Toxin Damage Flashcards
(24 cards)
What are the 3 major types of toxins?
- Pore-forming toxins
- Membrane-damaging enzymes
- Intracellular-acting toxins
What are pore-forming toxins?
Proteins that oligomerise (assemble) to form transmembrane pores in host cell membranes
What is the impact of pore-forming toxins?
Ion imbalance
Osmotic lysis
Cell death
What is an example of a pore forming toxin?
- Pneumolysin (S. pneumoniae
- Hemolysin (E. coli)
What does pneumolysin make pores in?
- Erythrocytes
- Neurons
- Epithelial cells
What are membrane-damaging enzymes?
Toxins that enzymatically degrade phospholipids (main component of membranes)
What is an example of a membrane-damaging enzyme?
a-toxin of Clostridium perfringens
What is the effect of membrane-damaging enzyme a-toxin?
It is a phospholipase C, which cleaves phospholipids
- Destroys cell membranes; causes tissue necrosis
What is an intracellular-acting toxin?
Toxins that enter host cells and interfere with internal processes like protein synthesis or signalling
What is the entry mechanism of intracellular acting toxins?
Typically clathrin mediated endocytosis.
Some toxins use retrograde transport to reach the ER
What are AB toxins?
A type of intracellular-acting toxin, made up of different domains (A and B)
What is an example of a simple AB toxin?
Diphtheria toxin
Halts intracellular translation
What is the function of the A domain of AB toxins?
- Active/catalytic part
- Causes damage inside the cell
What is the function of the B domain of AB toxins?
Binds to receptors on host cell for uptake
What are AB5 toxins?
Consist of 1 A and 5 B subunits
What are some examples of AB5 toxins?
- Cholera toxin (Vibrio cholerae)
- Shiga toxin (Shigella spp.)
What transport do AB5 toxins use?
Retrograde transport, allowing them to access Golgi and ER
What is the effect of Cholera toxin?
- Activates Cl- secretion
- Watery diarrhoea
What is the effect of Shiga toxin?
Inhibits 60S ribosomal subunit
Stops protein synthesis
What secretion system do pathogens use to inject effector proteins?
T3SS (injectisome)
What is an example of a pathogen that uses T3SS?
Salmonella uses SPI-1 T3SS to invade epithelial cells
What is the effect of the effector proteins injected by SPI-1 T3SS?
Effectors promote:
- Actin rearrangement
- Formation of Salmonella-containing vacuoles
- Inflammation
What are the Salmonella-containing vacuoles?
Niches for Salmonella replication
