Transmissible Spongiform Encephalopathies (TSEs) Essay

In bovine spongiform encephalopathy (BSE), the disease is caused by the misfolding of proteins that cause proteins and peptides to develop a fibrillary structure. The PrPc is a correctly folded prion and the misfolded form is called PrPSc. BSE occurs when the normal PrPc come into contact with the toxic PrPSc and the normal prion takes on the shape of the PrPSc. The normal chaperones are unable to convert the PrPSc back to the normal form. The PrPSc now takes on the role of chaperone and the conversion of PrPc prions continue over and over. PrPSc, now being hydrophobic avoids the water of the inner cell and begin to accumulate and form plaques along the neuronal cell membranes. The aggregation of the prions on the cell membrane eventually lead to cell death which produces the sponge-like appearance in the brain of cattle infected with BSE (Thompson, 2014).

The cell is the basic unit of life in eukaryotic organisms. The inside of the cell is comprised of multiple subunits called organelle that all function together to maintain homeostasis and function. Each individual organelle is assigned a specific task and purpose for the cell. These tasks and purposes can range from structural support all the way to the disposal of malfunctioning organelle.1 Similarity to a machine, if one part stops functioning to full potential, serious if not fatal consequences can be faced. A shining example of the effects of a malfunctioning organelle occurs in Tay-Sachs disease. Tay- Sachs disease is a lysosomal disorder that is caused by a faulty lysosome.1 Recent studies and research have been investigating the causes and pathways Tay-Sachs disease with great success, which is amazing news for the scientific community.

Variant Creutzfeldt-Jakob disease (vCJD) is a rare and fatal human neurodegenerative condition falling under the category of Transmissible Spongiform Encephalopathy (TSE) because of having characteristic of spongy degeneration of the brain that it causes and its ability to be transmitted. First it was described in the United Kingdom in March 1996 and it has been connected with exposure to a TSE of cattle known as Bovine Spongiform Encephalopathy (BSE) sometimes called Classical BSE, having been reported first in 1986 in the United Kingdom.

     Mad Cow Disease, scientifically referred to as (BSE) Bovine Spongiform Encephalopathy, is a disease that affects those humans who eat the meat from infected cows. Mad Cow Disease is one of several fatal brain diseases called (TSE) Transmissible Spongiform Encephalopathy. (USDA) There was evidence of a new illness resembling the sheep disease scrapie. It was technically named BSE but quickly acquired the mad cow tag because of the way infected cattle behave. (CNN) In 1997, there was an award given to Stanley Prusiner, for concluding that a distorted protein called a prion was responsible for Mad Cow Disease, noted the long incubation period made it difficult to distinguish (Bryant).

Humans have to deal with many different diseases and the ones most disliked are the ones with no cures. Like cancer, transmissible spongiform encephalopathies have no cure, but they are more rare. These diseases are prion diseases which cause the brain to deteriorate. Prions are proteins that sometimes behave like viruses, which mean that they should have some form of nucleic acid, but since they don’t, they cause abnormalities. The nervous system contains many normal prions, but when an abnormal prion comes along, it transforms all the normal prions into abnormal ones. Bovine spongiform encephalopathy is found in cattle, but it can be transmitted to humans.

Abnormal changes happen in the brain, and it appears as a sponge-like holes and gaps, causing deterioration in the areas of the brain. This can turn into spongiform degeneration that results in the progressive neurological and neuromuscular symptoms that are associated with CJD. This disorder is a result from a mutation in the gene that regulates the production of the human protein or direct transmission with abnormal protein in infected brain tissue. Scientist believe that there is a transmissible agent that is responsible for causing CJD. This is a slow virus, since it can take many years from exposure to the appearance of

Although mad-cow disease is always fatal, it is not really much of a worry in the United States. There have only been four cases of mad-cow disease ever recorded in the United States. In every case, the United States Department of Agriculture has intervened and recalled tons of beef, 10,400 lbs. in the first case to be exact, in order to insure that the meat did not reach the plates of United States citizens.

