Short answers, pulled from the story.
Stanley B. Prusiner coined the term prion in 1982 to describe a protein that could cause disease without containing any genetic material. He was a neurologist at the University of California, San Francisco, and his discovery challenged the central dogma of molecular biology. Prusiner was awarded the Nobel Prize in Physiology or Medicine in 1997 for this research.
The normal form of the prion protein, known as PrPC, consists of 209 amino acids in humans and has a structure dominated by alpha-helices. The infectious isoform, PrPSc, has a higher proportion of beta-sheet structure, which makes it resistant to proteases and allows it to accumulate in the brain. This structural change enables PrPSc to convert normal PrPC molecules into the infectious form, creating a chain reaction that spreads through the nervous system.
The story of prions began in the 18th and 19th centuries with a disease called scrapie, which affected sheep and goats. This disease is probably the first transmissible spongiform encephalopathy to be recorded and is characterized by a long incubation period. The disease caused affected animals to lie down, bite at their feet and legs, and rub their backs against posts before becoming lame.
The outbreak of mad cow disease in the United Kingdom in the 1980s led to a global crisis with thousands of cattle being culled and millions of people affected. The disease was linked to the practice of feeding cattle meat and bone meal, which contained prions from infected animals. This crisis highlighted the need for stricter regulations on animal feed and the importance of monitoring prion diseases in livestock.
In the early 1990s, Reed Wickner discovered proteins showing prion-type behavior in the yeast Saccharomyces cerevisiae, which were termed yeast prions. These prions do not always cause disease in their hosts and may have a useful role in adapting to diverse environments. Research into fungal prions has provided strong support for the protein-only concept by demonstrating that purified protein can convert the normal form of the protein into a misfolded form in vitro.
Despite decades of research, there are no effective treatments for prion diseases as of 2018. Clinical trials in humans have not met with success and have been hampered by the rarity of prion diseases. While some drugs can be prescribed to control specific symptoms, no known way exists to extend the life of a patient with prion disease.