused for Parkinson’s, surgeons should take extra care, the researchers said.

There’s also a theory that has yet to be proved that Parkinson’s might be caused by mutant prions, Prusiner’s team noted.

And, they said, their findings show that MSA is distinct from Parkinson’s. Sometimes doctors try the standard Parkinson’s treatment levodopa in MSA patients. This study suggests researchers need to take a new approach.

However, there’s no known treatment for any of the prion diseases, including BSE and CJD.

Maggie Fox is a senior writer for NBC News and TODAY, covering health policy, science, medical treatments and disease.


Persistent neurological problems in survivors

Goldman says that more research is needed to understand the reasons why some post-COVID-19 patients continue to experience symptoms.

The researchers are now examining autopsies on patients who died several months after recovering from COVID-19 to learn more.

They are also examining the brains from patients who were critically ill with acute respiratory distress syndrome (ARDS) before the COVID-19 pandemic to see how much of COVID-19 brain pathology is a result of the severe lung disease.


Why are prions only found in the brain?

In short, they are not. Prions are misfolded, aberrant proteins. These "buggy" proteins (not specifically prions) are found in all cells in all organisms. Prions (there are many types of them) are unique because they can cause other similar proteins to become aberrant, and therefore are considered to be "infectious" (the name prion is derived from the words protein and infection). The brain is especially susceptible because the blood brain barrier stops these proteins from leaving as waste.

Why don't proteins (e.g. the HSP family) refold prions, or why aren't they tagged with ubiquitin?

Firstly, remember the "Central Dogma" of molecular biology - DNA -> RNA -> Protein. While we now know that there are TONS of exceptions to this general rule (including prions), it's still a useful framework.

Our DNA has genes (discrete units of DNA that code for a specific protein) that code for proteins. Different proteins are expressed in different places. For example, you don't typically see high melanin expression in the brain. If there was, the body would be wasting resources on unnecessary protein production. So, different cells get specialized with different proteins. Cell differentiation is the process through which cells become specialized from stem cells. Gene regulation is the mechanism by which they become specialized.

Prions are misfolded proteins. They are made when "templates", or other misfolded proteins, cause correctly folded proteins to misfold. In humans, the only prions (that I'm familiar with, anyways) that infect us are misfolded versions of proteins found in the central nervous system.

So, the reason the prions we hear about a lot in the news are only found in the brain is because they are produced with regular proteins that are only found in the brain. And they are only found in the brain because they perform a specific function for the central nervous system.


Prions diseases

Prion diseases (collectively known as transmissible spongiform encephalopathies) comprise multiple conditions that can affect both humans and other animals. The most commonly known prion disease that affects humans is Creutzfeldt-Jakob Disease (CJD) and its variations. Some other known diseases are Scrapie (Sheep) and Bovine spongiform encephalopathies (commonly known as Mad Cow Disease).

Brain tissue &ndash variant Creutzfeldt-Jakob Disease. (Photo Credit: Sherif Zaki MD PhD Wun-Ju Shieh MD PhD MPH / Wikimedia Commons)

Prions cause neurodegenerative damage by accumulating outside the cells in the extracellular space. This happens in the central nervous system. Moreover, they come together to form amyloid fibers, which are toxic to the neurons and cause their death, leaving holes in the tissue, giving it a spongy look.

Studies have indicated that our body has two ways of degrading prions. First is lysosomal degradation and second is autophagy. So, why do prions still affect us? Because prions are smart and take out these mechanisms so that they can propagate! For example, Rab7 is a protein involved in lysosomal maturation, but it is observed that Rab7 is present in reduced levels in prion-affected cells. If Rab7 levels drop, it would affect lysosomal maturation. This means that fewer lysosomes will be present to degrade prions! Prions also affect the autophagy, which further helps them to advance and affect the neurons. These effects, in turn, affect our cells and help prions induce cell death. This induction of cell death results in the depolarization of the mitochondrial membrane, which quickens the process!


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Comments:

  1. Senusnet

    Excuse me for what I intervene… At me a similar situation. I invite to the discussion.

  2. Galahad

    Nothing special.

  3. Zuluramar

    Congratulations, very good idea

  4. Danaus

    gee in the drive ...



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