By Renata Trister DO
Antimicrobial action of Amyloid and Prion Protein PrP
Many neurological conditions are characterized by the formation of proteins or protein plaques in brain tissue. These proteins include amyloid beta and prion protein (PrP). Amyloid plaques are associated with Alzheimer’s disease. Prion protein has been found in patients with Parkinson’s disease, schizophrenia, bipolar disorder, and in some cases of depression. Prion protein is most famously found in Mad Cow Disease. In Mad Cow Disease and other “prion disorders” PrP protein is believed to fold incorrectly.
It is currently thought by many scientists that both amyloid beta and PrP are the causes of neurological inflammation and disease. In Alzheimer’s, amyloid beta “plaque” is believed to exacerbate symptoms and degeneration.
Recent studies at Mass General Hospital in Boston and Lund University in Sweden have called these ideas into question. These studies showed that both amyloid beta and PrP have another, previously unknown function: they are antimicrobial peptides. These antimicrobial peptides are natural, broad-spectrum antibiotics. They can kill bacteria, enveloped viruses, fungi and even cancer cells.
Therefore, if amyloid beta and PrP are antimicrobial, they likely have a protective function in patients with these neurological conditions. Amyloid and PrP most likely are actually the immune system’s response to infection in patients suffering from these diseases. Amyloid beta protects against fungal and bacterial infections. Mouse brains infected with Salmonella Typhi murium, amyloid beta formed in response to the infection. This data demonstrates that amyloid beta deposition, maybe a mediated response of the innate immune system to a perceived infection.
PrP protein is also an antimicrobial peptide. PrP peptides can destroy Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus.
PrP had an anti-fungal effect against Candida. PrP expression was found to increase in patients with H. Pylori infection, with levels returning to normal as the infection clears.
PrP has been found in skin cells of patients with psoriasis, contact dermatitis, squamous cell carcinomas, and viral warts. These conditions associated with micro biome imbalance of the skin. These findings also point to the possibility that prion protein is actually a response to an infection.
The pathology of these diseases may have an infectious component. The specific infectious agent in these neurological conditions is not yet identified. It is also possible that these proteins fight infection initially, but then with increasing levels cause more problems. Many Alzheimer’s medications are aimed at destroying amyloid deposits. These new findings call this approach into question.