Lizzie Flashcards
Listeria invasin InIA mediates high affinity interaction between bacteria and…
cell-cell adhesion protein E-cadherin (found on epithelial cell surface - mediate formation of Ca2+ dependent intercellular junctions
InB
binds hepatocyte growth factor receptor met which is expressed on all cell types –> internalization
T/F: Zipper and trigger mechanisms of invasion utilise same eukaryotic cell processes
FALSE:
Zipper - receptor mediated endocytosis
Trigger/ruffle: macropinocytosis
T/F: Shigella exploits host cell GTPases for invasion
TRUE:
Shigella activates host Rho family of GTPases to induce Arp2/3 and N-WASP dependent actin polymerization and membrane ruffling
T/F: Listeria and Shigella both utilise ARP2/3 AND N-WASP to induce actin filament formation which supports actin based motility
FALSE:
Shigella: N-wasp and arp2/3
Listeria: VASP and ARP2/3
IcsA Shigella protein
Required for actin based motility
Expressed at one pole of bacterium
Autotransporter proten
Binds directly to N-WASP via a glycine rich repeat region to recruit actin
Avoid destruction in phagosome by: (4)
- escaping into cytoplasm
- arresting development of phagosome to avoid identification
- remodelling phagosome by interacting with factors from ER
- adapting to survive in lysosome
T/F:Salmonella has 2 T3SS- one for invasion by ruffling and one for intracellular survival
TRUE:
2 T3SS and 2 sets of effector proteins
T/F: Legionella replicates in a vacuole that has characteristics of late endosomes
FALSE:
Does not interact with endocytic pathway, interacts with EXOCYTIC pathway - ER-exit vesicles
Transport across GN bacterial inner membrane by Sec translocase:
is assisted by SecB chaperone
T2SS
Protein for export carries an N-terminal signal peptide, which is cleaved by a specific signal peptidase
There is a periplasmic intermediate
Sec Dependent
T/F: T1SS are sec-dependent and utilise periplasmic intermediate
FALSE: T1 secrete proteins in one step
Sec independent and no periplasmic intermediate
DOT/ICM SS in legionella:
Translocates ~300 effector proteins
Forms an apparatus that spans inner and outer membrane of bacterium
=T4SS
close homologue to Coxiella
T6SS
Comprises components that are similar to bacteriophage proteins and type 4SS proteins
Advantages of invasion
No competition Inaccessible to complement and antibodies Do not need to adhere Ready access to nutrients May require host cell environment
Cytosolic niche
e. g. SHIGELLA AND LISTERIA
1. invade cells
2. escape vacuole and proliferate
3. recruit host cell cytoskeletal proteins
4. induce actin polymerization
5. formation of actin tails propels bacteria into adjacent cells
cytosolic niche shigella
- invade through ruffling using T3SS AND IpA proteins
IcsA: formation of actin tail =polar, glycine rich repeat region
CYTOSOLIC NICHE: listeria
- invade using zipper
ActA: expressed at pole, binds VASP and Arp2/3 for actin polymerization
Oxygen dependent resipiratory burst
NADPH oxidase
O2-
H2O2
OCl- (reactive oxygen species)
Oxygen independent
low pH (lysosome) proteolytic enzymes lysosyme lactoferrin membrane damaging proteins
Intralysosomal niche
e.g. coxiella
Grows optimally at pH <5
Dot Icm SS
vacuole contains markers for late endosomal lysosomal compartments
Intravacuolar niche (delayed maturation)
e.g. Salmonella, Legionella
Salmonella intravacuolar niche
Prevents phagolysosome fusion
SPI1: cytoskeletal rearrangements, diarrhoea, inflammation, INVASION
SPI2: INTRACELLULAR SURVIVAL AND REPLICATION, modification of vacuole trafficking, inhibition of respiratory burst (prevents NADPH assembly)
SifA: Induces Sif formation - maintains SCV integrity
Legionella: intravacuolar niche
Facultative intracellular pathogen
Replicates in alveolar macrophage, amoebae=natural host
Phagosomes fail to acidify and fuse with lysosomes –> ER-like organelle
General Secretory system (sec)
Common to GP and GN
Leader sequence (20aa) binds to SecB chaperone
Exports UNFOLDED proteins
SecB: tetramer, keeps proteins unfolded and delivers to SecA
SecA: Dimer, ATPase for energy, binds SecYEG which forms protein-conducting channel
TAT PATHWAY = TWIN ARGININE TRANSPORT SYSTEM
GP AND GN
FOLDED proteins
Autotransporters/T5SS
Protein deliver to periplasm via Sec
Sec system
B domain inserts into outer membrane and forms a pore structure
BAM complex assembles/inserts B-barrel in outer membrane
TWO PARTNER SECRETION SYSTEM: SINGLE ACCESSORY PATHWAY
Similar to autotransporter + 1 additional protein
Secretes large virulence proteins
Chaperone Usher pathway
Sec dependent
Transport pili
Chaperones FimC prevent pilin subunits from folding into final configuration
Usher: export pilin
T2SS
SEC dependent
Related to type 4 pili
Outer membrane pore made up of GspD
T1SS
Secretion of toxins, proteases, lipases
Sec independent
Secreted proteins bind ABC transporter protein via C-terminal signal sequence with glycine rich repeat
Signal sequence not cleaved
T3SS
GN pathogens: e.g. Salmonella/shigella - invasion, EPEC-colonization
Sec independent
Directly secrete toxins
Contact dependent
Injectosome: molecular syringe, ATP dependent
T4SS
Related to Bacterial conjugation systems
12 proteins form tunnel
Transfers Ti plasmid and proteins from bacterium to plant cell –> tumor in plants
e.g. legionella
T6SS
Share structural features with bacteriophage cell puncturing protein
Prototype = pseudomonas
Similar to Dot/Icm
T7SS
Some GP
Transports proteins through thick mycobacterial cell wall
e.g. mycobacterium tuberculosis
