Lecture 1: Introduction to Prions Flashcards
What are prions?
Prions are an infectious particles.
What are prions made up of?
Prions are protein molecules, made entirely of amino acids; they are not a living organism but can be transmitted in the same way as infectious organisms.
How are prion proteins made?
Prion proteins are encoded by PrP genes. Abnormal folding of the prion proteins leads to the formation of infection and harmful prions.
What are the 2 classes of prion proteins?
PrP-sen and PrP-res.
What are the PrP-sen prion proteins?
Non-disease causing prion protein that is produced by a typical, non-variant gene formed normally by the body. Structure of gene means it can be acted upon by an enzyme to be broken down.
What are the PrP-res prion proteins?
Disease causing prion protein that forms atypical, variant protein that cannot be broken down by an enzyme, so accumulates in the brain. Accumulation of PrP-res leads to progressive neurological degradation of the brain
How are the 2 different types of prion protein differentiated?
By their ability to be broken down by enzymes to prevent accumulation within the body.
In what way are PrP-res and PrP-sen similar?
PrP-sen and PrP-res have the same amino acid sequence but different folding/ morphologies.
Why are PrP encoded proteins potentially damaging?
PrP genes are damaging because they are involved in communication between nerve cells and are involved in sleep patterns and cell death. Accumulation of prion proteins blocks nerve communication
How do prion particles replicate, if no genetic material is present?
Believed that upon contact with the PrP-sen isoform, PrP-res is capable of converting the sen into res; this leads to eventual increase in the number of resistant PrP proteins in the brain and other parts of the body.
How does PrP-res cause damage?
Accumulation of of PrP-res leads to the formation of amyloid fibres which are responsible for nerve cell death; amyloid fibres are toxic to nerve cells.
What are the role of astrocytes?
Astrocytes move through the brain and digest dead nerve cells, leaving gaps in the nerve tissue. Astrocytes do not remove the amyloid fibres, so they are capable of destroying further nerve cells.
How does the formation of amyloid fibres interfere with cellular communication?
Amyloid fibres replace nerve cells and form a barrier between adjacent nerve cells, that ultimately leads to the inhibition of communication between the nerve cells; responsible for the symptoms such as lack of movement and coordination.
Why are there many different prion associated diseases?
Different prions affect different regions of the brain and so symptoms can vary between diseases.
What diseases are associated with prions that target the brain stem?
Scrapie, BSE and chronic wasting disease
