Lecture 6 Flashcards
How can you classify the stage of an endosome?
Markers on the outside
What is a common marker of the early endosome?
Rab5
What is a common marker of the late endosome?
Rab7
What is a common marker of the lysosome?
LAMP1
What size particle will be taken up by phagocytosis?
Anything >0.2µm
What are the stages of phagolysosome maturation?
- Fusion with early endosome
- Fusion with multivesicular body to form intermediate
- Fusion with late endosome
- Fusion with lysosome to form phagolysosome and degrade phagocystised particle
What is the main benefit to intracellular lifestyle?
Avoid the immune system
Nutrious environment
How does Mycobacterium tuberculosis modulate phagosome maturation?
Inhibits maturation past the early endosome
How does Legionella pneumophila modulate phagosome maturation?
Converts ints endosome its endoplasmic reticulumk by recruiting ribosomes to the surface - protecting itself from maturation to the lysosome
How does Listeria monomytogenes modulate phagosome maturation?
Degrades early endosome membrane using phospholipases
How does Coxiella burnetti modulate phagosome maturation?
Delays maturation of the endosome
What are the three main ways to avoid lysosomal breakdown?
- Inhibit maturation of endosome to lysosome
- Remove yourself from the degradative compartment, convert it to ER for example Legionella
- Escape into the cytosol
What bacteria was recently shown to have persistance by phagocytosis?
Salmonella phagocytised into macrophages
What is essential for Salmonella’s ability to persist?
Acidic pH
How do bacteria maintain their vacuolar compartments?
- Cytoskeletal recruitment
- Cholesterol modulation
- Secreted microbial factors
- Selective fusion with host vesicular traffic
How does Salmonella use its Type III secretory system?
- Type III secretory system on SPI1 used to inject cell with proteins to cause phagocytosis
How are proteins secreted through a Type III system?
Chaperone proteins bring folded proteins to the T3S system and an ATPase provides energy to unfold the protein and pass it through the needle as a pirece of string
Which part of the protein is involved in targetting to the T3S system?
The N-terminus
Shown by Sory, truncated protein will still be passed through the system as long as has last 50 residues on N terminus
How do bacteria ensure enough chaperone is being made?
Often encoded directyl beside the virulence proteins that need to be secreted
What type of pathogen is Chalymdia?
An obligate pathogen - cannot live outside of the host cell and is dependent on host cell products to survive
Outline the life cycle of Chlamydia
- Infectious elementary body enters cells
- EB differentiates to a reticulate body
- This RB can then then become dormant in the persistent form or associate with the inclusion membrane to release proteins into cell
- RB to EB differntiation
- EB accumulation and then exocytosis
Why can Chlamydia not be genetically modified?
Always inside the host cell
Cannot grow in LB broth
How was it possible to add penicilin gene into Chlamydia?
Fused the E.coli and chlamydia plasmids together inferring the resistance
What does SopB do?
Manipulates the phophoinostides to alter the endosomal membrane
What is the role of spvC of salmonella?
Phosphothreonine Lyase
Removing the phosphate and oxygen group from phosphorylated threonine
Inhibits MAPK and hence inhibits phosphorylation of Erk - decreasing potency of the lysosomes
What are the five T3S virulence stratergies?
- Colonisation
- Invasion
- Cytotoxicity
- Immunity
- TJ disruption
