PRION BASICS Human Diseases
Like animal prion diseases, human prion diseases involve misfolded prion proteins and the death of brain cells. Human prion diseases are rare, but they are serious, causing progressive brain damage that results in patients eventually losing their ability to speak or move. All prion diseases are fatal.
Recent evidence suggests that the way proteins misfold in human neurodegenerative diseases such as Alzheimer’s, Parkinson’s and Huntington’s is similar to how prions misfold. These neurological diseases affect hundreds of thousands of Canadians each year, and their incidence is increasing. Looking at these neurodegenerative diseases from a prion perspective presents a new approach to seek discoveries in understanding diagnoses and potential treatments of these diseases.
Human prion and prion-like protein misfolding diseases include the following:
Creutzfeldt-Jakob Disease (CJD)
- The most common prion disease in humans with an approximate occurrence of one in a million;
- The majority of cases (85-90 per cent) are spontaneous, and their cause is unknown;
- Some cases (5-10 per cent) are caused by an inherited genetic mutation of the gene that encodes prion protein; and
- Death often occurs within months of the onset of clinical symptoms.
Variant Creutzfeldt-Jakob Disease (vCJD)
- Acquired from eating BSE-infected material;
- Only two people in Canada have ever died from vCJD, which they acquired prior to coming to Canada; and
- No cases have been linked to eating Canadian beef.
- A progressive, degenerative and fatal disease that destroys brain cells;
Two proteins misfold:
- Beta-amyloid aggregates into plaques;
- Tau aggregates into tangles (tangles are insoluble, twisted protein strands that destroy cell transport systems); and
- It’s the most common type of dementia (64 per cent of dementia cases).
- Affects a part of the brain that produces dopamine (a crucial neurotransmitter);
- The loss of dopamine disrupts messages that control body movement; and
- Alpha-synuclein (a protein that regulates dopamine transporters) clumps together – this causes cell death and dysfunction.
- An inherited brain disease caused by a faulty gene;
- An abnormal DNA sequence produces an abnormally long protein called huntingtin. This protein breaks into pieces, the pieces misfold and clump together, and they disrupt cell function; and
- Huntington’s results in behavioural changes, inability to control movement and severe dementia.
Amyotrophic Lateral Sclerosis (ALS or commonly known as Lou Gehrig’s disease)
- A fatal, degenerative neuromuscular disease that causes muscle wasting, disability and paralysis;
- Most cases are spontaneous; and
- The cause is unknown but could be due to the overproduction of free radicals that cause oxidative stress leading to cell death. Normally SOD-1 neutralizes free radicals, but it becomes inoperative if SOD-1 misfolds.
Currently, there are no vaccines against, cures or effective long-term treatments for these diseases. The Alberta Prion Research Institute funds research in this area with the goal of better understanding these neurological diseases and improving the quality of life for those suffering from them.