Proteinaceous Infectious Particles, commonly known as Prions, are extremely rare misfolds of the protein PrPc, which cause fatally neurodegenerative diseases, and are theorized to be infectious only by the protein itself (U.S National Library of Medicine, 1998). This “protein-only theory” is still heavily debated today, as some scientists deny the theory, and there isn’t a significant amount of evidence on each side to qualify the theory or disprove it (Soto, C. 2011). The base “Prion” protein is encoded in the gene PRNP, while being non-infectious. Prions are most commonly found in human prion diseases, but they can also be in other animals in the form of Mad Cow Disease and Chronic Wasting Disease, classified as Bovine Spongiform Encephalopathies

Bovine Spongiform Encephalopathy “is a progressive neurological disorder of cattle that results from infection by an unusual transmissible agent called a prion”. (Center for Disease Control & Prevention, 2015).

This disease gets its name from the German neurologist Hans Gerhard Creutzfeldt and Alfons Maria Jakob that first identified this disease. (Victor, 2015) VCJD is primarily found in the brain of the cattle. Abnormal proteins called prions have thought to be the cause of this disease in both cattle and in humans. These prions cause tiny holes that look like a sponge under a microscope. (Melissa Conrad Stöppler, 2015) Unlike most viruses and bacteria these prions unfortunately do not die when exposed to heat, ultraviolet light, and radiation. Disinfectants that are usually used to kill viruses and bacteria also do not work to kill prions. Even cooking the meat very well will not lower the risk of prions in the

The prion protein (PrP) is unusual in that it has two stable isoforms. The cellular or normal form of the prion protein is termed PrPC, while the disease form is termed PrPSC. Sharing the same sequence of amino acids, or primary structure, PrPC and PrPSC differ in their secondary, tertiary, and quaternary structures. The normal prion protein has N- and C-terminals, three alpha helices, and two beta sheets (Soto, 2006, 40). Its function is still not completely understood. However, scientists have found evidence that point to various possibilities. 1) Because most PrPC are located in lipid rafts, membrane structures involved in signaling, it is suggested that PrPC may also be a mediator in neuroprotective signaling pathways. 2) Interaction between PrPC and Bcl-2, a ligand involved in protecting neurons from apoptosis, suggests the possibility that PrPC may be an antiapoptotic protein. 3) PrPC has also been linked to copper metabolism in the brain. In one particular study, PrP knockout mice, or mice that were genetically altered to not express PrP, were found to have lower levels of copper in their brains and higher levels in their serum (Soto, 2006, 42). However, in other studies with PrP knockout mice, most of the animals did not display any obvious disorders, and those that did were found to have been affected by the increase in concentration of another protein known as doppel.

Creutzfeldt - Jakob disease is a prion disease characterized by the degeneration of the cerebral cortex, basal ganglia, cerebellum, brainstem and spinal cord. CJD is classified into 4 types: sporadic, familial, iatrogenic, and contaminated meat. CJD represents approximately 85% of all human prion diseases . Although it is common in older ages (50-70), both men and women have an equal chance of acquiring the disease. Recently, there has been a new variant CJD that is thought to be from the ingestion of cattle products in Great Britain. The central characteristic that differentiates vCJD and CJD is that it occurs more commonly in younger people and also has different pathogenic findings. The second variant form is the panencephalopathic form, which is found in Japan.

However, under pathological conditions calpain is hyperactivated due to extreme calcium influx causing cellular damage and neurotoxicity. Calpains play a key role in neuropathologic events following different types of insults including traumatic brain injury, stroke, epilepsy and organ injury (Wang 2000). The activation of calpain has been associated with several neurodegenerative disorders. For example, calpain alters the processing of various proteins (tau, amyloid precursor protein, several cytoskeletal proteins) associated with Alzheimer's disease (AD). Cell culture studies have shown that calpain activation does not cause PrPC degradation (Wang et al.,

Prions are infectious protein agents that cause aggregation of the peptide PrPC and form large amyloid fibrils. These fibrils resist proteoysis and can have a detrimental effect of the functionality of cells and ultimately cause their death. (3). Misfolded PrPC will form stable aggregates denoted as PrPSc. PrPC is a soluble protein that is present in all organism whose function is still not totally clear (3). When PrPc converts to PrPSc there is an increase in the number of β sheets in the protein, which can allow for interaction and stacking of other misfolded PrPSc proteins, causing an amyloid fibre to form (5).

There are a number of other proteins that display prion-like behaviour despite they do not fit in the previous definitions. These functional prion-like proteins differ from pathogenic prions and prionoids in two important aspects: First, the conversion to the aggregated state is regulated by a physiological signal, and second, the prion-like conformation exerts a defined novel function.